Techno-economic and environmental assessment of four clay-based adsorbents in a solar-driven adsorption desalination system for enhanced energy efficiency and sustainability

This study addresses the challenges of conventional desalination technologies, including high energy consumption, environmental impact, and economic constraints, by proposing a solar-powered desalination/cooling system that relies on waste heat, while testing the heat recovery (HR) option. For the first time, four clay adsorbents were evaluated: raw bentonite (Bent), Bent/HCl, Mont/HCl, and Bent/CaCl₂. An integrated annual evaluation of performance, economic feasibility, and environmental impact was conducted using MATLAB and TRNSYS, including specific daily water production (SDWP), coefficient of performance (COP), gain ratio (GOR), and specific cooling power (SCP), comparing the presence/absence of heat recovery. Bent/CaCl₂ was found to be superior in terms of performance and cost. In summer, with HR activated, SDWP was 28.9 m³//ton per day (TPD) and GOR was 0.68; While without HR, the SDWP was 11.6 m³/TPD, the SCP was 328 W/kg, and the COP was 0.48. The optimal water cost was $4.7/m³ with solar in summer and $0.88/m³ with waste heat, with costs in June reduced by 35.5 %, 35 %, 38 %, and 40 % for Bent/CaCl₂, Mont/HCl, Bent/HCl, and raw Bent, respectively, thanks to HR. Although the cost is higher than some technologies (such as ED, MD, AD-HR-SG, and MCV), the system demonstrates a clear environmental advantage: up to 1,228 tons of CO₂ can be avoided over 30 years compared to MSF, strengthening its viability as a low-carbon alternative. The selection of the absorbent material and the control of the heat transfer rate remain critical factors to maximize performance and reduce cost, especially when a strong solar energy source or waste heat is available.