Evaluating environmental implications of dragon fruit- in-fused TiO2 coating in solar distillation

Addressing the critical issue of hydrological insufficiency and aqueous resource depletion in agrarian and metropolitan environments, this study introduces an innovative approach to augmenting the operational efficacy of a solitary solar distillation apparatus (SSD). The proposed methodology focuses on the design and rigorous assessment of modifications to optimize the SSD productivity. A critical component of this methodology involves the implementation of an advanced matte black coating, engineered with a chromogenic compound, titanium dioxide nanoparticles (TiO2 NPs), and Hylocereus polyrhizus (dragon fruit peel extract, DFPE), applied to the absorber plate of the solar distillation unit. The efficacy of conventional solar stills (CSS) and single solar distillers (SSDs) was assessed across varying DFPETN compositions (10 %, 20 %, 30 %, 40 %). Ultraviolet–visible (UV–Vis) spectroscopy analysis revealed that the coating, with peak absorbance in the 300–500 nm range, significantly augments the photothermal efficiency of TiO2. Comprehensive evaluations encompassing thermal, energetic, ecological, and economic parameters were conducted, comparing coated SSDs with CSS, both with and without DFPETN. The DFPETN@30 % coating yielded a remarkable daily distillate output of 9.018 kg/m2 in summer and 7.938 kg/m2 in winter, compared to 2.698 kg/m2 (summer) and 2.528 kg/m2 (winter) for the CSS. This represents a substantial 178.9 % enhancement in SSD performance. Furthermore, the DFPETN@30 % coating significantly improved system efficacy, achieving a 838.87 % increase in summer and a 34.69 % increase in winter. Exergy efficiency for the coated SSD reached 5.80 %, compared to 8.23 % (summer) and 7.14 % (winter) for the CSS. From an environmental standpoint, the 30 % DFPETN-coated solar still decreased carbon emissions to about 12 tons of CO2 per year. From a financial perspective, it reduced drinking water production costs to $0.24 per liter in summer and $0.10 per liter in winter, showing strong economic benefits.