Synergistic thermal energy storage and enhanced evaporation in a u-shaped double-slope solar distiller using Zea mays-derived self-poled ZnO–Ag–MCM-41/activated carbon nanocomposite: A 4E experimental analysis

The planet is constantly threatened by a variety of issues, such as wastewater contamination and freshwater scarcity. Global climate change and population increase due to fast urban and industrial development are two of the main causes of these issues. Low yield per distillate, limited thermal energy storage capacity, irregular solar radiation, and ineffective pollution removal during distillation have all hindered the practical application of solar desalination, despite it being a recognized sustainable and ecologically friendly method of producing freshwater. ZAMA nanocomposite consists of self-poled ZnO–Ag coated on Zea mays -derived MCM-41/activated carbon. The ZAMA nanocomposite and iron–silver balls were incorporated into a U-shaped basin double-slope solar still (IUDSS-ZAMA) to enhance all four 4E performance metrics, enabling efficient passive solar desalination. The ZAMA nanocomposite was synthesized using sol–gel and co-precipitation techniques and subsequently characterized using standard analytical methods. Optical characterizations revealed a decrease in band gap energy from 3.2 eV to 2.8 eV, which led to improved photocatalytic activity and visible light absorption efficiency. Under both summer and winter climatic conditions, the following distiller configurations were analyzed in this study: the conventional double-slope solar still (CDUSS), ZnO–MCM-41/activated carbon (ZMAC), Ag–MCM-41/activated carbon (AMAC), and ZnO–Ag–MCM-41/activated carbon (ZAMA). The freshwater productivity, evaporation rate, thermal efficiency, photocatalytic degradation efficiency, and 4-E indicators (Energy, Exergy, Economics, and Environment) of the different kinds of stills were then systematically analyzed. The incorporation of iron–silver balls in the UDSS (IUDSS) improved water purification, with the ZAMA-integrated IUDSS showing better performance than the other configurations. In comparison to CDUSS, which produced 5.29 L/day, the ZAMA-integrated IUDSS produced a maximum of 7.52 L/day in the summer and 7.34 L/day in the winter, a 42.2% increase. Furthermore, thermal efficiency reached 62.3% and the evaporation rate rose from 0.95 kg/m 2 /h to 1.35 kg/m 2 /h. With IUDSS-ZAMA combinations, energy efficiency increased from 7.8% with CDUSS to 12.5%. In summary, after 120 min, the ZAMA nanocomposite decomposed over 91% of the methylene blue (20 mg/L), but the ZAMA alone only degraded 31%. The environmental assessment of these tests found a 35% decrease in CO 2 emissions, and the economic assessment found a 27% decrease in the cost of producing freshwater. When combined with ZnO, Ag nanoparticles, mesoporous MCM-41, thermal energy storage spheres, activated carbon significantly improved solar absorption, heat retention, evaporation, fresh water production, and pollutant degradation related to solar distillation. In isolated, water-scarce places, the ZAMA-IUDSS system offers a scalable, economically feasible, and environmentally friendly solution to the dual problems of solar desalination and wastewater treatment.