Development of a floating adsorbent for cadmium derived from modified drinking water treatment plant sludge

Abstract

Abstract Adsorbents produced from solid waste materials have received a lot of attention in recent years. The purpose of this study was to assess the aqueous phase cadmium adsorption capacity of a floating adsorbent derived from a drinking water treatment sludge. Unmodified sludge, phosphoric acid modified sludge powder, and granular encapsulated sludges were investigated. Parameters such as adsorbent concentration, contact time, pH of the solution, and the initial concentration of cadmium ions were investigated using batch sorption experiments. SEM, FTIR, and elemental analysis techniques were utilized for the characterization of the adsorbent. The Langmuir model was employed to determine the adsorption capacity of all four adsorbents. The maximum cadmium load increased from 25 mg/g for the unmodified sludge to 40.3 mg/g for the phosphoric acid modified material. The alginate gel-encapsulated sludge adsorbed 30 mg/g, slightly higher than that of the raw sludge. The granular form of the encapsulated material made it easier to remove the adsorbent from the aqueous phase after the adsorption process. The findings of this research have important implications for the removal of aqueous phase cadmium using sludge based, low-cost adsorbents.