Biosorption of Toxic Heavy Metals on Sawdust

Abstract

The present investigation deals with the biosorption of Zn2+, Cr3+, and Pb2+ in the liquid phase on the surface of zinc sequestering bacterium VMSDCM (accession no. HQ108109) cells immobilized on pineapple peel powder particles (the term sawdust has been used for immobilized microorganisms). In batch studies, the biosorption data design and regression model for predicting the relationship between the metal ion and their biosorption capacity used were Minimum Run Res V Design and quantitative ion character activity relationship (QICAR), respectively. The values of qmax calculated by the Langmuir isotherm were found to be in increasing order of Cr3+ < Zn2+ < Pb2+. The results of the present investigation showed that the pH and contact time played an important role in the removal of Zn2+ from the liquid phase. In case of Cr3+, the significant independent parameters associated with metal ion removal were the initial concentration of the metal ion and the pH. The important independent parameters for Pb2+ removal were the temperature (°C) and pH, respectively. In QICAR modeling, among all six physico‐chemical characteristics only the ionization potential (eV) played a negative role in the biosorption of metal ions. The rationale behind the inverse relationship between the removal of metal ions and eV was the variation of the corresponding covalent index. The rest of the remaining five physico‐chemical properties showed that regression models fitted quite well and were characterized by high values of the linear regression coefficient (R2), adjusted R2, and low values of the error function (χ2). In the present work, it was concluded that the immobilized cells of sawdust can be a suitable alternative for the removal of heavy metal ions from the liquid phase. The initial concentration of all the metals was kept at 50 mg L−1 each in the liquid phase. The residual concentrations of Zn2+, Cr3+, and Pb2+ after the biosorption were 0.4, 1.2, and 0.2 mg L−1, respectively.