Cotton-based bionic tree-shaped photothermal evaporator for extraction of heavy metals from river sediment

Abstract

Pollution of river sediments with heavy metals poses significant threats to both ecological and human health. Thus, in-situ extraction of heavy metals from sediments has emerged as a challenging and important research issue. To address this issue, a cotton-based bionic tree-shaped photothermal evaporator was designed to enhance water evaporation and facilitate heavy metals extraction from sediment porewater. The evaporator demonstrated a remarkable evaporation flux of 3.25 kg m-2 h-1 under 1 sun illumination. Over a 28-day solar-driven evaporative remediation (SDER) process, the removal efficiencies of total Pb and Cd were 17.4% and 29.9%, respectively. Importantly, the bioavailable fractions of residual Pb and Cd were also reduced by 46.3% and 25.0%, respectively. Furthermore, cabbage cultivation experiments to assess the practical efficacy of SDER showed that accumulation of Pb and Cd in cabbage roots was decreased by 66.0% and 46.3%, respectively, and accumulation in shoots was decreased by 57.2% and 55.7%, respectively. Thus, SDER was demonstrated to effectively reduce biological toxicity in sediment. This study introduces a novel approach that efficiently utilizes sunlight for the rapid extraction of heavy metals from sediment, presenting a promising general strategy for the low energy remediation of heavy metals-contaminated sediments.