The potential use of acid-treated biomass of Trichoderma gamsii to remove hexavalent chromium ions from electroplating industrial effluent was evaluated. Electroplating industrial effluent contaminated with 5000？mg/L of Cr(VI) ions, collected from industrial estate of Gujarat, India, was mixed with acid-treated biomass of T. gamsii at biomass dose of 10？mg/mL. Effect of contact time and initial Cr(VI) ions was studied. The biosorption of Cr(VI) ions attained equilibrium at time interval of 240 minutes with maximum removal of 87% at preadjusted initial Cr(VI) concentration of 100？mg/L. The biosorption of Cr(VI) ions by biomass of T. gamsii increased as the initial Cr(VI) ion concentration of the effluent was adjusted in increasing range of 100–500？mg/L. At 500？mg/L, initial Cr(VI) concentration, acid-treated biomass of T. gamsii showed maximum biosorption capacity of 44.8？mg/g biomass from electroplating effluent. The Cr(VI) biosorption data were analysed using adsorption isotherms, that is, Freundlich and Langmuir isotherm. The correlation regression coefficients ( ) and isotherm constant values show that the biosorption process follows Freundlich isotherm ( , , and ). The kinetic study shows that biosorption of Cr(VI) ions by acid-treated biomass of T. gamsii follows pseudo-second-order rate of reaction at increasing concentration of Cr(VI). In conclusion, acid-treated biomass of T. gamsii can be used as biosorbent for Cr(VI) ions removal from Cr(VI)-contaminated wastewater generated by industries. 1. Introduction Variety of anthropogenic sources including leather tanning, electroplating, wood preservation, metal finishing, pigment, and dye industries contribute towards hexavalent chromium in the environment [1–3]. The hexavalent chromium is classified in group A of human carcinogens by United State Environmental Agency (USEPA). Therefore, USEPA has regulated/limited the industrial discharge of Cr(VI) to surface water up to <0.05？mg/L. Many conventional methods including chemical precipitation, chemical coagulation, ion exchange, electrochemical methods, adsorption using activated carbon and natural zeolite, membrane process, and ultrafiltration have been employed by several industries to remove Cr(VI) from their effluent [4–6]. However, these methods suffer from several disadvantages which include high operating cost, excess production of sludge, decrease in removal efficiency in presence of other metals, and large consumption of chemicals . Hence, remediation of Cr(VI) demands some cost effective, economic, efficient, and eco-friendly methods. In
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