Review of Eco-Friendly Biochar Used in the Removal of Trace Metals on Aqueous Phases

A. B. Duwiejuah^{1, 2,} , S. J. Cobbina² and N. Bakobie²

¹Department of Biotechnology, Faculty of Agriculture, University for Development Studies

²Department of Ecotourism and Environmental Management, Faculty of Natural Resources and Environment, University for Development Studies

Cite this paper:
A. B. Duwiejuah, S. J. Cobbina and N. Bakobie. Review of Eco-Friendly Biochar Used in the Removal of Trace Metals on Aqueous Phases. International Journal of Environmental Bioremediation & Biodegradation. 2017; 5(2):27-40. doi: 10.12691/ijebb-5-2-1

Abstract

Eco-friendly biochar produced from cost-effective and readily available agricultural waste will likely pose no threat on the aqueous phases, other environmental media, human health and emission of greenhouse gases to the atmosphere. Optimising biochar for an intended application could require careful selection of a biomass feedstock as well as production pyrolysis technique and conditions for the production of biochars with specific characteristics. Previous studies have explores the relationships that exist between biochar production conditions, characteristics, and possible end-uses of biochar. This review provides an overview of the production and utilisation of biochar as absorbents for adsorption of trace metals in contaminated aqueous environment. Biochar has great affinity to adsorb molecular ions that is making it possible to be used for various toxicological remediation strategies. It has proven effective and useful for mitigating aqueous metals, organic compounds, suspended solids, and organic hydrocarbons in a various kind of industrial applications such as urban and residential storm water runoff, landfill leachates, industrial runoff, resource extraction runoff, and industrial wastewater filtration. Specifically designed biochar could be very effective in the removal of trace metals from contaminated aqueous environment. The multiple factors that determine the adsorption of the trace metals in aqueous environment or phases needs to be carefully examined. Cost-effectiveness of biomass feedstock and eco-friendliness of techniques need to also be given much consideration by way of making comparison with existing contaminant mitigation technologies.

Keywords:
aqueous phases biochar cost-effective biomass feedstock removal trace metals

This work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

References:

[1]	European Biochar Certificate (EBC) (2012). Guidelines for a Sustainable Production of Biochar.' European Biochar Foundation (EBC), Arbaz, Switzerland. http://www.europeanbiochar.org/en/download. Version 6.2 E of 04th February 2016.
[2]	Kajitani S, Tay LH, Zhang S, Li ZC (2013). Mechanisms and kinetic modelling of steam gasification of brown coal in the presence of volatile-char interactions. Fuel 103: 7-13.
[3]	Mittal A, Thakur V, Gajbe V (2012). Evaluation of adsorption characteristics of an anionic azo dye brilliant yellow onto hen feathers in aqueous solutions. Environ. Sci. Pollut. R. 19(6): 2438-2447.
[4]	Onundi YB, Mamun AA, AL Khatib MF, Ahmed YM (2010). Adsorption of copper, nickel and lead ions from synthetic semiconductor industrial wastewater by palm shell activated carbon. J. Environ. Sci. Tech. 7: 751-758.
[5]	Lin SH (1993). Adsorption of disperse dye by various adsorbents. J. Chem. Tech. Biotechnol. 58(2): 107-210.
[6]	Lenntech R (2004). Water treatment and air purification. Available online: http//www.excelwater.com/thp/filters/Water-Purification.htm (Accessed on 12th May, 2016).
[7]	Subhashini V, Swamy AVVS (2013). Phytoremediation of Pb and Ni contaminated soils using Catharanthus roseus (L.). Universal J. Environ. Res. Technol 3: 465-472.
[8]	Jadia CD, Fulekar MH (2008). Phytoremediation: the application of vermicompost to remove zinc, cadmium, copper, nickel and lead by sunflower plant. Environ. Engineer. Manage. J 7: 547-558.
[9]	Ismail S, Khan F, Zafar Iqbal M (2013). Phytoremediation: Assessing tolerance of tree species against trace metal (PB and CD) toxicity. Pakistan J Botany 45: 2181-2186.
[10]	Adriano DC (2001). Trace elements in terrestrial environments: biochemistry, bioavailability and risks of metals. 2nd Ed, Springer-Verlag, New York.
[11]	Wuana RA, Okieimen FE (2011). Heavy metals in contaminated soils: A review of sources, chemistry, risks and best available strategies for remediation. Communicat Soil Sci. Plant Anal 42: 111-122.
[12]	Parizanganeh AH, Bijnavand V, Zamani AA, Hajabolfath A (2012). Concentration, distribution and comparison of total and bioavailable trace metals in top soils of Bonab district in Zanjan province. Open J. Soil Sci 2: 123-132.
[13]	Verheijen F, Jeffery S, Bastos AC, van der Velde, M, Diafas I (2010). Biochar application to soils. A critical scientific review of effects on soil properties processes and functions. JRC Sci. technic. report. pp 1-166.
[14]	Angin D (2013). Effect of pyrolysis temperature and heating rate on biochar obtained from pyrolysis of safflower seed press cake. Bioresour. Technol 128: 593-597.
[15]	Shivaram P, Leong YK, Yang H, Zhang DK (2013). Flow and yield stress behaviour of ultrafine Mallee biochar slurry fuels: the effect of particle size distribution and additives. Fuel 104: 326-332.
[16]	Demirbas A (2004). Effects of temperature and particle size on bio-char yield from pyrolysis of agricultural residues. J Analytical and Applied Pyrol 72(2): 243-248.
[17]	Winsley P (2007). Biochar and bionenergy production for climate change. New Zealand Sci Rev 64 (1): 1-10.
[18]	Yang L, Jin M, Tong C, Xie S (2013). Study of dynamic sorption and desorption of polycyclic aromatic hydrocarbons in silty-clay soil. J. Hazard. Mat 244-245: 77-85.
[19]	Amonette JE, Jospeh S (2009). Characteristics of biochar: microchemical properties. In: J. Lehmann, Joseph, S. (Editor), Biochar for Environmental Management Science and Technology. Earthscan, London.
[20]	Liu Z, Zhang F (2009). Removal of lead from water using biochars prepared from hydrothermal liquefaction of biomass. J. Hazard. Mat 167(1-3): 933-939.
[21]	Tsai W, Liu S, Hsieh C (2012). Preparation and fuel properties of biochars from the pyrolysis of exhausted coffee residue. J. Anal. Applied Pyrol 93: 63-67.
[22]	Beeseley L, Marmiroli M (2011). The immobilisation and retention of soluble arsenic, cadmium and zinc by biochars. Environ. Pollut 159(2): 474-480.
[23]	Xu T, Lou L, Luo L, Cao R, Duan D, Chen Y (2012). Effect of bamboo biochar on pentachlorophenol leachability and bioavailability in agricultural soil. Sci. Tot. Environ 414: 727-731.
[24]	Cao X, Harris W (2010). Properties of dairy-manure-derived biochar pertinent to its potential use in remediation. Bioresour. Technol 101(14): 5222-5228.
[25]	Song W, Guo M (2012). Quality variations of poultry litter biochar generated at different pyrolysis temperatures. J Anal Applied Pyrol 94: 138-145.
[26]	Lu H, Zhang W, Yang Y, Huang X, Wang S, Qiu R (2012). Relative distribution of Pb2+ sorption mechanisms by sludge-derived biochars. Water R 46(3): 854-862.
[27]	González-Chávez MC, Carrillo-González R, Gutiérrez-Castorena MC (2009). Natural attenuation in a slag heap contaminated with cadmium: The role of plants and arbuscular mycorrhizal fungi. J. Hazard. Mat 161: 1288-1298.
[28]	De M, Azargohar R, Dalai AK, Shewchuk SR (2013). Mercury removal by bio-char based modified activated carbons. Fuel, 103: 570-578.
[29]	Collison M, Collison L, Sakrabani R, Tofield B, Wallage Z (2009). Biochar and carbon sequestration: a regional perspective a report prepared for east of England development agency (EEDA). Project funded under the single programme – DA1 Carbon Reduction. Reference Number: 7049.
[30]	Spokas KA, Cantrell KB, Novak JM, Archer DA, Ippolito JA, Collins HP, Boateng AA, Lima IM, Lamb MC, McAloon AJ, Lentz RD, Nichols KA (2012). Biochar: A synthesis of its agronomic impact beyond carbon sequestration. J. Environ. Qual. 41: 973-989.
[31]	Zhang M, Gao B, Varnoosfaderani S, Hebard A, Yao Y, Inyang M (2013). Preparation and characterization of a novel magnetic biochar for arsenic removal. Bioresour. Technol 130: 457-462.
[32]	Asensio V, Vega FA, Andrade ML, Covelo EF (2013). Tree vegetation and waste amendments to improve the physical condition of copper mine soils. Chemosph 90(2): 603-610.
[33]	Obemah DN, Baowei Z (2014). Biochar preparation, characterization, and adsorptive capacity and its effect on bioavailability of contaminants: An Overview. Adv. Mat. Sci. Engineer, Article ID 715398, 12 pages.
[34]	Agrafioti E, Bouras G, Kalderis D, Diamadopoulos E (2013). Biochar production by sewage sludge pyrolysis. J Anal Appl Pyrol. 101: 72.
[35]	Meyer S, Glaser B, Quicker P (2011). Technical, economical, and climate-related aspects of biochar production technologies: a literature review. Environ. Sci. Technol 45(22): 9473-9483.
[36]	Yao Y, Gao B, Inyang M, Zimmerman AR, Cao X, Pullammanappallil P, Yang L, (2011). Biochar derived from anaerobically digested sugar beet tailings: characterization and phosphate removal potential. Bioresour. Technol 102: 6273-6278.
[37]	Ahmad M, Lee, SS, Dou X, Mohan D, Sung JK, Yang JE, Ok YS (2012). Effects of pyrolysis temperature on soybean stover-and peanut shell-derived biochar properties and TCE adsorption in water. Bioresour. Technol 118: 536-544.
[38]	Chen Z, Chen B, Chiou CT (2012). Fast and slow rates of naphthalene sorption to biochars produced at different temperatures. Environ. Sci. Technol 46: 11104-11111.
[39]	Oliver DP, Pan YF, Anderson JS, Lin TF, Kookana, RS, Douglas, GB, Wendling, LA (2013). Sorption of pesticides by a mineral sand mining by-product, neutralised used acid (NUA). Sci Tot Environ 442: 255-262.
[40]	Dowie A, Crosky A, Muroe P (2009). Physical properties of biochar, in BC for environmental management, J. Lehmann and S. Joseph, Eds., pp. 47-82, Earthscan, London, UK.
[41]	Pellera FM, Giannis A, Kalderis D, Anastasiadou K, Stegmann R, Wang JY, Gidarakos E (2012). Adsorption of Cu (II) ions from aqueous solutions on biochars prepared from agricultural by-products. J. Environ. Manage 96(1): 35-42.
[42]	Gao Y, Yue Q, Gao B, Sun Y, Wang W, Li Q, Wang Y (2013). Preparation of high surface area-activated carbon from lignin of papermaking black liquor by KOH activation for Ni (II) adsorption. Chem. Engineer. J 217: 345-353.
[43]	Harmsen J, Naidu R (2013). Bioavailability as a tool in site management. J. Hazard. Mat 261: 840-846.
[44]	Dong XL, Ma LQ, Li YC (2011). Characteristics and mechanisms of hexavalent chromium removal by biochar from sugar beet tailing. J. Hazard. Mat. 190(1-3): 909-915.
[45]	Haefele SM, Konboon Y, Wongboon W, Amarante S, Maarifat AA, Pfeiffer EM, Knoblauch C (2011). Effects and fate of biochar from rice residues in rice-based systems. Field Crops R 121(3): 430-440.
[46]	Yu JT, Dehkhoda AM, Ellis N (2011). Development of biochar-based catalyst for transesterification of canola oil. Energ. Fuels 25(1): 337-344.
[47]	Qiu Y, Zheng Z, Zhou Z, Sheng GD (2009). Effectiveness and mechanisms of dye adsorption on a straw-based biochars. Bioresour Technol 100(21): 5348-5351.
[48]	Hale ES, Hanley K, Lehmann J, Zimmerman A, Cornelissen G (2011). Effects of chemical, biological, and physical aging as well as soil addition on the sorption of pyrene to activated carbon and biochars. Environ. Sci. Technol 45(24): 10445-10453.
[49]	Cao X, Ma L, Gao B, Harris W (2009). Dairy-manure derived biochar effectively sorbs lead and atrazine. Environ. Sci. Technol 43(9): 3285-3291.
[50]	Qiu R, Lu H, Zhang W, Yang Y, Huang X, Wang S (2012). Relative distribution of Pb2+ sorption mechanisms by sludge-derived biochars. Wat. Res 46(3): 854-862.
[51]	Wu M, Pan B, Zhang D, Xiao D, Li H, Wang C, Ning P (2013). The sorption of organic contaminants on biochars derived from sediments with high organic carbon content. Chemosph 90(2): 782-788.
[52]	Kannan N, Rengasamy G (2005). Comparison of cadmium ion adsorption on various activated carbons. Water, Air, and Soil Pollut 163(1-4): 185-201.
[53]	Uchimiya M, Lima IM, Klasson KT, Chang S, Wartelle LH, Rodgers JE (2010). Immobilization of heavy metal ions (Cu II, Cd II, Ni II, and Pb II) by broiler litter-derived biochars in water and soil. J. Agric. and Food Chem 58(9): 5538-5544.
[54]	Harvey OR, Herbert BE, Rhue RD, Kuo L (2011). Metal interactions at the biochar-water interface: Energetics and structure-sorption relationships elucidated by flow adsorption microcalorimetry. Environ. Sci. Technol 45(13): 5550-5556.
[55]	Swiatkowski A, Pakula M, Biniak S, Walczyk M (2004). Influence of the surface chemistry of modified activated carbon on its electrochemical behaviour in the presence of lead (II) ions. Carbon 42(15): 3057-3069.
[56]	Uchimiya M, Wartelle LH, Lima IM, Klasson KT (2010). Sorption of deisopropylatrazine on broiler litter biochars. J. Agric. Food Chem. 58(23): 12350-12356.
[57]	Chen X, Chen G, Chen L, Chen Y, Lehmann J, McBride MB, Hay AG (2011). Adsorption of copper and zinc by biochars produced from pyrolysis of hardwood and corn straw in aqueous solution. Bioresour. Technol 102(19): 8877-8884.
[58]	Zheng W, Guo M, Chow T, Bennett DN, Rajagopalan N (2010). Sorption properties of greenwaste biochar for two triazine pesticides. J. Hazard. Mat 181(1-3): 121-126.
[59]	Lou L, Luo L, Cheng G, Wei Y, Mei R, Xun B, Xu X, Hu B, Chen Y. (2012). The sorption of pentachlorophenol by aged sediment supplemented with black carbon produced from rice straw and fly ash. Bioresour. Technol 112: 61-66.
[60]	Houben D, Evrard L, Sonnet P (2013). Mobility, bioavailability and pH-dependent leaching of cadmium, zinc and lead in a contaminated soil amended with biochars. Chemosph 92(11): 1450-1457.
[61]	Inyang M, Gao B, Ying Yao Y, Yingwen Xue Y, Zimmerman AR, Pullammanappallil P, Cao X (2012). Removal of trace metals from aqueous solution by biochars derived from anaerobically digested biomass. Bioresour Technol 110: 50-56.
[62]	Subramanian B, Namboodiri V, Khodadoust AP, Dionysiou DD (2010). Extraction of pentachlorophenol from soils using environmentally benign lactic acid solutions. J. Hazard. Mat 174(1-3): 263-269.
[63]	Rhodes AH, Carlin A, Semple KT (2008). Impact of black carbon in the extraction and mineralization of phenanthrene in soil. Environ. Sci. Technol 42(3): 740-745.
[64]	Yu X, Ying G, Kookana RS (2009). Reduced plant uptake of pesticides with biochar additions to soil. Chemosph 76(5): 665-671.
[65]	Uchimiya M, Cantrell KB, Hunt PG, Novak JM, Chang S (2012). Retention of heavy metals in a Typic Kandiudult amended with different manure-based biochars. J. Environ. Qual. 41: 1138-1149.
[66]	Lima IM, Boykin DL, Klasson KT, Uchimiya M (2014). Influence of post-treatment strategies on the properties of activated chars from broiler manure, Chemosph 95: 96-104.
[67]	Paz-Ferreiro J, Lu H, Fu S, Méndez A, Gascó G (2014). Use of phytoremediation and biochar to remediate trace metal polluted soils: a review. Solid Earth, 5: 65-75.
[68]	Tana X, Liua Y, Zenga G, Wang X, Hua X, Gua Y, Yanga Z (2015). Review Application of biochar for the removal of pollutants from aqueous solutions. Chemosphere 125: 70-85.
[69]	Khare P, Dilshad U, Rout PK, Yadav V, Jain S (2013). Plant refuses driven biochar: application as metal adsorbent from acidic solutions. Arab. J. Chem.
[70]	Uchimiya M, Chang SC, Klasson, KT (2011). Screening biochars for heavy metal retention in soil: Role of oxygen functional groups. J. Hazard. Mater, 190: 432-444.
[71]	Kong H, He J, Gao Y, Wu H, Zhu X (2011). Cosorption of phenanthrene and mercury (II) from aqueous solution by soybean stalk-based biochar. J. Agric. Food. Chem 59: 12116-12123.
[72]	Sun J, Lian F, Liu Z, Zhu L, Song Z (2014). Biochars derived from various crop straws: characterization and Cd (II) removal potential. Ecotoxicol. Environ. Saf 106: 226-231.
[73]	Méndez A, Barriga S, Fidalgo JM, Gascó G (2009). Adsorbent materials from paper industry waste materials and their use in Cu (II) removal from water. J. Hazard. Mater. 165: 736-743.
[74]	Park J, Hung I, Gan Z, Rojas OJ, Lim KH, Park S (2013). Activated carbon from biochar: influence of its physicochemical properties on the sorption characteristics of phenanthrene. Bioresource Technology 149: 383-389.
[75]	Wu W, Yang M, Feng Q, McGrouther K, Wang H, Lu H, Chen Y (2012). Chemical characterization of rice straw-derived biochar for soil amendment. Biomass Bioenerg. 47: 268-276.
[76]	Cantrell KB, Hunt PG, Uchimiya M, Novak JM, Ro KS (2012). Impact of pyrolysis temperature and manure source on physicochemical characteristics of biochar. Bioresour. Technol 107: 419-428.
[77]	Choppala GK, Bolan NS, Megharaj M, Chen Z, Naidu R (2012). The influence of biochar and black carbon on reduction and bioavailability of chromate in soils. J. Environ. Qual. 41:1175-1184.
[78]	Xu X, Cao X, Zhao L, Wang H, Yu H, Gao B (2013). Removal of Cu, Zn, and Cd from aqueous solutions by the dairy manure-derived biochar. Environ. Sci. Pollut. Res 20: 358-368.
[79]	Xu X, Cao X, Zhao L (2013). Comparison of rice husk-and dairy manure-derived biochars for simultaneously removing heavy metals from aqueous solutions: role of mineral components in biochars. Chemosph 92: 955-961.
[80]	Ding W, Dong X, Ime IM, Gao B, Ma LQ (2014). Pyrolytic temperatures impact lead sorption mechanisms by bagasse biochars. Chemosph 105: 68-74.
[81]	Samsuri A, Sadegh-Zadeh F, Seh-Bardan B (2014). Characterization of biochars produced from oil palm and rice husks and their adsorption capacities for heavy metals. Int. J. Environ. Sci. Technol 11: 967-976.
[82]	Wang Y, Wang L, Fang G, Herath H, Wang Y, Cang L, Xie Z, Zhou D (2013). Enhanced PCBs sorption on biochars as affected by environmental factors: humic acid and metal cations. Environ. Pollut 172: 86-93.
[83]	Tsai WT, Chen HR (2013). Adsorption kinetics of herbicide paraquat in aqueous solution onto a low-cost adsorbent, swine-manure-derived biochar. International Journal of Environmental Science and Technology 10: 1349-1356.
[84]	United Nations Environmental Protection and Global Program of Action (2004). Why the marine environment needs protection from trace metals. Available online: http://www.oceansatlas.org/ unatlas/uses/uneptextsph/wastesph/2102gpa (Accessed on 12th May, 2016).
[85]	Amaral A, Cruz JV, Cunha RT, Rodrigues A (2006). Baseline levels of metals in volcanic soils of the Azores (Portugal). J. Soil and Sediment Contaminat 15:123-130.
[86]	Kaizer AN, Osakwe SA (2010). Physicochemical characteristics and heavy metal levels in water samples from five river systems in Delta State, Nigeria. J. Applicat. Sci. Environ. Manage 14(1): 83-87.
[87]	Taiwo AM, Adeogun AO, Olatunde KA, Adegbite KI (2011). Analysis of groundwater quality of hand-dug wells in peri-urban areas of Obantoko, Abeokuta, Nigeria for selected physico-chemical parameters. Pacific J. Sci. Technol 12(1): 527-534.
[88]	Sardar K, Ali S, Hameed S, Afzal S, Fatima S, Shakoor MB, Bharwana SA, Tauqeer HM (2013). Heavy metals contamination and what are the impacts on living organisms. Greener J Environ. Manag. and Public Saf (4): 172-179.
[89]	Akpor OB, Ohiobor GO, Olaolu TD (2014). Trace metal pollutants in wastewater effluents: sources, effects and remediation. Adv. Biosci. Bioengineer 2(4): 37-43.
[90]	Eman NA, Sabreen RA, Mashita MY, Md Lutfor R (2015). Environmentally friendly biosorbent from Moringa oleifera leaves for water treatment. Int. J. Environ. Sci. Develop 6(3): 165-169.
[91]	Cushnie GC (1985). Electroplating wastewater pollution control technology. Noyes Publication: New Jersey: pp. 375-377.
[92]	Wei C, Wang C, Yang L (2008). Characterising spatial distribution and sources of heavy metals in the soils from mining-smelting activities in Shuikoushan Hunan Province. China. J Environ Sci 21: 1230-1236.
[93]	Christensen TH, Kjeldsen P, Bjerg PL, Jensen DL, Christensen JB, Baun A, Albrechtsen HJ, Heron G (2001). Biogeochemistry of landfill leachate plumes. Applied geochemistry 16: 659-718.
[94]	Hagberg L, Lofgren E (2007). Soil and plant contamination by textile industries at ZFILM, Managua. Project work in aquatic and environmental engineering, 10 ECTS, Uppsala University Project course, 10 ECTS, Swedish University of Agricultural Sciences.
[95]	Begum RA, Zaman MW, Mondol AT, Ismal MS, Hossain KMF (2011). Effects of textile industrial wastewater and uptake of nutrients on the yield of rice. Bangladesh J. Agric. Res 36(2): 319-331.
[96]	Barakat MA (2011). New trends in removing heavy metals from industrial wastewater. Review Article. Arabian J. Chem 4: 361-377.
[97]	Babel S, Kurniawan TA (2003). Low cost adsorbent for trace metals uptake from contaminated water. Hazard Mat 97: 219-243.
[98]	Monu A, Bala K, Shweta R, Anchal R, Barinder K, Neeraj M (2008). Heavy metal accumulation in vegetables irrigated with water from different sources.
[99]	Ejaz ul I, Yang X, He ZL, Mahmood Q (2007). Assessing potential dietary toxicity of trace metals in selected vegetables and food crops. J. Zhejiang Univ. Sci. B, 8(1): 1-13.
[100]	Aryee BNA, Ntibery BK, Atorkui E (2003). Trends in the small-scale mining of precious mineralsin Ghana: A perspective on its environmental impact. J. Clean Prod. 11: 131-140.
[101]	Paruchuri Y, Siuniak A, Johnson N, Levin E, Mitchell K, Goodrich JM, Renne EP, Basu N (2010). Occupational and environmental mercury exposure among small-scale gold miners in the Talensi-Nabdam District of Ghana’s Upper East region. Sci. Total Environ. 408: 6079-6085.
[102]	Abdullahi MS (2013). Toxic effects of lead in humans: an overview. Global Adv. J. Environ. Sci. Toxicol 2(6): 157-162.
[103]	Duruibe JO, Ogwuegbu MOC, Egwurugwu JN (2007). Trace metal pollution and human biotoxic effects. Int. J. Physical Sci 2(5): 112-118.
[104]	Salem HM, Eweida EA, Farag A (2000). Heavy metals in drinking water and their environmental impact on human health. ICEHM, 2000: 542-556.
[105]	Nolan K (2003). Copper toxicity syndrome. J. Orthomolecular Psychiatry, 12: 270-282.
[106]	Galadima A, Garba ZN (2012). Heavy metals pollution in Nigeria: causes and consequences. Elixir J. Pollut 45: 7917-7922.
[107]	Lin X, Burns RC, Lawrance GA (2005). Heavy metals in wastewater: the effect of electrolyte composition on the precipitation of cadmium (II) using lime and magnesia. Water, Air and Soil Pollut 165: 131-152.
[108]	European Union (2002). Heavy metals in wastes. European Commission on Environment. Available at: http://ec.europa.eu/environment/waste/studies/pdf/heavy_metalsreport.pdf.
[109]	Young RA (2005). Toxicity profiles: toxicity summary for cadmium, risk assessment information system, RAIS, University of Tennessee. Available at www.rais.ornl.gov/tox/profiles/cadmium.shtml.
[110]	Igwe JC, Ogunewe DN, Abia AA (2005). Competitive adsorption of Zn (II), Cd (II) and Pb (II) ions from aqueous and non-aqueous solution by maize cob and husk. Afr. J. Biotechnol. 4(10): 1113-1116.
[111]	Ajmal M, Rao R, Ahmad R, Ahmad J (2000). Adsorption studies on Citrus reticulata (fruit peel of orange) removal and recovery of Ni (II) from electroplating wastewater. J. Hazard. Mater. 79: 117-131.
[112]	Babel S, Kurniawan TA (2004). Cr (VI) removal from synthetic wastewater using coconut shell charcoal and commercial activated carbon modified with oxidizing agents and/or chitosan. Chemosph 54 (7): 951-967.
[113]	Bansode PR, Losso JN, Marshall WE, Rao RM, Portier RJ (2003). Adsorption of metal ions by pecan shell-based granular activated carbons. Bioresour. Technol. 89: 115-119.
[114]	Amana T, Kazi AA, Sabri MU, Banoa Q (2008). Potato peels as solid waste for the removal of trace metal copper (II) from waste water/industrial effluent. Colloids Surf. B: Biointerfaces 63: 116-121.
[115]	Bishnoi NR, Bajaj M, Sharma N, Gupta A (2003). Adsorption of Cr (VI) on activated rice husk carbon and activated alumina. Bioresour. Technol. 91(3): 305-307.
[116]	Tang P, Lee CK, Low KS, Zainal Z (2003). Sorption of Cr (VI) and Cu (II) in aqueous solution by ethylenediamine modified rice hull. Environ. Technol. 24: 1243-1251.
[117]	Rao KS, Mohapatra M, Anand S, Venkateswarlu P (2010). Review on cadmium removal from aqueous solutions. Int. J. Engineer, Sci. and Technol 2(7): 81-103.
[118]	Benaissa H (2006). Screening of new sorbent materials for cadmium removal from aqueous solutions. Hazard Mat 132: 189-195.
[119]	Fu F, Wang Q (2011). Removal of heavy metal ions from wastewaters: A review. J. Environ. Manage 92: 407-418.
[120]	Gadd GM (2008). Accumulation and transformation of metals by microorganisms, biotechnology set, Wiley-VCH Verlag GmbH, 225-264 pp.
[121]	Sahmoune MN, Louhab K, Boukhiar A (2011). Advanced biosorbents materials for removal of chromium from water and wastewaters. Environ. Prog. Sust. Energ 30: 284-293.
[122]	dos Santos WNL, Cavalcante DD, da Silva EGP, das Virgens CF, Dias FDS (2011). Biosorption of Pb (II) and Cd (II) ions by Agave sisalana (sisal fiber). Microchem. J 97: 269-273.
[123]	Pino GH, de Mesquita LMS, Torem MML, Pinto GAS (2006). Biosorption of cadmium by green coconut shell powder. Miner. Eng. 19: 380-387.
[124]	Alves VN, Coelho NMM (2013). Selective extraction and preconcentration of chromium using Moringa oleifera husks as biosorbent and flame atomic absorption spectrometry. Microchem. J 109: 16-22.
[125]	Saeed A, Iqbal M (2003). Bioremoval of cadmium from aqueous solution by black gram husk (Cicer arientinum). Wat. Res 37: 3472-3480.
[126]	Ajmal M, Rao RAK, Anwar S, Ahmad J, Ahmad R (2003). Adsorption studies on rice husk: removal and recovery of Cd (II) from wastewater. Bioresour. Technol. 86: 147-149.
[127]	Goh KH, Lim TT, Dong Z (2008). Application of layered double hydroxides for removal of oxyanions: a review. Water R 42: 1343-1368.
[128]	Langmuir I (1918). The adsorption of gases on plane surfaces of glass, mica and platinum. J. Am. Chem. Soc. 40: 1361-1403.
[129]	Freundlich HMF (1906). Uber die adsorption in losungen. Z Phys Chem 57: 385-470.
[130]	Hu XJ, Wang JS, Liu YG, Li X, Zeng GM, Bao ZL, Zeng XX, Chen AW, Long F (2011). Adsorption of chromium (VI) by ethylenediamine-modified cross- linked magnetic chitosan resin: isotherms, kinetics and thermodynamics. J. Hazard. Mater 185: 306-314.
[131]	Zhang W, Mao S, Chen H, Huang L, Qiu R (2013). Pb (II) and Cr (VI) sorption by biochars pyrolyzed from the municipal wastewater sludge under different heating conditions. Bioresour. Technol 147: 545-552.
[132]	Agrafioti E, Kalderis D, Diamadopoulos E (2014). Arsenic and chromium removal from water using biochars derived from rice husk, organic solid wastes and sewage sludge. J. Environ. Manage. 133: 309-314.
[133]	Yang Y, Lin X, Wei B, Zhao Y, Wang J (2014). Evaluation of adsorption potential of bamboo biochar for metal-complex dye: equilibrium, kinetics and artificial neural network modeling. Int. J. Environ. Sci. Technol 11: 1093-1100.
[134]	Kim WK, Shim T, Kim YS, Hyun S, Ryu C, Park YK, Jung J (2013). Characterization of cadmium removal from aqueous solution by biochar produced from a giant Miscanthus at different pyrolytic temperatures. Bioresour. Technol 138: 266-270.
[135]	Kołodyn´ska D, Wne˛trzak R, Leahy J, Hayes M, Kwapin ´ski W, Hubicki Z (2012). Kinetic and adsorptive characterization of biochar in metal ions removal. Chem. Eng. J. 197: 295-305.
[136]	Boutsika LG, Karapanagioti HK, Manariotis ID (2014). Aqueous mercury sorption by biochar from malt spent rootlets. Water, Air, Soil Pollut 225: 1-10.
[137]	Ho YS, McKay G (1998). Kinetic models for the sorption of dye from aqueous solution by wood. Process Saf Environ Prot 76(B2): 183-191.
[138]	Reddy D, Lee SM (2013). Application of magnetic chitosan composites for the removal of toxic metal and dyes from aqueous solutions. Adv. Colloid Interface Sci 201: 68-93.
[139]	Ho YS, McKay G (1999). Pseudo-second order model for sorption processes. Process Biochem 34: 451-465.
[140]	Chojnacka K (2010). Biosorption and bioaccumulation – the prospects for practical applications. Environ Int 36: 299-307.
[141]	Trakal L, Sigut R, Sillerova H, Faturikova D, Komarek M (2014). Copper removal from aqueous solution using biochar: Effect of chemical activation. Arab. J Chem 7: 43-52.
[142]	Castro RSD, Caetano L, Ferreira G, Padilha PM, Saeki MJ, Zara LF, Martines MAU, Castro GR (2011). Banana peel applied to the solid phase extraction of copper and lead from river water: Preconcentration of metal ions with a fruit waste. Industrial and Engineering Chemistry Research 50(6): 3446-3451.
[143]	Song Z, Lian F, Yu Z, Zhu L, Xing B, Qiu W (2014). Synthesis and characterization of a novel MnOx-loaded biochar and its adsorption properties for Cu2+ in aqueous solution. Chemical Engineering Journal, 242: 36-42.
[144]	Gupta VK, Rastogi A (2008). Biosorption of lead (II) from aqueous solutions by non-living algal biomass Oedogonium spp. and Nostoc spp. a comparative study. Colloids Surf. B: Biointerfaces, 64: 170-178.
[145]	Tong X, Xu R (2013). Removal of Cu (II) from acidic electroplating effluent by biochars generated from crop straws. J. Environ. Sci. 25: 652-658.
[146]	Tong X, Li J, Yuan J, Xu R (2011). Adsorption of Cu (II) by biochars generated from three crop straws. Chem. Eng. J. 172: 828-834.
[147]	Jain M, Garg VK, Kadirvelu K, Sillanpa¨a¨, M (2015). Adsorption of heavy metals from multi-metal aqueous solution by sunflower plant biomass-based carbons. Int. J. Environ. Sci. Technol ISSN 1735-1472. Int. J. Environ. Sci. Technol.
[148]	El-Sikaily A, El Nemr A, Khaled A, Abdelwehab O (2007). Removal of toxic chromium from wastewater using green alga Ulva lactuca and its activated carbon. J. Hazard. Mater. 148: 216-228.
[149]	Štefušová, K. Lovás M, Zubrik A, Matik M, Václavíková M (2012). Removal of Cd2+ and Pb2+ from aqueous solutions using bio-char residues. Nova Biotechnologica Et Chimica 11(2): 139-146.
[150]	Mirimichi Green – ECO. 2016. Effective earth solution. Environ. Services.
[151]	www.biochar-international.org. September 19 (2014). Rebuilding “Who-ville” – Our Lost and Forgotten Underworld Communities.
[152]	Lehmann J (2007). Bioenergy in the black. Front Ecol. Environ 5(7): 381-387.