A biomimetic interfacial solar evaporator for heavy metal soil remediation

Interfacial solar evaporation is a sustainable and efficient way to enhance water evaporation during seawater desalination and wastewater treatment. In this work, this concept is applied for heavy metal (HM) soil remediation, which is a major global challenge currently limiting food production and endangering human health. Inspired by natural transpiration remediation processes in plants, here a tree inspired evaporator structure is used to accelerate the extraction of HM containing liquids from soil. Coating of simple biomimetic leaf structures with reduced graphene oxide (rGO) can realize a high evaporation rate (3.1 kg m−2h−1) under 1.0 sun illumination. Four-week indoor solar evaporation tests of the evaporator shows that evaporation performance is generally stable and HMs (As, Cd, Cr, Pb, and Zn) in soil pore water are reduced to varying degrees. After solar driven evaporative remediation (SDER) a plant assay in the treated soil shows that relative to an untreated control soil, HM content in broccoli roots decreases by 37.2, 56.4, 25.9, 46.3 and 26.9% for As, Cd, Cr, Pb and Zn, respectively. This work successful demonstrates a new direction in solar evaporator design by enhancing water evaporation to achieve efficient soil contaminant remediation.