Sorbents Materials for Controlling Environmental Pollution: Current State and Trends

Sorbents Materials for Controlling Environmental Pollution: Current State and Trends presents data on current use and future trends regarding sorbent materials employed against soil, water, and air pollution. The book is organized first by use and research for a variety of geographic areas. It will then focus on different sorbent materials and their uses, followed by various pollutants and their management. Including updated and extensive data from an assortment of sources, the book is organized to be very accessible, including with an interactive table to help identify the results of appropriate sorbents for each environmental compartment.

The growing concern regarding soil, water and air pollution all over the world has implications for climate change and sustainability, making Sorbents Materials for Controlling Environmental Pollution: Current State and Trends an important reference for environmental scientists to identify tools for moving forward in solving these problems.

• Includes data and examples from various geographic locations worldwide
• Synthesizes data for a variety of sorbent material from different sources
• Presents data for various kinds of pollutants across environmental spheres, including soil, water, and air
• Utilizes an interactive table for quicker access to data and results

• Language: English
• Publisher: Elsevier Science
• Release date: Feb 16, 2021
• ISBN: 9780323851848

Book preview

China

Chapter 1: Introduction

Avelino Núñez-Delgadoa; Esperanza Álvarez-Rodrígueza; María J. Fernández-Sanjurjoa; David Fernández-Calviñob; Manuel Conde-Cidb; Manuel Arias-Estévezb    a Department of Soil Science and Agricultural Chemistry, Engineering Polytechnic School, University of Santiago de Compostela, Lugo, Spain

b Soil Science and Agricultural Chemistry, Faculty of Sciences, University of Vigo, Ourense, Spain

Abstract

In this chapter, we present some introductory details, focusing on definitions and fundamentals of sorption and adsorption derived from sources of reference. We also introduce the overall current situation on publications about sorbent materials to control environmental pollution. To do that, we selected data from two searching tools widely used in science. Both Google Scholar and Web of Science showed interesting details, each of them complementing to another, as evidenced in the text and graphs included later.

Keywords

Adsorption; Desorption; Sorbent materials; Retention of pollutants

Acknowledgments

This work was supported by the Spanish Ministry of Economy and Competitiveness [grant numbers RTI2018-099574-B-C21 and RTI2018-099574-B-C22]. It also received funds from the European Regional Development Fund (ERDF) (FEDER in Spain) being a complement to the previous grants without additional grant numbers. D. Fernández-Calviño holds a Ramón y Cajal contract (RYC-2016-20411) financed by the Spanish Ministry of Economy, Industry, and Competitiveness. M. Conde-Cid holds a predoctoral contract (FPU15/0280, Spanish Government). The sponsors had not involvement in study design; in the collection, analysis, and interpretation of data; in the writing of the report, and in the decision to submit the article for publication.

1.1: Brief comments on definitions and fundamentals of sorption and adsorption processes

Sorption is defined by IUPAC (1997/2019) as The process by which a substance (sorbate) is sorbed (adsorbed or absorbed) on or in another substance (sorbent). Regarding the concept of adsorption, the International Adsorption Society (IAS, 2019) indicates that it is The use of solids for removing substances from either gaseous or liquid solutions, and involves the preferential partitioning of substances from the gaseous or liquid phase onto the surface of a solid substrate. Focusing mainly on soil science, Thompson and Goyne (2012) indicated that sorption is Any removal of a compound from solution to a solid phase, whereas the release of ions or molecules from soil solids into solution is desorption. These authors also indicate that when knowledge of the actual sorption mechanism is available, We can refer to the accumulation of chemicals at the solid-liquid interface as adsorption, the accumulation of molecules within existing solids as absorption, and the incorporation of substances within an expanding three-dimensional solid as precipitation. Thompson and Goyne (2012) also added that When discussing sorption processes, we call the adsorbing/absorbing solid phase the sorbent; solutes in the liquid phase that could potentially sorb are known as sorptives, and constituents that accumulate on or within a solid are termed sorbates.

Dealing with sorption processes that involve different sorbent materials and paying special attention to removal of pollutants, there are quality papers published in research journals, as well as book chapters, which explore details or show fundamentals. As example, Niazi et al. (2016) focus on the use of biosorbents and biochars (the latter specifically derived from biowastes) for the removal and recovery of precious metals and heavy metals from water and wastewater. Interestingly, these authors not only limit their investigation to efficacy in removal but also emphasize on the fact that Recovery of these metals from their aqueous solutions has emerged as an exciting area of research as a result of increasing or fluctuating prices of metals, limited availability of their deposits, and the ever-increasing demand and time- and energy-consuming processes needed to mine metal deposits.

Regarding retention of organic pollutants different publications could be considered as quality examples, going from some rather classical, such as the work from Breen and Watson (1998), to recent papers, such as that from Awad et al. (2019).

To illustrate some of the main tasks involved in standard studies focused on sorbents and sorption/desorption processes, we include graphical examples discussed later.

Figs. 1.1 and 1.2 show pictures with examples of sampling and of some low-cost by-products used as sorbent materials.

Fig. 1.1 Examples of field sampling. Images original from authors, not previously published.

Fig. 1.2 Examples of sorbent materials that could be added to soils. Images original from authors, not previously published.

Figs. 1.3 and 1.4 show main steps related to standard studies carried out to characterize different solid materials, and to perform investigation on sorption/desorption processes.

Fig. 1.3 Some of the main steps in the study of sorption/desorption processes, starting with pretreatment, sieving, milling, and basic characterization. Images original from authors, not previously published.

Fig. 1.4 Other main steps in the study of sorption/desorption processes, including shaking, centrifuging, filtering and quantification of pollutants. Images original from authors, not previously published.

Fig. 1.5 shows specific equipment used in studies focused on dynamics, related to investigation of sorption/desorption (or retention/release) processes, and complementing batch-type experiments.

Fig. 1.5 Examples of devices used in dynamic studies related to retention/release processes. Images original from authors, not previously published.

1.2: Current situation

Searching for Sorbents controlling pollution in Google Scholar, from years 1800 to 1900 just 8 results are shown; from 1901 to 1960, 115 results; from 1961 to 1980, 1460 results; from 1981 to 2000, 14,000 results; and from 2001 to 2010, 18,600 results. Detailing the past years, in 2011, 5380 results are found; in 2012, 6240 results; in 2013, 6960 results; in 2014, 7300; in 2015, 7890 results; in 2016, 9030; in 2017, 9230; in 2018, 10300; and up to the middle of December 2019, 7900 results. These numbers show that as per this source of scientific information, the field of research has been growing for decades and the trend is maintained last years. These results are shown graphically in Fig. 1.6.

Fig. 1.6 Results of searching for Sorbents controlling pollution in Google Scholar; (A) in intervals of up to each of the years indicated in the graph; (B) in specific years.

Restricted to 2019, sorting by Relevance, the first three publications shown by Google Scholar are from some of the authors of this chapter (specifically, Núñez-Delgado et al., 2019; Núñez-Delgado, 2019; Romar-Gasalla et al., 2019), whereas in Web of Science the first three papers are from Núñez-Delgado (2019), Pandey and Alam (2019), and Gong et al. (2019).

For the whole period covered, Web of Science indicates that the first three papers receiving most citations are from Crini (2006), with 2614, Bailey et al. (1999), with 2280, and Karickoff et al. (1979), with 2086 citations. There are other nine papers that have received more than 1000 citations up to now and were published in Journal of Hazardous Materials (two of these nine papers), Environment International, Journal of Environmental Sciences, Chemosphere, Environmental Science and Technology (three of these nine papers), and Journal of Microcolumns Separations. These nine works were published between 1999 and 2014. Considering the number of citations per year, the paper situated in first place (218 citations per year) is from Ahmad et al. (2014), also placed seventh in total number of citations.

Searching for Sorbents controlling pollution in Web of Science, a total number of 6658 results is shown. Fig. 1.7 shows an overall trend to increase the number of publications by year, considering from 1995 to 2019, although the ascension reflected for the past years (2014–18) is not totally maintained in 2019 (with data available up to the middle of December). By countries, most papers are from China (1421 + 529), followed by the United States (1484), Spain (519), and other countries indicated in Fig. 1.7. By institutions, Fig. 1.8 shows that the first one is the Chinese Academy of Sciences, followed by the Spanish CSIC, the US Department of Energy, the French CNRS, and the US EPA, followed by different universities around the world, including the University of Santiago de Compostela (Galicia, Spain), where some of the authors of this chapter work currently.

Fig. 1.7 Main results of searching for Sorbents controlling pollution in Web of Science; (A) results by years, covering from 1995 to 2019; (B) results by country.

Fig. 1.8 Main results of searching for Sorbents controlling pollution in Web of Science, showing number of publications by institution.

Fig. 1.9 shows results provided by Web of Science, referred to number of citations, considering the whole period of time covered and the past 23 years. Both graphs indicate that the number of citations has been growing systematically, and the trend is still maintained.

Fig. 1.9 Main results of searching for Sorbents controlling pollution in Web of Science, regarding number of citations; (A) number of citations by year, for the whole period; (B) number of citations by year, from 1996 to 2019.

1.3: Conclusions

In this introductory chapter, after presenting some details regarding definitions and fundamentals of sorption and desorption, we made use of two classical searching tools, which showed that the field of investigation delimited by the words Sorbents controlling pollution has been increasing for decades, as well as during the past years, and it seems that it may continue to grow, although trending to stabilize. Further specific details derived from both tools aid to provide a more illustrated picture of the current situation for this field of research.

References

Ahmad M., Rajapaksha A.U., Lim J.E., Zhang M., Bolan N., Mohan D., Vithanage M., Lee S.S., Ok Y.S. Biochar as a sorbent for contaminant management in soil and water: a review. Chemosphere. 2014;99:19–33. doi:10.1016/j.chemosphere.2013.10.071.

Awad A.M., Shaikh S.M.R., Jalab R., Gulied M.H., Nasser M.S., Benamor A., Adham S. Adsorption of organic pollutants by natural and modified clays: a comprehensive review. Sep. Purif. Technol. 2019;228:1383–5866. doi:10.1016/j.seppur.2019.115719.

Bailey S.E., Olin T.J., Bricka R.M., Adrian D.D. A review of potentially low-cost sorbents for heavy metals. Water Res. 1999;33(11):2469–2479. doi:10.1016/S0043-1354(98)00475-8.

Breen C., Watson R. Polycation-exchanged clays as sorbents for organic pollutants: influence of layer charge on pollutant sorption capacity. J. Colloid Interface Sci. 1998;208(2):422–429. doi:10.1006/jcis.1998.5804.

Crini G. Non-conventional low-cost adsorbents for dye removal: a review. Bioresour. Technol. 2006;97(9):1061–1085. doi:10.1016/j.biortech.2005.05.001.

Gong Y., Huang Y., Wang M., Liu F., Zhang T. Application of iron-based materials for remediation of mercury in water and soil. Bull. Environ. Contam. Toxicol. 2019;102(5):721–729. doi:10.1007/s00128-019-02559-4.

IAS. The International Adsorption Society. https://www.int-ads-soc.org/what-is-adsorption/. 2019 (Visited on 3 December 2019).

IUPAC, 2019. Compendium of Chemical Terminology, second ed. (the Gold Book). Compiled by McNaught, A.D., Wilkinson, A. Blackwell Scientific Publications, Oxford (1997). Online version (2019) created by S. J. Chalk. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook.

Karickoff S.W., Brown D.S., Scott T.A. Sorption of hydrophobic pollutants on natural sediments. Water Res. 1979;13(3):241–248. doi:10.1016/0043-1354(79)90201-X.

Niazi N.K., Murtaza B., Bibi I., Shahid M., White J.C., Nawaz M.F., Bashir S., Shakoor M.B., Choppala G., Murtaza G., Wang H. Removal and recovery of metals by biosorbents and biochars derived from biowastes. In: Prasad M.N.V., Shih K., eds. Environmental Materials and Waste. Academic Press; 2016:149–177. doi:10.1016/B978-0-12-803837-6.00007-X.

Núñez-Delgado A. Editorial: Technically-based use of by-products as a tool to control pollution. J. Environ. Manag. 2019;242:65–67. doi:10.1016/j.jenvman.2019.04.049.

Núñez-Delgado A., Álvarez-Rodríguez E., Fernández-Sanjurjo M.J. Low cost organic and inorganic sorbents to fight soil and water pollution. Environ. Sci. Pollut. Res. 2019;26(12):11511–11513. doi:10.1007/s11356-019-04901-z.

Pandey S., Alam A. Peat moss: a hyper-sorbent for oil spill cleanup - a review. Plant Science Today. 2019;6(4):416–419. doi:10.14719/pst.2019.6.4.586.

Romar-Gasalla A., Nóvoa-Muñoz J.C., Arias-Estévez M., Fernández-Sanjurjo M.J., Álvarez-Rodríguez E., Núñez-Delgado A. Controlling risks of P water pollution by sorption on soils, pyritic material, granitic material, and different by-products: effects of pH and incubation time. Environ. Sci. Pollut. Res. 2019;26(12):11558–11564. doi:10.1007/s11356-018-2267-9.

Thompson A., Goyne K.W. Introduction to the sorption of chemical constituents in soils. Nat. Educ. Knowl. 2012;4(4):7.

Part 1

Global case studies

Chapter 2: Data on the use of sorbents to control pollution in Europe, with main focus on Spain and Galicia

Avelino Núñez-Delgadoa; Esperanza Álvarez-Rodrígueza; Manuel Conde-Cidb; David Fernández-Calviñob; Manuel Arias-Estévezb; María J. Fernández-Sanjurjoa    a Department of Soil Science and Agricultural Chemistry, Engineering Polytechnic School, University of Santiago de Compostela, Lugo, Spain

b Soil Science and Agricultural Chemistry, Faculty of Sciences, University of Vigo, Ourense, Spain

Abstract

In this chapter, we show results corresponding to the publications found by the searching tools Google Scholar and Web of Science on the subject sorbents controlling pollution for Europe, and then specifically for Spain, and for Galicia. Google Scholar shows a clearly higher number of results in all searches, whereas Web of Science provided numbers that were clearly insufficient (more specifically, in the search focusing on Galicia). This fact could be relevant for all those working with searching tools focused on sciences, to be aware of substantial limitations affecting to them, with clear differences from one to another. In addition, a selection of the main papers published by the authors of the chapter on the subject, in previous years is also included. Overall, a trend to increase is found for publications on the matter in Europe, Spain, and Galicia, with a variety of soils and different sorbent materials covered including low-cost sorbents.

Keywords

Europe; Galicia; Pollution; Sorbents; Spain

Acknowledgments

This work was supported by the Spanish Ministry of Economy and Competitiveness [grant numbers RTI2018-099574-B-C21 and RTI2018-099574-B-C22]. It also received funds from the European Regional Development Fund (ERDF) (FEDER in Spain) being a complement to the previous grants, without additional grant number. D. Fernández-Calviño holds a Ramón y Cajal contract (RYC-2016-20411) financed by the Spanish Ministry of Economy, Industry and Competitiveness. M. Conde-Cid holds a predoctoral contract (FPU15/0280, Spanish Government). The sponsors had not involvement in study design; in the collection, analysis and interpretation of data; in the writing of the report and in the decision to submit the article for publication.

2.1: Introduction

The use of sorbents as materials aiding to control pollution has deserved interest for years at scientific and overall society levels. The works by Weir and Dodd (1938) and by Gibbons (1940) are among the first dealing with the problem, whereas more than 2000 papers were published on the matter just during January 2020, as per searching tools.

In fact, an approximate measure of the overall scientific relevance of the subject can be seen by means of scientific searching tools. As an example, using Google Scholar to search for Sorbents controlling pollution, an overall score of 33,800 results is shown. By adding specific words the score reaches 17,900 for Sorbents controlling pollution Europe, 10,200 for Sorbents controlling pollution Asia, 20,800 for Sorbents controlling pollution America, 12,600 for Sorbents controlling pollution Africa, or 15,600 for Sorbents controlling pollution Oceania. But these are very high numbers, probably avoiding that all those papers can be read or evaluated in detail in a reasonable lag of time. So, these results could be considered just as a first-step to compare the amount of work or information on the theme. In fact, searching for Sorbents controlling pollution China the score is 21,800, whereas it was just 10,200 for Asia. Also, changing words that could be considered equivalent, the resulting scores may be highly different. It is the case when the search is carried out based on Sorbents control pollution, which gives 70,200 results (more than doubling that of 33,800 corresponding to the same search but just substituting controlling by control).

With these limitations in mind regarding accuracy and variability, in this chapter, we performed searches to have a first idea on the amount of work published on the theme, differencing at the scale of Europe, Spain, and Galicia, using Google Scholar and Web of Science as contrasting tools. In addition, we focused specifically on the papers published on the subject by the authors of the chapter (all of them working in Galicia, and selecting just those related to soils and sorbents sampled or produced in Galicia), finding surprising results when compared with these provided by one of the searching tools.

2.2: Data on the overall situation in Europe

Searching for Sorbents controlling pollution Europe in Google Scholar, and considering periods of years, the total number of publications was 856 from 1900 to 1990; 4060 from 1991 to 2000; 10,600 from 2001 to 2010; and 17,200 from 2011 to 2020, as reflected in Fig. 2.1A. This shows a clear trend to increase.

Fig. 2.1 Results of searching for Sorbents controlling pollution Europe in Google Scholar; (A) in intervals of up to each of the years indicated in the graph (first period starting in 1900 and ending in 1990); (B) in specific years (last years, going from 2015 to 2019).

For the past years, the scores are 2790 publications for 2015; 3220 for 2016; 3250 for 2017; 3560 for 2018; and 3310 for 2019 (Fig. 2.1B), which shows some further increase but decreasing during 2019.

However, when the search on Sorbents controlling pollution Europe is carried out in Web of Science, the total number of results is reduced to 294. Analyzing these results by years (Fig. 2.2A), it is shown that the number of publications increased from 1995 to 2002, then decreased or stabilized till 2012, with some increase during 2013–15, and a final oscillation and decrease taking place, reaching 12 publications during the year 2019.

Fig. 2.2 Main results of searching for Sorbents controlling pollution Europe in Web of Science: (A) results by years, covering from 1995 to 2019; (B) results by country.

Regarding number of publications by country (Fig. 2.2B), most of them are from Spain (73), followed by United Kingdom + England + Scotland (23 + 22 + 4), Germany (24), and other European countries. To note that also the United States (11 publications) and Canada (4 publications) appear in the list of the 25 countries with higher numbers.

As regards institutions where authors work (Fig. 2.3), the highest score corresponds to the Spanish CSIC (15 + 13 publications) followed by the Catalonian University Rovira i Virgili (11 + 10 results), the Galician University of Santiago de Compostela (6 + 5 publications), the Portuguese University of Porto (5 + 5 results), and other European universities, including various other in Spain.

Fig. 2.3 Main results of searching for Sorbents controlling pollution Europe in Web of Science, showing number of publications by institution.

2.3: Data on the situation in Spain

Searching for Sorbents controlling pollution Spain in Google Scholar, and considering periods of years, the total number of publications was 218 from 1900 to 1990, 2070 from 1991 to 2000, 4260 from 2001 to 2010, and 11,000 from 2011 to 2020. As in the case of overall results for Europe, this shows a clear trend to increase.

For the past years, the scores are 1190 for 2015, 1250 for 2016, 1340 for 2017, 1390 for 2018, and 1550 for 2019. In view that the number of publications regarding just Spain is not affected by the decrease which took place during 2019 for those that included the whole Europe in the search.

When the search is carried out in Web of Science, also using the words Sorbents controlling pollution Spain, just 76 results are shown (Fig. 2.4). Considering the results by years (Fig. 2.5), it is shown that the number of publications increased during 2001 and 2002, then decreased or stabilized till 2012 (as in the case of the whole Europe), and (also as in Europe) it is shown that some increase takes place during 2013–15, followed by a final oscillation and decrease, to reach three publications during 2019.

Fig. 2.4 Results of searching for Sorbents controlling pollution Spain in Google Scholar; (A) in intervals of up to each of the years indicated in the graph (first period starting in 1900 and ending in 1990); (B) in specific years (last years, going from 2015 to 2019).

Fig. 2.5 Main results of searching for Sorbents controlling pollution Spain in Web of Science covering from 1983 to 2019.

Regarding institutions (Fig. 2.6), the first place is for CSIC (11 + 7 + 2 + 2 publications), followed by University Rovira i Virgili (11 + 10 results), University of Santiago de Compostela (6 + 5 publications), University of Almería (5 + 5 results), and other universities.

Fig. 2.6 Main results of searching for Sorbents controlling pollution Spain in Web of Science, showing number of publications by institution.

2.4: Data on the situation in Galicia (NW Spain)

Searching for Sorbents controlling pollution Galicia in Google Scholar, and considering for periods of years, the total number of publications is 30 from 1900 to 1990, 141 from 1991 to 2000, 701 from 2001 to 2010, and 1890 from 2011 to 2020.

For the past years, the scores are 223 for 2015, 214 for 2016, 243 for 2017, 224 for 2018, and 277 for 2019, showing some fluctuations but an overall trend to increase from 2015 to 2019.

Searching for Sorbents controlling pollution Galicia in Web of Science, just four results are shown (Fig. 2.7). Fig. 2.8 shows the number of publications by year, whereas Fig. 2.9 shows publications by institutions.

Fig. 2.7 Results of searching for Sorbents controlling pollution Galicia in Google Scholar; (A) in intervals of up to each of the years indicated in the graph (first period starting in 1900 and ending in 1990); (B) in specific years (last years, going from 2015 to 2019).

Fig. 2.8 Main results of searching for Sorbents controlling pollution Galicia in Web of Science, showing all four results and the specific years where they were found by this searching tool.

Fig. 2.9 Main results of searching for Sorbents controlling pollution Galicia in Web of Science, showing number of publications by institution.

It is clear that the results of this last search using Web of Science are insufficient, as just taking into account the papers on the matter published by the authors of this chapter (limited to those focused on sorbent materials developed or sampled in Galicia), the number is more than 50.

Regarding other rapid comparisons, searching for Sorbents AND controlling AND pollution in Scopus, just 120 publications are found, and no one is found when including Galicia as additional word in the search. Mendeley shows 3236 results for Sorbents controlling pollution (1401 of them being documents), and a total of 13 references are shown when adding the word Galicia to the search. But, for the last result, no one of the papers is really related to Galicia, and no one of the more than 50 papers published by the authors or the chapter in Galicia on the subject are included.

In fact, Table 2.1 shows a selection of the main papers on the matter published by the authors of this chapter, all of them carried out in Galicia and focusing on soils and sorbents sampled in Galicia. Although it is just a selection (not all papers published by these authors on the subject are included), the number is approximately 50. In addition, other researchers have published on sorbents used to fight pollution in Galicia, further increasing the total number of results.

Table 2.1

GM, Granitic material; HW, hemp waste; MS, mussel shell; OA, oak ash; PB, pine bark; PM, pyritic material; SA, mussel shell ash; SD, sawdust; SF, slate waste fines; WM, waste mixtures.

As shown in Table 2.1, even restricted to the main papers published on the matter by the authors of this chapter, there is a real variety of sorbents (including soils and by-products) for diverse kinds of pollutants, including inorganic and organic, cationic and anionic, and the overall number of papers is increasing in the past years, indicating that the field of research is open and seems not have reached a declining phase.

2.5: Conclusions

In this chapter, two scientific searching tools are used to have a first idea of the amount of works on sorbents controlling pollution published at the scales of Europe, Spain, and Galicia. Both tools showed an overall trend to increase but with some trend to stabilize last years. Web of Science gave clearly poorer results than Google Scholar, especially regarding the search Sorbents controlling pollution Galicia. Specifically, the total number of results provided by WOS for this search was four, whereas just the authors of the chapter (working in Galicia, with sorbents produced or sampled in Galicia) published more than 50 papers on this matter. Google Scholar provided more than 2700 results for the same search. Obviously, results from web-searching tools must be seen with prevention on its accuracy and should be rather considered for providing an approach and/or an overall view. Regarding main results, it is shown that there is a huge variety of soils and sorbent materials (including low-cost sorbents) that have been studied to retain many different pollutants, going from heavy metals to emerging pollutants. It is clear that it is a main field of research affecting public and environmental health all over the world, and it is expected that it will continue to grow or at least maintain its importance for years.

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Paradelo R., Cutillas-Barreiro L., Soto-Gómez D., Nóvoa-Muñoz J.C., Arias-Estévez M., Fernández-Sanjurjo M.J., Álvarez-Rodríguez E., Núñez-Delgado A. Study of metal transport through pine bark for reutilization as a biosorbent. Chemosphere. 2016a;149:146–153. doi:10.1016/j.chemosphere.2016.01.087.

Paradelo R., Conde-Cid M., Cutillas-Barreiro L., Arias-Estévez M., Nóvoa-Muñoz J.C., Álvarez-Rodríguez E., Fernández-Sanjurjo M.J., Núñez-Delgado A. Phosphorus removal from wastewater using mussel shell: investigation on retention mechanisms. Ecol. Eng. 2016b;97:558–566. doi:10.1016/j.ecoleng.2016.10.066.

Paradelo R., Conde-Cid M., Arias-Estévez M., Nóvoa-Muñoz J.C., Álvarez-Rodríguez E., Fernández-Sanjurjo M.J., Núñez-Delgado A. Removal of anionic pollutants by pine bark is influenced by the mechanism of retention. Chemosphere. 2017;167:139–145. doi:10.1016/j.chemosphere.2016.09.158.

Pateiro-Moure M., Bermúdez-Couso A., Fernández-Calviño D., Arias-Estévez M., Rial-Otero R., Simal-Gándara J. Paraquat and diquat sorption on iron oxide coated quartz particles and the effect of phosphates. J. Chem. Eng. Data. 2010;55:2668–2672. doi:10.1021/je900945h.

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Peña-Rodríguez S., Bermúdez-Couso A., Nóvoa-Muñoz J.C., Arias-Estévez M., Fernández-Sanjurjo M.J., Álvarez-Rodríguez E., Núñez-Delgado A. Mercury removal using ground and calcined mussel shell. J. Environ. Sci. 2013;25(12):2476–2486. doi:10.1016/S1001-0742(12)60320-9.

Quintáns-Fondo A., Ferreira-Coelho G., Paradelo-Núñez R., Nóvoa-Muñoz J.C., Arias-Estévez M., Fernández-Sanjurjo M.J., Álvarez-Rodríguez E., Núñez-Delgado A. Promoting sustainability in the mussel industry: mussel shell recycling to fight fluoride pollution. J. Clean. Prod. 2016a;131:485–490. doi:10.1016/j.jclepro.2016.04.154.

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Quintáns-Fondo A., Fernández-Calviño D., Nóvoa-Muñoz J.C., Arias-Estévez M., Fernández-Sanjurjo M.J., Álvarez-Rodríguez E., Núñez-Delgado A. As(V) sorption/desorption on different waste materials and soil samples. Int. J. Environ. Res. Public Health. 2017;14:803. doi:10.3390/ijerph14070803.

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Chapter 3: Sustainable origin-sorbents for heavy metal contamination: Research progress within an Australian context

Megan L. Murray; Koray Bugdayli    School of Life Sciences, University of Technology Sydney, Ultimo, NSW, Australia

Abstract

Heavy metal contamination is a major land management issue for Australia with long-lasting impacts on human communities and natural environments. Sorbent materials are an important tool to evaluate to determine which solutions are the most effective for target contaminants, particularly in areas where there may be more than one contaminant present. It is also important to consider which materials are the most viable for larger-scale production within a geographic region to reduce the requirement for ongoing sorbent material importation. This chapter evaluates scientific information on 17 different kinds of terrestrial sorbents for decontamination effectiveness of Cd, Cr (III), Cr (IV), Hg, Pb, and Zn in surface soil environments, and considers sorbent origins, general production requirements, and ongoing environmental availability (e.g., major or minor existing waste stream) of sorbent materials in an immediate to longer-term timeframe.

Keywords

Decontamination; Sustainable origin; Soil pollution; Removal efficacy

3.1: Contaminated land in Australia

Terrestrial surface pollution is an environmental challenge of global significance. Since the dawn of the industrial revolution, humans have introduced contaminants into soils at exponential rates through multiple pathways (Bailey et al., 1999; Etim, 2012). Major sources of soil contamination include commercial and industrial wastes, domestic waste disposal, agricultural run-off, metal smelting, and mining wastes (Kumar Yadav et al., 2018). In Australia, contaminated soils were the leading form of hazardous waste produced by weight, contributing 21% of the total of all hazardous wastes produced between 2014 and 2015 (Latimer, 2017). Regarding the fate of contaminated soils in Australia during this period, 51% of contaminated soil was buried in landfill, 14% of soil underwent specific decontamination treatments to remove or reduce contaminants, and 13% were temporarily stored for later release into management infrastructure (Latimer, 2017). Among the contaminants in contaminated soils are heavy metals such as Fe, Zn, Cu, Ni, Cr, Pb, and Cd, which present significant ecological and human health threats to ecological communities, food chains, and human populations due to their prolonged persistence within the environment (Kumar Yadav et al., 2018; Soni and Kaur, 2018). Although some heavy metal elements are essential to the health of living organisms such as Cu, Ni, and Zn, higher concentrations of these heavy metals can cause health complications in humans and phytotoxicity in plants (Paz-Ferreiro et al., 2013; Soni and Kaur, 2018). Additionally, heavy metal elements such as As, Cd, Cr, Hg, and Pb are toxic to living organisms (Paz-Ferreiro et al., 2013).

Heavy metal pollutants are understood to be nephrotoxic, mutagenic, cytotoxic, neurotoxic, and act as endocrine disruptors in the human body (Kumar Yadav et al., 2018). Heavy metals also contribute to ecological degradation, damage and destruction by disrupting key ecological processes within ecosystems such as decomposition. As heavy metals accumulate in the environment and do not mineralize or degrade, the prevention of heavy metal contamination must remain a priority and this is probably best achieved through legislation and strict environmental assessments of potential sources of pollution. The reduction or elimination of heavy metal usage in industrial or commercial activities in vulnerable or protected environments is also critical to the prevention of the severe impacts of heavy metal environmental degradation. However, eliminating sources of heavy metal pollution is not always a viable land management option, which establishes an urgent need to investigate methods to remediate heavy metal pollution; specifically, more efficient and sustainable options that can mitigate the environmental impacts of soil contamination (Paz-Ferreiro et al., 2013).

3.1.1: Utility of sorbents for terrestrial contamination

Terrestrial sorbents are placed on (or around) contamination sources to decontaminate soils and prevent the further spread of contaminants across environments. Sorbents are often applied directly to contaminated areas as loose materials or powders, in woven or felted mats, or are deployed as booms where the sorbent fillings are encased in long lengths of mesh material. In some instances where water and soils meet, sorbents are used as membranes for contaminated liquids to pass through (Khulbe and Matsuura, 2018). Generally, plastic-origin polypropylene has been used as a sorbent material of choice for land managers, as it is cheap, effective, and can store for long periods of time. A significant downside to polypropylene technology is lack of natural biodegradation, as well as an ongoing need to generate plastic, which means the sorbent generates a large amount of contaminated landfill after application. Sustainable origin sorbents are a growing field of research which aims to address some of these issues. Sorbents recycled from waste pathways and manufacturing by-products (e.g., agriculture, food and industrial) are particularly important, as reducing landfill is a priority for most global nations. Although individual studies often report the efficacy of a sorbent on a target contaminant of interest, there are few available comparisons of products across a wider spectrum of contaminants. This chapter synthesizes data and information from a wide range of sources to compare which products are the most effective decontaminators of major heavy metals and which are most likely to be useful in decontaminating Australian soils.

3.1.2: Identifying sustainable-origin sorbents that can decontaminate heavy metals

A comprehensive literature search of potential and suitable soil sorbents was conducted to determine which materials can decontaminate heavy metal-polluted soils. In parallel, a comparative index of sorbents was created to compare and contrast sorbents and heavy metal decontamination capacity. Many of the sorbents identified are raw by-products from waste processes (i.e., coffee waste) and may be low-cost to source. Other sorbents may involve more expense to process and implement (i.e., chitosan powder) but may be more effective. Research was conducted utilizing keyword searches of peer-reviewed heavy metal sorbent literature sourced within Web of Science and Google Scholar databases, and potential sorbent retailers found online by the Google search engine. Scientific literature was only included within the report if it was peer-reviewed. The total number of original research papers used in the study is 39, after removing duplicate data, with 17 unique sorbents tested in terrestrial and heavy metal contexts (Table 3.1). Keywords utilized for peer-reviewed sorbent literature searches included combinations of sorbent, remediation, heavy metal ion, soil leaching, chitosan, chitosan modified biochar, modified biochar, biochar, activated carbon, bark, eucalyptus bark, adsorption, sorption, extraction, review, phytoremediation, environmental, remediation, soil, seaweed, brown algae, removal, low cost, coir, sawdust, arthropod, compost, fertilizer, biosorption, biomass, decomposition, Australian, contamination, risk, heavy metal uptake, renewable, sustainable, agricultural waste, removal, organic, inorganic, carbon, chitin, pollutant, biological, bioaccumulation, and biomagnification. Keywords utilized for Google searches for sorbent retailers included combinations of seaweed, chitosan, Australia, biochar, bulk, lab grade, pure, and domestic.

Table 3.1

Data and information collected from these sources were compiled and reproduced into a comparative scientific index. The major decontaminating sorbents with evidence published within peer-reviewed scientific journals are as follows:

3.1.3: Chitin and chitosan products

Chitosan is a biosorbent that is chemically produced from chitin and well-recognized for heavy metal decontamination due to its physical and properties including ready biodegradability, nontoxicity, and potential biocompatibility (Zhang et al., 2016). The chitin that forms chitosan is currently considered one of the most abundant and affordable biopolymers in nature; mostly sourced from fisheries industries as a waste product, prawn and crustacean shells, as well as the cell walls of some fungi and insect species on a smaller scale (Fig. 3.1) (Bailey et al., 1999).

Fig. 3.1 Pathways for chitin and chitosan production, including seafood wastes ( Jardine and Sayed, 2016).

Chitosan must be formed into composites through physical means such as films, gels, or beads to prevent issues such as low thermal and low acid stability, resistance to mass transfer, low porosity, and surface area (Zhang et al., 2016). Chemical alterations such as grafting, impregnation, and cross-linking that take place mostly on the amino groups of chitosan can improve flexibility, chemical stability, and susceptibility in acid media (Zhang et al., 2016). Chitosan has been utilized to adsorb Cd, Cr (III, VI), Hg, Pb, and Cu effectively (Bailey et al., 1999). The adsorption process of chitosan is heavily influenced by pH levels, as pH interacts with degree of ionization, speciation of metal and surface characteristics of modified chitosan adsorbents, for the majority of heavy metal cation removal using modified chitosan, the optimal pH was determined to be pH 5.0, 5.5, or 6.0 (Zhang et al., 2016).

In comparison with bark and activated sewage sludge, chitosan exhibits superior binding capacity that is greater than 1 mmol metal/g for most heavy metals excluding Cr (Bailey et al., 1999). Modified chitosan also displays a high level of regeneration which allows for separation of contaminant and sorbent, losing only 6% of adsorption efficiency after five adsorption and desorption cycles (Zhang et al., 2016). This property of modified chitosan allows for sorbent recycling for continued contaminant removal while decreasing operational costs and the production of secondary wastes (Zhang et al., 2016). Chitosan’s fertilizing properties using foliar spraying and seed soaking promote higher fruit yields, increased tuber size, plant growth, photosynthesis rates, leaf chlorophyll content, and phenolic content in plants (Malerba and Cerana, 2018). By fertilizing plants with chitosan, phytoremediation efficiency may increase. Chitosan also aids in controlling plant pathogens such as viruses, bacteria nematodes and fungi, which may assist in reducing phytoremediation operational costs by reducing plant fatalities and reducing the need to medicate plants with antiviral, antibacterial, and antifungal medicine (Malerba and Cerana, 2018). The properties and capabilities of chitosan present a strong case for future inclusion in phytoremediation research, as it may directly benefit plant health, phytoremediation efficiency, and growth rates while adsorbing heavy metal ions in soil simultaneously and is a renewable biological resource.

Raw material availability is a major consideration which will contribute to its overall expense and the likelihood of a sorbent being processed for use within a country. The Australian prawn farming industry grows and harvests > 5000 t of product annually (2014/2015) with an economic value estimated to be $87.7 million AUD (Australian Prawn Farmers Association (APFA), 2019). This indicates that it is likely to be a common and available source of waste that can be diverted from landfill and locally processed into viable sorbent products.

3.1.4: Seaweed products

Seaweed is an abundant source of biomass that occurs in Australian coastal regions (Ahmady-Asbchin et al., 2009). Seaweed is also treated as domestic waste in many countries which indicates a high availability for seaweed as a sustainable-origin resource (Ahmady-Asbchin et al., 2009). Additionally the worldwide harvest of brown algae is estimated at 16 million tonnes per year (Figueira et al., 2000). Seaweed mainly consists of brown macroalga which contains polysaccharides such as alginate that may potentially bind with metallic ions (Ahmady-Asbchin et al., 2009; Bailey et al., 1999). It is understood that brown seaweeds are capable of biosorption of Pb² +, Cd² +, Mn² +, Cu² +, and Cr²O² − metal ions after being dried out, ground into particles between 0.21 and 0.31 mm in size and saturated in ultrapure water (Lee and Park, 2012). Biosorption in seaweed is primarily attributed to the cell walls that are composed of cellulose fibrillar skeletons and an amorphous embedding of matrix, which contains large quantities of alginate that facilitates electrostatic attraction and complexation of metals into seaweed biomass (Figueira et al., 2000). Alginate formed from algin in brown seaweed forms a metal-alginate after biosorption of metal ions (Bailey et al., 1999). Seaweed displays extremely high Cd adsorption capacities of 67 mg/g; however, the biomass is understood to disintegrate and swell when utilized in remediation projects (Bailey et al., 1999). Like chitosan, modifications such as cross-linking and polyethyleneimine embedding can improve mechanical stability to prevent complications but may cause reductions in sorption capacity (Bailey et al., 1999). Seaweed is also commonly used fresh and dry in the agricultural industry to stimulate plant growth and productivity (Eyras et al., 2008). Seaweed aids in germination rates, root growth, plant yields, tolerances to stressors, and resistance to insect and infections, which may greatly benefit phytoremediation projects (Eyras et al., 2008). This is due to seaweed containing trace elements, all major plant nutrients, organic compounds and substances that behave as growth stimulants and antibiotics (Crouch and van Staden, 1993). By including seaweed in phytoremediation sites with nutrient deficient soils, reductions in plant growth rates and phytoremediation efficiency may be circumvented (Eyras et al., 2008). Additionally, seaweed may behave as both a fertilizer for phytoremediation crops and as a heavy metal ion sorbent in contaminated soils, amending, and purifying soils for future site remediation processes (Eyras et al., 2008). Seaweed in soils may also aid in increasing soil pH and increase concentrations of bioavailable P in soil, which may enhance plant growth and phytoremediation efficiency (Eyras et al., 2008). However, decomposer species such as fungi, invertebrates, and microbes may readily decompose seaweed and other organic sources of carbon which may contain heavy metal ions causing bioaccumulation and spreading of heavy metal contaminants into food webs, which is problematic as this may conflict with the purposes and aims of soil remediation (Fig. 3.2) (Soni and Kaur, 2018).

Fig. 3.2 Unprocessed seaweed ( Wicks, 2020). Source: https://unsplash.com/photos/_thl1SQCbPE

3.1.5: Biochar

Biochar is carbon-rich substance synthesized through the pyrolysis of biological material such as wood residues, organic manure, dead animals, sewage sludge, and industrial waste in anoxic environments (Lahori et al., 2017). Biochar has gained attention in the scientific community as an economically viable solution for heavy metal soil remediation, due to its applicability, availability and affordability, and physical properties. Biochar is highly porous due to a large abundance of micropores and has a large surface area which allows for efficient sorption of heavy metal ions and dissolved organic matter (Lahori et al., 2017). Biochar also has a diverse potential of reducing the bioavailability of heavy metals such as Pb (Table 3.1) and the uptake of heavy metals in plants by increasing soil pH, cation exchange capacity and P contents of soil, which is beneficial for phytoremediation as these factors may alleviate stressors on phytoremediation plants by reducing the concentration of toxic heavy metals and providing soil fertilization (Lahori et al., 2017). Biochar also displays synergy with phytoremediation projects, as biochar behaves as a soil conditioner, organic fertilizer while increasing soil water capacity, carbon sequestration, microbial activity, cycles plant nutrients, and increases soil pH (Lahori et al., 2017). A secondary benefit to biochar is that it mitigates the effect of atmospheric carbon pollution by reducing the amount of greenhouse gas emitted by soils while significantly improving plant growth and yields in calcareous and infertile dry croplands with soils with organic carbon deficiencies (Zhang et al., 2011). By utilizing biochar in large scale remediation operations, additional benefits such as large-scale greenhouse gas emission minimization and carbon sequestration may aid in the mitigation of climate change and air pollution (Fig. 3.3) (Zhang et al., 2011).

Fig. 3.3 Vegetation growth through a layer of applied biochar ( Robillard, 2019).

A major consideration for the application of biochar is that it may act as a source of soil contamination itself, as it may contain contaminants that are concentrated during the pyrolysis process (Hilber et al., 2017). Contaminants may be introduced by its source materials that may contain heavy metals or improper pyrolysis that produce polycyclic aromatic hydrocarbons (Hilber et al., 2017). This may contradict the feasibility of biochar use in remediation projects as environmental damage may be instigated by utilizing impure sources of biochar (Hilber et al., 2017). Additionally, biochar characteristics differ depending on feedstock materials used and pyrolysis conditions during biochar production, and future research into developing production systems to create specific soil remediation biochar products for heavy metals may be necessary to attain efficient remediation of contaminated soils (Zhang et al., 2013). It is understood that long-term field studies may be necessary to address and better understand the sustainability of biochar in remediation projects (Hilber et al., 2017).

3.1.6: Chitosan-modified biochar

Chitosan-modified biochar combines the soil amending qualities, relatively large surface area and porosity of biochar with the chemical affinity and binding capacity of chitosan by cross-linking into beads, membranes, and solutions (Hussain et al., 2017). The combination of these environmentally sustainable substances creates a low cost and novel substance capable of more efficient heavy metal ion sorption than unmodified biochar (Hussain et al., 2017). Chitosan-modified biochar contains higher nitrogen, hydrogen, and oxygen content from the presence of the chitosan and is understood to enhance the removal of heavy metals such as Pb² +, Cu² +, and Cd² + than unmodified biochar forms (Zhou et al., 2013). Additionally, unmodified biochar forms contain 75% more carbon, which may influence phytoremediation efficiencies (Zhou et al., 2013). However, there is a noteworthy lack of widespread published literature on chitosan-modified biochar, as published literature of the substance only first became available in 2013. While current published peer-reviewed scientific literature does suggest that chitosan-modified biochar may be implemented as a low-cost and eco-friendly sorbent to remediate heavy metal contamination in soil, more research may be required to assess the feasibility of chitosan modified biochar in Australian contexts (Zhou et al., 2013).

3.1.7: Plant-origin substances (i.e., barks, coir, coffee waste, peat moss, and tea waste)

Plant-origin substances including bark, coir, sawdust, and nut shells are often an affordable and accessible source of sorbent material as they can be sourced as by-products or waste material from timber and agricultural industries, woodworking workshops and cafes (Bailey et al., 1999). Within tannin-rich substances, the polyhydroxy polyphenol groups of tannins are understood to facilitate ion exchange, as metal cations displace adjacent phenolic hydroxyl groups, which form a chelate that immobilizes heavy metal ions by ionic bonding (Fig. 3.4) (Bailey et al., 1999).