Towards sustainable development of microalgal biosorption for treating effluents containing heavy metals

Document Type: Review Paper


Department of Chemical Engineering. Faculty of Engineering, University of Abuja, P.M.B. 117, Airport Road, main campus, FCT, Abuja, Nigeria.


Effluents containing heavy metals are hazardous to human health and the environment even at low concentrations. It is costly and unsustainable to use conventional methods to remove heavy metals from dilute effluents. Microalgal biomass owing to its high metal biosorption capacity, is a promising alternative biosorbent for treating dilute heavy metal solutions. However, the application of freely suspended algal biomass for metal removal has a number of drawbacks such as small particle size, low chemical resistance, low mechanical strength, and difficulty in separation of biomass and effluent. The present article reviews the techniques used to address these drawbacks. It also discusses the key factors affecting biosorption efficiency including initial concentration of metal ions, contact time, solution pH, solution temperature, biosorbent concentration, agitation rate, and competing ions. Biomass cross-linking with appropriate agents such as polysolfane, formaldehyde, or chlorohydrin could improve mechanical strength, chemical resistance, and separation of the biomass from the effluent. However, cross-linked biomass usually shows low sorption capacity and slow rate of metal uptake. These disadvantages could be minimized by using physical and/or chemical pretreatments prior to biomass cross-linking. Alkaline detergent, sodium hydrogen carbonate without autoclaving, sodium hydroxide or sodium carbonate plus autoclaving, or supercritical carbon dioxide at mild conditions are among the most effective pretreatments. Apart from liberating more latent metal binding sites on the biomass, supercritical CO2 could also improve the porosity of the biomass thereby improving sorption rate of the cross-linked biomass. High sorption capacity and rapid metal uptake will allow substantial reduction in size of biosorption columns, which will consequently improve the economic and sustainability features of algal-based metal biosorption processes.

Graphical Abstract

Towards sustainable development of microalgal biosorption for treating effluents containing heavy metals


  • Biosorbents for heavy metals removal were reviewed.
  • Microalgae show promising biosorption capacity.
  • Microalgae need to be cross-linked for effective biosorption.
  • Biomass pretreament prior to cross-linking could improve sorption capacity and rate.



On the cover

Despite the high biosorption capacity of microalgae, freely suspended microalgae is not attractive because of a number of disadvantages, i.e., small particle size, low chemical resistance, low mechanical strength, and difficulty in separation of biomass from the treated effluent. However, these shortcomings can be addressed by using immobilized microalgae in a biosorption packed bed. In this issue of Biofuel Research Journal, Dr. Kamoru A. Salam comprehensively reviews the essentials of microalgal biosorption for treating effluents containing heavy metals. He presents and critically discusses the different immobilization techniques used to enhance this process with a focus on cross-linking as the most promising approach. The author emphasizes that an ideal microalgal biosorbent should exhibit high sorption capacity, rapid sorption rate, good mechanical stability, high chemical resistance, easy separability, and reusability to ensure a cost effective and sustainable biosorption process. Cover art by BiofuelResJ.


[1] Abdel-Ghani, N.T., El-Chaghaby, G.A., 2014. Biosorption of metal ions removal from aqueous solutions: a review of recent studies. Int. J. Latest Res. Sci. Technol. 3(1), 24-42.

[2] Ahuja, P., Gupta, R., Saxena, R.K., 1999. Zn2+ biosorption by Oscillatoria anguistissima. Process Biochem. 34(1), 77-85.

[3] Aksu, A., 2001. Equilibrium and kinetic modelling of cadmium (II) biosorption by C. vulgaris in a batch system: effect of temperature. Sep. Purif. Technol. 21(3), 285-294.

[4] Aksu, Z., 1998. Immobilized algal technology for wastewater treatment purposes, in: Tam, N.F.Y., Wong, Y.S. (Eds). Wastewater treatment with algae. Springer-verlag, New York.

[5] Al-Daghistani, H., 2012. Bio-remediation of Cu, Ni and Cr from rotogravure wastewater using immobilized, dead, and live biomass of indigenous thermophilic bacillus species. Internet J. Microbiol. 10(1).

[6] Alfarraa, A., Frackowiak, E., Beguin, F., 2004. The HSAB concept as a means to interpret the adsorption of metal ions onto activated carbons. Appl. Surf. Sci. 228(1-4), 84-92.

[7] Al-Gheethi, A., Mohamed, R., Noman, E., Norli, I., Kadir, O., 2017. Removal of heavy metal ions from aqueous solutions using Bacillus subtilis biomass pre-treated by supercritical carbon dioxide.Clean-Soil Air Water. 45(10), 1700356.

[8] Arivalagan, P., Singaraj, D., Haridass, V., Kaliannan, T., 2014. Removal of cadmium from aqueous solution by batch studies using Bacillus cereus. Ecol. Eng. 71, 728-735.

[9] Asmal, M., Khan, A.H., Ahmad, S., Ahmad, A., 1998. Cole of sawdust in the removal of copper (II) from industrial wastes. Water Res. 32(10), 3085-3091.

[10] Atkinson, B.W., Bux, F., Kasan, H.C., 1998. Considerations for application of biosorption technology to remediate metal-contaminated industrial effluents. Water S.A. 24(2), 129-135.

[11] Bai, R.S., Abraham, T.E., 2001. Biosorption of Cr (VI) from aqueous solution by Rhizopus nigricans. Bioresur. Technol. 79(1), 73-81.

[12] Bai, R.S., Abraham, T.E., 2003. Studies on chromium (VI) adsorption-desorption using immobilized fungal biomass. Bioresour. Technol. 87(1), 17-26.

[13] Barka, N., Abdennouri, M., El Makhfouk, M., Qourzal, S., 2013. Biosorption characteristics of cadmium and lead onto eco–friendly dried cactus (Opuntia ficus indica) cladodes. J. Environ. Chem. Eng. 1(3), 144-149.

[14] Benefield, L.D., Judkins, J.F., Weand, B.L., 1982. Process Chemistry for water and wastewater treatment. Englewood Cliffs, New Jersey.

[15] Blazquez, G., Hernainz, F., Calero, M., Martn-Lara, M.A., Tenorio, G., 2009. The effect of pH on the biosorption of Cr (III) and Cr (VI) with olive stone. Chem. Eng. J. 148(2-3), 473-479.

[16] Britton, H.T.S., 1943. The application of electrometric methods to the study of some ionic reactions. Ann. Rep. Prog. Chem. 40, 43-59.

[17] Brown, P.A., Gill, S.A., Allen, S.J., 2000. Metal removal from wastewater using peat. Water Res. 34(16), 3907-3916.

[18] Bueno, B.Y.M., Torem, M.L., Molina, F., de Mesquita, L.M.S., 2008. Biosorption of lead (II), Chromium (III) and Copper (II) by R. opacus: equilibrium and kinetic studies. Miner. Eng. 21(1), 65-75.

[19] Bulgariu, D., Bulgariu, L., 2012. Equilibrium and kinetics studies of heavy metal ions biosorption on green algae waste biomass. Bioresour. Technol. 103(1), 489-493.

[20] Burrows, A., Holman, J., Parsons, A., Pilling, G., 2009. Chemistry3: introducing inorganic, organic, and physical chemistry. Oxford Univ. Press, New York.

[21] Cayllahua, J.E.B., de Carvalho, R.J., Torem, M.L., 2009. Evaluation of equilibrium, kinetic and thermodynamic parameters for biosorption of nickel (II) ions onto bacteria strain Rhodococcus opacus. Miner. Eng. 22(15), 1318-1325.

[22] Cheng, J., Yin, W., Chang, Z., Lundholm, N., Jiang, Z., 2016. Biosorption capacity and kinetics of cadmium (II) on live and dead Chlorella vulgaris. J. Appl. Phycol. 29(1), 211-221.

[23] Chojnacka, K., Chojnacki, A., Gorecka, H., 2005. Biosorption of Cr3+, Cd2+, and Cu2+ ions by blue-green algae Spirulina sp.: kinetics, equilibrium and the mechanism of the process. Chemosphere. 59(1), 75-84.

[24] Costa, A.C.A., Franca, F.P., 1998. The behaviour of the microalgae Tetraselmis chuii in cadmium-contaminated solutions. Aquacult. Int. 6(1), 57-66.

[25] Costa, A.C.A., Franca, F.P., 2003. Cadmium interaction with micro algal cells, cyanobacteria cells, and seaweeds; toxicology and biotechnological potential for wastewater treatment. Mar. Biotechnol. 5(2), 149-156.

[26] Crini, G., 2006. Non-conventional low-cost adsorbents for dye removal: a review. Bioresour. Technol. 97(9), 1061-1085.

[27] Darnall, D.W., Greene, B., Hosea, M., McPherson, R.A., Henzl, M., Alexander, M.D., 1986. Recovery of heavy metals by immobilized algae:in trace metal removal from aqueous solutions, Industrial division of the Royal Society of Chemistry Annual Chemical Congress, Thomson, R. (Ed.), 1-24, UK.

[28] Ekmekyapar, F., Aslan, A., Bayhan, Y.K., Cakici, A., 2006. Biosorption of copper (II) by nonliving lichen biomass of Cladonia rangiformis hoffm. J. Hazard. Mater. 137(1), 293-298.

[29] Elliott, H.A., Huang, C.P., 1981. Adsorption Characteristic of Some Cu (II) Complexes on Alumino Silicates. Water Res. 15(7), 849-855.

[30] El-Sayed, M.T., 2012. The use of Saccharomyces cerevisiae for removing cadmium (II) from aqueous waste solutions. Afr. J. Microbiol. Res. 6(41), 6900-6910.

[31] Esposito, A., Pagnanell, F., Veglio, F., 2002. pH-related equilibria models for biosorption in single metal systems. Chem. Eng. Sci. 57(3), 307-313.

[32] Farooq, U., Kozinski, J.A., Khan, M.A., Athar, M., 2010. Biosorption of heavy metal ions using wheat based biosorbents-a review of the recent literature. Bioresour. Technol. 101(14), 5043-5053.

[33] Fiol, N., Villaescusa, I., Martinez, M., Miralles, N., Poch, J., Serarols, J., 2006. Sorption of Pb (II), Ni (II), Cu (II) and Cd (II) from aqueous solution by olive stone waste. Sep. Purif. Technol. 50(1), 132-140.

[34] Flouty, R., Estephane, G., 2012. Bioaccumulation and biosorption of copper and lead by a unicellular algae Chlamydomonas reinhardtii in single and binary metal systems: a comparative study. J. Environ. Manage. 111, 106-114.

[35] Fraile, A., Penche, S., Gonzalez, F., Blazquez, M.L., Munoz, J.A., Ballester, A., 2005. Biosorption of copper, zinc, cadmium and nickel by Chlorella vulgaris. Chem. Ecol. 21(1), 61-75.

[36] Gadd, G.M., 2009. Biosorption: critical review of scientific rationale, environmental importance and significance for pollution treatment. J. Chem. Technol. Biotechnol. 84(1), 13-28.

[37] Geisweid, H.J., Urbach, W., l983. Sorption of cadmium by the green microalgae Chlorella vulgaris, Ankistrodesmus braunii and Bremosphaera viridis. Zeitschrift für Pflanzenphysiologie. 109(2), 127-141.

[38] Gipps, J.F., Coller, B.A., 1980. Effect of physical and culture conditions on uptake of Cadmium by Chlorella pyrenoidosa. Mar. Freshwater Res. 31(6), 747-755.

[39] Gray, N.F., 1999. Water Technology. John Wiley and Sons, New York.

[40] Greene, B., Hosea, M., McPherson, R., Henzl, M., Alexander, M.D., Dennis, W., Darnall, D.W., 1986. Interaction of gold (I) and gold (III) complexes with algal biomass. Environ. Sci. Technol. 20(6), 627-632.

[41] Grima, E.M., Belarbia, E.H., Fernandez, F.G.A., Medina, A.R., Chisti, Y., 2003. Recovery of microalgal biomass and metabolites: process options and economics. Biotechnol. Adv. 20(7-8), 491-515.

[42] Gupta, V.K., Rastogi, A., 2008. Equilibrium and kinetic modelling of cadmium (II) biosorption by nonliving algal biomass Oedogonium sp. from aqueous phase. J. Hazard. Mater. 153(1-2), 759-766.

[43] Gupta, V.K., Rastogi, A., Nayak, A., 2010. Biosorption of nickel onto treated alga (Oedogonium hatei): application of isotherm and kinetic models. J. Colloid Interface Sci. 342(2), 533-539.

[44] Holan, Z.R., Volesky, B., Prasetyo, I., 1993. Biosorption of Cadmium by biomass of marine algae. Biotechnol. Bioeng. 41(8), 819-825.

[45] Horsfall, M., Ayebaemi, I., 2005. Effect of metal ion concentration on the biosorption of Pb2+ and Cd2+ by Caladium bicolor (wild cocoyam). Afr. J. Biotechnol. 4(2), 191-196.

[46] Huang, F., Guo, C.L., Lu, G.N., Yi, X.Y., Zhu, L.D., Dang, Z., 2014. Bioaccumulation characterization of Cadmium by growing Bacillus cereus RC-1 and its mechanism. Chemosphere. 109, 134-142.

[47] Huang, Y.C., Koseoglu, S.S., 1993. Separation of heavy metals from industrial waste streams by membrane separation technology. Waste Manage. 13(5-7), 481-501.

[48] Ismail, E.S., Vieira, J.D.G., Amaral, A., 2015. Principle, techniques and application of biocatalyst immobilization for industrial application. Appl. Microbiol. Biotechnol. 99(5), 2065-2082.

[49] Javanbakht, V., Alavi, S.A., Zilouei, H., 2014. Mechanisms of heavy metal removal using microorganisms as biosorbent. Water Sci. Technol. 69(9), 1775-1787.

[50] Jjemba, P.K., 2004. Interaction of metals and metalloids with microorganisms in the environment, in: Jjemba, P.K. (Ed.), Environmental Microbiology-Principles and Applications. Science Publishers, New Hampshire. 257-270.

[51] Junlian, Q., Lei, W., XiaoHua, F., GunagHong, Z., 2010. Comparative Study on the Ni2+ biosorption capacity and properties of living and dead Pseudomonas putida cells. Iran. J. Chem. Chem. Eng. 29(2), 159-167.

[52] Kim, K.W., Kang, S.Y., 2006. Bacterial Biosorption of trace elements, in Prasad, M.N.V., Sajwan, K.S., Naidu, R. (Eds.), Trace elements in environment: Biogeochemistry, Biotechnology and Bioremediation. CRC Press, Boca Raton.

[53] Kok, F.N., Bozoglu, F., Hasirci, V., 2001. Immobilization of acetylcholine-esterase and choline oxidase in/on pHEMA membrane for biosensor construction. J. Biomater. Sci. Polym. 12(11), 1161-1176.

[54] Kök, F.N., Hasirci, V., Arica, M.Y., 2001. In: Wise, D.L., Trantolo, D.J., Cichon, E.J., Inyang, H.I., Stottmeister, U. (Eds.), Bioremediation of contaminated soils. CRC Press.

[55] Leusch, A., Holan, Z.R., Volesky, B., 1995. Biosorption of heavy metals (Cd, Cu, Ni, Pb, Zn) by chemically-reinforced biomass of marine algae. J. Chem. Technol. Biotechnol. 62(3), 279-288.

[56] Levy, J.L., Angel, B.M., Stauber, J.L., Poon, W.L., Simpson, S.L., Cheng, S.H., Jolley, D.F., 2008. Uptake and internalisation of copper by three marine microalgae: comparison of copper-sensitive and copper-tolerant species. Aquat. Toxicol. 89(2), 82-93.

[57] Li, H., Lin, Y., Guan, W., Chang, J., Xu, L., Guo, J., We, G., 2010. Biosorption of Zn (II) by live and dead cells of Steptomyces ciscaucasicus strain CCNWHX 72-14. J. Hazard. Mat. 179(1-3), 151-159.

[58] Li, X., Li, D., Yan, Z., Ao, Y., 2018. Adsorption of Cadmium by live and dead biomass of plant growth-promoting rhizobacteria. RSC. Adv. 8(58), 33523-33533.

[59] Ligler, F.S., Taitt, C.R., 2011. Optical biosensors: today and tomorrow. Elsevier.

[60] Liu, Y., Qilin, C., Luo, F., Chen, J., 2009. Biosorption of Cd2+, Cu2+, Ni2+ and Zn2+ ions from aqueous solutions by pretreated biomass of brown algae. J. Harzard. Mater. 163(2-3), 931-938.

[61] Lodeiro, P., Barriada, J.L., Herrero, R., De Vicente, M.S., 2006. The marine macroalga Cystoseira baccata as biosorbent for cadmium (II) and lead (II) removal: kinetic and equilibrium studies. Environ. Pollut. 142(2), 264-273.

[62] Machado, M.D., Janssens, S., Soares, H.M.V.M., Soares, E.V., 2009. Removal of heavy metals using a brewer’s yeast strain of Saccharomyces cerevisiae: advantages of using dead biomass. J. Appl. Microbiol. 106(6), 1792-1804.

[63] Mack, C., Wilhelmi, B., Duncan, J.R., Burgess, J.E., 2007. Biosorption of precious metals. Biotechnol. Adv. 25(3), 264-271.

[64] Madrid, Y., Camara, C., 1997. Biological substrates for metal preconcentration and speciation. TrAC, Trends Anal. Chem. 16(1), 36-44.

[65] Mata, Y.N., Blazquez, M.L., Ballester, A., Gonzalez, F., Munoz, J.A., 2008. Characterization of the biosorption of Cadmium, Lead and Copper with the brown alga Fucus vesiculosus. J. Hazard. Mater. 158(2-3), 316-323.

[66] Monteiro, C.M., Castro, P.M.L., 2012. Metal uptake by microalgae: underlying mechanisms and practical applications. Biotechnol. Prog. 28(2), 299-311.

[67] Munoz, R., Alvarez, M.T., Munoz, A., Terrazas, E., Guieysse, B., Mattiasson, B., 2006. Sequential removal of heavy metal ions and organic pollutants using an algal-bacterial consortium. Chemosphere. 63(6), 903-911.

[68] Nordstrom, D.K., Majzlan, J., Königsberger, E., 2014. Thermodynamic properties for arsenic minerals and aqueous species. Rev. Mineral. Geochem. 79(1), 217-255.

[69] Oves, M., Khan, M.S., Zaidi, A., 2013. Biosorption of heavy metals by Bacillus thuringiensis strain OSM29 originating from industrial effluent contaminated north Indian soil. Saudi J. Biol. Sci. 20(2), 121-129.

[70] Ozer, A., Ozer D., 2003. Comparative study of the biosorption of Pb (II), Ni (II), and Cr (VI) ions onto S. cerevisiae: determination of biosorption heats. J. Hazard. Mater. 100(1-3), 219-229.

[71] Ozer, A., Ozer, D., Ekiz, H.I., 2005. The Equilibrium and Kinetic Modelling of the Biosorption of Copper (II) ions on Cladophora crispate. Adsorption. 10(4), 317-326.

[72] Padmavathy, V., Vasudevan, P., Dhingra, S.C., 2003. Biosorption of nickel (II) ions on Baker’s yeast. Process Biochem. 38(10), 1389-1395.

[73] Parsons, J.G., Gardea-Torresdey, J.L., Tiemann, K.J., Gamez, G., 2003. Investigation of trace level binding of PtCl6 and PtCl4 to alfalfa biomass (Medicago sativa) using Zeeman graphite furnace atomic absorption spectrometry. Anal. Chim. Acta. 478(1), 139-145.

[74] Pawlik-Skowronska, B., 2003. Resistance, accumulation and allocation of zinc in two ecotypes of the green alga Stigeoclonium tenue Kutz. coming from habitats of different heavy metal concentrations. Aquat. Bot. 75(3), 189-198.

[75] Pearson, R.G., 1963. Hard and Soft Acids and Bases. J. Am. Chem. Soc. 85(22), 3533-3539.

[76] Pearson, R.G., 1966. Acids and Bases. Science. 151, 172-177.

[77] Pereira, S., Micheletti, E., Zille, A., Santos, A., Moradas-Ferreira, P., Tamagnini, P., De Philippis, R., 2011. Using extracellular polymeric substances (EPS) producing cyanobacteria for the bioremediation of heavy metals: do cations compete for the EPS functional groups and also accumulate inside the cell?. Microbiology. 157(2), 451- 458.

[78] Perez-Rama, M., Lopez, C.H., Alonso, J.A., Vaamonde, E.T., 2001. Class III metalothioneins in response to cadmium toxicity in the marine microalga Tetraselmis suecica (Kylin) Butch. Environ. Toxicol. Chem. 20(9), 2061-2066.

[79] Puranik, P.R., Paknikar, K.M., 1999. Biosorption of lead, Cadmium, and Zinc by citrobacter strain MCM B-181: characterization studies. Biotechnol. Prog. 15(2), 228-238.

[80] Raize, O., Argaman, Y., Yannai, S., 2004. Mechanisms of biosorption of different heavy metals by brown marine macroalgae. Biotechnol. Bioeng. 87(4), 451-458.

[81] Ray, L., Paul, S., Bera, D., Chattopadhyay, P., 2006. Bioaccumulation of Pb (II) from aqueous solutions by Bacillus cereus M1 16. J. Hazard. Subst. Res. 5.

[82] Robinson, P.K., 1998. Immobilized algal technology for wastewater treatment purposes, in Tam, N.F.Y., Wong, Y.S. (Eds.), Wastewater treatment with algae. Springer-verlag, New York.

[83] Romera, E., Gonzalez, F., Ballester, A., Blazquez, M.L., Munoz, J.A., 2007. Comparative study of biosorption of heavy metals using different types of algae. Bioresour. Technol. 98(17), 3344-3353.

[84] Salleh., A.B., Abdul-Rahman, R.N.Z.R., Basri, M., 2006. New lipases and proteases. Nova Publishers.

[85] Saltah, K., Sari, A., Aydin, M., 2007. Removal of ammonium ion from aqueous solution by natural Turkish (Yildizeli) zeolite for environmental quality. J. Hazard. Mater. 141(1), 258-263.

[86] Sari, A., Tuzen, M., Uluozlu, O.D., Soylak, M., 2007. Biosorption of Pb (II) and Ni (II) from aqueous solution by lichen (Cladonia furcata) biomass. Biochem. Eng. J. 37(2), 151-158.

[87] Sengil, I.A., Ozacar, M., 2009. Competitive biosorption of Pb2+, Cu2+, and Zn2+ ions from aqueous solutions onto valonia tannin resin. J. Hazard. Mater. 166(2-3), 1488-1494.

[88] Silver, S., Phung, L.T., 2005. A bacterial view of the periodic table: genes and proteins for toxic inorganic ions. J. Ind. Microbiol. Biotechnol. 32(11-12), 587-560.

[89] Skowroriski, T., 1984a. Energy-dependent transport of Cadmium by Stichococcus bacillaris. Chemosphere. 13(12), 1379-1384.

[90] Skowroriski, T., 1984b. Uptake of Cadmium by Stichococcus bacillaris. Chemosphere. 13(12), 1385-1389.

[91] Skowroriski, T., 1986. Adsorption of Cadmium on green microalga Stichococcus bacillaris. Chemosphere. 15(l), 69-76.

[92] Sulaymon, A.H., Mohammed, A.A., Al-Musawi, T.J., 2013. Competitive biosorption of lead, cadmium, copper, and arsenic ions using algae. Environ. Sci. Pollut. Res. 20(5), 3011-3023.

[93] Talaro, K.P., Chess, B., 2015. Foundations in microbiology. McGraw-Hill Education, New York.

[94] Taylor, R.F., Schultz, J.S., 1996. Handbook of chemical and biological sensors. CRC Press.

[95] Tchounwou, P.B., Yedjou, C.G., Patlolla, A.K., Sutton, D.J., 2012. Heavy Metals Toxicity and the Environment. EXS. 133-164.

[96] Terry, P.A., Stone, W., 2002. Biosorption of cadmium and copper contaminated water by Scenedesmus abundans. Chemosphere. 47(3), 249-255.

[97] Trevors, J.T., Stratton, G.W., Gadd, G.M., 1986. Cadmium transport, resistance, and toxicity in bacteria, algae, and fungi. Can. J. Microbiol. 32(6), 447-464.

[98] Tsezos, M., Remoudaki, E., Angelatou, V., 1996. A study of the effects of competing ions on the biosorption of metals. Int. Biodeterior. Biodegrad. 3(1), 19-29.

[99] Tunzun, I., Bayramoglu, G., Yalcin, E., Basaran, G., Celik, G., Arica, M.Y., 2005. Equilibrium and kinetic studies on biosorption of Hg(II), Cd(II), and Pb(II) ions onto microalgae Chlamydomonas reinhardtii. J. Environ. Manage. 77(2), 85-92.

[100] Ucun, H., Bayhan, Y.K., Kaya, Y., Cakici, A., Faruk Algur, A.O., 2002. Biosorption of chromium (VI) from aqueous solution by cone biomass of Pinus sylvestris. Bioresour. Technol. 85(2), 155-158.

[101] US, EPA., 2009. National Primary Drinking Water Regulations. United States Environmental Protection Agency EPA 816-F-09-004.

[102] Vannela, R., Verma, S.K., 2006. Co2+, Cu2+ and Zn2+ accumulation by cyanobacterium Spirulina platensis. Biotechnol. Prog. 22(5), 1282-1293.

[103] Vijayaraghavan, K., Yun, Y.S., 2008. Bacterial biosorbents and biosorption. Biotechnol. Adv. 26(3), 266-291.

[104] Volesky, B., Holan, Z.R., 1995. Biosorption of heavy metals. Biotechnol. Prog. 11(3), 235 -250.

[105] Volesky, B., 2001. Detoxification of metal-bearing effluents: biosorption for the next century. Hydrometallurgy. 59(2-3), 203-216.

[106] Volesky, B., 2007. Biosorption and me. Water Res. 41(18), 4017-4029.

[107] Wang, J., Chen, N., 2009. Biosorbents for heavy metals removal and their future. Biotechnol. Adv. 27(2), 195-226.

[108] Weber, W.J., Jr, 1985. Adsorption Theory, Concepts, and Modelsm, in Adsorption Technology: A Step-by-Step Approach to Process Evaluation and Application. Slejko, F. L. (Ed.), Marcel Dekker, New York. 1-35.

[109] Worms, I., Simon, D.F., Hassler, C.S., Wilkinson, K.J., 2006. Bioavailability of trace metals to aquatic microorganisms: importance of chemical, biological and physical processes on biouptake. Biochimie. 88(11), 1721-1731.

[110] Xiao, X., Luo, S., Zeng, G., Wei, W., Wan, Y., Chen, L., Guo, H., Cao, Z., Yang, I., Chen, J., Xi, Q., 2010. Biosorption of cadmium by endophytic fungi (EF) Microshaeropsis sp. LSE 10 isolated from cadmium hyperaccumulator solanum nigrum L. Bioresour. Technol. 101, 1668-1674.

[111] Yan, G., Viraraghava, T., 2000. Effect of pretreatment on the bioadsorption of heavy metals on Mucor rouxii. Water SA-Pretoria. 26(1), 119-124.

[112] Yang, J., Cao, J., Xing, G., Yuan, H., 2015. Lipid production combined with biosorption and bioaccumulation of Cadmium, Copper, Mangenese and Zinc by oleaginous microalgae Chlorella minutissima UTEX 2341. Bioresur. Technol. 175, 537-544.

[113] Zhou, P., Huang, J., Alfred, W.F., Wei, S., 1999. Heavy metals removal from wastewater in fluidized bed reactor. Water Res. 33(8), 1918-1924.