Advanced solar-driven hydrogel sponge for efficient heavy metal wastewater purification and clean water production through interfacial evaporation

Abstract

Solar-driven interfacial evaporation (SDIE) technology represents a promising solution for freshwater harvesting, characterized by its cost-effectiveness, eco-friendliness, and sustainability. Nevertheless, achieving efficient removal of heavy metal ions during the SDIE process remains a significant challenge. In this study, we present a cost-effective method to construct a hybrid hydrogel evaporator by incorporating the konjac glucomannan (KGM) and reduced graphene oxide (rGO) into a polyvinyl alcohol (PVA) network. The hybrid hydrogel evaporator features a three dimensional layered structure, full spectrum absorption capability, high stability and inherent salt diffusion ability. These characteristics enabling an evaporation rate of 1.61 kg m−2 h−1 from wastewater across varying pH values (2–12) and high salinity levels (1 kW m−2). Significantly, the hybrid polymer network within the hydrogel is rich in -OH groups, enabling concurrent wipe off heavy metal ions and organic dyes from wastewater. The results in a ten thousand times reduction in the concentration of heavy metals such as Cr3+, Mn2+, Cu2+, Zn2+, and Pb2+ in the wastewater. This study provides new insights into solar evaporation technology and contributes to addressing challenges related to water scarcity.