Adsorption isotherms and kinetics of phosphate on waste mussel shell

Abstract

In this study, removal of phosphate (PO43−) from aqueous solutions using waste mussel shell (WMS) was examined. The physicochemical characteristics of WMS were identified. In the batch experiments, the effects of contact time and adsorbent dosage (m) on the PO43− adsorption by the WMS were scrutinised. The maximum PO43− removal efficiency (E) was 83.4% at 144 h contact time for WMS dosage of 10 g. A comparison of kinetic models applied to the adsorption of PO43− onto WMS was evaluated using pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models. The experimental data was fitted well with the PSO kinetic model. In the isotherm studies, Langmuir and Freundlich isotherm models were applied. The Langmuir isotherm model was well described with the PO43− adsorption. The results indicated that WMS has a good potential to adsorb PO43− from water and thus could improve environmental quality. Furthermore, this study investigated on how the Langmuir isotherm for basic adsorption could be applied to predict E or required m under a given set of initial conditions (i.e., initial solute concentration, solution volume, and adsorbent dosage). This was accomplished by combining the Langmuir isotherm with mass balance of solutes between liquid solution and solid adsorbent phases.