Removal of Ni (II) ions from aqueous solutions using modified rice straw in a fixed bed column

This paper investigates the ability of modified rice straw, an agricultural biomaterial, to remove Ni (II) ions from aqueous solution in a fixed-bed column. The experiments were performed with different bed heights (1.5 and 2.0 cm), influent Ni (II) concentrations (50, 75 and 100 mg/L) using flow rates (500 μl/min) in order to obtain experimental breakthrough curves. The maximum adsorption capacity of rice straw powder (RSP) was 43 mg/L at 75 mg/L influent concentration of divalent Ni (II) ions at 2 cm bed depth. Adams–Bohart model, Thomas model and Yoon and Nelson kinetic models were used to analyze the column performance. The value of rate constant for Adams–Bohart and Yoon and Nelson model decreased with increase of influent concentration, but increased with increasing bed depth. The rate constant for Thomas model increased with initial influent Ni (II) ions concentration, decreased with increase in bed depth.