Polyvinyl Chloride Ultrafiltration Membrane Research Articles

Preparation of a novel polyvinyl chloride ultrafiltration membrane modified with graphene oxide nanoparticle derived from plastic waste for wastewater purification

AbstractThe purpose of this study is to improve the performance of polyvinyl chloride (PVC) ultrafiltration membrane with graphene oxide (GO) that was synthesized from the pyrolysis of polypropylene (PP) bottles. The amount of GO loading in the membrane structure was 0.05, 0.15, and 0.25 wt%. x‐ray diffractometer, FTIR, scanning electron microscopy (SEM), contact angle (CA), water content, porosity, mechanical strength were used to characterize the synthesized membranes. Cross‐sectional SEM results of membranes indicated that the modification of the membrane caused the formation of finger‐like pores in the bottom part and also these holes increased the dye rejection efficiency in the membranes of (18 wt% PVC/2 wt% PVP/0.15 wt% GO) and (14 wt% PVC/2 wt% PVP/0.25 wt% GO). The CA of the synthesized membranes were decreased from 70 in (18 wt% PVC/2 wt% PVP) to 62 in (14 wt% PVC/2 wt% PVP/0.15 wt% GO), which indicates the increase in hydrophilicity of these membranes. The results showed that the best performance is related to the membranes (18 wt% PVC/2 wt% PVP/0.15 wt% GO) and (14 wt% PVC/2 wt% PVP/0.25 wt% GO) with a rejection efficiency of 92% and 83% for 100 ppm methyl blue.

Structurally stable copolymer ultrafiltration membranes prepared via vinyl chloride suspension copolymerization and tannic acid in-situ modification integration

Polyvinyl chloride ultrafiltration membranes, widely used in various industries, are hindered by their high susceptibility to contamination. To address this concern, researchers have investigated diverse modification methods, encompassing surface modification and physical blending. Although surface modification provides stability, but it is intricate, expensive, and may result in pore clogging. Physical blending is a simpler approach but lacks durability and stability. Tannic acid (TA), a natural compound, has attracted attention for its potential in membrane modification due to its diverse benefits. However, the existing methods, such as TA-metal networks, encounter challenges of weakened stability and reduced permeability of membrane. To solve these issues, this research presents a novel approach that integrates suspension copolymerization, polyaddition, and a sol–gel process to fabricate structurally stable copolymer ultrafiltration membranes. Active sites for sol–gel reactions were embedded into the copolymer through copolymerization. Subsequently, TA was added to the copolymer casting solution, and isocyanate propyltriethoxysilane was decorated onto TA through a polyaddition reaction. Following this, a non-solvent induced phase separation method was used for membrane fabrication. During the formation of the membrane, a sol–gel reaction occurred between the copolymer and the modified TA, ensuring both stable chemical cross-linking. The membrane demonstrates excellent permeability, fouling resistance, and long-term operational stability. This innovative approach not only addresses compatibility and leakage issues associated with traditional methods but also ensures the stable integration of hydrophilic functional monomers within the copolymer matrix. The proposed method holds promise for advancing applications of ultrafiltration membrane technology in various complex environments.

‘Green’ fabrication of PVC ultrafiltration membranes with high-flux and improved hydrophilicity by in-situ interpenetration of hydrophilic crosslinking networks

High-flux polyvinyl chloride (PVC) membranes with hydrophilic interpenetrating networks were fabricated by a ‘green’ (without toxic initiator) in-situ method in this study. The interpenetration between the polyvinyl chloride (PVC) molecules and the hydrophilic network was formed during the phase separation process, where the cross-linking was initialized by water in a solidification bath between siloxanes in aminopropyltrimethoxysilane-b-poly (ethylene glycol) diglycidyl ether synthesized in the PVC dissolution process. From the reconstruction of the PVC membrane, high hydrophilicity and porosity, and narrow pore size distribution have been achieved. As results, compared to the pristine membrane. the pure water flux was increased 17 times to 1177.4 L m−2 h−1, the flux recovery rate was increased by 15.9 %, and the strength was also increased slightly.

Novel polyvinyl chloride ultrafiltration membranes blended with amphiphilic polyethylene glycol-block-poly(1, 2-dichloroethylene) copolymer for oily wastewater treatment

Amphiphilic di-block copolymer consisting of polyethylene glycol (PEG) and poly(1,2-dichloroethylene) (PDCE) blocks was synthesized following the atom transfer radical polymerization (ATRP) procedure. The chemical structure of the obtained di-block copolymer PEG-b-PDCE was confirmed by different characterization techniques. Polyvinyl chloride (PVC) blend PEG-b-PDCE ultrafiltration (UF) membranes (PVC/PEG-b-PDCE) were prepared using the non-solvent induced phase separation (NIPS) technique and their characteristics were investigated as a function of the PEG-b-PDCE blending ratio in the casting solution. Water contact angle, permeate flux, and oil–water emulsion separation tests were performed to evaluate the hydrophilic character, permeability and anti-fouling membrane performance. It was found that the presence of PEG-b-PDCE copolymer affected the morphological structure of the membrane showing its good pore-forming capability. The oil rejection ability and anti-fouling properties of the blend membranes were improved by increasing the PEG-b-PDCE content up to 0.075 wt%. Compared to PVC membrane, the blend membrane prepared with 0.075 wt% PEG-b-PDCE exhibited about four times higher permeability with an excellent oil rejection factor, 98.78 %, indicating that the PVC/PEG-b-PDCE blend membranes have high potential in oily wastewater treatment.

Improvement of persistent hydrophilicity and pore uniformity of polyvinyl chloride ultrafiltration membranes by in-situ crosslinking reaction assisted phase separation

A novel in-situ crosslinking reaction assisted phase separation strategy was proposed for persistent hydrophilization and pore size regulation of polyvinyl chloride (PVC) membranes. In-situ cross-linking between PVC molecular chains was achieved through grafting of 3-aminopropyltrimethoxysilane (APTMS) during the dissolution process and cross-linking reactions between siloxanes in APTMS molecules initiated by the coagulation bath (water). The effect of in-situ crosslinking reaction on the structure, separation and anti-fouling performance of the PVC membranes was studied. Through in-situ crosslinking reaction induced phase separation, the migration and curing of polymer molecular chains in the phase separation process were regulated, which endowed the modified membrane with improved hydrophilicity, higher porosity and narrow pore size distribution. The pure water flux of the obtained membrane increased 3.5 times as much as that of the pure PVC membrane. In addition, the flux recovery rate (FRR) of the obtained membrane was increased by 15.9% and the strength was also increased slightly at the same time. The stability of the membranes was also improved, without chemical agents leaching during filtration, avoiding secondary pollution to our environment.

CuCr NLDH-Graphene oxide blended polyvinyl chloride ultrafiltration membrane with improved permeability and antifouling behavior

The modification of filtration membranes with the aim of improving their permeability, stability, and antifouling properties is essential, which can be achieved by the development of novel materials or methods. In this context, the utilization of new nanomaterials is one of the considered approaches for polymeric membrane modification. In this study, the applicability of CuCr NLDH-GO incorporation with the objective of improving hydrophilicity, permeability, and antifouling properties of polyvinyl chloride (PVC) ultrafiltration membrane is reported. After synthesis of CuCr NLDH-GO by co-precipitation method, its effect on the performance of PVC membrane was investigated by incorporation of different concentrations (0–2 wt%) of CuCr NLDH-GO. The significant decline of the water contact angle from 76.4° to 63.5° indicated the hydrophilicity improvement. This hydrophilic property was effective for almost twofold enhancement of the pure water permeability from 23.7 L/m2.h.bar of the bare membrane to 53.7 L/m2.h.bar of the membrane containing 1 wt% CuCr NLDH-GO. Moreover, the modified membranes indicated improved antifouling performance by increasing flux recovery ratio values from 54.3 % to 65 %. The performance of membranes in rejection of two different dyes, including reactive yellow 160 (RY160) and reactive black 5 (RB5) showed that the incorporation of CuCr NLDH-GO is not only effective for antifouling behavior but also suitable for improving dye rejection of membranes.

Preparation and characterization of polyvinyl chloride membranes decorated with designed novel zinc oxide particles for mitigating uncontrollable agglomeration

The use of nanomaterials in the fabrication of polymeric composite membranes has a great potential for improving separation performance by altering the membrane characteristics. However, homogeneous dispersion of these fillers in the matrix and stability issues have remained major drawbacks to take a step forward for the commercial applications of such membranes. In this study, polyvinyl chloride ultrafiltration membranes were prepared via direct blending of designed zinc oxide (ZnO) powders (MicNo®), that were intentionally agglomerated in hexagonal platelet forms, into the casting solution by immersion precipitation method. The impact of MicNo® loading on the development of membrane microstructure, separation performance and bulk properties were evaluated in comparison to neat PVC and commercial ZnO-doped membranes. Water flux (456 L/m2h) of the 0.05% wt. MicNo® platelets containing membranes had 30.6% and 9% higher values with respect to pristine PVC and 0.5% commercial ZnO (c-ZnO) containing membranes, respectively. Although the amount of MicNo® platelets (0.05%), added to the membrane casting solution was ten times less than c-ZnO nanoparticles (0.5%), rejection and antifouling properties of the membranes were enhanced significantly due to the large active hydrophilic surface area of MicNo® powders. The highest FRR value after SA removal tests was achieved as 89.9% in the case of PVC/0.05 MicNo® membrane with 19% enhancement compared with the pristine membrane. Overall, incorporating MicNo® into PVC-based membrane matrix could be a promising approach to cope with the uncontrolled agglomeration and leaching issues with minimal embedment of fillers.

Poly(ionic liquid) copolymer blended polyvinyl chloride ultrafiltration membranes with simultaneously improved persistent hydrophilicity and pore uniformity

Persistent hydrophilicity and uniform pore structure are key features of antifouling ultrafiltration membranes. Here, a poly(ionic liquid) copolymer, poly(methyl methacrylate)-b-poly(1-butyl-3-vinylimidazolium tetrafluoro-borate) (PMMA-b-PBVImBF4), was designed and synthesized by a simple free radical polymerization method and was employed to manipulate the hydrophilicity and pore structure of polyvinyl chloride (PVC) ultrafiltration membranes through the classic non-solvent induced phase separation. The hydrophobic PMMA segment, which has a carbonyl group, could be twined with the PVC chain, thus ensuring that the copolymer was stably anchored in the PVC skeleton, while the hydrophilic PBVImBF4 segment was segregated on the membrane surface. Membrane hydrophilicity and pore size uniformity were simultaneously enhanced. A 100 % increase in pure water flux, 45.8 % increase in mechanical strength, and 80 % increase in flux recovery rate were achieved when 3.85 wt% PMMA-b-PBVImBF4 was added. After 3 cycles of BSA filtration, the pure water flux of the copolymer-modified membrane was 267.0 L·m−2·h−1, approximately 4 times that of the pristine PVC membrane. Due to the stable existence of PMMA-b-PBVImBF4 in the membrane, the improved membrane hydrophilicity was maintained after 30 days of continuous washing.

Positively charged PVC ultrafiltration membrane via micellar enhanced ultrafiltration for removing trace heavy metal cations

One of the major focuses in the field of sewage is the development of low-pressure driven and high-efficiency filtration membrane, particularly for removing extremely low-concentration heavy metals cations. A new type of polyvinyl chloride (PVC) blended ultrafiltration (UF) membrane was fabricated to reject heavy metal cations (e.g., Cd2+, Co2+, Ni2+, Cu2+, and Zn2+) from simulated waters using micellar enhanced ultrafiltration (MEUF) in this research. The positively charged PVC UF membrane was fabricated by blending PVC and amphiphilic poly (methyl methacrylate-co- dimethylaminoethyl methacrylate) (PMD) which was in-situ quaternized by methyl iodide (CH3I), then the PVC/PMD blended membrane was fabricated via nonsolvent induced phase separation (NIPS) process. The membranes' pore morphology, surface chemical compositions, surface charge, water contact angle, mechanical strength and water flux were investigated in detail. The influence of pH, transmembrane pressure, sodium dodecylbenzene sulfonate (SDBS) concentration on the filtration of pure SDBS solution was studied. SDBS was subsequently used as surfactant to remove heavy metal ions by micellar enhanced ultrafiltration (MEUF). For a molar ratio of 40:1 (SDBS: metal cation), the rejection of feed solution containing 10 ppm metal cations (e.g., Cd2+, Co2+, Ni2+, Cu2+, and Zn2+) surpassed 96% with MEUF method. The results showed that the prepared membrane had low-pressure driven and high-efficiency performance, which provided a potential solution for the high-efficiency removal of trace heavy metals cations.

Effects of GO-PEG on the performance and structure of PVC ultrafiltration membranes

In this work, neat and nanocomposite polyvinyl chloride (PVC) membranes with various contents of graphene oxide-poly ethylene glycol (GO-PEG) nanosheets were fabricated via non-solvent phase separation (NIPS) method. The results of field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses approved the successful synthesis of GO-PEG nanosheets. Fabricated PVC/GO-PEG membranes were characterized by atomic force microscopy (AFM), water content, FESEM, contact angle, porosity, pure water flux (PWF), abrasion resistance and tensile strength tests. FESEM images illustrated the increased porosity of membranes after embedding of GO-PEG. The results showed that by addition of nanosheets, abrasion resistance of membranes enhanced as a reason of good mechanical properties of GO. Moreover, PWF was improved from 50 L/m2 h in neat PVC to around 211 L/m2 h in 0.15 wt.% PVC/GO-PEG membrane. Finally, MBR filtration test was utilized for 360 min to evaluate membranesʼ performance. In this case, Reversible Fouling Ratio (RFR) increased (from 9% in neat PVC membrane to 33% in PVC/GO-PEG 0.15 wt.% membrane) and Irreversible Fouling Ratio (IFR) decreased (from 51% in neat PVC to 37% in PVC/GO-PEG 0.15 wt.% membrane) by addition of GO-PEG nanosheets. The improved antifouling properties of PVC/GO-PEG membranes can be attributed not only to the hydrophilicity effect of GO-PEG nanosheets which prevents the foulants from attaching to membranes surface but also to the increased flux of PVC/GO-PEG membranes.

Long-term fouling evolution of polyvinyl chloride ultrafiltration membranes in a hybrid short-length sedimentation/ ultrafiltration process for drinking water production

Despite the rapid increase of ultrafiltration (UF) membranes in water treatment, the UF performance in large-scale drinking water treatment plants (DWTPs) in long-term operation has not been well understood. This study was carried out to investigate the fouling evolution of two types of polyvinyl chloride (PVC) hollow fiber UF membranes in a hybrid coagulation/short-length sedimentation/UF process. Water quality analysis showed that safe drinking water could be produced in the life time (i.e., 5 years) of the UF membranes. The fractions with large molecular weight (e.g., biopolymers), microbial by-product and aromatic protein II in raw water were easily removed, and the formation potentials of most disinfection by-products except trihalomethanes were found to decrease in the DWTP. Constant filtration fluxes were maintained for both types of UF membranes, while PVC composite membranes exhibited higher anti-fouling properties than PVC alloy membranes. The key fouling factors varied with operation time, and the top three factors were hydraulically cleaning efficiency, temperature and chemical oxygen demand using statistical analyses. Finally, the evolution model of membrane fouling in the first 5-year with potential fouling factors was established using artificial neural network, and membrane fouling of another year was predicted after UF membranes were replaced with new ones.

Towards enhanced fouling resistance of PVC ultrafiltration membrane using modified montmorillonite with folic acid

The main aim of this study is to develop the highly permeable and fouling resistant polyvinyl chloride (PVC) ultrafiltration membranes consisting different amounts of natural and modified montmorillonites with folic acid (Mt-FA). Mt. was modified with folic acid to achieve the better dispersion in the PVC matrix. Mt-FA was confirmed by XRD, FTIR and TGA. The effect of the Mt. and Mt-FA on the membrane morphology, porosity, hydrophilicity, roughness, mechanical strength, pure water flux and antifouling property in humic acid removal were investigated. XRD patterns revealed the formation of exfoliated clay mineral layers in 0.5 and 1.0 wt% loading of Mt-FA and the intercalated structure for the upper concentration of Mt-FA and the PVC/Mt-0.5 membrane. All the nanocomposite membranes showed higher hydrophilicity and roughness than the neat PVC membrane. The results demonstrated that the pure water flux, porosity and mechanical strength of the membranes were enhanced with the addition of Mt-FA up to a loading of 1.5 wt%. The PVC/Mt-FA-1.0 membrane exhibited high flux recovery ratio (FRR) and humic acid rejection of 92% and 90%, respectively. This was due to the exfoliated structure, surface hydrophilicity and electrostatic repulsion between negative charge of Mt-FA and humic acid. In addition, the reusability of the optimum membrane was evaluated for the filtration of the surface water in five permeation-cleaning cycles and the results confirmed that the modified membrane with 1.0 wt% Mt-FA can offer the excellent FRR as well as the reversible fouling ratio (RFR) in the filtration process.

Optimal synthesis, characterization and antifouling performance of Pluronic F127/bentonite-based super-hydrophilic polyvinyl chloride ultrafiltration membrane for enhanced oilfield produced water treatment

Pluronic F127 (PF127-) and PF127/bentonite-blended PVC ultrafiltration membranes are prepared in salt coagulation baths involving NaCl, KCl, NH4Cl, MgCl2 and CaCl2. Saturated KCl-coagulation bath delivers super-hydrophilic membrane with improved surface-porosity (10.64 %), pore density (49.26 μm−2), roughness (51.12 nm) and hydrophilicity (contact angle <10°), which endows remarkable enhancement of pure water flux at 100 kPa (i.e., 1610.0 Lm−2 h-1) and antifouling performance (flux recovery ratio: 75.8 %). Membrane performance is further improved by maximizing permeate flux and oil rejection simultaneously for actual oilfield produced water treatment using PVC-, PF127- and bentonite-loading, feed pH and feed temperature as decision variables and Pareto-optimal solution is obtained.

High-performance chlorinated polyvinyl chloride ultrafiltration membranes prepared by compound additives regulated non-solvent induced phase separation

To enable wider deployment of ultrafiltration (UF) membrane technology, novel advanced membrane materials are still highly desired. Chlorinated polyvinyl chloride (CPVC) shares most of the outstanding features of polyvinyl chloride (PVC) and possesses improved thermal stability, indicating a promising material for UF membrane. To date, however, the separation performance of the current CPVC UF membranes is far below the requirements for application. In this study, propylene glycol and polyoxyethylene-20-sorbaitan monolaurate (Tween-20) were selected as compound additives to manipulate the structure and separation performance of CPVC membrane fabricated by the non-solvent induced phase separation process. The results demonstrated that the synergistic effect of compound additives led to instantaneous demixing to increase the ratio of polymer lean phase in the initial casting film, and the rapid precipitation fixed the phase separation structure immediately. Consequently, the prepared membranes possessed improved porosity and pore size uniformity. The obtained CPVC UF membranes exhibited a high pure water flux up to 955.2 L m-2 h-1·bar-1 with a BSA rejection above 95.0%, which is 11 times higher than CPVC membrane fabricated without additive and comparable to that of commercial UF membranes. In addition, thanks to the more uniform pore size distribution and smooth top surface, the obtained CPVC membranes also exhibited good antifouling performance. Moreover, the CPVC UF membrane showed good thermal stability and reuse performance, which would facilitate its post-functionalization and practical application.

Improved permeability and antifouling properties of polyvinyl chloride ultrafiltration membrane via blending sulfonated polysulfone

To improve the permeability and antifouling properties of polyvinyl chloride (PVC) ultrafiltration (UF) membrane, amphiphilic sulfonated polysulfone (SPSF) was introduced into PVC matrix. Three types of PVC/SPSF blend membranes containing different SPSF with the sulfonation degree (SD) of 20%, 30%, and 50% were fabricated by non-solvent induced phase separation (NIPS) process. The excellent compatibility between PVC and SPSF was confirmed by differential scanning calorimetry (DSC). Surface chemical compositions, morphology, roughness, charge, hydrophilicity, permeability and antifouling properties of the pristine PVC membrane and the PVC/SPSF blend membranes were systematically compared and characterized. Due to the improved hydrophilicity and endowed negative charge, the blend membrane showed high water permeability (i.e. 880 L m−2h−1 bar−1), high bovine serum albumin (BSA) rejection (i.e. 95.7%), and high flux recovery ratio (i.e. 96%), which outperformed ever reported and commercialized PVC membranes. Furthermore, the permeability and rejection properties of PVC/SPSF UF membranes were maintained after soaking in acidic and alkaline solutions for 30 days, indicating their outstanding acid and alkali tolerance. Therefore, SPSF was expected as a potential versatile modifier for fabricating high performance UF membranes.

Investigation of characteristic and performance of polyvinyl chloride ultrafiltration membranes modified with silica‐oriented multi walled carbon nanotubes

AbstractThe complicated and dynamic nature of membrane fouling is one of the most challenging issues that need to be addressed to obtain an efficient membrane. In this work, silica‐oriented multiwalled carbon nanotubes (Si‐MWCNTs) are synthesized by the sol–gel method and characterized using several analytical techniques. Novel polyvinyl chloride (PVC) ultrafiltration membranes are fabricated by incorporation of Si‐MWCNT nanoparticles at varying loading levels (0–2 wt%) using the phase inversion method. Membrane morphology, chemical composition, thermal behavior, crystallinity, roughness, hydrophilicity, and mechanical strength are characterized and filtration performance is tested to compare the results with those of pristine PVC membranes. The results reveal that the addition of 0.5% Si‐MWCNT nanoparticles into the casting solution exhibits the highest flux (400 L/m2h), sodium alginate (SA) rejection rate (96%), and flux recovery ratio (93%) due to having the highest hydrophilicity, an improved structure, and surface properties revealed by surface morphology and bulk property analysis. Furthermore, the results of dynamic mechanical and nanoindentation analyses confirm that mechanical properties such as hardness, Young's modulus, and stiffness of the pristine membrane are significantly improved by the addition of Si‐MWCNT nanoparticles.

Enhanced performance of salt-induced Pluronic F127 and bentonite blended polyvinyl chloride ultrafiltration membrane for the processing of oilfield produced water

Pluronic F127 blended polyvinyl chloride (PVC) ultrafiltration (UF) membranes using different loading of inorganic salts (like NaCl, KCl, NH4Cl, MgCl2 and CaCl2) in casting solution involving N-methyl-pyrrolidone solvent are prepared for the cleaning of oilfield produced water with 200 ppm oil concentration. The effect of salt loading in casting solution on the performance of blended PVC membranes is studied by determining the thermodynamic and kinetic effect, membrane hydrophilicity, morphology, pure water flux, oilfield produced water permeate flux, oil rejection and fouling resistance ability. A better performing membrane is obtained using KCl in polymer casting solution involving PVC-14.0 (g), NMP-80.0 (g), Pluronic F127-5.0 (g) and KCl-1.0 (g) with enhanced (i) pure water flux (i.e., 607.8 L m−2 h-1), (ii) produced water permeate flux (i.e., 265.7 L m−2 h-1) and (iii) oil rejection (> 92.8 %) with higher fouling resistance (i.e., flux recover ratio > 71.65 %) when trans membrane pressure is kept at 100 kPa, compared to PVC UF membranes involving CaCl2, MgCl2, NaCl and NH4Cl salts in casting solution. The addition of bentonite nanoclay in Pluronic F127 and KCl-induced PVC casting solution has a significant impact to improve the UF performance and results super-hydrophilic membrane with water contact angle < 10°. An enhancement in pure water and oilfield produced water permeate flux by 42.25 % and 37.61 %, respectively, with oil rejection > 92.0 % is obtained over UF membrane without bentonite.

Incorporation of graphene oxide/nanodiamond nanocomposite into PVC ultrafiltration membranes

Polyvinylchloride (PVC) ultrafiltration membranes with different amounts of graphene oxide-nanodiamond (GO-ND) nanocomposite were prepared via phase inversion method. The results of XRD and FTIR analyses showed that GO-ND nanocomposite was successfully synthesized and FESEM images showed that ND nanoparticles were uniformly attached on GO nanosheets with no agglomeration. Then, fabricated PVC/GO-ND membranes were characterized using a set of analyses including FESEM, AFM, Raman spectroscopy, contact angle, pure water flux, abrasion resistance, tensile strength, elongation and pore size distribution. The results showed that the hydrophilicity and surface roughness of membranes were improved with addition of GO-ND nanocomposite. Moreover, pure water flux was increased from 200Lm−2h−1 for neat PVC membrane to 440Lm−2h−1 for 0.15wt. % GO-ND embedded membrane due to the enhancement of hydrophilicity and number of pores on surface surface of nanocomposite membranes. Besides, tensile strength and abrasion resistance of membranes were improved because of the reinforcement effect of GO-ND nanocomposite which can be attributed to the uniform dispersion of nanocomposite throughout PVC matrix. Finally, performance of membranes was evaluated in filtration of 1.0gL−1 BSA solution and it was revealed that antifouling properties and BSA rejection of membranes were enhanced with increasing GO-ND content up to 0.10wt. % and then were decreased.

Properties of polyvinyl chloride (PVC) ultrafiltration membrane improved by lignin: Hydrophilicity and antifouling

Usually seen as a waste with low chemical value and limited commercial potential, lignin produced in large quantity from paper industry performs abundant valuable hydrophilic groups which make it a potential hydrophilic assistant. In this contribution, in order to improve hydrophilicity and antifouling properties of PVC ultrafiltration membrane, lignin was doped into PVC to prepare a uniform sol under strengthening heat and mass transfer process, and then PVC/lignin ultrafiltration membranes were prepared via phase inversion strategy. The resulted PVC/lignin ultrafiltration membranes were characterized by SEM, FT-IR, XPS, DSC and were also tested by oily wastewater. According to the results of SEM, XRD and DSC analyses, PVC is compatible with lignin and the homogeneous PVC/lignin sol can be formed. The hydrophilicity of membrane is significantly enhanced with water contact angle (WCA) decreasing from 106.73° to 41.53°. Particularly, the PVC/lignin ultrafiltration membranes exhibit attractive properties with oil rejection of 97.36% and oily wastewater permeation flux of 156.55 L m−2 h−1 (0.1 MPa), nearly 2.5 times that of pure one (65.06 L m−2 h−1). Lignin suggests to be a superior additive to improve hydrophilic and anti-fouling properties of PVC membranes, and the lignin-modified membranes are promising candidates for cleaning oily wastewater and sewage.

Performance enhancement of polyvinyl chloride ultrafiltration membrane modified with graphene oxide

A novel polyvinyl chloride (PVC) membrane was modified with graphene oxide (GO) via phase inversion method to improve its hydrophilicity and mechanical properties. The GO presented a large amount of hydrophilic groups after the modification through the modified Hummers method. It was observed that with the addition of low fraction of GO powder, the GO/PVC hybrid membranes exhibited a significant enhancement in hydrophilicity, water flux, and mechanical properties. With optimal dosage (0.1wt%), the pure water flux of GO/PVC membrane increased from 232.6L/(m2hbar) to 430.0L/(m2hbar) and the tensile strength increased from 231.3cN to 305.3cN. The improved properties of the PVC/GO hybrid membranes are mainly attributed to the strong hydrophilicity of functional groups on the GO surface, indicating that GO has a promising candidate for modification of PVC ultrafiltration membranes in wastewater treatment.