Zeolite fixed-bed system enhanced with recirculation for improved copper ion removal from wastewater: Kinetic models and comparison with batch system

Abstract

This research investigates the feasibility of a novel approach involving a fixed-bed column system with recirculation for copper ion removal from wastewater. Adsorption kinetics of zeolites were examined using a well-established batch system and compared to a fixed-bed column recirculation system, a configuration for which only limited investigations exist. Zeolite was chosen as the adsorbent due to its efficiency, affordability, availability, and eco-friendliness. The recirculation system was designed for comparative analysis with the batch system, assessing adsorption kinetics, reaction rate constants, and orders under various initial copper concentrations (100, 300, and 500 mg dm⁻³). Zeolite particles (2–3 mm) were used in the recirculation system, while finer particles (63 µm) were employed in the batch system. Experimental conditions, such as adsorbent dosage and initial pH, were kept constant to ensure the comparability of the two systems. Copper concentrations in the filtrate were measured using an atomic absorption spectrophotometer (AAS). Three experimental kinetic models were developed to describe the adsorption processes. The results indicate that the adsorption processes correlate best with Ho’s pseudo-second-order (PSO) kinetic model. Results revealed superior removal efficiency (9.77 mg g⁻¹) with the recirculation system using coarser particles compared to the batch system (7.82 mg g⁻¹) with finer particles, highlighting enhanced adsorption driving forces in the recirculation configuration. The fixed-bed column system with recirculation demonstrates superior efficiency over batch systems and reduced processing time compared to conventional fixed-bed configurations.