“Environmental friendly and cost effective caramel for congo red removal, high flux, and fouling resistance of polysulfone membranes”

Efficient cationic dye removal from water through Arachis hypogaea skin-derived carbon nanospheres: a rapid and sustainable approach

The present study investigates the potential of Arachis hypogaea skin-derived carbon nanospheres (CNSs) as an efficient adsorbent for the rapid removal of cationic dyes from aqueous solutions. The CNSs were synthesized through a facile, cost-effective, catalyst-free and environmentally friendly process, utilizing Arachis hypogaea skin waste as a precursor. This is the first reported study on the synthesis of mesoporous carbon nanospheres from Arachis hypogaea skin. The structural and morphological characteristics of the CNSs were confirmed by different nano-characterization techniques. The adsorption performance of the carbon nanospheres was evaluated through batch adsorption experiments using two cationic dyes-methylene blue (MB) and malachite green (MG). The effects of the initial dye concentration, contact time, adsorbent dosage, and pH were investigated to determine the optimal conditions for dye removal. The results revealed that the obtained CNSs exhibited remarkable adsorption capacity and rapid adsorption kinetics. Up to ∼98% removal efficiency was noted for both dyes in as little as 2 min for a 5 mg L-1 dye concentration, and the CNSs maintained their structural morphology even after adsorption. The adsorption data were fitted to various kinetic and isotherm models to gain insights into the adsorption mechanism and behaviour. The pseudo-second-order kinetic model and Redlich-Peterson model best described the experimental data, indicating multi-layer adsorption and chemisorption as the predominant adsorption mechanism. The maximum adsorption capacity was determined to be 1128.46 mg g-1 for MB and 387.6 mg g-1 for MG, highlighting the high affinity of the carbon nanospheres towards cationic dyes. Moreover, CNS reusability and stability were examined through desorption and regeneration experiments, which revealed sustained efficiency over 7 cycles. CNSs were immobilised in a membrane matrix and examined for adsorption, which demonstrated acceptable efficiency values and opened the door for further improvement.

Lignin particles as green pore-forming agents for the fabrication of microporous polysulfone membranes

Templating polymeric membranes with micro-nano-scaled solid materials is an effective method to simultaneously improve the water flux and retention ratio. However, the fabrication of a green, recyclable, and size-controlled template material remains a challenge. Here, a new green pore-forming agent, lignin particles (LP), was developed to prepare porous polysulfone (PSF) membranes via the phase inversion technique. A series of LP have uniform sizes from ~200 nm to ~1800 nm. The performances of the templated PSF membranes cast at different sizes and contents of LP were examined for their surface and crosssection morphologies. The LP-templated PSF membranes displayed a remarkable enhancement in flux, porosity, and moisture content. Particularly, the PSF membranes cast with LP from ~200 to 1800 nm broke the traditional trade-off to a certain degree, which possessed stable retentions of bovine serum albumin (> 85 %) and significantly improved water flux (174.275 to 254.775 L m^-2 h^-1). In addition, the LP pore-forming agent is low-cost and environmentally friendly as it was prepared from industrial by-products and can be easily recycled. Overall, this study shows that lignin particles are green pore-forming agents that can be used for the fabrication of porous polymeric membranes with improved performance for water treatment.

Biomimetic mineralization of nacre-inspired multiple crosslinked PVA/CaAlg/SiO2 membrane with simultaneously enhanced mechanical and separation properties

Inspired by the natural nacre structure, we propose a new strategy to fabricate mineralized, multiple crosslinked hydrogel membranes with the "rigid silica in soft polymer" nacre-like structure. In-situ SiO₂ nanoparticles (NPs) and polyvinyl alcohol/sodium alginate (PVA/NaAlg) are used to simulate the rigid "bricks" and soft "mortar" compositions of nacre, respectively. The nacre-like mineralized (PVA/CaAlg/SiO₂) membrane showed a higher tensile strength of 4.1 ± 0.08 MPa, excellent pure water flux of 170 ± 3 L/m²h, and an oil/water rejection rate of 99 %. The interwoven hierarchal structure, similar to nacre, was determined by SEM analysis. In addition, incorporating SiO₂ NPs increases the anti-swelling, roughness, and hydrophilicity of the membranes. PVA/CaAlg/SiO₂ membrane exhibited excellent superhydrophilicity (WCA value was 0°) and superoleophobicity underwater (OCA value was 162°). PVA/CaAlg/SiO₂ membrane also showed excellent separation performance for water-soluble organic pollutants and can be used for dye separation with rejection efficiencies of 99.5 %, 99.1 %, and 98.3 % for Congo red (CR), Alizarin red (AR), and Sunset yellow (SY), respectively. Moreover, PVA/CaAlg/SiO₂ membrane had outstanding long-term filtration and antifouling performance. The biomineralization-inspired structure provides a promising technique that can be used to prepare high-performance organic-inorganic membranes with great promise for wastewater separation application.

Recent Advances on the Fabrication of Antifouling Phase-Inversion Membranes by Physical Blending Modification Method

Membrane technology is an essential tool for water treatment and biomedical applications. Despite their extensive use in these fields, polymeric-based membranes still face several challenges, including instability, low mechanical strength, and propensity to fouling. The latter point has attracted the attention of numerous teams worldwide developing antifouling materials for membranes and interfaces. A convenient method to prepare antifouling membranes is via physical blending (or simply blending), which is a one-step method that consists of mixing the main matrix polymer and the antifouling material prior to casting and film formation by a phase inversion process. This review focuses on the recent development (past 10 years) of antifouling membranes via this method and uses different phase-inversion processes including liquid-induced phase separation, vapor induced phase separation, and thermally induced phase separation. Antifouling materials used in these recent studies including polymers, metals, ceramics, and carbon-based and porous nanomaterials are also surveyed. Furthermore, the assessment of antifouling properties and performances are extensively summarized. Finally, we conclude this review with a list of technical and scientific challenges that still need to be overcome to improve the functional properties and widen the range of applications of antifouling membranes prepared by blending modification.

Preparation and Characterization of Electrospun Poly(lactic acid)/Poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol)/Silicon Dioxide Nanofibrous Adsorbents for Selective Copper (II) Ions Removal from Wastewater

The problem of industrial wastewater containing heavy metals is always a big concern, especially Cu²⁺, which interprets the soil activity in farmland and leaves a negative impact on the environment by damaging the health of animals. Various methods have been proposed as countermeasures against heavy-metal contaminations, and, as a part of this, an electrospun nanofibrous adsorption method for wastewater treatment is presented as an alternative. Poly(lactic acid) (PLA) is a biopolymer with an intrinsic hydrophobic property that has been considered one of the sustainable nanofibrous adsorbents for carrying adsorbate. Due to the hydrophobic nature of PLA, it is difficult to adsorb Cu²⁺ contained in wastewater. In this study, the hydrophilic PLA/poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PEG-PPG-PEG) nanofibrous adsorbents with different silicon dioxide (SiO₂) concentrations were successfully prepared by electrospinning. A hydrophilic group of PEG-PPG-PEG was imparted in PLA by the blending method. The prepared PLA/PEG-PPG-PEG/SiO₂ nanofibrous adsorbents were analyzed with their morphological, contact angle analysis, and chemical structure. The Cu²⁺ adsorption capacities of the different PLA/PEG-PPG-PEG/SiO₂ nanofibrous adsorbents were also investigated. The adsorption results indicated that the Cu²⁺ removal capacity of PLA/PEG-PPG-PEG/SiO₂ nanofibrous adsorbents was higher than that of pure ones. Additionally, as an affinity nanofibrous adsorbent, its adsorption capacity was maintained after multiple recycling processes (desorption and re-adsorption). It is expected to be a promising nanofibrous adsorbents that will adsorb Cu²⁺ for wastewater treatment.

Treatment of Tuna Cooking Juice via Ceramic Ultrafiltration Membrane: Optimization Using Response Surface Methodology

In the present work, optimized ultrafiltration conditions, using a ceramic multi tubular titania membrane (150 KDa), were investigated for the treatment of tuna cooking juice, for water reuse in the industrial process. The interactive effects of the volume concentrating factor (VCF) (1.03-4.25), feed temperature (T) (20-60 °C), and applied transmembrane pressure (ΔP) (2-5 bar) on protein removal (R protein) and permeate flux (J) were determined. A Box-Behnken experimental design (BBD) with the response surface methodology (RSM) was used for statistical analysis, modeling, and optimization of the operating conditions. The analysis of variance (ANOVA) results proved that the protein removal and permeate flux were significant and represented good correlation coefficients of 0.9859 and 0.9294, respectively. Mathematical modeling showed that the best conditions were VCF = 1.5 and a feed temperature of 60 °C, under a transmembrane pressure of 5 bar. The fouling mechanism was checked by applying a polarization concentration model. Determination of the gel concentration confirmed the results found in the mass balance calculation and proved that the VCF must not exceed 1.5. The membrane regeneration efficiency was proven by determining the water permeability after the chemical cleaning process.

Efficient Removal of Organic Dye from Aqueous Solution Using Hierarchical Zeolite-Based Biomembrane: Isotherm, Kinetics, Thermodynamics and Recycling Studies

Bio adsorbents have received tremendous attention due to their eco-friendly, cheap and non-toxic nature. Recently, bio-adsorbent-based membranes have been frequently employed for water treatment. The work reports the preparation of a novel adsorbent membrane from hierarchical zeolite, polyvinyl alcohol, carboxymethyl cellulose and agar. The fabricated membrane was characterized spectroscopically and microscopically with several techniques such as XRD, UTM, TGA, optical microscopy and FT-IR, as well as contact-angle studies. The result showed that the hierarchical-zeolite-loaded membrane is superior in terms of thermal stability, mechanical properties and surface roughness. The fabricated membrane was investigated for its efficiency in the removal of Congo red dye in aqueous conditions. The influence of pH, temperature, contact period and the initial concentration of dye and zeolite loading on the adsorption process are also explored. The adsorption results highlighted the maximum sorption property of Congo red on agar/zeolite/carboxymethyl cellulose/polymer biomembrane was found to be higher (15.30 mg/g) than that of zeolite powder (6.4 mg/g). The adsorption isotherms and kinetic parameters were investigated via Langmuir, Freundlich and pseudo-first order, pseudo-second order and the intraparticle diffusion model, respectively. The adsorption isotherms fitted well for both considered isotherms, whereas pseudo-second order fitted well for kinetics. The thermodynamic parameter, ΔG at 303 K, 313 K and 323 K was −9.12, −3.16 and −0.49 KJ/mol, respectively. The work further explores the antibacterial efficacy of the prepared membrane and its reusability.

Green synthesis of P − ZrO2CeO2ZnO nanoparticles using leaf extracts of Flacourtia indica and their application for the photocatalytic degradation of a model toxic dye, Congo red

In the present work P−ZrO2CeO2ZnO nanoparticles were synthesised for the first time using phytochemical extracts from Flacourtia indica leaves and applied in the photocatalytic degradation of Congo Red in the presence of Light Emitting Diode warm white light. The photocatalytic degradation was optimized with respect to P−ZrO2CeO2ZnO nanoparticle dosage, initial Congo Red concentration, and degradation time. The optimum conditions for P−ZrO2CeO2ZnO nanoparticle synthesis was pH 9, leaves extracts of F. indica dosage 4 g 100 mL⁻¹, Zirconia, Cerium and Zinc metal ion concentration 0.05 mg/L and metal ion to plant volume ratio of 1:4. The leaves extract dosage, pH and metal concentration had the most significant effects on the synthesis of the nanoparticles. The nanoparticles followed type III physisorption adsorption isotherms with surface area of 0.4593 m³g⁻¹, pore size of 6.80 nm, pore volume 0.000734 cmg−13 and average nanoparticle size 0.255 nm. A degradation efficiency of 86% was achieved and the optimum degradation conditions were 0.05 g/L of P−ZrO2CeO2ZnO nanoparticle dosage, 10 mg/L initial Congo red concentration, and 250 minutes irradiation time. Data from kinetic studies showed that the degradation followed pseudo first order kinetics at low concentration, with a rate constant of 0.069 min⁻¹. The superoxide, h+ holes and light were the main determinants of the reaction mechanisms for the degradation of Congo Red. The investigation outcomes demonstrated that P−ZrO2CeO2ZnO nanoparticles offer a high potential for photocatalytic degradation of Congo Red.

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The most significant factors on P−ZrO2CeO2ZnO nanoparticles synthesis were plant leaves dosage, pH and initial metal concentration.

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The nanoparticles exhibited high catalytic activity towards photocatalytic degradation of Congo red.

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Superoxide, h+ holes and light were the main determinants of the photocatalytic degradation mechanisms.

Nitrogenated Graphene Oxide-Decorated Metal Sulfides for Better Antifouling and Dye Removal

Nitrogenated graphene oxide-decorated copper sulfide nanocomposites (Cu _x S-NrGO, where x = 1 and 2) are designed to be incorporated in polysulfone (PSF) membranes for effective fouling resistance of PSF membranes and their dye removal capacity. The developed membranes possess more hydrophilicity and an enhancement in pure water flux (PWF). Also, the highest bovine serum albumin (BSA) rejection of 89% was observed when compared to membranes with pristine PSF (5 L/m² h PWF and 88% BSA rejection) and CuS-incorporated PSF membranes (14 L/m² h PWF and 83% BSA rejection) because of N doping and enhanced permeability. It is also found that the Cu _x S-NrGO-incorporated PSF membranes exhibited a significantly higher fouling resistance, a larger permeate flux recovery ratio (FRR) of nearly 82%, and a congo red dye rejection of 93%. Cu _x S-NrGO nanoparticles thus demonstrate the potential efficacy of enhancing the hydrophilicity, leading to a better flux, dye removal capacity, and antifouling capacity with a very high FRR value of 82% because of a strong interaction between the N-active sites of the NrGO, Cu _x S, and polysulfone matrix, and negligible leaching of nanoparticles is observed.

Comprehensive Analysis of Spinel-Type Mixed Metal Oxide-Functionalized Polysulfone Membranes toward Fouling Resistance and Dye and Natural Organic Matter Removal

Nanostructured polymeric membranes are of great importance in enhancing the antifouling properties during water filtration. Nanomaterials with tunable size, morphology and composition, surface modification, and increased functionality provide considerable opportunities for effective wastewater treatment. Thus, in this work, an attempt has been made to use spinel-structured MnCo₂O₄ as a nanofiller in the fabrication of nanostructured polysulfone (PSF) mixed matrix membranes and is investigated in terms of morphology, hydrophilicity, permeability, protein and natural organic matter separation, dye removal, and, finally, antifouling properties. The MnCo₂O₄ nanomaterials are synthesized and characterized via X-ray diffraction and field emission scanning electron microscopy and are loaded into a membrane matrix with varied concentrations (0 to 1.5 wt %). PSF nanocomposite membranes are prepared via a nonsolvent-induced phase-separation process. The results show an enhancement in hydrophilicity, porosity, and permeability with respect to the modified nanocomposite membranes because of oxygen-rich species in the membrane matrix, which increases affinity toward water. It was also found that the modified membranes display remarkably greater pure water flux (PWF) (220 L/m² h), higher Congo red rejection coefficient (99.86%), higher humic acid removal (99.81%), higher fouling resistance, and a significant flux recovery ratio (FRR) (88%) when tested with bovine serum albumin protein when compared to a bare PSF membrane (30 L/m² h PWF and 35% FRR). This is because the addition of MnCo₂O₄ nanoparticles into the polymeric casting solution yielded tighter PSF membranes with a denser skin layer and greater selectivity. Thus, the enhanced permeability, greater rejection coefficient, and antifouling properties show the promising potential of the fabricated PSF-spinel nanostructured membrane to be utilized in membrane technology for wastewater treatment.

Removal of anionic dye Congo red from aqueous environment using polyvinyl alcohol/sodium alginate/ZSM-5 zeolite membrane

In this study, a novel PVA/SA/ZSM-5 zeolite membrane with good regeneration capacity was successfully prepared by solvent casting technique. The properties of the membranes were assessed by employing different characterization techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), optical microscopy (OP), thermogravimetric analysis (TGA), contact angle and universal testing machine (UTM). XRD, TGA and UTM results revealed that the crystallinity and thermo-mechanical performance of the membrane could be tuned with zeolite content. The successful incorporation of zeolite into the polymer matrix was confirmed by FT-IR, SEM and OP analysis. The adsorption ability of the as-prepared membrane was evaluated with a model anionic dye, Congo red. Adsorption studies show that the removal efficiency of the membrane could be tuned by varying zeolite content, initial concentration of dye, contact time, pH and temperature. Maximum dye adsorption (5.33 mg/g) was observed for 2.5 wt% zeolite loaded membrane, at an initial dye concentration of 10 ppm, pH 3 and temperature 30 °C. The antibacterial efficiency of the membrane against gram-positive (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli) was also reported. The results show that membrane inhibits the growth of both gram-positive and gram-negative bacteria. The adsorption isotherm was studied using two models: Langmuir and Freundlich isotherm. The results show that the experimental data fitted well with Freundlich isotherm with a high correlation coefficient (R2 = 0.998). Meanwhile, the kinetic studies demonstrate that pseudo-second-order (R2 = 0.999) model describe the adsorption of Congo red onto PVA/SA/ZSM-5 zeolite membrane better than pseudo-first-order (R2 = 0.972) and intra particle diffusion model (R2 = 0.91). The experimental studies thus suggest that PVA/SA/ZSM-5 zeolite could be a promising candidate for the removal of Congo red from aqueous solution.

An integrated electrocoagulation-nanofiltration process for carwash wastewater reuse

In the present work, advanced treatment of carwash wastewater with an integrated electrocoagulation-nanofiltration (EC-NF) process to reuse the treated wastewater as rinsing water was investigated. The wastewater was pretreated by EC process under various operating parameters such as temperature (25 °C, 35 °C, 45 °C), stirring speed (150 rpm, 250 rpm, 350 rpm), and electrode connection mode (MP-P, MP-S, BP-S) using Fe electrode. The best results were achieved at 25 °C, 250 rpm and MP-P connection mode for EC, considering both pollutant removals and energy consumptions. EC sludge was characterized scanning electron microscopy-energy dispersive index (ESEM-EDX) analysis. The pretreated carwash wastewater using EC process was further treated by NF process using NF 270 and Desal 5DL membranes. Desal 5 DL membrane provided the highest treatment performance for chloride (92%), conductivity (80%) and total hardness (90%) parameters for EC-NF process. Resistance in series model was used for a deeper discussion of the reasons for flux decline. In addition, Fourier transform infrared (FTIR) spectroscopy and contact angle measurements were conducted for membrane fouling characterization. The foulants mainly accumulated on the membrane surface forming a cake layer and lower extent of membrane fouling was occurred for both membranes. As a result, this study showed that the water quality for reuse in carwashing process could be achieved with an integrated EC-NF process.

Congo red filtration by polyacrylonitrile-based copolymer membranes

In this study, Congo red removal from wastewater by a filtration method was studied via membranes obtained from polyacrylonitrile-co-poly(2-ethylhexylacrylate) copolymers having various monomer ratios and polyacrylonitrile-co-poly(2-ethylhexylacrylate)/polyaniline blends with various polyaniline contents. It was found that the dye rejection value increased with acrylonitrile content in polyacrylonitrile-co-poly(2-ethylhexylacrylate) membranes. Also, blending copolymers with polyaniline enhanced the dye rejection rate. The performance of membranes showed incremental increase with increase in the polyaniline content. Both pH and concentration effects on the dye rejection rate of membranes were evaluated. The performance of polyacrylonitrile-co-poly(2-ethylhexylacrylate) membranes did not change significantly, whereas polyaniline-containing membranes had higher dye rejection rates at acidic pH levels. PAN(92)-co-P2EHA(8)-PANI(15%) demonstrated the highest dye rejection value of 99.7% at pH 3 when the feed concentration was 50 ppm. It also showed good resistance to increase in feed concentration. It had dye rejection values of 97.2% and 88.5% for 100 and 200 ppm feed concentrations, respectively.

Method matters: Development of characterization techniques for branched and glucose-poly(lactide-co-glycolide) polymers

Defining the qualitative sameness of parenteral formulations comprised of poly(lactide-co-glycolide) (PLGA) requires assays of the relevant properties of polymer from each formulation. Gel-permeation chromatography with quaternary detection (GPC-4D) has been previously applied to other polymers, and the relevant mathematical parameters for their characterization are available; however, such parameters have not been described for branched PLGA polymers. Little information is available for the determination of glucose within glucose-PLGA (Glu-PLGA) branched polymers. This study describes the experimental methods of defining the mathematical parameters for characterization of branched PLGA polymers and the validation of these parameters using known branched-PLGA standards. The glucose, used as an initiator, was tracked through the synthesis of Glu-PLGA by both ¹³C NMR and enzymatic analysis. The analytical determination of the relevant parameters defining Glu-PLGA, such as the branching number, and the presence of glucose, requires the use of appropriate procedures experimentally validated in a systematic manner. The procedures described in this study were developed for characterization of Glu-PLGA with the lactide:glycolide (L:G) ratio of 55:45 used in Sandostatin® LAR. The procedures can also be used for characterization of Glu-PLGAs made of different L:G ratios.

Polysulfone Membranes Embedded with Halloysites Nanotubes: Preparation and Properties

In the present study, nanocomposite ultrafiltration membranes were prepared by incorporating nanotubes clay halloysite (HNTs) into polysulfone (PSF) and PSF/polyvinylpyrrolidone (PVP) dope solutions followed by membrane casting using phase inversion method. Characterization of HNTs were conducted using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and thermogravimetric (TGA) analysis. The pore structure, morphology, hydrophilicity and mechanical properties of the composite membranes were characterized by using SEM, water contact angle (WCA) measurements, and dynamic mechanical analysis. It was shown that the incorporation of HNTs enhanced hydrophilicity and mechanical properties of the prepared PSF membranes. Compared to the pristine PSF membrane, results show that the total porosity and pore size of PSF/HNTs composite membranes increased when HNTs loadings were more than 0.5 wt % and 1.0 wt %, respectively. These findings correlate well with changes in water flux of the prepared membranes. It was observed that HNTs were homogenously dispersed within the PSF membrane matrix at HNTs content of 0.1 to 0.5 wt % and the PSF/HNTs membranes prepared by incorporating 0.2 wt % HNTs loading possess the optimal mechanical properties in terms of elastic modulus and yield stress. In the case of the PSF/PVP matrix, the optimal mechanical properties were obtained with 0.3 wt % of HNTs because PVP enhances the HNTs distribution. Results of bovine serum albumin (BSA) filtration tests indicated that PSF/0.2 wt % HNTs membrane exhibited high BSA rejection and notable anti-fouling properties.

Functionalized Leather: a Novel and Effective Hazardous Solid Waste Adsorbent for the Removal of the Diazo Dye Congo Red from Aqueous Solution

The leather industry produces a high yield of solid hazardous wastes that generate a major impact on the environment. At the same time, the use of dyes by different manufacturing industries, including the footwear industry, creates large amounts of colored wastewater that is hard to treat. In this paper, potential adsorbents based on the functionalization of solid waste from leather in the removal of anionic dye Congo Red were studied. Twelve different functionalized adsorbents were analyzed in terms of dye removal. From those, the best adsorbents were characterized and tested to determine their life cycle, pH dependency and the resulting phytotoxicity of the treated dye baths. Different kinetic models were evaluated to describe this adsorption process. It was found that functionalized leather adsorbents presented multi-linearity behavior when removing Congo Red. Life cycle analysis showed that the adsorbents presented a high yield of absorption until the third cycle of operation, while phytotoxicity tested showed reductions up to 50% in the toxicity of the treated dye baths.