Biosorption of Cd²+ and Cu²+ onto wheat straw using batch and continuous fixed-bed column systems

Abstract

Biosorption of Cd²+ and Cu²+ by wheat straw (Triticum Sativum) using a batch system and a continuous upflow mode in a fixed bed column was studied. For batch system, the effect of pH over a range from 3.0 to 7.0 and the temperature from 20 to 40ºC on the metal removal was investigated. Various initial metal concentrations from 20 to 150 mg/L were used. Adsorption of metal ions was observed to increase with liquid pH and temperature. Among the three widely used isotherms, namely the Langmuir, Freundlich, and Timken models, the experimental data better fitted the Langmuir isotherm model. For the continuous upflow mode in a fixed bed (4-inch diameter), experiments were performed over a range of flow rate from 0.3-1.0 LPM and varied bed height of 0.5-2.0m. The results obtained also agree (BDST) model. In addition, for estimations of the parameters that are necessary for the design of a fixed bed adsorber in paractical application, the experimental data were fitted to the Thomas, Adams-Bohart, Yan and Yoon-Nelson models. Thomas model appeared to describe the experimental results well. Mathematical model was developed to simulate the concentration changes at the experimental time instances.