A Multistage Wastewater Purification System for the Effective Removal and Conversion of Water-Soluble VOCs: Leveraging White-Body Photothermal Evaporators

A novel multistage wastewater purification and conversion system (MWPCS) was designed to effectively remove and convert water-soluble dinitrotoluene (DNT). The MWPCS comprises a unique configuration, including the U-shaped solar evaporator (U-SE) with a white body, a polyelectrolyte multilayer (PEM)-coated roof dome, and a catalytic filter. The U-SE achieved a DNT removal efficiency (RE) of 78.5%, constituting the first stage of purification. Upon integration of the PEM-coated roof dome, the RE increased to 84.7%, representing the second purification capability of MWPCS. Additionally, the catalytic filter facilitated the conversion of toxic DNT into valuable diaminotoluene (DAT) with a conversion rate of 94.2%, marking the third purification stage of MWPCS. The U-SE with a white body exhibited a water evaporation rate of 2.17 kg/m2 h, which decreased to 1.37 kg/m2 h within the dome. However, with improved ventilation provided by the dome with holes, the evaporation rate increased to 1.85 kg/m2 h. A high water evaporation rate-based MWPCS is anticipated to be a multistage wastewater purification system capable of effectively removing and converting water-soluble DNT.