Enhanced water permeability and fouling resistance properties of ultrafiltration membranes incorporated with hydroxyapatite decorated orange-peel-derived activated carbon nanocomposites

Effective adsorption of Cr(VI) from aqueous solution by Mg-Fe LDH supported on orange peel activated carbon: isotherm, kinetic, thermodynamics and mechanism studies

The toxic Cr(VI) contaminating water released from the metallurgical, dyeing, and electroplating industries is getting worse day by day and is extremely hazardous to human health. Thus, the development of a cost-effective, quick, and efficient adsorbent is highly essential for the Cr(VI) decontamination from wastewater. Herein, a microwave-assisted carbon-based composite called Mg-Fe LDH@OPAC was prepared by assembling Mg-Fe LDH onto orange peel-activated carbon (OAPC). Prior to investigating deeply into the adsorption behavior of the composite, the Mg-Fe LDH@OPAC formation was confirmed by using instrumental techniques like FESEM, EDS, Zeta potential, XRD, FTIR, Raman, XPS, and BET analyzer. The material had a high surface area of 143.9 m2/g and showed a good monolayer Langmuir uptake capacity of 118.36 mg/g. Under ideal circumstances, the maximum amount of Cr(VI) was removed within just 120 min and showed high efficiency in the presence of other coexisting anions respectively. The adsorption was accounted by pseudo-second-order kinetics and spontaneous in nature. Ultimately, a possible adsorption mechanism was suggested, confirmed by XPS studies; which showed that oxidation-reduction, electrostatic interaction, and surface complexation reaction were responsible for Cr(VI) adsorption on Mg-Fe LDH@OPAC surface.

Preparation and Characterization of Polyethersulfone/Activated Carbon Composite Membranes for Water Filtration

Ultrafiltration membrane technology holds promise for wastewater treatment, but its widespread application is hindered by fouling and flux reduction issues. One effective strategy for enhancing ultrafiltration membranes involves incorporating activated carbon powder. In this study, composite polyethersulfone (PES) ultrafiltration membranes were fabricated to include activated carbon powder concentrations between 0 and 1.5 wt.%, with carbon size fixed at 200 mesh. The ultrafiltration membranes were evaluated in terms of membrane morphology, hydrophilicity, pure water flux, equilibrium water content, porosity, average pore size, protein separation, and E-coli bacteria removal. It was found that the addition of activated carbon to PES membranes resulted in improvements in some key properties. By incorporating activated carbon powder, the hydrophilicity of PES membranes was enhanced, lowering the contact angle from 60° to 47.3° for composite membranes (1.0 wt.% of activated carbon) compared to the pristine PES membrane. Water flux tests showed that the 1.0 wt.% composite membrane yielded the highest flux, with an improvement of nearly double the initial value at 2 bar, without compromising bovine serum albumin rejection or bacterial removal capabilities. This study also found that the inclusion of activated carbon had a minor impact on the membrane's porosity and equilibrium water content. Overall, these insights will be beneficial in determining the optimal concentration of activated carbon powder for PES ultrafiltration membranes.

Cd2+ Detection by an Electrochemical Electrode Based on MWCNT-Orange Peel Activated Carbon

This study reports the development of a new electrochemical sensor based on a carbon paste electrode (CPE) composed of biomass-based orange peel activated carbon (ACOP) and multiwalled carbon nanotubes (MWCNTs), and this composite is used for the electrochemical detection of cadmium ions (Cd2+). The ACOP/MWCNT composite was characterized by FTIR, Raman, and electrochemical impedance spectroscopy. The electrochemical evaluation of Cd2+ was performed using square wave and cyclic voltammetry. The ACOP/MWCNT-CPE electrochemical sensor exhibited a coefficient of determination r2 of 0.9907, a limit of detection of 0.91 ± 0.79 μmol L-1, and a limit of quantification of 3.00 ± 2.60 μmol L-1. In addition, the developed sensor can selectively detect Cd2+ in the presence of different interferents such as Zn2+, Pb2+, Ni2+, Co2+, Cu2+, and Fe2+ with a relative standard deviation (RSD) close to 100%, carried out in triplicate experiments. The ACOP/MWCNT-CPE presented high sensitivity, stability, and reproducibility and was successfully applied for the detection of Cd2+ in river water samples with recovery rate values ranging from 97.33 to 115.6%, demonstrating to be a very promising analytical alternative for the determination of cadmium ions in this matrix.

Preparation and Characterization of Polyethersulfone-Ultrafiltration Membrane Blended with Terbium-Doped Cerium Magnesium Aluminate: Analysis of Fouling Behavior

In this study, various techniques, including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS) mapping, X-ray photoelectron spectroscopy (XPS), and water-contact-angle goniometry (WCAG), were used to characterize the crystalline structure and morphological properties of terbium-doped cerium magnesium aluminate (Ce0.67Tb0.33MgAl11O19 or CMAT) in powder form. The results demonstrated that CMAT was successfully synthesized with a particle size of less than 5 µm and a fully evident distribution of elements, as revealed by the SEM images. This was further confirmed by the XRD and HRTEM images. XPS analysis confirmed the presence of all necessary components in CMAT. Additionally, WCAG results showed that the contact angle of CMAT was more hydrophilic with a value of 8.4°. To evaluate its performance, CMAT particles were dispersed in a Polyethersulfone (PES) solution and used to modify a PES ultrafiltration membrane through a phase-inversion method. The resulting membranes were characterized by SEM, atomic force microscopy (AFM), thermogravimetric analysis (TGA), WCAG, and permeability performance and fouling experiments. The addition of CMAT to the PES membranes did not have a significant effect on the structure of the SEM images of the top layer and cross-section of surface properties. However, increasing the concentration of CMAT improved the membrane surface roughness in AFM, and the modified membranes had the ability to resist fouling. The addition of CMAT did not lead to significant energy loss, indicating that the heat flux loss observed can indeed be explained by the amount of C-OH on the PES membrane’s surface. The contact angle of the membranes became more hydrophilic with increasing concentration of CMAT from PES G0 to PES G7. The PES origin membrane showed a higher permeation than the membranes mixed with CMAT, and the modified membranes with CMAT displayed significant fouling resistance.

Oxidized carbide-derived carbon as a novel filler for improved antifouling characteristics and permeate flux of hybrid polyethersulfone ultrafiltration membranes

Polyethersulfone (PES) is a widely used polymer for ultrafiltration (UF) membrane fabrication. In the current study, carbide-derived carbon (CDC) oxidized by acid treatment was utilized as a filler to fabricate a novel PES composites UF membranes. The successful oxidation of CDC was validated from presence of oxygen containing functional groups and improved oxygen content, from 5.08 at.% for CDC to 26.22 at.% for oxidized CDC (OCDC). The OCDC PES UF membranes were prepared at different loadings of OCDC between 0.5 and 3.0 wt%. The membrane porosity, pore size and surface free energy found to be improved while a noticeable reduction in water contact angle was observed with OCDC loading implying the improved hydrophilicity of PES membranes. Consequently, the pure water flux found to improve from 151.6 to 569.6 (L/(m². h)) for the 3.0 wt% modified OCDC membrane (M-3) which is 3.8 folds of the bare PES membrane. The antifouling characteristics were evaluated by humic acid (HA) filtration. The results revealed a significant enhancement in HA rejection with OCDC loading, the highest rejection was 96.8% for M-3 membrane. Additionally, the adsorption capacity of OCDC modified membranes found to decrease with OCDC loading indicating improved rejection of HA from the membrane surface. Moreover, M-3 demonstrated the maximum flux recovery ratio (FRR) of 92.3%. Reusability of the fabricated membranes was evaluated by deionized water/humic acid cycling filtration. The FRR was higher than 86.7% over three cycles of pure water/HA filtration for 140 min, indicated the excellent stability and reusability of the membranes. Overall, the OCDC was an effective filler for enhancing the PES UF membranes antifouling and permeability properties.

Synthesis and Characterization of Orange Peel Modified Hydrogels as Efficient Adsorbents for Methylene Blue (MB)

In recent years, due to the developments in the textile industry, water contaminated with synthetic dyes such as methylene blue (MB) has become an environmental threat based on the possible impacts in terms of chemical and biochemical demand, which leads to disturbance in aquatic plants photosynthesis, besides their possible toxicity and carcinogenicity for humans. In this work, an adsorbent hydrogel is prepared via free radical polymerization comprising acrylic acid (PAA) as a monomer and orange peel (OP) as a natural modifier rich in OH and COOH present in its cellulose and pectin content. The resulting hydrogels were optimized in terms of the content of OP and the number of cross-linkers and characterized morphologically using Scanning electron microscopy. Furthermore, BET analysis was used to follow the variation in the porosity and in terms of the surface area of the modified hydrogel. The adsorption behavior was found to follow pseudo-second-order as a kinetic model, and Langmuir, Freundlich, and Temkin isotherm models. The combination of OP and PAA has sharply enhanced the adsorption percent of the hydrogel to reach 84% at the first 10 min of incubation with an adsorption capacity of more than 1.93 gm/gm. Due to its low value of pHPZc, the desorption of MB was efficiently performed at pH 2 using HCl, and the desorbed OP-PAA were found to be reusable up to ten times without a decrease in their efficiency. Accordingly, OP-PAA hydrogel represents a promising efficient, cost-effective, and environmentally friendly adsorbent for MB as a model cationic dye that can be applied for the treatment of contaminated waters.

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.

A Comparative Analysis of the Effect of Carbonaceous Nanoparticles on the Physicochemical Properties of Hybrid Polyethersulfone Ultrafiltration Membranes

Numerous studies have been previously reported on the use of nanoscale carbonaceous fillers, such as multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO), in polymeric ultrafiltration (UF) membranes; however, no insight has been clearly reported on which material provides the best enhancements in membrane performance. In this study, a comparative analysis was carried out to establish a comprehensible understanding of the physicochemical properties of hybrid polyethersulfone (PES) UF membranes incorporated with MWCNTs and GO nanoparticles at various concentrations. The hybrid membranes were prepared via the non-solvent-induced phase separation process and further characterized by field emission scanning electron microscopy and atomic force microscope (AFM). The AFM images showed homogeneous membrane surfaces with a reduction in the membrane surface roughness from 2.62 nm for bare PES to 2.39 nm for PES/MWCNTs and to 1.68 nm for PES/GO membranes due to improved hydrophilicity of the membranes. Physicochemical properties of the hybrid PES membranes were assessed, and the outcomes showed an enhancement in the porosity, pore size, water contact angle, and water permeability with respect to nanoparticle concentration. GO-incorporated PES membranes exhibited the highest porosity, pore size, and lowest contact angle as compared to PES/MWCNTs, indicating the homogeneous distribution of nanoparticles within the membrane structure. PES/MWCNTs (0.5 wt.%) and PES/GO (1.0 wt.%) hybrid membranes exhibited the highest water flux of 450.0 and 554.8 L m^-2 h^-1, respectively, at an applied operating pressure of 1 bar. The filtration and antifouling performance of the PES hybrid membranes were evaluated using 50 mg L^-1 of humic acid (HA) as a foulant at pH = 7. Compared to the bare PES membrane, the MWCNTs and GO-incorporated PES hybrid membranes exhibited enhanced permeability and HA removal. Moreover, PES/MWCNTs (0.5 wt.%) and PES/GO (1 wt.%) hybrid membranes reported HA rejection of 90.8% and 94.8%, respectively. The abundant oxygen-containing functional groups in GO-incorporated PES membranes resulted in more hydrophilic membranes, leading to enhanced permeability and fouling resistance. The antifouling properties and flux recovery ratio were improved by the addition of both nanoparticles. Given these findings, although both MWCNTs and GO nanoparticles are seen to notably improve the membrane performance, PES membranes with 1 wt.% GO loading provided the highest removal of natural organic matter, such as HA, under the same experimental conditions.

Water Treatment Using High Performance Antifouling Ultrafiltration Polyether Sulfone Membranes Incorporated with Activated Carbon

Membrane fouling is a continued critical challenge for ultrafiltration membranes performance. In this work, polyether sulfone (PES) ultrafiltration (UF) membranes were fabricated via phase-inversion method by incorporating varying concentrations of APTMS modified activated carbon (mAC). The mAC was thoroughly characterized and the fabricated membranes were studied for their surface morphology, functional groups, contact angle, water retention, swelling (%) porosity, and water flux. The hydrophilicity of mAC membranes also resulted in lower contact angle and higher values of porosity, roughness, water retention as well as water flux. Also, the membranes incorporated with mAC exhibited antibacterial performance against model test strains of gram-negative Ecoil and gram-positive S. aureus. The antifouling studies based on bovine serum albumin protein (BSA) solution filtration showed that mAC membranes have better BSA flux. The higher flux and antifouling characteristics of the mAC membranes were attributed to the electrostatic repulsion of the BSA protein from the unique functional properties of AC and network structure of APTMS. The novel mAC ultrafiltration membranes developed and studied in present work can provide higher flux and less BSA rejection thus can find antifouling applications for the isolation and concentration of proteins and macromolecules.

Mitigation of organic fouling of ultrafiltration membrane by high-temperature crayfish shell biochar: Performance and mechanisms

The paper applied crayfish shell (CFS) biochar to the mitigation of ultrafiltration (UF) membrane fouling induced by humic acid (HA) and sodium alginate (SA). Results indicated that the high adsorption capacity of CFS800 to HA made it effective in alleviating the irreversible membrane fouling induced by HA, and the cross-linking reaction between the hydroxyl calcium components on CFS800 and SA reduced the reversible membrane fouling induced by SA rapidly. Further analysis showed that the "hydrogel flocs" generated by the cross-linking reaction would accumulate on the surface of the substrate membrane and form an amorphous hydrogel layer to intercept the subsequent foulant and purify the water quality further. Meanwhile, the mitigation performance of CFS800 was twice more than that of commercial powder activated carbon (PAC), and the dosage was the main factor affecting its practical application performance and thus could be considered as a promising material in alleviating membrane fouling induced by HA and SA. More importantly, the findings of the present study gave a new sight towards the application of biochar.

Effects of electroflocculation/oxidation pretreatment on the fouling characteristics of ultrafiltration membranes

In order to reduce the membrane pollution of ultrafiltration caused by natural organic matter and improve the treatment efficiency, electroflocculation/oxidation is used as the premembrane treatment method. The membrane specific flux attenuation characteristics was compared and analyzed under the conditions of direct ultrafiltration and electroflocculation/oxidation-ultrafiltration. Combined with the analysis of the reversibility of membrane fouling, the mechanism of electroflocculation/oxidation pretreatment to alleviate ultrafiltration membrane fouling was evaluated, and the membrane pore clogging model was used to fit the fouling law. The results show that, in the continuously fed filtration experiment, the electroflocculation/oxidation process involved in the pretreatment and the direct ultrafiltration membrane filtration decreased the ultrafiltration membrane flux to 79.1% and 28.5%, respectively. The reversible resistance generated by ultrafiltration and electroflocculation/oxidation-ultrafiltration processes accounted for 37.70% and 62.26% of their total pollution resistance, whereas the irreversible resistance generated accounted for 47.30% and 12.40%, respectively. Meanwhile, the direct correlation between the the flux dropped and complete clogging became less than that of the ultrafiltration process. The pretreatment significantly strengthened irreversible fouling resistance of the membrane pores. The membrane permeation flux was significantly increased after the electroflocculation/oxidation pretreatment.

A critical review of advanced nanotechnology and hybrid membrane based water recycling, reuse, and wastewater treatment processes

One of the modern challenges is to provide clean and affordable drinking water. Water scarcity is caused by the growing population in the world and pollutants contaminate all remaining water sources. Innovative water treatment solutions have been provided by nanotechnology. Microorganisms, organic suspensions, and inorganic heavy metal ions, among other things, are common water contaminants. Since antiquity, a wide range of water clean-up methods have been employed to address this issue. Breakthroughs in water purification procedures have occurred during the previous four decades, with the most significant one being the use of nanomaterials and nanomembranes. Nanoparticles and nanomembranes (polymeric membranes) have recently been used in engineered materials (TiO₂, ZnO, CuO, Ag, CNT's and mixed oxide nanoparticles, for example). Engineered nanomembranes, nanocomposites and nanoparticles have been used in this review article's discussion of water purification technologies. The review also discusses the risk and solutions of using nanoparticles and nanocomposites in the future.

Bioactive Surface Modifications through Thermally Sprayed Hydroxyapatite Composite Coatings: A Review over Selective Reinforcements

Hydroxyapatite (HA) has been an excellent replacement for the natural bone in orthopedic applications, owing to its close resemblance; however, it is brittle and has low strength. Surface modification techniques...