In this paper, a facile fabrication of enhanced direct contact membrane distillation membrane via immobilization of the hydrophilic graphene oxide (GO) on the permeate side (GOIM-P) of a commercial polypropylene supported polytetrafluoroethylene (PTFE) membrane is presented. The permeate side hydrophilicity of the membrane was modified by immobilizing the GO to facilitate fast condensation and the withdrawal of the permeate water vapors. The water vapor flux was found to be as high as 64.5 kg/m2·h at 80 °C, which is 15% higher than the unmodified membrane at a feed salt concentration of 10,000 ppm. The mass transfer coefficient was observed 6.2 × 10−7 kg/m2·s·Pa at 60 °C and 200 mL/min flow rate in the GOIM-P.

Membrane distillation (MD) is emerging as an important desalination technology that can operate at relatively low temperatures and can handle high salt concentrations. In this Article, we present microwave-induced membrane distillation (MIMD) where microwave radiation is used to heat the saline water for MD. Pure water vapor flux from MIMD was compared to that generated by conventional heating, and the enhancement reached as high as 52%. Because of the higher dielectric constants, flux enhancement was more significant at high salinity, and the mass transfer coefficient at 150 000 ppm was found to be nearly 99% higher than what was observed under conventional heating. Performance enhancement in MIMD was attributed to nonthermal effects such as the generation of nanobubbles, localized superheating, and breaking down of the hydrogen-bonded salt−water clusters. These effects were investigated using FTIR, ion mobility measurements, and dynamic light scattering. In addition, microwave heating consumed nearly 20% less energy to heat water to the same temperature. The combination of energy savings and higher flux represents a significant advancement over the state of the art for MD.

Membrane distillation (MD) is an emerging technology that has much potential in desalination and treatment of saline waste.

Membrane distillation (MD) is fast evolving as a desalination technology for high-salinity waters where scaling remains a major challenge. This paper reports the scaling reduction in carbon nanotube-immobilized membranes (CNIMs) and by the use of the antiscalant polyacrylic acid. High concentrations of CaSO 4 , CaCO 3 , and BaSO 4 were deliberately used to initiate scaling on the membranes. It was observed that after ten hours of operation in a highly scaling CaSO 4 environment, the CNIM showed 127% higher flux than what was observed on a membrane without the CNTs. The trends were similar with CaCO 3 and BaSO 4 , where the CNIM showed significantly improved antiscaling behavior. The normalized flux declination for CNIM was found to be 45%, 30%, and 53% lower compared to the pristine membrane with CaSO 4 , CaCO 3 , and BaSO 4 solutions, respectively. The use of antiscalant in the feed solution was also found to be effective in improving antiscaling behavior, which reduced salt deposition up to 28%, and the water vapor flux was 100% and 18% higher for the pristine polypropylene and CNIM, respectively. Results also showed that the presence of CNTs facilitated the removal of deposited salts by washing, and the CNIM regained 97% of its initial water flux, whereas the polypropylene only regained 85% of the original value.

Membrane distillation (MD) is a promising desalination technology for the treatment of high salinity water. Here, we investigated the fouling characteristics of produced water obtained from hydraulic fracturing by implementing a carbon nanotube immobilized membrane (CNIM) via direct contact membrane distillation. The CNIM exhibited enhanced water vapor flux and antifouling characteristics compared to the pristine membrane. The normalized flux decline with the polytetrafluoroethylene (PTFE) membrane after 7 h of operation was found to be 18.2% more than the CNIM. The addition of 1-Hydroxy Ethylidene-1, 1-Diphosphonic acid (HEDP) antiscalant was found to be effective in reducing the membrane fouling. The salt deposition on the membrane surface was 77% less in the CNIM, which was further reduced with the addition of HEDP in the feed by up to 135.4% in comparison with the PTFE membrane. The presence of carbon nanotubes (CNTs) on the membrane surface also facilitated the regenerability of the membrane. The results indicated that the CNIM regained 90.9% of its initial water flux after washing, whereas the unmodified PTFE only regained 81.1% of its initial flux after five days of operation.