Dynamic adsorption studies for the removal of Cd (II) and Ni (II) from aqueous solutions using mahogany leaves

Abstract

A dynamic adsorption study was carried out using mahogany leaves (ML) powder as an adsorbent for the removal of Cd (II) and Ni (II) from their aqueous solutions. The effects of contact time, adsorbent dose (5, 10 and 15 g), initial concentration (10, 15 and 20 mg/L), particle size (212, 150 and 106 μm) and pH of zero charge (pH_pzc) on the adsorption of Cd (II) and Ni (II) ions onto mahogany leaves powder at pH of 4.5 were investigated. The results showed that, an increase in contact time and adsorbent dose increase the percentage removal of metals. The adsorption was found to be more effective at higher concentrations of metals and with smaller adsorbent particle size. The physicochemical characteristics of the adsorbent such as attrition loss, moisture content, bulk density, pore (void) volume, iodine number/surface area, SEM and FTIR of the stationary phase were investigated. Modelling of dynamics of the fixed-bed adsorption process was studied, and the application of different models to describe the breakthrough curves showed that, Yoon–Nelson is the best fit model with values of correlation coefficient R² of 0.9048 and 0.8557 for cadmium and nickel respectively gave better results for the operating conditions. Recommendation was made such that, mahogany leaves should be studied for the remediation of other heavy metals, such as lead, chromium, mercury, zinc and uranium among others.

Keywords: adsorption, cadmium, mahogany, nickel