Surface water removal of Aluminum(III), Iron(III) and Manganese(II) using sustainable natural serpentinite mining tailings, proof of concept

To remediate surface water as the Doce River and spring waters from Minas Gerais, Brazil, this study examined the possibility of natural serpentinite mining tailings as a sustainable alternative for removing aluminum (III), iron (III), and manganese (II). The study used a Box-Behnken experimental design to examine how initial metal concentration, adsorbate dosage, and adsorption time affect metal removal effectiveness. Results demonstrated impressive performance, with removal rates exceeding 80 % for Al(III) and Fe(III) within the initial 5 min, and 60 % for Mn(II) within 30 min. This study delves deeper into the removal mechanisms, kinetics, adsorption isotherms and characterization identify physisorption and chemisorption pathways in which complex formation with released OH- groups and ion exchange with Mg(II) from serpentinite emerged as key contributors to the removal process. Furthermore, ion metal adsorption and regeneration cycles were assessed, exhibit sustained removal efficacy without notable capacity reduction. Each cycle shows an average metal adsorption capacity of 0.32 mg g- 1 and an average Mg(II) release capacity of 0.98 mg g- 1. Remarkably, the application of serpentinite successfully lowered the metals content of the Doce River and spring water to drinkable standards. A batch and continuous process is proposed for scaling-up serpentinite's metal adsorption. Overall, this study shows serpentinite's potential as a foundation for sustainable and cost-effective methods to treat surface water contamination with Al(III), Fe(III), and Mn(II).