Water desalination using CaCO3/blend of polyphenylene oxide and polystyrene mixed matrix membranes in a direct contact membrane distillation (DCMD) unit

The present study examines the impact of integrating hydrophobic calcium carbonate (CaCO3) nanoparticles into porous membranes composed of a polyphenylene oxide (PPO)/polystyrene (PS) blend on desalination performance. CaCO3 filler was added to polymeric solution at concentrations of 2-10 wt% and prepared samples were characterized using ATR-FTIR, FE-SEM, EDX, AFM, liquid entry pressure (LEP), contact angle, and porosity measurement analyzes. Surface porosity of the samples was determined by the Digimizer software. The desalination performance of the membranes was evaluated using a laboratory-scale direct contact membrane distillation (DCMD) unit. Results showed that nanoparticles did not affect the membrane's finger-like structure but altered the surface pore size and porosity. Adding 10 wt% CaCO3 to the membrane caused the maximum surface pore size to decrease from 35.4 to 17.4 nm, leading to an increase in the LEP value from 0.9 to 2.1 bar. The MMM with 2 wt% CaCO3 nanoparticles exhibited the highest flux of 34.92 kg/m(2)h (similar to 20% higher than pure membrane) due to its higher surface porosity, also the rejection was achieved above 99.9%. Physical properties along with thermal efficiency and temperature polarization coefficient of the prepared membranes were compared. Fouling properties and scaling of the prepared membranes were investigated using different organic and inorganic solutions. Results showed that fouling resistance of samples containing CaCO3 filler was improved.