Interfacial solar steam generation (ISSG) has recently received much attention as a low-carbon-footprint and high-energy-efficient strategy for seawater desalination and wastewater treatment. However, achieving the goals of a high evaporation rate, ecofriendliness, and high tolerance to salt ions in brine remains a bottleneck. Herein, a novel hydrogel-based evaporator for effective solar desalination was synthesized on the basis of sodium alginate (SA) and carboxymethyl chitosan (CMCS) incorporating a carbon nanotube (CNT)-wrapped melamine sponge (MS) through a simple dipping-drying-cross-linking process. The hydrogel-based evaporator reaches a high evaporation rate of 2.18 kg m-2 h-1 in 3.5 wt % brine under 1 sun irradiation. Furthermore, it demonstrated excellent salt ion rejection in high-concentration salt water. Simultaneously, it exhibits excellent purification functionality toward heavy metals and organic dyes. This study provides a simple and efficient strategy for seawater desalination and wastewater treatment.