Photothermal air gap membrane distillation for the removal of heavy metal ions from wastewater

As the world population grows, pure water becomes increasingly scarce, making wastewater treatment necessary. However, the processes currently used to treat industrial wastewater are generally energy-intensive, highlighting the need to develop environmentally friendly wastewater treatment technologies. To address this issue, a photothermal air–gap membrane distillation system was developed and tested for the first time to remove heavy metal ions from wastewater. Activated carbon particles at different concentrations were used in the prepared polyvinylidene fluoride membranes as components for solar energy recovery. Zinc, one of the most common heavy metals in industrial wastewater in the United Arab Emirates, was used as a model contaminant in this study. The results showed that the use of Activated Carbon particles to modify Polyvinylidene fluoride membranes can significantly improve solar absorption (97%) and porosity (60.6%), resulting in a permeate flux of 0.32 L/m²h and a rejection of 97% of Zn ions. Additionally, the optimized membrane was tested using a synthetic heavy metal solution and showed high rejection rates for most of the tested heavy metals (Zn²⁺, Fe³⁺, Cu²⁺, Cr³⁺, and Ni²⁺), which can be potentially used in the industrial heavy metal removal process. The developed photothermal water treatment system can provide a highly efficient and scalable water treatment process.