Elaboration, characterization and application of polysulfone and polyacrylic acid blends as ultrafiltration membranes for removal of some heavy metals from water

Novel MXene-Modified Polyphenyl Sulfone Membranes for Functional Nanofiltration of Heavy Metals-Containing Wastewater

In this work, MXene as a hydrophilic 2D nanosheet has been suggested to tailor the polyphenylsulfone (PPSU) flat sheet membrane characteristics via bulk modification. The amount of MXene varied in the PPSU casting solution from 0-1.5 wt.%, while a series of characterization tools have been employed to detect the surface characteristics changes. This included atomic force microscopy (AFM), scanning electron microscopy (SEM), contact angle, pore size and porosity, and Fourier-transform infrared spectroscopy (FTIR). Results disclosed that the MXene content could significantly influence some of the membranes' surface characteristics while no effect was seen on others. The optimal MXene content was found to be 0.6 wt.%, as revealed by the experimental work. The roughness parameters of the 0.6 wt.% nanocomposite membrane were notably enhanced, while greater hydrophilicity has been imparted compared to the nascent PPSU membrane. This witnessed enhancement in the surface characteristics of the nanocomposite was indeed reflected in their performance. A triple enhancement in the pure water flux was witnessed without compromising the retention of the membranes against the Cu²⁺, Cd²⁺ and Pd²⁺ feed. In parallel, high, and comparable separation rates (>92%) were achieved by all membranes regardless of the MXene content. In addition, promising antifouling features were observed with the nanocomposite membranes, disclosing that these nanocomposite membranes could offer a promising potential to treat heavy metals-containing wastewater for various applications.

Separation Mechanisms and Anti-Fouling Properties of a Microporous Polyvinylidene Fluoride-Polyacrylic Acid-Graphene Oxide (PVDF-PAA-GO) Composite Membrane with Salt and Protein Solutions

This research demonstrates the preparation of composite membranes containing graphene oxide (GO) and investigates the separation mechanisms of various salts and bovine serum albumin (BSA) solutions. A microporous polyvinylidene fluoride-polyacrylic acid-GO (PVDF-PAA-GO) separation layer was fabricated on non-woven support. The GO-incorporating composite resulted in enlarged pore size (0.16 μm) compared with the control membrane (0.12 μm). The zeta potential of the GO composite was reduced to -31 from -19 mV. The resulting membranes with and without GO were examined for water permeability and rejection efficiency with single salt and BSA solutions. Using the non-woven/PVDF-PAA composite, the permeance values were 88-190 kg/m²hMPa, and the salt rejection coefficients were 9-28% for Na₂SO₄, MgCl₂, MgSO₄, and NaCl solutions. These salt removals were based on the Donnan exclusion mechanism considering the ion radii and membrane pore size. Incorporating GO into the separation layer exhibited limited impacts on the filtration of salt solutions, but significantly reduced BSA membrane adhesion and increased permeance. The negatively charged protein reached almost complete removal (98.4%) from the highly negatively charged GO-containing membrane. The GO additive improved the anti-fouling property of the composite membrane and enhanced BSA separation from the salt solution.

Simultaneous Removal of Polymers with Different Ionic Character from Their Mixed Solutions Using Herb-Based Biochars and Activated Carbons

Nettle and the sage herbs were used to obtain carbonaceous adsorbents. For the biochar preparation the precursors were dried and subjected to conventional pyrolysis. Activated carbons were obtained during precursor impregnation with phosphoric(V) acid and multistep pyrolysis. The textural parameters and acidic-basic properties of the obtained adsorbents were studied. The activated carbons prepared from the above herbs were characterized by the largely developed specific surface area. The obtained carbonaceous adsorbents were used for polymer removal from aqueous solution. Poly(acrylic acid) (PAA) and polyethylenimine (PEI) were chosen, due to their frequent presence in wastewater resulting from their extensive usage in many industrial fields. The influence of polymers on the electrokinetic properties of activated carbon were considered. PAA adsorption caused a decrease in the zeta potential and the surface charge density, whereas PEI increased these values. The activated carbons and biochars were used as polymer adsorbents from their single and binary solutions. Both polymers showed the greatest adsorption at pH 3. Poly (acrylic acid) had no significant effect on the polyethylenimine adsorbed amount, whereas PEI presence decreased the amount of PAA adsorption. Both polymers could be successfully desorbed from the activated carbons and biochar surfaces. The presented studies are innovatory and greatly required for the development of new environment protection procedures.

Magnetic Beads of Zero Valent Iron Doped Polyethersolfun Developed for Removal of Arsenic from Apatite-Soil Treated Water

The drop immerses calcium chloride aqueous solution was utilized to prepare the zero valent iron-doped polyethersulfone beads (PES/ZVI) for the efficient removal of arsenic from apatite-soil treated waters. The proposed beads can assist in promoting uptake efficiency by hindering ZVI agglomeration due to a high porosity and different active sites. The PES/ZVI beads were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and vibrating sample magnetism (VSM). The main objective of this study was to investigate the function of new PES/ZVI beads with an increased removal efficiency for the remediation of arsenic ions from the apatite-soil treated waters. A maximum adsorption removal of 82.39% was achieved when the experiment was performed with 80 mg of adsorbent for a contact time of 180 min. Based on the results, a removal efficiency >90% was obtained after 300 min of shaking time with an arsenic concentration of 20 mg·L^-1. The experimental process was fitted with the Langmuir model due to the high R² (0.99) value compared to the Freundlich model (0.91) with an adsorption capacity of 41.32 mg·g^-1. The adsorption process speed was limited by pseudo-second-order (R² = 0.999) and the adsorption mechanism nature was endothermic and physical.

An In Situ Incorporation of Acrylic Acid and ZnO Nanoparticles into Polyamide Thin Film Composite Membranes for Their Effect on Membrane pH Responsive Behavior

This paper focuses on an in situ interfacial polymerization modification of polyamide thin film composite membranes with acrylic acid (AA) and zinc oxide (ZnO) nanoparticles. Consequent to this modification, the modified polyamide thin film composite (PA–TFC) membranes exhibited enhanced water permeability and Pb (II) heavy metal rejection. For example, the 0.50:1.50% ZnO/AA modified membranes showed water permeability of 29.85 ± 0.06 L·m⁻²·h⁻¹·kPa⁻¹ (pH 3), 4.16 ± 0.39 L·m⁻²·h⁻¹·kPa⁻¹ (pH 7), and 2.80 ± 0.21 L·m⁻²·h⁻¹·kPa^−1 1 (pH 11). This demonstrated enhanced pH responsive properties, and improved water permeability properties against unmodified membranes (2.29 ± 0.59 L·m⁻²·h⁻¹·kPa⁻¹, 1.79 ± 0.27 L·m⁻²·h⁻¹·kPa⁻¹, and 0.90 ± 0.21 L·m⁻²·h⁻¹·kPa⁻¹, respectively). Furthermore, the rejection of Pb (II) ions by the modified PA–TFC membranes was found to be 16.11 ± 0.12% (pH 3), 30.58 ± 0.33% (pH 7), and 96.67 ± 0.09% (pH 11). Additionally, the membranes modified with AA and ZnO/AA demonstrated a significant pH responsiveness compared to membranes modified with only ZnO nanoparticles and unmodified membranes. As such, this demonstrated the swelling behavior due to the inherent “gate effect” of the modified membranes. This was illustrated by the rejection and water permeation behavior, hydrophilic properties, and ion exchange capacity of the modified membranes. The pH responsiveness for the modified membranes was due to the –COOH and –OH functional groups introduced by the AA hydrogel and ZnO nanoparticles.

Performance of polycaprolactone/TiO2 composite membrane for the effective treatment of dairy effluents

This work is the first, to the best of our knowledge, to use polycaprolactone (PCL)-based membrane for the treatment of dairy wastewater. PCL is a biodegradable polymer with high biocompatibility and good oil resistance. The chlorine tolerance analysis of PCL-based membranes exhibited a good tolerance against chlorine. The PCL/TiO₂ nanocomposite membrane with the addition of polyethylene glycol was prepared and tested for protein separation. The dependency of contact angle with time was analysed for the membrane, and the contact angle value reduced from 74.5 ± 2° to a steady value of 65 ± 2° in 120 s. The proteins were removed using a cross-flow filtration unit at an operating pressure of 0.4 MPa at room temperature with permeate flux of 10 L/m² h and a relative permeate flux of about 0.10. The removal of proteins was measured qualitatively using native polyacrylamide gel electrophoresis (PAGE) and quantitatively using Lowry's test. A percentage rejection of 97.6 was obtained and the native PAGE showed the complete removal of all the major proteins present in the milk sample.

Cesium removal from a water system using a polysulfone carrier containing nitric acid-treated bamboo charcoal

Laboratory scale sorption and desorption experiments were performed to investigate the cesium (Cs) removal efficiency of a bead-shaped polysulfone carrier containing HNO₃-treated bamboo charcoal (BC). The average Cs removal efficiency of BC only and of polysulfone carrier without BC after 1 h sorption reaction was 53 and 18%, respectively. However, the Cs removal efficiency for the polysulfone carrier with 5% HNO₃-treated BC (P-5N-BC) after 1 h and 24 h reaction was 66 and 98%, respectively. The Cs removal efficiency after 24 h reaction remained >85% over a wide range of pH and temperature conditions, suggesting that using P-5N-BC as the Cs adsorbent is feasible in a variety of aquatic environments. The maximum Cs sorption capacity (q_m) of P-5N-BC, as calculated from a Langmuir isotherm model, was 60.9 mg/g, which is much higher than those of other adsorbents from previous studies for 1 h of sorption time. The Cs desorption rate of P-5N-BC for 24 h desorption time was <17%, showing that the Cs was stably enough attached to the HNO₃-treated BC for long-term use. The results of continuous column experiments showed that the total amount of treated water from the column packed with P-5N-BC increased more than nine times when compared with that from the only BC-granule-packed column. The P-5N-BC maintained more than 68% Cs removal efficiency after 90 pore volumes of flushing, suggesting that only 15 g of P-5N-BC (with only 0.75 g of HNO₃-treated BC) could clean 5 L of Cs-contaminated water (initial Cs concentration: 1.0 mg/L; effluent concentration: < 0.09 mg/L). The present results demonstrate that P-5N-BC has remarkable potential for removal of Cs from diverse water systems.

Ultrafiltration treatment of wastewater contained heavy metals complexed with palygorskite

Palygorskite was applied in complexation-ultrafiltration treatment of heavy metals in wastewater under different pH and ionic strength. The results indicated that the rejection of heavy metals increased significantly with pH value, and decreased slightly with an increase of ionic strength of Na+ and Cl–. A certain concentration of NaCl significantly reduced the rejection rate of Cu2+. The rejection of Cu2+, Zn2+ and Cd2+ could reach over 86.8%, 93.6% and 93.7% at pH of 7 and 0.1 mol/L NaCl. The rejection of heavy metals was severely affected by low molecular weight competing complexing agents and the effect of sodium tartrate was greater than triethanolamine. In the presence of sodium tartrate, the rejection of Cu2+, Zn2+ and Cd2+ could arrive over 81.4%, 57.6% and 60.5% at pH of 7 in 20 min. Palygorskite was offered a potential complexing agent for the removal of heavy metals in wastewater at the complexation-ultrafiltration process.

Cu2+ ion-sensitive surface on graphite electrodes

A new electrochemical interface based on polyacrylic acid (PAAcid) immobilized in a Nafion® polymeric matrix on graphite screen-printed electrodes for detecting copper is presented. The copper is retained in the surface due to the capacity of the polyacid to chelate metals, and quantified using square wave voltammetry. The response was characterized by spectroscopic techniques (UV-vis-IR), which confirmed the chelation from the Cu²⁺ ions by the acid. A calibration curve is presented, showing good linearity and repeatability and its usefulness as a sensor. The range of operation goes from 15 to 50 μM, with a detection limit of 12 μM, making the sensor useful for measurements in environmental samples (after a preconcentration step) and in drinking water.

Development of in situ synthesized Y-based nanoparticle/polyethersulfone adsorptive membranes by adjusting the composition of the coagulation bath for enhanced removal of fluoride

The composition of coagulation bath significantly altered the membrane structure, composition and adsorption performance for defluoridation by affecting the phase inversion kinetics.

Application and modification of polysulfone membranes

Polysulfone (PSf) is a favorite polymer for the production of membrane due to its excellent physicochemical properties, including thermal stability; good chemical resistance to different materials such as different bases, acids, and chlorine; sufficient mechanical strength; and good processability. The present study offers an overview of the recent development in the application and modification of PSf membranes, focusing on some applications such as water and wastewater treatment, membrane distillation, pollutant removal, gas separation, separator for lithium ion battery, and support of composite membranes. In general, there are two major difficulties in the use of membranes made of PSf: membrane fouling and membrane wetting. Therefore, PSf membrane with good anticompaction and antifouling properties is reviewed. Finally, important issues related to the modification of PSf membranes for real applications are discussed. This article provides an intelligent direction for the progress of PSf membranes in the future.

Selective sorption of Fe(II) ions over Cu(II) and Cr(VI) ions by cross-linked graft copolymers of chitosan with acrylic acid and binary vinyl monomer mixtures

Low-cost and environment-friendly polymeric adsorbents for sorption of heavy metal ions were synthesized by simultaneous graft copolymerization and cross-linking of acrylic acid alone and with comonomers glycidyl methacrylate, acrylamide and acrylonitrile onto chitosan using free radical initiator and cross-linker in aqueous medium. Structural aspects of cross-linked graft copolymers have been characterized by FTIR, SEM, TGA/DTA, XRD and swelling behavior at pH 2.2, 7.0 and 9.4. An attempt has been made to study sorption of Cr(VI), Cu(II) and Fe(II) ions on cross-linked graft copolymers by equilibration method and to establish a relationship between structural aspects of graft copolymers and metal ion uptake efficiency and selectivity. Solutions of individual ions were used for non-competitive sorption onto synthesized bio-adsorbents as a function of change in contact time, temperature, pH and metal ion concentration in feed. Competitive sorption investigation was performed from an aqueous solution of ternary metal ions by batch equilibration at 25°C and at 7.0pH. Cross-linked graft copolymers showed better results than unmodified chitosan and showed preferential sorption of Fe(II) ions than Cu(II) and Cr(VI) ions.

Novel modified poly vinyl chloride blend membranes for removal of heavy metals from mixed ion feed sample

Herein, an attempt has been made to prepare a novel membrane with good efficiency for removal of heavy metal ions namely lead (Pb), cadmium (Cd) and chromium (Cr). 4-amino benzoic acid (ABA) was covalently grafted onto the poly vinyl chloride (PVC) backbone by CN bond to enhance the hydrophilicity. ¹H NMR and ATR-IR spectroscopy analysis confirmed the chemical modification of PVC. Further the modified polymer was blended in different compositions with polysulfone (PSf) for optimization. Morphological changes that occurred in blend membranes, due to the incorporation of modified PVC was studied by AFM and SEM techniques. The effect on hydrophilicity and performance of blends owing to incorporation of modified PVC was evaluated by water uptake, contact angle and flux studies. The density of functional groups in blends was analyzed by its ion-exchange capacity. Batch wise filtration of metal ions was carried out and the effect of pressure, feed pH and interference of ions was thoroughly investigated. Essentially, 100% rejection was obtained for all the metal ions in acidic pH with a productivity of 2.56l/m²h. The results were correlated with the results of commercially available NF 270 membrane under the same operating conditions.

High-performance cellulose acetate/polysulfone blend ultrafiltration membranes for removal of heavy metals from water

Neat cellulose acetate (CA) and CA/polysulfone (PSf) blend ultrafiltration membranes in the presence of polyvinylpyrrolidone as a pore former were prepared via a phase inversion technique. The prepared membranes were characterized by Fourier transform infrared, scanning electron microscopy, mechanical strength, water content, porosity, permeate flux and heavy metals (Pb²⁺, Cd²⁺, Zn²⁺ and Ni²⁺) rejection to comprehend the impact of polymer blend composition and additive on the properties of the modified membranes. The water flux expanded by increasing of PSf content in the polymer composition. CA/PSf (60/40) had the highest flux among prepared membranes. Prepared blend membranes were able to remove heavy metals from water in the following order: Pb²⁺ > Cd²⁺ > Zn²⁺ > Ni²⁺. The CA/PSf (80/20) blend membrane had great performance among prepared membranes due to the high heavy metals removal and permeate flux.

Plasma polyacrylic acid and hollow TiO2 spheres modified with rhodamine B for sensitive electrochemical sensing Cu(ii)

A rhodamine B-modified nanocomposite-based electrochemical sensor was fabricated for selectively and sensitively detecting Cu(ii) in environmental fields.

Synthesis and characterization of novel sulfanilic acid–polyvinyl chloride–polysulfone blend membranes for metal ion rejection

A novel facile method is developed for the modification of polyvinyl chloride and blend membranes are fabricated for heavy metal removal. This method is straightforward, has a high efficiency and is done at low pressure.

Preparation and evaluation of heavy metal rejection properties of polyetherimide/porous activated bentonite clay nanocomposite membrane

The acid activated bentonite clay with 1.0 to 4.0 wt% was incorporated into PEI membranes and was extensively studied for its morphology, hydrophilicity and other properties. The modified membrane exhibited an increment in porosity, hydrophilicity and a reduction in hydraulic resistance. The membranes showed rejection of 69.3%, 76.2% and 82.5% for 250 ppm of Cd(ii), Ni(ii) and Cu(ii) ion solutions, respectively.

Nanofibrous electrospun barrier membrane promotes osteogenic differentiation of human mesenchymal stem cells

An electrospun polysulfone (PSU) was prepared as a barrier membrane for guided bone regeneration. The membrane was in nanoscale to prevent fibrous tissue infiltration and highly porous to allow permeation of oxygen and nutrients. The morphology and attachment, viability and proliferation, and differentiation and mineralization of human bone marrow mesenchymal stem cells (HBMSCs) were determined. Cells adhered and spread well on the PSU membrane with characteristic polygonal, fusiform shapes and radial extensions. The live/dead staining revealed that the membrane had no negative influence on cell viability. The proliferation rates of HBMSCs on PSU membranes were lower in comparison with tissue-culture polystyrene plate after 3 days of culture. However, differentiation activity was particularly expressed at high levels when cells were cultured on PSU membranes. The results based on the data suggest that the PSU electrospun membrane promoted the osteogenic differentiation of HBMSCs, displayed desirable in vitro biocompatibility, and has good potential as a barrier membrane.