Bionic Solar-Powered Heavy Metal Trap for Eco-Friendly Sludge Drying and Simultaneous Electricity Generation

Sludge, a rapidly accumulating by-product of wastewater treatment worldwide, holds great potential as an ideal coal substitute following dehydration and drying. Here, we present a solar-powered heavy metal trap (SPHT) designed for sludge drying and concurrent electricity generation, validated using a PPy-coated super hydrophilic wood (PPy-H-Wood). The SPHT in this work uniquely integrates sludge drying, heavy metal removal, and electricity generation characteristics. The indoor experiments demonstrate a rapid decrease in sludge water content from 90 % to 31 %, accompanied by an impressive 94 % reduction in free heavy metal content achieved through synergistic adsorption and evaporation. Harnessing the hydrovoltaic effect, the SPHT can generate an initial potential of 0.10 V. By monitoring this hydrovoltaic potential, the sludge drying process can be self-detected. Furthermore, we have constructed a 20 m² pilot-scale SPHT device, achieving a sludge drying ratio of over 80 % and a heavy metal removal ratio exceeding 75 %. Life cycle assessment (LCA) indicates that replacing traditional heat drying technology with the SPHT can cut CO₂ emissions by ∼98 %. Our work provides an eco-friendly approach to sludge disposal and resource recovery, and may inspire more innovative solutions supportive of global Sustainable Development Goals.