Daryoush Emadzadeh

Synthesis and characterization of novel thin film nanocomposite reverse osmosis membranes with improved organic fouling properties for water desalination

In this study, a new type of thin film nanocomposite (TFN) reverse osmosis (RO) membranes was prepared by incorporating different amounts of halloysite nanotubes (HNTs) into the polyamide (PA) selective layer via in situ interfacial polymerization. The effect of HNTs incorporation into the PA selective layer on the surface morphology, separation performance and antifouling properties of the membranes were thoroughly investigated and discussed. The presence of HNTs in PA layer was verified using EDX, XRD and FTIR analysis. The “leaf-like” outgrowth morphology of PA layer was observed using FESEM. Upon addition of HNTs, the hydrophilicity, surface roughness and water flux of TFN membranes have all increased. The water flux enhancement can be ascribed to higher hydrophilicity and additional water pathways through porous HNTs in TFN membranes. It is noteworthy that the TFN membrane that was embedded with 0.05 wt/v% HNTs (labeled as TFN0.05) could exhibit water flux as high as 36 L m−2 h−1 (at 15 bar gauge) with NaCl rejection maintained at 95.6%. In comparison to the control thin film composite (TFC) membrane, the water flux of TFN0.05 membrane was 90% higher. Although further increase in HNTs loading to 0.1 wt/v% could result in greater water flux, its RO performance was compromised by a significant decrease in NaCl rejection. Besides offering greater water flux, the TFN0.05 membrane also showed better antifouling affinity than HNTs-free TFC membrane. It is most probably due to the increase in hydrophilicity as well as surface negative charge upon addition of HNTs. Based on the results obtained in this work, it can be concluded that incorporating an appropriate amount of HNTs into PA rejection layer could potentially improve the performance of TFC membrane during RO applications.

Surface modification of thin film composite membrane by nanoporous titanate nanoparticles for improving combined organic and inorganic antifouling properties

In this study, nanoporous titanate (NT) nanoparticle synthesized by the solvothermal method was used to modify polyamide layer of thin film composite membranes with the aim of improving membrane resistances against organic and inorganic fouling. Thin film nanocomposite membranes (NMs) were synthesized by adding mNTs (modified nanoparticles) into polyamide selective layer followed by characterization using different analytical instruments. The results of XPS and XRD confirmed the presence of mNTs in the polyamide layer of NMs, while FESEM, AFM, zeta potential and contact angle measurement further supported the changes in physical and chemical properties of the membrane surface upon mNTs incorporation. Results of fouling showed that NM1 (the membrane incorporated with 0.01w/v% mNTs) always demonstrated lower degree of flux decline compared to the control membrane when membranes were tested with organic, inorganic and multicomponent synthesized water, brackish water or seawater. Besides showing greater antifouling resistance, the NM also displayed significantly higher water flux compared to the control M membrane. The findings of this work confirmed the positive impact of mNTs in improving the properties of NM with respect to fouling mitigation and flux improvement.

Effect of air-gap length on carbon dioxide stripping performance of a surface modified polysulfone hollow fiber membrane contactor

Surface Modifying Macromolecule (SMM) blended PSf hollow fibers were spun at different air-gaps to evaluate CO2 stripping from aqueous DEA solution and water. The fabricated membranes were firstly subjected to different characterization methods such as contact angle and liquid entry pressure measurement to evaluate the membranes hydrophobicity and wetting resistance, respectively. To determine pore size and effective porosity of the membranes, a pure helium permeation test was performed. Morphological study of the membranes was conducted by scanning electron microscopy (SEM) and atomic force microscopy (AFM). A CO2 stripping test was carried out to investigate the effects of operating variables such as liquid and gas velocity, temperature and DEA concentration on the CO2 stripping flux. It was found that the increase of liquid velocity resulted in enhanced CO2 stripping flux. On the other hand, the increase in gas velocity did not exert significant influence on the stripping flux. The increase in temperature and DEA concentration both enhanced the stripping flux. Lastly, it was concluded that the hollow fibers spun in this work at a 15 cm air-gap could achieve the best stripping flux among all the membranes fabricated so far for CO2 stripping.

Application of copper sulfide nanoparticles loaded activated carbon for simultaneous adsorption of ternary dyes: Response surface methodology

Copper sulfide nanoparticles were synthesized and loaded on activated carbon (CuS-NPs-AC) for ternary dye removal. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD) and scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) were used to characterize the synthesized materials. The performance of the materials was subsequently evaluated for simultaneous ultrasound assisted adsorption of Disulphine Blue (DB), Eosin Yellow (EY) and Safranin O (SO) dyes in ternary solution under different conditions that include variation in solution pH, initial concentrations of dyes, sonication time and adsorbent dosage. Response surface methodology (RSM) using central composite design (CCD) was employed to obtain the optimum experimental conditions. The maximum removal efficacies (88.39%, 68.49% and 55.69% for DB, EY and SO, respectively) were found at the optimum conditions: 3.63 min of sonication time, 0.02 g of CuS-NPs-AC, 7.76mg L-1 of DB, 8.89mg L-1 of EY, 9.87mg L-1 of SO and pH 6.5. Very high adsorbent capacities of 198.12, 165.0, 139.58mg g-1 for DB, EY and SO, respectively, were yielded from Langmuir isotherm as best fitted model. Kinetic study indicated that the pseudo-second-order kinetic model was well fitted to the experimental data of ternary adsorption process. The results of the study display very good adsorption efficiency of the synthesized adsorbent for dye removal with high adsorption capacity under optimum conditions.