Exploring the application of solar irradiation in driving a stand-alone membrane distillation unit

Abstract

This work presents the evaluation of a solar energy-driven membrane distillation process with significant promise for generating high-quality water from seawater, brackish water, and hard groundwater. In addition, PVDF/EPS blended membranes were developed through the addition of triacetin, silicone oil, and polydimethyl siloxane (PDMS). Scanning electron microscopy revealed that with immersion in an ethanol–water coagulation bath, the porosity of the membranes increases with the triacetin membrane exhibiting the highest porosity as seen on the SEM and supported by the permeate fluxes. The addition of the PDMS and silicone oil led to an increase in contact angle with the membrane modified with PDMS having a contact angle of 109 ± 3.5 and 108 ± 2.63 and the silicone oil membrane had a contact angle of 101.39 ± 1.73 and 101.1 ± 1.28. The triacetin membrane had better permeate flux of 9.19 kg/m²h compared to PDMS and silicone which had 4.53 and 5.52 kg/m²h respectively at the highest operational temperature of 65 °C. The developed solar irradiation device was able to double the ambient air temperature during the MD process and the highest recorded temperature was 62 °C. Heat generation was dependent of environment temperatures; however, the peak temperature was maintained for a period of 3 h after the environmental temperature had started declining. The salt rejection for synthetic NaCl solution, hard groundwater and seawater was 99 %. The findings of this study demonstrated that the readily available solar energy can be directly incorporated to heat feedwater in a scalable stand-alone setup and subsequently be deployed in highly irradiated regions.