Clean water generation through a multifunctional activated carbon-TiO2 interfacial solar distillation system

Abstract

Solar distillation is emerging as an environmentally friendly and energy-effective technology for clean water generation. However, bulk water heating and the possibly complex composition of water matrices of source water could undermine the system efficacy. In this study, an interfacial evaporation device consisting of activated carbon combined with P25 TiO₂ as the top layer and polyethylene foam as the bottom layer (AC-P25/foam device) was established. With the excellent optical absorbance of AC and the heat localization effect contributed by the PE foam, the evaporation rate (r_evp) of the device (r_evp = 2.1 kg m⁻² h⁻¹) was improved by 209% and 71% compared with that of the water-only (r_evp = 0.68 kg m⁻² h⁻¹) and conventional evaporation (i.e., submerged AC-P25) systems (r_evp = 1.23 kg m⁻² h⁻¹), respectively. The reusability test showed the stable evaporation performance of AC-P25/foam within 7 cycles; this interfacial evaporation was also found to be less affected by suspended solids in water due to a reduction in the influence of light scattering. The AC-P25/foam device not only possessed photothermal ability for water distillation but was also able to prevent enrichment of volatile organic compounds (i.e., phenol) with ∼95% removal efficiency through adsorption and photocatalytic reactions under illumination. Additionally, an outdoor solar distillation test performed with synthetic saline water demonstrated the desalination ability of the AC-P25/foam device, with the concentrations of all ions in the distilled water ≤3.5 mg L⁻¹, far below the drinking water guideline value provided by the World Health Organization. The materials of the AC-P25/foam photothermal device are readily available and easily fabricated, showing the practical feasibility of this device for clean water generation.