fatemeh rekabdar

The evaluation of critical flux and pollutant removal in a lab-scale submerged membrane bioreactor (MBR) was performed for the wastewater of a domestic oil refinery. The flux step method and its behavior vs. transmembrane pressure (TMP) were studied to determine the critical flux of the membrane and the effect of TiO2 nanoparticles (NP) incorporation into polyvinylidene fluoride (PVDF) matrix on the membrane filterability. The effectiveness of MBR for treating effluent stream of dissolved air floatation (DAF) unit of the Tehran oil refinery wastewater plant was studied, and the results showed that TiO2 NP improved the efficiency of phenol removal. Ultimately, according to this study, 70 % enhancement in the critical flux of the PVDF/TiO2 membrane was obtained as a result of TiO2 NP tendency to reduce the fouling of PVDF membranes.

The main objective of this research is to investigate the effect of surface modification of Polyvinylidene fluoride (PVDF) membrane on its filtration performance and fouling reduction. Considering Titanium dioxide (TiO2) nanoparticles properties in fouling reduction of polymeric membranes and in order to obtain ultrafine and stable nanodispersions on the membrane surface which is the main challenge in this field, composite PVDF/TiO2 ultrafiltration membranes were prepared via phase inversion and colloidal precipitation method. Among various prepared membranes, the PVDF/TiO2 composite membrane using 0.05 g/L of TiO2 in the coagulation bath was selected as the optimum membrane. Roughness reduction of about %24.34 and permeation increase of %15 for the optimum membrane were obtained. The result of the fouling analysis of nanocomposite membranes with BSA showed the improved effect of colliudal precipitation method in naoparticle dispersion on the membrane surface and fouling reduction of the prepared membranes. Indeed, the effect of TiO2 nanoparticle addition via colloidal precipitation method on membrane fouling reduction in membrane bioreactors for refinery wastewater treatment was investigated.

In this study, polyvinylidene fluoride (PVDF) ultrafiltration membranes were prepared via immersion precipitation method using a mixture of two solvents triethyl phosphate (TEP) and dimethylacetamide (DMAc), which had different affinities with the nonsolvent (water). Properties of the prepared membranes were characterized using scanning electron microscope (SEM) and contact angle and membrane porosity measurements. The prepared membranes were further investigated in terms of pure water flux and BSA rejection in cross flow filtration experiments. The results showed that by using a mixture of DMAc and TEP as solvent and changing the mixed solvent composition, membranes with different morphologies from sponge-like to macrovoid containing were obtained.
Maximum flux of the prepared membranes with different solvent mixing ratios was obtained for the one with 60%wt TEP in the casting solution of PVDF/TEP-DMAc/ PEG which equals to 76.8 lm-2h-1. The effect of addition of polyethylene glycol with different molecular weight on morphology and performance of the membranes has also been discussed.

A series of experiments on the synthesis of poly (ethylene terephthalate) (PET)/organo-montmorillonite (MMT) nanocomposites were carried out in a pressurized reactor using alkyl ammonium exchanged smectite clays, (Closite 30B).Given the degradation of organoclay at high temperatures, the in situ polymerization process was carried out at mild temperatures ranging from 210 to 230°C for 40 minutes followed by solid state polymerization (SSP) at 245°C for 30 minutes at a pressure of 5 mbar. The nanocomposites were prepared using different weight percentages (1-5)of organoclay. The reaction completed when the mixing torque ceased to change as recorded by the auto data acquisition system of the pressure reactor. The DSC analysis provided information on the course of the thermal characterization of the PET nanocomposites versus regular PET. As shown by the results of DSC cooling scan, all the PET nanocomposite samples have higher crystallization temperatures (Tc) and faster crystallization rates (∆HC/t) compared to regular PET. Furthermore, the opposite behavior is observed for t1/2. This is due to the fact that the nucleation of organoclay nanoparticles reduces the crystallite size in the PET nanocomposites. The XRD results indicated that the peaks in the 2θ angle from 1° to 7° were disappeared, which is an indication of an exfoliated MMT.In addition, The atomic force microscope (AFM) results showed broken mirror like lamellae, confirming the exfoliated results of the XRD analysis. The peaks are indexed according to the 2θ angle from 10° to 30° known assignments of the triclinic unit cell dimensions for PET. The comparative crystallite size of the PET nanocomposites samples (1-5%wt organoclay) can be deduced from the peak ratio change of 2θ angle from 10° to 30°. Heat distortion (or deflection) temperature (HDT) was enhanced by increasing the amount of organoclay in PET nanocomposites compared to regular PET. The tensile test results of 2%wt organoclay show an increase of 58% in the tensile strength of this sample. As a result of MMT agglomeration, due to the high temperature instability of Closite 30B, the relative oxygen pressure drop data shows fluctuations. However, as an overall trend, PET nanocomposite gives about 50% greater reduction in O2 pressure drop or relative oxygen permeability compared with a homo structure.

Polybutadiene nanoparticles were synthesized via batch emulsion polymerization of butadiene in the presence of potassium persulfate, disproportionate rosinate potassium cation and t-dodecyl mercaptane as initiator, emulsifier and chain transfer agent, respectively. Polymerization reaction was performed at different temperatures (60, 70 and 80 °C). Conversion was measured at the various time intervals by gravimetry method. Particle size and its distribution of the polybutadiene latex were measured by dynamic light scattering (DLS) and SEM analyses. Polymer microstructure was investigated by FT-IR spectroscopy. By increasing the polymerization temperature, average diameter of polybutadiene nanoparticles decreased from 104 nm (at final conversion of 80.6%) at 60 °C to 88.7 nm (at final conversion of 98.0%) at 80 °C. Dominant microstructure, i.e. 1,4-trans isomer content, in the synthesized polymers was calculated to be about 60%. Results showed that by increasing the reaction temperature, particles’ size decreases while number of the polymer particles and polymerization rate increase.

In the present work, the effects of operating conditions including pH, transmembrane pressure, oil concentration, and temperature on fouling resistance and the rejection of turbidity for a polymeric membrane in an ultrafiltration system of wastewater treatment were studied. A new modeling technique called evolutionary polynomial regression (EPR) was investigated. EPR is a method based on regression algorithm, which combines the best properties of the conventional numerical regression technique. This paper employs the capability of EPR as a powerful tool to develop a formula with a variable number of polynomial coefficients. Herein, the evolutionary polynomial regression approach is adopted on two parametric studies, i.e. total fouling resistance and rejection rate. These parameters are all evaluated as a function of some mentioned independent variables. Maximum average error and minimum average error are obtained to be equal to 4.25% and 0.05%, respectively. Therefore, EPR is a practical and useful method to describe a membrane performance.

Batch emulsion polymerization of butadiene was performed at 70°C in a Buchi reactor equipped with mechanical stirrer (300 rpm) in the presence of potassium persulfate (KPS), and disproportionate rosinate, potassium cation (DPR) as initiator and emulsifier, respectively. t-Dodecyl mercaptane was used as a chain transfer agent in polymerization reactions. Conversion was measured at various time intervals by gravimetry. Polymerization rate was then calculated from the slope of conversion versus time curves. Particle size and its distribution of the polybutadiene latex (PBL) were measured by dynamic light scattering (DLS) and scanning electron microscopy (SEM). Depending on the emulsion polymerization conditions, PBL latices were obtained with average particles’ diameter and particle size distribution in the range of 88.5-189 nm and 35-400 nm, respectively. The number of particles per unit volume of the continuous phase was calculated from the average particle size data, from which polymerization rate per particle or equally its number of growing chains per particle was evaluated. Results showed that by increasing the emulsifier concentration, the average particle size decreases while polymerization rate increases. Moreover, the number of growing chains per particle decreased slightly by increasing the emulsifier concentration. Unlike classic emulsion polymerization, particle size and polymerization rate were observed to be more or less independent of initiator concentration. The results obtained from investigation of the reaction trend showed that kinetics of the emulsion polymerization of butadiene follows case 1(n<<0/5) of the Smith-Ewart kinetics. The observed behaviour was attributed to the lower efficiency of initiator in the particle nucleation and growth processes