Solar steam generation is an environmentally friendly water treatment method that produces clean water using solar energy. However, it is still a challenge to effectively prevent the performance deterioration when most photothermal conversion materials are used to evaporate high-concentration salt-containing wastewater or strong acid/alkali solution. Herein, a stable and effective solar evaporator is designed using natural sugarcane, where sucrose is simply dehydrated into carbon particles by hydrothermal reaction in sulfuric acid. With a honeycomb structure, it not only enables water transport capacity but also promotes sunlight absorption. Sulfuric acid hydrothermal carbonized sugarcane (SHCSC) can reach up to 95.36% solar absorption in a wide wavelength range (200–2500 nm) and a high evaporation rate of 2.32 kg m−2 h−1 under 1 sun illumination. More importantly, SHCSC has an excellent adsorption capacity with ion removal rate of 99.9% even under artificial wastewater containing 1000 mg L−1 of mixed metal ions. SHCSC also can perform efficiently and stably at a high evaporation rate above 2.2 kg m−2 h−1 in strong acidic or alkaline wastewater. These findings suggest that SHCSC can be potentially applied to the efficient harvest of clean water from the high-concentration wastewater containing acid, alkali, and mixed metal ions.
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