Investigation of sustainable waste-derived adsorbents for arsenic and copper in water treatment

Abstract

Arsenic contamination in drinking water is a global issue, affecting millions and posing serious health risks such as cancer and neurological disorders. This is particularly critical in communities relying on groundwater. This research explores using mussel shells and agricultural waste, including date seeds and orange peels, as sustainable adsorbents for removing arsenic and copper from water. Nanoparticles were incorporated into calcined mussel shell powder and biochars derived from these biomass wastes to enhance adsorption capacity. The adsorbents were characterized to evaluate their surface properties, and adsorption mechanisms were studied to understand their effectiveness. Batch experiments were conducted to examine the effects of pH, adsorbent dosage, initial metal concentrations, and contact time. These experiments identified optimal conditions for maximizing removal efficiency. Statistical methods were used to optimize the adsorption processes. The results showed that modified mussel shells have high arsenic adsorption potential, while TiO₂-modified orange peel biochar performed well as a low-cost option for copper removal. Both biochars also demonstrated strong copper adsorption performance. Kinetic and isotherm models helped describe the rate and equilibrium behavior of arsenic and copper adsorption. Thermodynamic analysis indicated that the adsorption processes were spontaneous and endothermic. The mechanisms of arsenic removal by mussel shells were further studied, considering ionic strength, surface charge, and functional groups using various analytical techniques. Beyond batch tests, column studies were performed using mussel shells in point-of-use (POU) filtration systems. These tests assessed exhaustion capacity, the influence of co-existing ions, and reusability. Breakthrough curve analysis showed how initial arsenic concentration, flow rate, and adsorbent mass affected performance. Modified mussel shells demonstrated superior arsenic removal in POU cartridges compared to commercial activated carbon. This study offers a sustainable and cost-effective approach to arsenic removal, particularly for remote communities with limited access to centralized water treatment, by repurposing mussel shells and agricultural waste as effective adsorbents.