Water desalination using <scp> CaCO ₃ </scp> /blend of polyphenylene oxide and polystyrene mixed matrix membranes in a direct contact membrane distillation ( <scp>DCMD</scp> ) unit

Abstract The present study examines the impact of integrating hydrophobic calcium carbonate (CaCO 3 ) nanoparticles into porous membranes composed of a polyphenylene oxide (PPO)/polystyrene (PS) blend on desalination performance. CaCO 3 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% CaCO 3 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% CaCO 3 nanoparticles exhibited the highest flux of 34.92 kg/m 2 h (~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 CaCO 3 filler was improved. Highlights Adding hydrophobic CaCO 3 to neat polymer, enhanced DCMD performance. The fouling and scaling resistance of the MMM were better than neat polymer. MMMs showed a rejection higher than 99.5% due to non‐wetting effect of filler. Maximum surface porosity and flux was observed for 2.0 wt% of filler loading. Maximum flux was observed in sample with 2.0 wt% filler loading.