Enhancement of Heat and Mass Transfer in the DCMD Process Using UV-Assisted 1-Hexene-Grafted PP Membranes

The two main challenges for industrial application of membrane distillation (MD) are mitigation of temperature polarization and reduction of high-energy consumption. Despite the development of advanced materials and the configuration improvements of MD units, membrane surface modification is still one of the alternatives to overcome temperature polarization and improve membrane performance. This work reports a novel and simple method to modify the physical and chemical properties of the polypropylene membrane in order to improve its performance in direct contact membrane distillation (DCMD). The membrane was grafted by polymerization with 1-hexene, UV irradiation, and benzophenone as a photoinitiator. A grafting degree of up to 41% was obtained under UV irradiation for 4 h. The performance of the modified membrane in DCMD was evaluated at different temperatures and salt concentrations in the feed. First, it was found that there was an increase of the vapor permeate flux in the MD process within the range of tested temperatures and salt concentrations. The results were analyzed in terms of the physical properties of the membrane, the transport phenomena, and the thermal efficiency of the process. Theoretical analysis of the results indicated that grafting increased the transfer coefficients of mass and heat of the membrane. Hence, it improved the membrane performance and the thermal efficiency of the DCMD process.