Humanity is facing a global challenge of dwindling water resources and the situation is intensifying due to growing population leading to excessive water pollution. Nanofiltration is an important membrane-based technology for the production of clean and potable water for domestic and industrial setups. Hyper-cross-linked polyamide thin film composite nanofiltration (HCPA-TFC-NF) membranes have been fabricated by using multifunctional amine 1 (possessing two primary -NH₂ and two secondary -NH groups) and bifunctional terephthaloyl chloride 2 (TPC) through interfacial polymerization. The structure of the hyper-cross-linked polyamide network has been successfully confirmed by solid (CP-MAS) ¹³C NMR, XPS, AFM, FT-IR, elemental mapping, and EDX analysis. The membrane features such as surface morphology and hydrophilicity have been established by FE-SEM and water contact angle measurements. The FE-SEM analysis revealed the formation of uniform polyamide active layer on the surface of PS/PET support, and the pore structure of the membranes was tuned by studying the effect of curing temperature and curing time. The nanofiltration membranes efficiently rejected a series of divalent salts including MgCl₂, CaCl₂, Na₂SO₄, MgSO_4, and NaCl using cross-flow filtration setup. Based on the cross-flow filtration performance, the best conditions for the membrane fabrication were found to be curing temperature of 80 °C with a curing time of 1 h. The highest salt rejection was observed in case of MgCl₂ reaching to a value of 98.11% in case of HCPA-TFC-NF@M3 and it was found to be 97.45% in case of HCPA-TFC-NF@M2 while the rejection of MgCl₂ was reduced to 94.59% in case HCPA-TFC-NF@M1. HCPA-TFC-NF@M2 showed NaCl rejection of 87.36%. The hydrofluoric acid treatment of HCPA-TFC-NF-M2 increased the water flux while keeping the rejection high. The HCPA-TFC-NF@M2 showed a rejection of >99% for EBT with a permeate flux of 75 LMH.

Understanding the importance of reclaiming water from a huge oily wastewater stream generated during the drilling of oil in the petroleum industry and mitigating membrane fouling, a polymeric-inorganic nanocomposite membrane was fabricated with self-cleaning properties. The photocatalytic TiO₂ nanoparticles were embedded in the polyvinylidene fluoride (PVDF) matrix during wet phase inversion. To enhance the separation potential and photocatalytic activity of TiO₂ nanoparticles, a conjugated polypyrrole (PPy) was grown on the membrane through oxidative polymerization leading to an active layer composed of PPy@TiO₂ nano-photocatalyst. The study of membrane wettability revealed the hydrophilic and underwater superoleophobic nature of the PPy@TiO₂/PVDF membrane. The PPy@TiO₂/PVDF membrane was applied for treating water-containing emulsified oily feed. Different types of feeds contaminated by different oils such as motor oil, diesel oil, and crude oil were studied. The separation efficiency of the PPy@TiO₂/PVDF membrane stayed above 99% as the membrane allowed only water to permeate while oil was rejected. The permeate pure water flux was found to be dependent upon feed pressure and the nature of oil in the feed. While keeping the separation efficiency constant at 99%, the flux was decreased with increasing concentration of oil in the feed which is attributed to the fouling of the membrane. The fouled membrane was photo-catalytically cleaned by exposing the fouled PPy@TiO₂/PVDF membrane to solar-simulated visible light as the surface features of the cleaned membrane completely resembled that of the pristine PPy@TiO₂/PVDF membrane.

Ceramic membranes offer significant potential for addressing challenging and harsh wastewater streams such as produced water (PW) and surfactant-stabilized oil/water (O/W) emulsions. This study focuses on developing a stable and a uniformly structured active layer solely composed of MIL-125-NH₂ MOF on a ceramic Alumina support. A stable covalent bonding approach was employed using interfacial polymerization, with isophthaloyl chloride (IPC) acting as the organic crosslinker during interfacial polymerization reaction. Three distinct MIL-125-NH₂ decorated membranes M50, M75, and M100 were prepared by using varying MOF concentrations. Surface wettability analysis of the membranes indicated that the MIL-125-NH₂ MOF active layer displayed super-hydrophilic characteristics in the air (water contact angle = 0°) and super-oleophobic characteristics underwater (oil contact angle = 161.5°). In oil separation experiments, all the MIL-125-NH₂ deposited membranes displayed >99% oil rejection. Among the fabricated membranes, M50 demonstrated the highest water flux of 2100 Lm⁻² h⁻¹ under a transmembrane pressure of 2 bar. The MIL-125-NH₂ MOF deposited membranes also showed stable performance under longer-run filtration. This study would be a simple and effective method of decorating MOFs as an active layer on ceramic support for efficient O/W emulsion separation and desalination applications.