The principal objective of this study is to investigate the effect of Polyethylene Glycol (PEG) crosslinking in Polyvinylidene Fluoride (PVDF) in immobilization of Fe and bimetallic Fe/Cu and Cu/Fe zero valent particles on the membrane and its efficiency on removal of nitrate in wastewater. PVDF/PEG polymer solution of three weight compositions was prepared to manipulate the viscosity of the polymer. PEG crosslinking was indirectly controlled by the viscosity of the polymer solution. In this study, PEG was used as a modifier of PVDF membrane as well as a cross-linker for the immobilization of the zero valent particles. The result demonstrates improvement in immobilization of metallic particles with the increase in crosslinking of PEG. Nitrate removal efficiency increases too.

Coagulation process using aluminum sulfate ($Al_2(SO_4)_3$) and ferric chloride ($FeCl_3$) was employed as a treatment method for decolorization of a synthetic textile wastewater containing red dye in this paper. Factors such as initial pH, coagulant dosage, initial concentration, conductivity and mixing conditions that influence color removal efficiency were experimentally tested. It was found that $Al_2(SO_4)_3$ is more efficient than $FeCl_3$ as coagulant. When $40mgL^{-1}$ aluminum sulfate was used, results showed that color induced by the red dye was efficiently removed (> 90 %) and was obtained in a large range of initial pH from 4 to 8 with, and for a dye concentration lower than $235mg\;L^{-1}$. After addition of the coagulant, the medium had to be mixed for 30 min at 60 rpm, then allowed to settle for 40 min. The effects of water conductivity in the range $0.035-2.42mS\;cm^{-1}$ and dye concentration up to $380mg\;L^{-1}$ were also followed and discussed.

A series of laboratory scale experiments were performed to investigate the feasibility of membrane separation technology for natural rubber (NR) wastewater treatment and reuse. Three types of spiral wound membranes were employed in the cross-flow experiments. The NR wastewater pretreated by sand filtration and cartridge filtration was forced to pass through the ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes successively. The UF retentate, which containing abundant proteins, can be used to produce fertilizer, while the NF retentate is rich in quebrachitol and can be used to extract quebrachitol. The permeate produced by the RO module was reused in the NR processing. Furthermore, about 0.1wt% quebrachitol was extracted from the NR wastewater. Besides, the effluent quality treated by the membrane processes was much better than that of the biological treatment. Especially for total dissolved solids (TDS) and total phosphorus (T-P), the removal efficiency improved 53.11% and 49.83% respectively. In addition, the removal efficiencies of biological oxygen demand (BOD) and chemical oxygen demand (COD) exceeded 99%. The total nitrogen (T-N) and ammonia nitrogen (NH4-N) had approximately similar removal efficiency (93%). It was also found that there was a significant decrease in the T-P concentration in the effluent, the T-P was reduced from 200 mg/L to 0.34 mg/L. Generally, it was considered to be a challenging problem to solve for the biological processes. In brief, highly resource utilization and zero discharge was obtained by membrane separation system in the NR wastewater treatment.

In this study, a new method called as multi-dropped liquid membrane (MDLM) which is more practical and more effective than other liquid membrane techniques is applied for transport of Zn(II) has been studied. HCl as the stripping solution and D2EHPA dissolved in kerosene as the membrane solution, has been examined. The effects of stripping solution concentration, carrier concentration, temperature and pH in the feed phase on the transport of Zn(II) have also been investigated. As a result, the optimum transport conditions of Zn(II) were obtained, i.e., the concentration of HCl solution was 0.25 M, the concentration of D2EHPA was $8{\times}10^{-3}M$, and pH value in the donor phase was 5.00. Under the optimum conditions, the transport percentage of Zn(II) was up to >99% during the transport time of 80 min when the initial concentration of Zn(II) was $120mgL^{-1}$. The activation energy is calculated as $5.30kcalmol^{-1}$. The value of calculated activation energy indicates that the process is diffusionally controlled by Zn(II) ions. The experiments have demonstrated that D2EHPA derivative is a good carrier for Zn(II) transport through MDLM in the study.

Microscopic examination of the activated sludge and morphological characterization of the flocs provides detailed information about the treatment process. The aim of this study is to investigate the morphological parameters of flocs obtained from a thermophilic jet loop membrane bioreactor (JLMBR) in different sludge retention times (SRTs), considering EPS and SMP concentration, hydrophobicity, zeta potential. The results showed that irregularity decreased with the increasing SRT. The compactness value was calculated to be less than 1 for all SRTs. However, the sludge had a more compact structure when the SRT increased. Zeta potential increased whereas hydrophobicity and floc size reduced, with increasing SRT. Furthermore, 2-D porosity calculated using the hole ratio was higher at greater SRTs. Hence, there was a significant correlation between the results obtained using the imaging technique and operation conditions of thermophilic JLMBR.

Hollow fiber (HF) membranes are gaining wide interest over flat membranes due to their compaction and high area to surface volume ratio. This work addresses the fabrication of HF from polysulfone (PS) and polyethersulfone (PES) using N-methylpyrrolidone (NMP) as solvent in addition to other additives to achieve desired characteristics. The semi-pilot spinning system includes jacketed vessel, four spinneret block, coagulation and washing baths in addition to dryer and winder. Different parameters affecting dry-wet spinning phase inversion process were investigated. Dope compositions of PES, NMP and polyvinyl pyrrolidone (PVP) of varying molecular weights as additive were addressed. Some critical parameters of importance were also investigated. Those include dope flow rate, air gap, coagulation & washing baths and drying temperatures. The measured dope viscosity was in the range from 1.7 to 36.5 Pa.s. Air gap distance was adjusted from 20 to 45 cm and coagulation bath temperature from 20 to $46^{\circ}C$. The HF membranes were characterized by scanning electron microscope (SEM), atomic force microscope (AFM) and mechanical properties. Results indicated prevalence of finger like structure and average surface roughness from about 29 to 78.3 nm. Profile of stress strain characteristics revealed suitability of the fibers for downstream interventions for fabrication of thin film composite membrane. Different empirical correlations were formulated which enable deeper understanding of the interaction of the above mentioned variables. Data of pure water permeability (PWP) confirmed that the fabricated samples fall within the microfiltration (MF)-ultrafiltration (UF) range of membrane separation.

In this study, vacuum membrane distillation (VMD) was used to treat high-salinity wastewater (concentration about 17%) discharged by chlor-alkali plant after resin regeneration. The feasibility of VMD for the treatment of real saline wastewater by using Polyvinylidene fluoride (PVDF) microporous plate membrane with a pore diameter of $0.2{\mu}m$ was investigated. The effects of critical operating parameters such as feed temperature, velocity, vacuum degree and concentration on the permeate water flux were analyzed. Numerical simulation was used to predict the flux and the obtained results were in good agreement with the experimental data. The results showed that an increase in the operating conditions could greatly promote the permeate water flux which in turn decreased with an increase in the concentration. When the concentration varied from 17 to 25%, the permeate water flux dropped marginally with time indicating that the concentration was not sensitive to the decrease in permeate water flux. The permeate water flux decreased sharply until zero due to the membrane fouling resistance as the concentration varied from 25 to 26%. However, the conductivity of the produced water was well maintained and the average value was measured to be $4.98{\mu}s/cm$. Furthermore, a salt rejection of more than 99.99% was achieved. Overall, the outcome of this investigation clearly indicates that VMD has the potential for treating high-salinity wastewater.

Molecular dynamics simulations were used to study the removal of Cd(II) as a heavy metal from wastewater using armchair carbon nanotube, boron nitride nanotube and silicon carbide nanotubes under applied electric field. The system contains an aqueous solution of $CdCl_2$ as a heavy metal and a (7,7) nanotube as a nanostructured membrane, embedded in a silicon nitride membrane. An external electric field was applied to the considered system for the removal of $Cd^{2+}$ through nanotubes. The simulation results show that in the same conditions, considered armchair nanotubes were capable to remove $Cd^{2+}$ from wastewater with different ratios. Our results reveal that the removal of heavy metals ions through armchair carbon, boron nitride and silicon carbide nanotubes was attributed to the applied electric field. The selective removal phenomenon is explained with the calculation of potential of mean force. Therefore, the investigated systems can be recommended as a model for the water treatment.