Polymer Inclusion membranes with long term-stability in desalination via membrane distillation

Abstract

This work explored the feasibility of implement of polymer inclusion membranes (PIMs) in the desalination industry. The methyltrioctylammonium oleate (MTOAO) was imbedded in a blend of polyvinylidene fluoride (PVDF) and polysulfone (PSU) prepared via Non-Solvent Induced Phase Separation (NIPS). The investigation encompassed the analysis of the chemical compositions and morphologies of the novel PIMs, with the objective of identifying the optimal MTOAO concentration within the PVDF/PSU matrix. The membrane characterizations revealed that addition of 33% of MTOAO in PVDF/PSU significantly increased the porosity (from 73.4% to 89.8%) and conferred a highly-hydrophobic character (WCA=123°). In direct contact membrane distillation experiments, PVDF/PSU doped with 33% of MTOAO resulted in a flux of 21.9 kg·m−2·h−1 and a 99.98% NaCl rejection where the salinity and temperature were 30 g/L and 70 °C, respectively. Remarkably, the inclusion of the MTOAO led 625% in transmembrane flux of. Moreover, PVDF/PSU load with 33% of MTOAO demonstrated a long-term stable performance over 10 weeks, whereas the PVDF/PSU membrane exhibited a poor stability in terms of salt rejection because of pore wetting caused by the poor hydrophobic character. Lastly, the performance of the process was positively assessed by desalting seawater from Atlantic Ocean.