Multi-effect synergistic induction of unsaturated MnOx on sandy sediment for enhanced manganese adsorption and byproduct resource recovery in solar evaporation

Abstract

The efficient removal of Mn(II) from wastewater is crucial for safeguarding water quality, yet existing adsorbents face significant challenges, including high costs, poor resistance to ionic interference, and scalability limitations. This study addresses these challenges by utilizing abundant natural sandy sediment (SS) as a substrate to load unsaturated MnO_x via in-situ oxidation, creating a novel adsorbent (MOSS). MOSS exhibits a remarkable Mn(II) adsorption capacity of 1.35 mg·g^-1, representing a 6-7-fold increase compared to SS. The unsaturated nature of MnO_x in MOSS enables effective co-separation of transition metals, further enhancing its utility. It is observed that redox reactions, metal complex formation, and ions exchange processes may play a significant role in further enhancing its adsorption capacity and selectivity. In dynamic filtration tests, MOSS effectively maintains Mn(II) removal below 0.1 mg·L^-1 after continuous effluent and retains over 50% separation efficiency after three regeneration cycles. And the byproducts of Mn(II) adsorption were successfully repurposed as a photo-thermal material for solar evaporator, achieving an evaporation rate of 1.97 kg·h^-1·m^-2 and a conversion efficiency of 98.64%. This study presents a cost-effective, scalable, and sustainable method for Mn(II) removal, while offering novel insights into the high-value utilization of MOSS byproducts for environmental remediation and resource recovery.