Soheila Shokrollahzadeh

This study investigated the modification of polyethersulfone (PES) ultrafiltration membranes with TiO₂ and Fe₂O₃–TiO₂ nanoparticles to enhance their hydrophilicity and biofouling resistance against the marine microalgae Chlorella vulgaris. It is a common freshwater and marine microalga that readily forms biofilms on membrane surfaces, leading to significant flux decline and increased operational costs in ultrafiltration processes. The microalgae cells and their extracellular polymeric substances (EPS) adhere to the membrane surface, creating a dense fouling layer that impedes water permeation. The modified membranes were characterized using contact angle measurements, scanning electron microscopy, and pure water flux/resistance tests. Short-term ultrafiltration experiments evaluated the membranes’ antifouling performance by measuring flux decline, flux recovery ratio, and relative flux reduction during C. vulgaris filtration. The TiO₂ membrane showed improved hydrophilicity and antifouling over the pristine PES membrane, while the Fe₂O₃–TiO₂ nanocomposite membrane exhibited the best performance. It reduced the water contact angle and showed only a 5% relative flux reduction compared to 60% for the pristine membrane. SEM images confirmed reduced microalgal deposition on the nanocomposite surface. Long-term tests with microalgal cells under dark and visible light conditions in saline water further assessed the membranes’ biofouling resistance. The Fe₂O₃–TiO₂ membrane maintained 59 L/m² h water flux under visible light after immersion in the microalgal solution, outperforming the pristine (38 L/m² h) and TiO₂ (52 L/m² h) membranes. This superior antifouling was attributed to photocatalytic generation of reactive oxygen species inhibiting microalgal adhesion. This study demonstrates a promising strategy for mitigating biofouling in membrane-based water treatment and desalination processes.

Forward osmosis (FO) process has been extensively considered as a potential technology that could minimize the problems of traditional water desalination processes. Finding an appropriate osmotic agent is an important concern in the FO process. For the first time, a nonionic surfactant-based draw solution was introduced using self-assemblies of Tween 80 and choline chloride. The addition of choline chloride to Tween 80 led to micelles formation with an average diameter of 11.03 nm. The ¹H NMR spectra exhibited that all groups of Tween 80 were interacted with choline chloride by hydrogen bond and Van der Waals’ force. The influence of adding choline chloride to Tween 80 and the micellization on its osmotic activity was investigated. Despite the less activity of single components, the average water flux of 14.29 L m^‒2 h^‒1 was obtained using 0.15 M of Tween 80-choline chloride self-assembly as draw solution in the FO process with DI water feed solution. Moreover, various concentrations of NaCl aqueous solutions were examined as feed solution. This report proposed a possible preparation of nonionic surfactant-based draw solutions using choline chloride additive with enhanced osmotic activities that can establish an innovative field of study in water desalination by the FO process.

In the present study, the osmotic properties of blended amino-acids–metal-salts fertilizer draw solutions, and their forward osmosis (FO) performances were investigated. Considering the different types of amino-acids–metal-salts, the blending of arginine with ZnCl₂ solution in the molar ratio of 1 : 6 could lead up to 3.0 and 8.3 times higher osmotic pressure and water flux (i.e., 93.89 bar and 29.57 LMH), respectively, compared to the sum of their individual values. Furthermore, a very little reverse solute flux was noticed using ZnCl₂–amino-acids draw solutions. As an effect of solute–solvent interaction, the formation of the novel structure of amino acids with metal salts could enhance the osmotic pressure, providing high water flux and low inverse diffusion of the solute. The desalination of Caspian Sea water was also successfully tested using arginine–ZnCl₂ fertilizer draw solution. Therefore, the fertilizer-based draw solutions can present great potential in different applications of the FO process, due to their relatively high water flux and no need for recovery.

In this investigation, nano ZnO was sonochemically synthesized by a novel method using a methionine precursor. A narrow size distribution (41-50 nm) of nano ZnO was achieved that was immobilized on perlite and applied as a catalyst in catalytic ozonation. The catalyst was characterized by fourier transform infrared spectroscopy, BET surface area, and field emission scanning electron microscope. The ozonation of recalcitrant Remazol black 5 (RB5) di-azo dye solution by means of the synthesized catalyst was investigated in a bubble column slurry reactor. The influence of pH values (7, 9, 11), catalyst dosage (8, 12, 15, 20 g L-1) and reaction time (10, 20, 30, 60 min) was investigated. Although the dye color was completely removed by single ozonation at a higher reaction time, the applied nanocatalyst improved the dye declorination kinetics. Also, the degradation of the hazardous aromatic fraction of the dye was enhanced five-times by catalytic ozonation at a low reaction time (10 min) and a neutral pH. The second-order kinetics was best fitted in terms of both RB5 color and its aromatic fraction removal. The total organic carbon analysis indicated a significant improvement in the mineralization of RB5 by catalytic ozonation using the nano-ZnO/perlite catalyst.