Boosting adsorption of heavy metal ions in wastewater through solar-driven interfacial evaporation of chemically-treated carbonized wood.

Once the adsorbent is selected, almost introducing larger specific surface area and more surface functional groups becomes the only way to improve its adsorption performance. However, this approach is generally limited in practical application for intricate and costly engineering steps. Herein, we provided a novel avenue for boosting adsorption activities towards specific metal ions in wastewater. Solar-driven interfacial water evaporation produces the localized temperature field and concentration gradient of metal ions inside small pores, endowing with a new sorption mechanism. By using chemically-treated carbonized wood as all-in-one solar absorption and metal ion adsorption system, we achieved higher water evaporation rate and heavy metal ion removal efficiency than carbonization-only wood reported previously. In particular, this system exhibited a strong dependence of specific metal ion adsorption capacity on solar intensity. Pb2+ adsorption capacity was enhanced by over 225% with the solar intensity increased to 3.0 kW·m-2. This could originate from the formed temperature field localized specially on the surface of adsorbents that not only induces Pb2+ concentration gradient near to solid-liquid interface but also activate inactive adsorption sites. Besides, the chemical-treated & carbonized wood showed excellent cyclic stability and can be directly utilized for wastewater treatment, recovery and reuse.