Effect of sintering temperature on the performance of Co₃O₄-coated bentonite clay based interfacial solar evaporators: A sustainable solution for desalination

In this work, we prepared interfacial solar evaporators using bentonite clay with two different sintering temperatures such as 1000 °C and 800 °C, which are named as C-S1 and C-S2 evaporators. The as-prepared evaporators are investigated experimentally under indoor solar steam generation under 1000 W/m 2 for 60 min. It results in an evaporation rate (EV) of 0.57 and 0.75 kg/m 2 h with C-S1 and C-S2 respectively. Further, cobalt oxide (Co 3 O 4 ) nanomaterial is coated over the top evaporative surface of C-S1 and C-S2 evaporators, called C-S3 and C-S4 evaporators. It shows an EV of 0.78 and 1.01 kg/m 2 h, respectively. Among all the evaporators, C-S4 evaporator exhibits higher evaporation rate due to the following reasons: (i) Mercury intrusion porosimeter (MIP) analysis reveals that C-S2 (800 °C) exhibits a 12.5% higher total porosity and a 7.5% smaller median pore diameter compared to C-S1 (1000 °C), directly facilitating enhanced capillary-driven water supply as evidenced by the higher evaporation rate (ii) the Co 3 O 4 coating over the top evaporative surface effectively uses the light energy usage for steam generation (iii) low thermal conductivity of the bentonite clay reducing the bulk water heating by hindering the heat flow (iv) increasing the surface roughness of the evaporator reducing the heat losses occurring via radiation (scattering and reflection). Additionally, C-S4 evaporator demonstrates an improved separation of dye molecules from dye water.