Solar-driven purification of highly polluted saline wastewater into clean water by carbonized lotus seedpod

Abstract

Purifying wastewater is one of the most practical methods to respond the global clean-water crisis. Among the various wastewaters, saline wastewater is hard to be treated by common water treatment technologies due to its high salinity. Interfacial solar water evaporation is a promising method for saline wastewater purification by completely separating water and solute only by renewable solar energy. Herein, inspired by lotus seedpods’ natural bi-functional structures: vascular bundles for water transport and “air chambers” for thermal insulation, we report a carbonized lotus seedpod for solar-driven saline wastewater decontamination. After photothermal evaporation, the COD (initial value: 365.3 mg L-1) removal efficiency of actual saline wastewater reaches 84.6%. And the concentrations of Na+, K+, Ca2+, and Mg2+ in condensate water reduced by approximately 3 orders of magnitude. These results demonstrate the talent of low-cost lotus seedpods ($3/kg) for solar wastewater purification, and provide inspirations for development of solar thermal-conversion devices.