Adsorptive removal of nitrate from aqueous solution by polyacrylonitrile–alumina nanoparticle mixed matrix hollow-fiber membrane

Nitrate removal study of synthesized nano γ-alumina and magnetite-alumina nanocomposite adsorbents prepared by various methods and precursors

The challenges in water treatment include the need for efficient removal of pollutants like nitrate, which poses significant environmental and health risks. Alumina's significance lies in its proven effectiveness as an adsorbent for nitrate removal due to its high surface area and affinity for nitrate ions. This study delves into the synthesis of differen nano-sized γ-alumina (γA1-5) employing diverse precursors and methods, including nepheline syenite, lime, aluminum hydroxide, precipitation, and hydrothermal processes at varying reaction times. Simultaneously, magnetite (Fe3O4) nanoparticles and magnetite/γ-alumina nanocomposites (Fn/γA5) were synthesized using the co-precipitation method with varying weight ratios (n). Our primary objective was to optimize γ-alumina synthesis by comparing multiple methods, shedding light on the influence of different precursors and sources. Hence, a comprehensive adsorption study was conducted to assess the materials' efficacy in nitrate removal. This study fills gaps in the literature, providing a novel perspective through the simultaneous assessment of magnetite/alumina nanocomposites and pure alumina performance. Structural and morphological properties were studied employing XRD, FT-IR, FESEM, EDX, XRD, and VSM techniques. The conducted experiments for γA5, F5/γA5, and F10/γA5 nanocomposites showcased the optimum pH of 5 and contact time of 45 min for all samples. The influence of nitrate's initial concentration on the removal percentage was investigated with initial concentrations of 10 ppm, 50 ppm, and 100 ppm. γA5, F5/γA5 and F10/γA5 nanocomposites had 17.3%, 55%, and 70% at 10 ppm, 18%, 55.16%, and 74% at 50 ppm, and 8.6%, 53.1%, and 63%, respectively. The results highlighted that F10/γA5 can be used as a remarkable adsorbent for wastewater treatment purposes.

Efficient removal of bovine serum albumin from water by cellulose acetate membranes modified with clay and titania nano particles

Modified cellulose acetate membranes with bentonite clay (CA/bent) and TiO₂ nanoparticles (CA/TiO₂) using the phase inversion method are successfully prepared and characterized. These Membranes are favored due to their high salt rejection properties and recyclability. The IR and EDX spectral data indicate the formation of modified membranes. The Scan Electron Microscope micrographs show that the modified membranes have smaller particle sizes with higher porosity than the neat membrane. The average pore diameter is 0.31 µm for neat cellulose acetate membrane (CA) and decreases to 0.1 µm for CA/0.05bent. All modified membranes exhibit tensile strengths and elongation percentages more than the neat membrane. The higher tensile strength and the maximum elongation% are 15.3 N/cm² and 11.78%, respectively, for CA/0.05bent. The thermogravimetric analysis of modified membranes shows higher thermal stability than the neat membrane. The modified membranes exhibit enhanced wettability and hydrophilicity compared with cellulose acetate, by measuring the contact angle which decreases from 60° (CA) to 40° (CA/0.1bent). The ultrafiltration tests indicated that the CA/bent and CA/TiO₂ are better than CA. The most efficient nanocomposite membrane is CA/0.05bent with 100% removal of (BSA) from industrial water with a flux equal to 9.5 mL/min under an applied pressure of 20 bar. Thus, this study introduces a novel ultrafiltration membrane (CA/0.05bent) that can be used effectively to completely remove bovine serum albumin from contaminated water.

Electrochemical ammonia synthesis by reduction of nitrate on Au doped Cu nanowires†

Electrochemical nitrate reduction reaction (NO₃⁻RR) to synthesize valuable ammonia (NH₃) is considered as a green and appealing alternative to enable an artificial nitrogen cycle. However, as there are other NO₃⁻RR pathways present, selectively guiding the reaction pathway towards NH₃ is currently challenged by the lack of efficient catalyst. Here, we demonstrate a novel electrocatalyst for NO₃⁻RR consisting of Au doped Cu nanowires on a copper foam (CF) electrode (Au–Cu NWs/CF), which delivers a remarkable NH₃ yield rate of 5336.0 ± 159.2 μg h⁻¹ cm⁻² and an exceptional faradaic efficiency (FE) of 84.1 ± 1.0% at −1.05 V (vs. RHE). The ¹⁵N isotopic labelling experiments confirm that the yielded NH₃ is indeed from the Au–Cu NWs/CF catalyzed NO₃⁻RR process. The XPS analysis and in situ infrared spectroscopy (IR) spectroscopy characterization results indicated that the electron transfer between the Cu and Au interface and oxygen vacancy synergistically decreased the reduction reaction barrier and inhibited the generation of hydrogen in the competitive reaction, resulting in a high conversion, selectivity and FE for NO₃⁻RR. This work not only develops a powerful strategy for the rational design of robust and efficient catalysts by defect engineering, but also provides new insights for selective nitrate electroreduction to NH₃.

Electrochemical nitrate reduction reaction (NO₃⁻RR) to synthesize valuable ammonia (NH₃) is considered as a green and appealing alternative to enable an artificial nitrogen cycle.

Fabrication of polysulfone mixed matrix membrane for wastewater treatment

Recent development in separation technologies has envisioned a green and sustainable future that encouraged energy preservation and waste minimization. The concept of a clean future emphasizes on retrieval and reutilization of valuable products from waste streams to improve the water quality. Membrane-based separations are currently explored as an auspicious substitution over traditional separation processes. The present study is designed to purify water using aluminum and gallium mixed matrix membranes from toxic metals (Lead and Mercury) and dyes (Rhodamine B, and Reactive Blue-4). Facile protocol i.e., immersion precipitation phase inversion method was used for the fabrication of mixed matrix membrane. The aluminium and gallium hybrids act as a filler and create heterogeneity and hydrophilicity within the membrane, affirming better water permeability and mechanical strength. The performance of fabricated mixed matrix membranes is evaluated using a lab-based dead-end membrane filtration unit. The result showed 30-71% rejection of Mercury, 24-65% rejection of Lead, 12-66% rejection of Reactive Blue-4, and 15-80% rejection of Rhodamine B.

From Classical to Advanced Use of Polymers in Food and Beverage Applications

Polymers are extensively used in food and beverage packaging to shield against contaminants and external damage due to their barrier properties, protecting the goods inside and reducing waste. However, current trends in polymers for food, water, and beverage applications are moving forward into the design and preparation of advanced polymers, which can act as active packaging, bearing active ingredients in their formulation, or controlling the head-space composition to extend the shelf-life of the goods inside. In addition, polymers can serve as sensory polymers to detect and indicate the presence of target species, including contaminants of food quality indicators, or even to remove or separate target species for later quantification. Polymers are nowadays essential materials for both food safety and the extension of food shelf-life, which are key goals of the food industry, and the irruption of smart materials is opening new opportunities for going even further in these goals. This review describes the state of the art following the last 10 years of research within the field of food and beverage polymer's applications, covering present applications, perspectives, and concerns related to waste generation and the circular economy.

Controllable reconstruction of copper nanowires into nanotubes for efficient electrocatalytic nitrate conversion into ammonia

The electrochemical reduction of nitrate to ammonia provides a green and delocalized route for ammonia synthesis under ambient conditions, which requires advanced catalysts with high activity and selectivity. In this work, we propose a two-step conversion strategy to construct hierarchical copper nanosheet-based Cu nanotubes using pre-synthesized Cu nanowires as the starting material for the electrocatalytic nitrate reduction reaction (NO₃RR). The conversion of Cu nanowires into Cu nanotubes could be realized through chemical oxidation followed by in situ electrochemical reduction, enabling the effective engineering of active sites and thus boosting the electrocatalytic nitrate-to-ammonia capability. Such a controllable reconstruction strategy provides a new avenue for constructing high-performance electrocatalysts for sustainable NH₃ synthesis and the elimination of NO₃^- contamination.

Adsorption Behavior of Methylene Blue Cationic Dye in Aqueous Solution Using Polypyrrole-Polyethylenimine Nano-Adsorbent

In this work, a polypyrrole-polyethyleneimine (PPy-PEI) nano-adsorbent was successfully synthesized for the removal of methylene blue (MB) from an aqueous solution. Synthetic dyes are among the most prevalent environmental contaminants. A new conducting polymer-based adsorbent called (PPy-PEI) was successfully produced using ammonium persulfate as an oxidant. The PEI hyper-branched polymer with terminal amino groups was added to the PPy adsorbent to provide more effective chelating sites for dyes. An efficient dye removal from an aqueous solution was demonstrated using a batch equilibrium technique that included a polyethyleneimine nano-adsorbent (PPy-PEI). The best adsorption parameters were measured at a 0.35 g dosage of adsorbent at a pH of 6.2 and a contact period of 40 min at room temperature. The produced PPy-PEI nano-adsorbent has an average particle size of 25–60 nm and a BET surface area of 17 m²/g. The results revealed that PPy-PEI nano-composite was synthesized, and adsorption was accomplished in the minimum amount of time. The maximum monolayer power, qmax, for MB was calculated using the isothermal adsorption data, which matched the Langmuir isotherm model, and the kinetic adsorption data, which more closely fitted the Langmuir pseudo-second-order kinetic model. The Langmuir model was used to calculate the maximum monolayer capacity, or qmax, for MB, which was found to be 183.3 mg g⁻¹. The as-prepared PPy-PEI nano-adsorbent totally removes the cationic dyes from the aqueous solution.

Synthesis and characterization of waste commercially available polyacrylonitrile fiber-based new composites for efficient removal of uranyl from U(VI)-CO3 solutions

The existing species of uranium determines the design of novel sorbents towards uranium extraction from the natural waters. Herein, three composites based on waste commercially available polyacrylonitrile fiber (WPANF), namely WPANF/TiO₂·xH₂O, WPANF/CTAB-bentonite, and WPANF/NZVI, were first prepared and employed for the removal of U(VI) from the carbonate coexisted aqueous solutions. Among them, the WPANF/TiO₂·xH₂O exhibited the optimum sorption capacity of ~40.6 mg·g^-1 (pH 8.0, C₀ = 50 mg·L^-1, and [CO₃]_Total = 2 mmol·L^-1), which is significantly greater than the WPANF/CTAB-bentonite (~12.6 mg·g^-1) and WPANF/NZVI (~10.3 mg·g^-1). All sorption capacities decreased with the increases of initial pH, [NaCl], and [CO₃]_Total, due to the species transformation from UO₂(CO₃)₂^2- and (UO₂)₂CO₃(OH)₃^- to UO₂(CO₃)₃^4- that enhanced the electrostatic repulsion and the competitive sorption. The XPS analysis and DFT calculations indicated that in the composites, WPANF was a role in strengthening the mechanical properties of composites rather than the main sorption sites for uranyl carbonates. The sorption mechanisms were mainly involved in -OH group coordination, Br^- anions exchanges, and redox reactions. Desorption, reusability and U(VI) sorption test in the simulated seawater demonstrated that WPANF/TiO₂·xH₂O could be an alternative candidate for acquiring uranium resource. This work has screened the potential composites for U(VI) extraction from the natural waters, especially based on the practical U(VI) speciation, and provides a novel research approach for the removal of U(VI) towards U(VI)-CO₃ systems.

Single-Atom Cu Catalysts for Enhanced Electrocatalytic Nitrate Reduction with Significant Alleviation of Nitrite Production

Metallic Cu is a well-known electrocatalyst for nitrate reduction reaction (NO₃ RR), but it suffers from relatively low activity, poor stability, and inducing nitrite accumulation during the long-term operation. Herein, it is found that Cu catalysts minimized at the single-atom level can overcome the limitations of bulk materials in NO₃ RR. A metal-nitrogen-carbon (M-N-C) electrocatalyst composed of carbon nanosheets embedding isolated copper atoms coordinated with N, Cu-N-C-800, is synthesized by pyrolysis of a Cu-based metal-organic framework at 800 °C. In comparison with Cu nanoparticles and Cu plate-800, kinetic measurements show that the Cu-N-C-800 electrocatalyst is more active and stable and distinctly suppresses the release of nitrite intermediate into the solution. The combined results of experimental data and density functional theory calculations indicate that Cu bound with N (particularly Cu-N₂ ) is the key to favorable adsorption of NO₃ ^- and NO₂ ^- . This strong binding is responsible for the enhanced rate of nitrate conversion to the end products of ammonia and nitrogen. These findings highlight the promise of single-atom Cu electrocatalysts for nitrate reduction with desirable performance.

Removal of As(V), Cr(VI) and Cu(II) using novel amine functionalized composite nanofiltration membranes fabricated on ceramic tubular substrate

Novel amine functionalized composite membranes were prepared over tubular ceramic substrate using facile dip-coating and cross-flow filtration approach. The two fabricated membranes, P-60S and P-60S-EDTA with polyethyleneimine (PEI) and EDTA-modified PEI as functional layers respectively, were characterized in terms of EDX, FTIR, XPS, FESEM, AFM and contact angle analyses which confirmed their stable physical and chemical structure for use in high pressure application. Clean water permeability and MWCO study revealed the superior permeability and rejection efficiency of the P-60S-EDTA compared to the P-60S membrane. Incorporation of bulky EDTA molecules in the membrane functional layer simultaneously decreased pore size and increased membrane hydrophilicity. The removal of As(V), Cr(VI) and Cu(II) heavy metals by both membranes were found to be highly pH dependent and overall rejection improved in case of P-60S-EDTA membrane [99.82% for Cu(II), 96.75% for As(V) and 97.22% for Cr(VI)]. Interestingly, rejection of As(V) and Cr(VI) was significantly improved in presence of Cu(II) due to volume resistance provided by EDTA-Cu(II) complex towards the passage of other heavy metal ions. Excellent stability of P-60S-EDTA membrane in continuous operation of 36 h in both ideal and practical water environment suggests its promising application in real field heavy metal contaminated waste water treatment.

Functionalized electrospun nanofiber membranes for water treatment: A review

Electrospun nanofiber membranes (ENMs) have high porosity, high specific surface area and unique interconnected structure. It has huge advantages and potential in the treatment and recycling of wastewater. In addition, ENMs can be easily functionalized by combining multifunctional materials to achieve different water treatment effects. Based on this, this review summarizes the preparation of functionalized ENMs and its detailed application in the field of water treatment. First, the process and influence factors of electrospinning process are introduced. ENMs with high porosity, thin and small fiber diameter have better performance. Secondly, the modification methods of ENMs are analyzed. Pre-electrospinning and post-electrospinning modification technology can prepare specific functionalized ENMs. Subsequently, functionalized ENMs show water treatment capabilities such as separation, adsorption, photocatalysis, and antimicrobial. Subsequently, the application of functionalized ENMs in water treatment capabilities such as separation, adsorption, photocatalysis, and antimicrobial capabilities were listed. Finally, we also made some predictions about the future development direction of ENMs in water treatment, and hope this article can provide some clues and guidance for the research of ENMs in water treatment.

Polyacrylonitrile homogeneous blend hollow fiber membrane with stable structure as a substrate to support Fe/Mn oxide and its enhanced capability to purify dye wastewater

Blending different molecular weight polyacrylonitrile (PAN) was adopted to solve the shrinkage problem of high molecular weight PAN hollow fiber membrane, to enhance the application performance of low molecular weight PAN membrane, and to adjust the porosity, pore size distribution, and hydrophilicity of the end product. The structurally-optimized membrane was chosen as a substrate to support Fe/Mn oxides and then used as a reactor to remove dyes from their solutions in the presence of H2O2. The results showed that the flux of methylene blue (MB) aqueous solution was 83.7 L/m2 h for the PAN homogeneous blend membrane, much higher than 29.1 L/m2 h of high molecular weight PAN membrane; MB removal efficiency was 97.3%, higher than 62.3% of low molecular weight PAN membrane, and it could be reused 25 times to remove dyes from their solutions without any loss in removal efficiency. The membrane was also found to have the application advantages of decreasing H2O2 dosage, reducing operation pressure, and raising MB removal efficiency compared with other membranes reported in the pieces of literature. Therefore, we were confident that the hollow fiber membrane fabricated by us would exhibit great application potential in the field of decontaminating dye wastewater.

A Process for the Recovery of Gallium from Gallium Arsenide Scrap

The recovery of gallium (Ga) from gallium arsenide (GaAs) scrap using a leaching-ion exchange method was investigated. The ground GaAs scrap was leached, using 2.0 N nitric acid at 30 °C for 1.0 h, and the dissolution of Ga and arsenic (As) reached 98%. The pregnant solution with a 1/20 dilution ratio was then passed through a weak acid chelating resin Diaion CR-11. Highly charged Ga3+ has the ability to form complexes with the chelating resin and separate from the coexisting H3AsO4 in the leachate with very low pH. The loaded column was eluted with 0.1 M H2SO4, and the final concentrated solution had 4.5 g/L of Ga with 99.3% purity. The effluent from the column was further processed to remove As by ferric arsenicate precipitation, and reused continuously as the dilution water for raw leachate.

Adsorptive nanocomposite membranes for heavy metal remediation: Recent progresses and challenges

Heavy metal contamination in aqueous system has attracted global attention due to the toxicity and carcinogenicity effects towards living bodies. Among available removal techniques, adsorptive removal by nanosized materials such as metal oxide, metal organic frameworks, zeolite and carbon-based materials has attracted much attention due to the large active surface area, large number of functional groups, high chemical and thermal stability which led to outstanding adsorption performance. However, the usage of nanosized materials is restricted by the difficulty in separating the spent adsorbent from aqueous solution. The shift towards the use of adsorptive composite membrane for heavy metal ions removal has attracted much attention due to the synergistic properties of adsorption and filtration approaches in a same chamber. Thus, this review critically discusses the development of nanoadsorbents and adsorptive nanocomposite membranes for heavy metal removal over the last decade. The adsorption mechanism of heavy metal ions by the advanced nanoadsorbents is also discussed using kinetic and isotherm models. The challenges and future prospect of adsorptive membrane technology for heavy metal removal is presented at the end of this review.

Application of modified electrospun nanofiber membranes with α-Fe2O3 nanoparticles in arsenate removal from aqueous media

In the present study, electrospun nanofiber membranes (ENMs) of polyacrylonitrile (PAN) were modified by dispersing α-Fe₂O₃ nanoparticles, synthesized using a thermal solvent process, in a PAN solution. The morphology and physiochemical properties of the prepared ENMs and the α-Fe₂O₃ were characterized using FESEM, EDX, BET, XRD, FTIR, porosity, and contact angle measurement. XPS was used to investigate the interaction of ENM with arsenate (As(V)) during the adsorption. Moreover, the effect of pH, the equilibrium isotherm, and the kinetics were investigated in batch experiments. The Langmuir isotherm best correlated the experimental results, indicating monolayer adsorption on ENMs, and the kinetics was best fitted, R² > 0.99, by the pseudo-second-order model. In addition, the effects of certain conditions on the filtration performance were examined, such as feed concentration and transmembrane pressure (TMP). By passing sodium hydroxide (0.1 M) for 20 min, the membrane was regenerated. The increase in TMP, along with the presence of co-ions including chloride, nitrate, and sulfate, had negative impacts on the removal of As(V). The results show that the modified ENMs with α-Fe₂O₃ nanoparticles are applicable for As(V) ion removal and possibly for eliminating other heavy metals from aqueous media.

In situ-generated yttrium-based nanoparticle/polyethersulfone composite adsorptive membranes: Development, characterization, and membrane formation mechanism

In this study, a series of in situ-generated yttrium-based nanoparticle (NP)/polyethersulfone (PES) composite adsorptive membranes were prepared by the phase inversion method for the first time. The Y(NO₃)₃·6H₂O as precursor, uniformly dispersed at the molecular level in casting solution, reacted with OH^- in a coagulation bath and ambient CO₂ during the phase inversion process. The Y(CO₃)_0.5(OH)₂ NPs were formed in situ and distributed homogeneously in a PES matrix, which was confirmed by X-ray photoelectron spectroscopy (XPS) and Energy Dispersive X-Ray Spectroscopy (EDS) results. The compatibility of the nanocomposite membranes was improved by an in situ preparation method. With the increase in content of Y-based NPs in composite membranes, the surface hydrophilicity and water permeability first increased from M1 to M2, and then slightly decreased from M3 to M5, which was mainly related to membrane structure. From M1 to M5, the demixing way changed from instantaneous demixing to delayed demixing process as a result of thermodynamic enhancement and viscosity hindrance in the phase inversion process. A higher demixing rate led to a structure with large finger-like macro-voids, i.e., M1, whereas a lower demixing rate caused the suppression of finger-like macro-voids, i.e., M5. More importantly, the adsorption study indicated that the nanocomposite adsorptive membranes were stable in the treatment of fluoride-containing water, with no leakage of Y-based NPs from membrane matrix to solution. It is expected that the in situ preparation technique could be used to produce next-generation nanocomposite adsorptive membranes with improved comprehensive properties for application in water treatment.

Polyethersulfone Membranes Prepared with 3-Aminopropyltriethoxysilane Modified Alumina Nanoparticles for Cu(II) Removal from Water

In this study, 3-aminopropyltriethoxysilane (APTES) modified γ-alumina nanoparticles were utilized to improve the copper removal efficiency of polyethersulfone (PES) membranes. Alumina nanoparticles were first modified by APTES silane coupling agent before impregnating into PES composite membranes. The PES membranes were fabricated by incorporating three different amounts of modified nanoparticles by a phase inversion process. The prepared membranes were characterized using field emission scanning electron microscopy, Fourier transform infrared, X-ray diffraction, thermogravimetric analysis (TGA), dynamic mechanical analysis, water contact angle, water flux, and porosity measurements. The Cu(II) removal and adsorption capacity of the membranes were also analyzed. The addition of nanoparticles increased the thermal stability, hydrophilicity, total porosity, Brunauer-Emmett-Teller surface area, and glass transition temperature of the membranes. TGA confirmed a suitable uptake of the nanoparticles during the membrane fabrication process. The water permeation of the membranes also increased significantly. Membranes synthesized with 4 wt % nanoparticles showed the highest rejection for copper ions of 87%. Adsorption isotherms were tested using Langmuir and Freundlich models, where the Freundlich isotherm model resulted in the best fitting.

Exfoliated Mg-Al-Fe layered double hydroxides/polyether sulfone mixed matrix membranes for adsorption of phosphate and fluoride from aqueous solutions

Mg-Al-Fe layered double hydroxides (LDHs) were exfoliated and incorporated in polyether sulfone membranes for the removal of phosphate and fluoride for the first time. The exfoliation methods, coagulation bath, LDH amount, interfering ions, adsorption isotherm, desorption and reuse of the membranes were investigated. It was found that LDHs could be quickly exfoliated in formamide/N,N-dimethylformamide (DMF) solvent mixtures with sodium carboxymethyl cellulose as a stabilizer. The membranes displayed much higher adsorption capacity for phosphate (5.61mg/g) and faster adsorption rate than the un-exfoliated materials. With increased DMF content in the coagulation bath, the static and dynamic adsorption capacity rose. Interference from Cl^- and SO₄^2- (50mg/L) on adsorption of phosphates was not apparent. The membranes displayed excellent reusability in dynamic adsorption/desorption. The membranes also showed high adsorption capacity for fluorides (1.61mg/g).

Development of a novel biochar/PSF mixed matrix membrane and study of key parameters in treatment of copper and lead contaminated water

Mixed matrix membrane (MMM) has attracted increasing attentions in various applications, such as water treatment. In this study, an innovative biochar/polysulfone (PSF) mixed matrix hollow fiber membrane was fabricated by incorporating micro-sized biochar particles in the PSF matrix. It was demonstrated that the membrane was more hydrophilic than the pure PSF membrane. Higher water flux was obtained. The adsorption of copper and lead on the MMM increased as the pH was increased with the maximum adsorption capacity observed at pH > 4.5. The adsorption equilibrium was established in 7 and 12 h for lead and copper, respectively. The adsorption kinetics and isotherm followed the intraparticle surface diffusion model and Freundlich isotherm, respectively. The presence of humic acid (HA) had a little effect on the adsorption, while the ionic strength showed an adverse effect on the removal. In addition, the feed concentration and cross flow rate significantly affected the removal efficiency in a continuous filtration mode. The increase in feed concentration and cross flow rate resulted in a reduction in the volume of treated permeate that had the copper/lead concentrations below the regulated levels for drinking water. The MMM exhibited an excellent regeneration-reuse performance in the removal of both copper and lead. Finally, our mechanism studies indicated that the uptake of heavy metals was controlled by a combination of key reactions of complexation, ion-exchange and precipitation. This study indicated that the MMM can be applied as an effective and eco-friendly material for the treatment of heavy metals contaminated water.

Filtration and removal performances of membrane adsorbers

Membrane adsorbers are promising candidates for the efficient and effective removal of heavy metals in waste water due to their unattainable adsorption and filtration capabilities. In the present study, zeolite nanoparticles incorporated polysulfone (PSf10) membrane was synthesized by means of non-solvent induced phase separation technique for the removal of lead and nickel ions in water. PSf10 showed a remarkable sorption capability and after repeated (adsorption/desorption)₅ cycles in batch experiments, it preserved 77% and 92% of its initial sorption capacity for the lead and nickel, respectively. Addition of nanoparticles increased the pore radius of the native PSf from 10 to 19nm, while bovine serum albumin rejection remained unchanged at 98%. Increments in the pore size and enhancement in hydrophilicity caused to increase hydraulic permeability of the native PSf from 23 to 57L/m²hbar. Cross-flow filtration studies revealed that the filtrate concentrations were inversely affected by the initial metal concentration and transmembrane pressure due to reaction limited region. Nonlinear rational regression model perfectly described the filtration behavior of the PSf10 within the experimental range and suggested that lower initial metal concentration and pressure with a short filtration time should be selected for the target response to be minimum.

Novel sandwich structure adsorptive membranes for removal of 4-nitrotoluene from water

Novel sandwich PES-SPES/PS-PDVB/PTFE adsorptive membranes were prepared by a filtration/immersion precipitation method and employed for the removal of 4-nitrotoluene from water. The static adsorption thermodynamics, kinetics, dynamic adsorption/desorption and membrane reusability were investigated. The results showed that the Freundlich model describes the adsorption isotherm satisfactorily. With increased PS-PDVB content, the maximum static adsorption capacity, partition coefficient, apparent adsorption rate constant, and dynamic adsorption capacity all significantly increased. The sandwich membranes showed much higher removal efficiency and adsorption capacity than those of mixed matrix membranes. With respect to dynamics adsorption/desorption, the sandwich membranes exhibited excellent reusability, with a removal efficiency greater than 95% even after five recycles.

Advances in nanomaterial based approaches for enhanced fluoride and nitrate removal from contaminated water

Various nanomaterials for fluoride and nitrate removal from contaminated water.

MOF–polymer enhanced compatibility: post-annealed zeolite imidazolate framework membranes inside polyimide hollow fibers

Zeolitic imidazolate frameworks and polyimide supports improved their affinity during thermal annealing and therefore the separation performance of the membrane.