Adsorbent minimisation in a two-stage batch adsorber for cadmium removal

Cadmium is a toxic metal prevalent in a variety of industrial effluents that is toxic to both humans and animals. This study utilizes nanochitosan, a polymer derived from crustacean shells, as an adsorbent for cadmium removal. The uptake capacity has been determined at 2.01 mmol/g and modelled by Langmuir, Freundlich and Sips isotherms, with the Sips isotherm the most suitable model for the adsorbent. In order to minimise the amount of adsorbent used in a batch treatment process for the cadmium removal, a two-stage batch treatment has been proposed and optimised. A detailed evaluation is made of the consequences of utilizing a less suitable isotherm, and on the benefits of utilizing a two-stage system over a single stage. Both errors from incorrect isotherms and advantages of a two-stage system are most significant at low influent concentrations and high target removal efficiencies, relevant to environmental regulatory discharge limits. (C) 2019 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.