Modification of active membrane surface is an auspicious way to enhance the membrane performance. In our study, commercially available composite polyamide Nanofiltration (NF) membrane was modified by immobilizing silver doped TiO₂ (Ag-TiO₂) nanoparticles. Ag-TiO₂ with different nanoparticles concentration (0.05, 0.1, and 0.5 wt. %) were coated on the surface of membrane by dip coating method. The evidence of successful coating was evaluated by Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) and Atomic Force Microscopy (AFM) images. Moreover the Fourier Transform Infrared Spectroscopy (ATR-FTIR), contact angle measurement and permeation tests were carried out in order to evaluate the membrane performance after coating. The antifouling property of modified membrane was evaluated for Gram-positive (Bacillus subtilis) and Gram negative (Escherichia coli) bacteria by colony counting method. The results indicated that the modified membranes keep efficient anti-bacterial efficacy against both type of bacteria. The bacterial growth reduced approximately 75% and 73% on modified membrane as compared to unmodified membrane for E.coli and B.subtilis respectively. Ag-TiO₂ nanoparticles imbedded nanofiltration membranes inhibit the biofilm formation and facilitate in cleaning membrane surface without using excessive chemical agents.

Capacitive deionization (CDI) is a desalination technology utilizing electrosorption and desorption of ionic salts. Carbon materials are the main components of electrodes in CDI, while addition of organic and inorganic materials with carbon materials enhances the desalination performance. In this study, powdered activated carbon (PAC) as well as PAC combined with titanium dioxide (TiO₂) electrodes was prepared. The deionization performance was evaluated using three CDI systems. Feed solution having concentration of 2,000 mg/L was used in small- and lab-scale CDI systems. PAC + TiO₂ electrodes showed 28% more salt removal as compared to PAC electrodes in the small-scale CDI system using one pair of electrodes. Laboratory-scale CDI system using six pairs of PAC + TiO₂ electrodes showed adsorption capacities of 2.64, 4.30, and 6.67 mg NaCl/g-adsorbent at 1.3, 1.6, and 1.8 volts, respectively. Pilot scale CDI system using 20 pairs of PAC + TiO₂ electrodes at 1.8 volts showed maximum salt removal of 84, 82, and 71% for the feed NaCl concentrations of 2,000, 2,500, and 3,000 mg/L with adsorption capacities of 7.7, 10.4, and 11.2 mg NaCl/g-adsorbent, respectively. As the amount of salt ions to adsorbent increases, the exchangeable sites on the adsorbent structure become saturated, which results in decrease of salt removal efficiency, while the adsorption capacities increased with increase in concentration due to elevated mass transfer rate of salt ions inside the pores.