Theoretical adsorption modeling and simulation of toxic arsenic ions removal in batch and continuous systems using Mn/Mg/Fe layered double hydroxides

Groundwater contaminated by arsenic (As) presents an increasingly important challenge in many countries throughout the world because of the danger it poses to the health of humans, flora and fauna. The main challenge in research on removing As from groundwater is the need to test under several experimental conditions to optimise the parameters for adsorption column studies. This study aims to develop a robust mathematical model that enhances the operational conditions of dynamic adsorption columns based on limited laboratory experimental data. In this study, after batch experiments, two columns experiment with a synthesized layered double hydroxide (Mn/Mg/Fe-LDH) adsorbent were applied to investigate the adsorbent’s performance in removing As ions, specifically As(III) and As(V), from synthetic water. Using the same experimental conditions (filtration rate 0.75 m/h, bed height 0.09 m, and inlet As concentration 0.33 mg/L), the exhaustion time for Mn/Mg/Fe-LDH in the removal of As(III) amounted to 280 days, which was longer than 180 days for As(V). The dynamic adsorption column model, which utilized the pore diffusion model (PDM) in conjunction with the Sips equation parameters, effectively simulated the breakthrough curves from the column experiments. The breakthrough curves were successfully simulated for a range of adsorption conditions such as bed height of 0.045–0.135 m, filtration rate of 0.75–1.25 m/h, and initial As(V) concentration of 0.033–3.333 mg/L. Characterization of the Mn/Mg/Fe-LDH adsorbent before and after the adsorption process indicated that the main mechanisms for As(III) and As(V) removal included oxidation-couples adsorption and reduction-coupled oxidation, respectively. • Column packed with Mn/Mg/Fe-LDH were investigated in As(III) and As(V) removal. • Oxidation/reduction-coupled adsorption as the main As(III)/As(V) removal mechanisms. • Removal process was well analysed using the integration of PDM and Sips equation. • Simulation of As removal process is successfully conducted with limited results.