Enhanced sorption of Cu2+ and Ni2+ by acid-pretreated Chlorella vulgaris from single and binary metal solutions

Abstract

The influence of HCl pretreatment (0.1 mM) on sorption ofCu2+ and Ni2+ by Chlorella vulgariswas tested using single and binary metal solutions. The optimal initial pH forsorption was 3.5 for Cu2+ and 5.5 for Ni2+. Second orderrate kinetics described well sorption by untreated and acid-pretreated cells.The kinetic constant qe (metal sorption at equilibrium) for sorptionof test metals from single and binary metal solutions was increased afterpretreatment of the biomass with HCl. The Langmuir adsorption isotherm wasdeveloped for describing the various results for metal sorption. In single metalsolution, acid pretreatment enhanced qmax for Cu2+ andNi2+ sorption by approximately 70% and 65%, respectively.Cu2+ and Ni2+ mutually interfered with sorption of theother metal in the binary system. The combined presence of Cu2+ andNi2+ led to their decreased sorption by untreated biomass by 19% and88%, respectively. However, acid-pretreated biomass decreased Cu2+and Ni2+ sorption by 15 and 22%, respectively, when both the metalswere present in the solution. The results suggest a reduced mutual interferencein sorption of Cu2+ and Ni2+ from the binary metal systemdue to the acid pretreatment. Acid-pretreated cells sorbed twice the amount ofCu2+ and ten times that of Ni2+ than the untreated biomassfrom the binary metal system. Acid pretreatment more effectively enhanced thesorption of Ni2+ form the binary metal solution. The total metalsorption by untreated and acid-pretreated biomass depended on theCu2+ : Ni2+ ratio in the binary metal system. Acidpretreatment of C. vulgaris could be an effective andinexpensive strategy for enhancing Cu2+ and Ni2+ sorptionfrom single and binary metal solutions.