Polyvinyl Chloride Hollow Fiber Membranes Research Articles

Investigation of fouling of surface modified Polyvinyl chloride hollow fiber membrane bioreactor via Zinc oxide-nanoparticles under coagulant for municipal wastewater treatment

In this study, hollow fiber PVC/ZnO-nanocomposite in an MBR was investigated for municipal wastewater treatment. The following parameter were evaluated: BOD, COD, TSS, NTU, TP, TKN. ZnO nanoparticles caused to decrease the contact angle from 78° to 67° for the neat PVC and 0.5 wt% ZNO-nanocomposite membrane, respectively. The majority of the neat membrane resistance was due to irreversible resistance. Because of the antibacterial properties of zinc oxide nanoparticles, with increasing nanoparticles loading, the resistance of irreversible part compared to the reversible resistance experienced a significant decrease. This confirm that the fabricated nanocomposite membranes did not show affinity toward adsorption of the sludge inside the pores hence substantially limited the membrane fouling. The FTIR results showed the reduction of proteins and polysaccharides onto the surface of the nanoparticle-incorporated membranes, approaching the clean PVC membrane. This was most likely due to the antibacterial properties of ZnO NPs. Nitrogen and phosphor removal for PVC0.5 membrane was 99% and 79% and TSS removal up to 100% was achieved. The findings of this study showed that modification of PVC polymer using ZnO nanoparticles with the presence of ferric chloride coagulant is a very effective technique for municipal wastewater treatment to meet the well-known standard levels.

Preparation and characterization of asymmetric hollow fiber polyvinyl chloride (PVC) membrane for forward osmosis application

• Asymmetric nanofiltration PVC hollow fiber membranes were fabricated via dry-wet spinning technique. • Delayed demixing was achieved by addition of high molecular weigh PVP. • Volatile solvent evaporation resulted in dense selective layer. • The effect of fabrication parameters were investigated in order to introduce best-suited membrane. • The effect of DS concentration and temperature were studied by means of Flux and SRSF. PVC hollow fiber (HF) membrane for forward osmosis (FO) application as a potential candidate for water desalination was fabricated by altering the spinning conditions. High molecular weight polyvinylpyrrolidone (PVP) was used as a blending additive to control the phase inversion process by increasing viscosity leading to delayed demixing as observed on the ternary phase diagram and confirmed by the simulation results, and forming dense barrier layer structure by providing chain entanglements with the PVC matrix. PVP/PVC ratio of 5/100 was proved to offer suited membrane morphology and selective layer. Different air gap distances and bore fluid flow rates were investigated to achieve proper fabrication parameters. The prepared membranes presented high flux and salt rejection in nanofiltration (NF) and FO tests. The best-suited membrane demonstrated the structural parameter of 389 µm with a narrow pore size distribution and a molecular weight cut-off of 490 Da. In different draw solution (DS) concentrations, it was observed that the membranes perform well in all conditions. Considering the PVC-PVP chain entanglements and mobility and the possibility of PVP being washed away, the membranes’ performance at different temperatures indicated that 25–45 °C would be the safe operating range for the fabricated membranes with stable values of 31.0–33.4 LMH and 0.17–0.18 (FO mode) and 33.0–33.4 LMH and 0.23–0.24 (PRO mode) for water flux and specific reverse salt flux.

Effect of on-line stretching treatment on the structure and performance of polyvinyl chloride hollow fiber membranes.

In this work, polyvinyl chloride (PVC) hollow fiber membranes were prepared via a melt-spinning method and on-line stretching treatment. Gamma-butyrolactone (GBL) and epoxidized soybean oil (ESO) were selected as the solvent and the thermal stabilizer, respectively. The effects of on-line stretching treatment on the membrane structure and performance were characterized by means of morphology, surface roughness, pore size distribution, permeation performance and so on. The morphology showed that the prepared PVC hollow fiber membrane belonged to a homogeneous membrane. The on-line stretching treatment decreased the roughness of the inner surface and the outer surface, but it increased the water contact angle, mean pore size, porosity and pure water flux. Meanwhile, the pore size distribution range remained stable and narrow. The rejection of Direct Black 19 particles was higher than 90% when it approached a steady value. This type of membrane filtration was a deep intercept. Furthermore, the tensile strength increased with the increment of stretching ratio, and the elongation at break showed the opposite trend. The biggest tensile strength could be obtained as the stretching ratio reached 3.0 and was 23.89 MPa.

Study on interface structure and performance of homogeneous-reinforced polyvinyl chloride hollow fiber membranes

Homogeneous-reinforced (HR) polyvinyl chloride (PVC) hollow fiber membranes consisting of coating and matrix layers were fabricated via coating process. The mixtures of polymer solutions were uniformly coated on the homogeneous PVC matrix membrane which was prepared by melt-spinning method. The influence of various pre-wetting solutions on interface structure and performance of HR membranes were investigated. The results showed that the HRPVC membranes had a dense and smooth outer surface with no obvious pores. A dense interface was formed in the HR membrane between the coating layer and the matrix membrane without pre-wetting process. Due to the filling of the pores of the outer edge of the matrix membrane by pre-wet solutions, the HRPVC hollow fiber membranes formed porous interface in the coating process. The pure water flux of the pre-wet HR membranes was higher than that of the un-pre-wet HR membrane, but lower than that of the matrix membrane. The optimum properties of HRPVC membranes were obtained as the ethanol weight fraction reached 60 wt% in the pre-wet solutions. In the optimum pre-wetting conditions, the tensile strength of HRPVC hollow fiber membranes was 9.5 MPa, while the elongation-at-break value was 97.4 %.

Hydrophilic modification of polyvinyl chloride hollow fiber membranes by silica with a weak in situ sol–gel method

A weak in situ sol–gel method is proposed for the hydrophilic modification of polyvinyl chloride (PVC) hollow fiber membranes by silica, which is generated by the soft hydrolysis of tetraethoxysilane (TEOS) in a deionized water bath.

Actual Application of a H2-Based Polyvinyl Chloride Hollow Fiber Membrane Biofilm Reactor to Remove Nitrate from Groundwater

To evaluate the actual performance of the H2-based polyvinyl chloride hollow fiber membrane biofilm reactor (HF-MBfR), we used HF-MBfR to remove nitrate from the nitrate contaminated groundwater with the dissolved oxygen (~6.2 mg/L) in Zhangqiu city (Jinan, China). The reactor was operated over 135 days with the actual nitrate contaminated groundwater. The result showed that maximum of nitrate denitrification rate achieved was over 133.8 gNO3--N/m3d (1.18 gNO3--N/m2d) and the total nitrogen removal was more than 95.0% at the conditions of influent nitrate 50 mg/L, hydrogen pressure 0.05 MPa, and dissolved oxygen (DO) 6.2 mg/L, with the nitrate in effluent under the value limits of drinking water. The fluxes analysis showed that the electron-equivalent fluxes of nitrate, sulfate, and oxygen account for about 81.2%, 15.2%, and 3.6%, respectively, which indicated that nitrate reduction could consume more electrons than that of sulfate reduction and dissolved oxygen reduction. The nitrate reduction was not significantly influenced by sulfate reduction and the dissolved oxygen reduction. Based on the actual groundwater quality on site, the Langelier Saturation Index (LSI) was 0.4, and the membrane could be at the risk of surface scaling.

Preparation and interface structure study on dual-layer polyvinyl chloride matrix reinforced hollow fiber membranes

Polyvinyl chloride (PVC) matrix reinforced hollow fiber membranes including separation layer and porous supported matrix were fabricated via dry–wet spinning process. The mixtures of PVC or polyvinylidene fluoride (PVDF) polymer solutions were uniformly coated on the homogeneous PVC matrix membrane which was prepared by a melt-spinning method. The influences of pre-wetting solutions and polymer concentration on structure and performance of homogenous-reinforced (HMR) PVC hollow fiber membranes were investigated. Furthermore, the interfacial bonding state of HMR PVC hollow fiber membranes was characterized by an indirect method and comparative analysis. The results showed that a dense interface formed in the HMR PVC hollow fiber membrane between these two layers without pre-wetting process. Compared with the matrix membrane which had a rougher outer surface with obvious big pores, the prepared HMR PVC hollow fiber membrane possessed a dense and smooth outer surface with no obvious big pores. Due to the filling of the pre-wet solutions into the pores in the outer edge of the matrix membrane, the HMR PVC hollow fiber membranes formed porous interface in the coating process which improved its permeability. The HMR PVC hollow fiber membranes had a more favorable interfacial bonding than the heterogeneous-reinforced (HTR) PVDF hollow fiber membranes. The tensile strength of prepared PVC matrix reinforced hollow fiber membranes was higher than 12MPa but lower than the original PVC hollow fiber matrix membrane.

Performance of different hollow fiber membranes for seawater desalination using membrane distillation

Membrane distillation requires a highly porous hydrophobic membrane with low surface energy. In this paper, we compare the direct contact membrane distillation (DCMD) performances of four different types of in-house fabricated hollow fiber membranes and two different commercially available hollow fiber membranes. Hollow fiber membranes are fabricated using wet-jet phase inversion technique and the polymeric matrices used for the fabrication are polyvinylidine fluoride (PVDF) and polyvinyl chloride (PVC). Commercial hollow fiber membrane materials are made of polytetrafluoroethylene (PTFE) and polypropylene (PP). PVDF hollow fibers showed a superior performance among all the hollow fibers tested in the DCMD process and gave a water vapor flux of 31 kg m−2h−1 at a feed and coolant inlet temperatures of 80 and 20°C, respectively. Under the same conditions, the water vapor flux observed for PP, PTFE, and PVC hollow fiber membranes are 13, 11, and 6 kg m−2h−1, respectively, with 99.99% salt rejection observed for all membranes used.

Effect of Ethanol Composition in Water Coagulation Bath on Structure and Performance of Homogeneous-Reinforced Polyvinyl Chloride Hollow Fiber Membranes

Homogeneous-reinforced (HR) polyvinyl chloride (PVC) hollow fiber membranes consisting of coating layer and matrix layer were fabricated via coating process. The mixtures of polymer solutions were uniformly coated on the homogeneous PVC matrix membrane which was prepared by melt-spinning method. The influences of ethanol composition in water coagulation bath on structure and performance of HR membranes were investigated. The results showed that the pure water flux of the HR PVC hollow fiber membranes increased with the increase of ethanol weight fraction in coagulation bath, while the porosity changed slightly. The increase of ethanol weight fraction in coagulation bath brought about the decrease of the protein permeation flux and rejection rate. The tensile strength of HR PVC hollow fiber membranes was about 9.5 MPa, while the elongation at break was higher than 97 %.

Structure design and performance study on homogeneous-reinforced polyvinyl chloride hollow fiber membranes

Homogeneous-reinforced (HR) polyvinyl chloride (PVC) hollow fiber membranes consisting of coating layer and matrix layer were fabricated via coating process. The mixtures of polymer solutions were uniformly coated on the homogeneous PVC matrix membrane which was prepared by melt-spinning method. The influences of PVC concentration and poly(ethylene glycol) (PEG) molecular weight in polymer solutions on structure and performance of HR membranes were investigated. The results showed that the HR PVC membranes had a dense and smooth outer surface compared with matrix membrane. The maximum pure water flux and protein permeation flux of HR PVC membranes were obtained as the PVC concentration reached to 10wt.% and PEG molecular weight was 2000. The increase of PVC concentration and PEG molecular weight brought about the increase of protein rejection rate and the decrease of membrane porosity. The high flux recovery rate (>85.00%) indicated that the HR membranes had excellent anti-fouling property. Moreover, the HR PVC membranes had a favorable interfacial bonding force between the coating layer and matrix membrane. The tensile strength of HR membranes decreased slightly compared with matrix membrane and was nearly 19MPa, but the elongation at break was opposite which was nearly 102%.

Fabrication and properties of polyvinyl chloride hollow fiber membranes plastified by dioctyl phthalate

ABSTRACT Polyvinyl chloride (PVC) hollow fiber membranes were prepared by twin-screw extrusion method. Dioctyl phthalate (DOP) as the plasticizer was used in this study. The influence of stretching and DOP weight fraction on morphology and performance were investigated. The membranes were characterized by scanning electron microscope, pure water flux, mean pore size measurement, and mechanical strength test. The results show that the PVC hollow fiber membrane was a kind of homogeneous membrane. The pure water flux increased with the theoretical draw ratio and the DOP weight fraction increment. The plastic deformation ratio increased with the theoretical draw ratio increment, but decreased with the DOP weight fraction increment. The deformation-recovery ratio was governed by the DOP weight fraction and was slightly controlled by theoretical draw ratio. Both stretching and increment of DOP weight fraction could increase the mean pore size. At the same time, the tensile strength increased and the elongation at break decreased with the increment of theoretical draw ratio. On the contrary, the tensile strength decreased and the elongation at break increased with the increment of DOP weight fraction.

Effluent Particle Size and Permeability of Polyvinylchloride Membranes after Sodium Hypochlorite Exposure

AbstractSodium hypochlorite (NaOCl) is a common cleaning agent for treating ultrafiltration (UF) membranes. Although it efficiently removes fouling, NaOCl accelerates membrane degradation and reduces membrane integrity. In this paper, new and polluted polyvinylchloride hollow fiber membranes were treated with NaOCl solutions. The effects on the membrane were evaluated by using transmembrane pressure, bovine serum albumin permeability, particle-size distribution of the effluent (PSDE), attenuated total reflectance-Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. The membrane pore size increased after exposure to solutions with a NaOCl mass fraction of 1%. The PSDE was successfully used to test membrane integrity. When the NaOCl mass fraction was <1%, the PSDE increased; otherwise, the PSDE decreased. The main reason for pore-size enlargement was the breaking of C–C and C–H ...

Fouling and Cleaning Characteristics of Ultrafiltration of Hydrophobic Dissolved Organic Matter by a Polyvinyl Chloride Hollow Fiber Membrane

Ultrafiltration membrane fouling is a significant problem in drinking water treatment. Many researchers believe that hydrophobic natural organic matter is the main foulant. In this research, fulvic acid, tannin, and aniline were used to represent hydrophobic acid, neutral, and base, respectively, to investigate modified polyvinyl chloride ultrafiltration membrane fouling characteristics. Four kinds of cleaning methods were used in this study: flushing, backwashing, flushing and backwashing, and chemical cleaning with 0.5% sodium hydroxide. Each was performed on the three hydrophobic dissolved organic matters (acid, neutral, and base) to identify the fouling mechanisms of polyvinyl chloride ultrafiltration membrane. Results showed that hydrophobic base fouled membranes the most and hydrophobic acid the least based on cleaning difficulty.

Autohydrogenotrophic denitrification of drinking water using a polyvinyl chloride hollow fiber membrane biofilm reactor

A hollow fiber membrane biofilm reactor (MBfR) using polyvinyl chloride (PVC) hollow fiber was evaluated in removing nitrate form contaminated drinking water. During a 279-day operation period, the denitrification rate increased gradually with the increase of influent nitrate loading. The denitrification rate reached a maximum value of 414.72 g N/m 3 d (1.50 g N/m 2 d) at an influent NO 3 −–N concentration of 10 mg/L and a hydraulic residence time of 37.5 min, and the influent nitrate was completely reduced. At the same time, the effluent quality analysis showed the headspace hydrogen content (3.0%) was lower enough to preclude having an explosive air. Under the condition of the influent nitrate surface loading of 1.04 g N/m 2d, over 90% removal efficiencies of the total nitrogen and nitrate were achieved at the hydrogen pressure above 0.04 MPa. The results of denaturing gel gradient electrophoresis (DGGE), 16S rDNA gene sequence analysis, and hierarchical cluster analysis showed that the microbial community structures in MBfR were of low diversity, simple and stable at mature stages; and the beta-Proteobacteria, including Rhodocyclus, Hydrogenophaga, and beta-Proteobacteria HTCC379, probably play an important role in autohydrogenotrophic denitrification.

Study on ultrafiltration for surface water by a polyvinylchloride hollow fiber membrane

Low pressure membrane filtration processes are increasingly competing against conventional surface water treatment plants. In comparison with conventional processes, UF technology has many advantages, but it is also important that a kind of membrane is suitably selected and operated. In this paper, a pilot plant study on a polyvinylchloride ultrafiltration (MWCO of 80 kD) hollow fiber membrane process was performed for the treatment of surface water. The new membrane had an optimized pore size distribution over membrane thickness while membrane material and fiber dimensions remained the same, the modification resulted in a much higher pure water flux (160 l/(m 2 h bar) at 20°C). The membrane system was operated in the dead-end filtration modes with different constant permeate fluxes. The results showed that the permeate quality was stable, regardless of different surface water for a long duration of filtration. The transmembrane pressure should be operated in less than 1 bar to avoid irreversible fouling. Treating cold raw water below 5°C in constant pressure operation mode was better than in constant permeate flux.

Ultrafiltration of dissolved organic matter in surface water by a polyvinylchloride hollow fiber membrane

Fouling of ultrafiltration membranes by dissolved organic matter in surface water is not well understood due to the complexity of the DOM mixture. In this study, fulvic acid, tannin, aniline, citric acid, polysucrose and oligopeptide were selected to represent fractions of DOM with different hydrophobicity and acid/base properties. The impact of each model compound as well as their mixture on the fouling and cleaning behavior of a modified polyvinyl chloride UF membrane was investigated. The results show that the interplay of molecular size/structure, charge, hydrophobicity, and functionality determines the membrane rejection and fouling potential of individual DOM compounds, although rejection is not directly related to the fouling potential. Furthermore, the overall fouling and cleaning behavior of DOM mixtures, e.g., natural water, cannot be simply predicted from fouling behavior of individual DOM compounds. Significant synergy exists presumably due to interactions between DOM compounds, leading to significantly greater fouling rate compared to the additive sum of contributions from individual DOM compounds.