Isotherm and Kinetic Models for Bio-sorption of Cadmium Ions from Aqueous Solutions using Dry Peanut Shells and Hazelnut Shells

Abstract

This work is aiming to investigate the removal Cd(II) ions from the aqueous solution using two types of biosorbent materials: peanut shells (PS) and hazelnut shells (HS). The effect of several variables on the batch bio-sorption was studied. The process was carried out at room temperature, shacking speed 200 rpm and using fixed adsorbent diameters of 0.75 mm. The highest removal efficiency of Cd(II) ions onto PS was 91.45% in the best conditions (pH=3, initial concentration of Cd(II) ions 50 mg/ L, amount adsorbent was 0.75 g, contact time was 120 min), while the highest removal efficiency when using HS was 85.62% at pH= 4, and contact time of 160 minutes using the same initial concentration of Cd(II) ions as well as the same amount of absorbent material. Isotherm was studied for bio-sorption of Cd(II) ions using these two adsorbents, and the pseudo- first and second order models were used to study bio-sorption kinetics. The results of the infrared spectroscopy (FTIR) of (PS) and (HS) samples before and after loading for Cd(II) ions showed that hydroxyl and carboxyl groups play a major role in bio-sorption of these ions.