Construction of a reduced graphene oxide/polyvinyl alcohol (PVA)-natural rubber (NR) porous rubber sponge toward solar-driven sustainable water purification

Solar-driven evaporation is an environmentally benign and sustainable technology to address the global water crisis. The abundant and renewable solar energy as its sole input energy, thus leading to zero-carbon emission and minimum environmental impact. Thus, in this work, a hydrophilic reduced graphene oxide (rGO)/polyvinyl alcohol (PVA)-natural rubber (NR) porous rubber sponge was obtained by emulsion ice template and vulcanizing at high temperature. The cross-linked NR rubber and the robust PVA endow rGO/PVA-NR sponge with excellent flexibility integrated outstanding mechanical robustness. The water evaporation rate of the resultant rGO/PVA-NR evaporator can reach up to 2.11 kg·m−2·h−1 under 3 sun illumination. Moreover, benefitting from the multi-scale porous structure and hydrophilicity of the rGO/PVA-NR sponge, water is continuously transported from the bulk water to the evaporation surface in whole evaporation process, ensuring a continuous water supply and salt self-cleaning. Moreover, the results of practical solar-driven interfacial evaporation under outdoor conditions indicated that rGO/PVA-NR evaporator has overall multifunctional purification for inorganic ions and wastewater contaminated with organic dyes. This investigation provides a convenient and environmentally friendly strategy toward developing high-performance solar steaming technologies based on rubber sponge for effective water purification to address the global water crisis.