Development of Advanced Photothermal Materials for Rapid Fertilizer Brine Evaporation and Sustainable Water Reuse in Controlled Environment Agriculture

Abstract

Ensuring sustainable water management is critical in Controlled Environment Agriculture (CEA) because fertilizer-rich wastewater generated from fertigation needs treatment before discharging into the environment. Conventional systems rely on evaporation ponds to naturally evaporate brine; however, they are inefficient, require extensive land, suffer from slow evaporation rates, and cause scaling issues with hard waters. To address these challenges, a photothermal MXene-candle soot composite foam-based interfacial solar steam generation (ISSG) system has been developed as a high-efficiency, low-cost alternative. This system accelerates brine evaporation and freshwater extraction, allowing continuous reuse of the same discharge water. Unlike open evaporation ponds, the proposed system enables localized and contained evaporation without direct brine exposure to surrounding soil, thereby reducing environmental contamination. The composite foam, which integrates MXene nanosheets and candle-soot particles, exhibits enhanced broad-spectrum light absorption (63.28% in dry conditions and 81.71% in wet conditions) while significantly improving water transport and salt resistance. Solar evaporation experiments confirmed an evaporation rate of 0.65 kg m^–2 h^–1 (40.81% efficiency) for fertilized brine versus 1.11 kg m^–2 h^–1 (69.68% efficiency) for seawater with 85% performance retention over 25 cycles. Water quality analysis demonstrated the suitability of the distillate for hydroponic reuse.