Upcycling waste polyester into cobalt-molybdenum sulfide-decorated carbon foam for photothermal desalination and parametric optimization using Taguchi design of experiments

Photothermal desalination is an emerging solar-powered technique for water desalination. One of the primary open issues in the field is the development of new materials that guarantee high photothermal efficiency and evaporation rates. In this study, waste polyethylene terephthalate (PET) bottles are upcycled into carbon foam, which is then decorated with Co-Mo2S3 via hydrothermal synthesis to prepare a photothermal evaporator. The as-synthesized Co-Mo2S3/carbon foam (CF) achieved an average evaporation rate of 2.13 kg m-2 h-1 during a 1-h experiment under 1,000 W m-2 irradiation using a 3.5% NaCl solution, compared to 1.55 kg m-2 h-1 obtained for CF. A Taguchi orthogonal-array design of experiments (DOE) was used to optimize the effect of input parameters on the evaporation rate of saline water. The experimental design matrix shows a maximum water evaporation rate of 1.77 kg m-2 h-1 under real sunlight. Taguchi analysis presents the optimal operating parameters for the evaporation rate as follows: salinity 30 g L-1 (level 1), saline water pH 5 (level 2), and time 2 h (level 2). The statistical outcomes show that salinity is the main factor affecting the evaporation rate. This study addresses water scarcity and promotes the circular economy by transforming plastic waste into a valuable resource for producing clean water and provides deeper insight into the optimization of the operating parameters using statistical tools.