Facile Hydrophilic Chitosan and Graphene Oxide Modified Sustainable Non-Woven Fabric Composite Sieve Membranes (NWF@Cs/Gx): Antifouling, Protein Rejection, and Oil-Water Emulsion Separation Studies

Efficient adsorption and photocatalytic removal of hexavalent chromium using chitosan-functionalized graphene oxide-MnO2 nanocomposite

Graphene oxide/MnO2/chitosan (GO/MnO2/CS) nanocomposite showed distinct morphological changes and improved adsorption properties in wastewater treatment as compared to individual GO. GO was synthesized using modified Hummer's method and then functionalized with MnO2 nanoparticles and chitosan to prepare two nanocomposites: GO/MnO2 and GO/Mn2/CS. Nanocomposites characterized by UV/Visible spectroscopy, XRD, FTIR, SEM, and TGA. The average crystallite sizes calculated from XRD analysis were 30 nm for GO/MnO2 and 31 nm for GO/MnO2/CS. The nanocomposite showed a red shift in band gap from 3.85 eV (GO) to 2 eV (GO/MnO2/CS), which led to enhanced adsorption capacity and photocatalytic activity. Adsorption experiments were conducted to assess the elimination of Cr (VI) ions by synthesized nanomaterials at various operational conditions. The maximum adsorption capacities (qmax) were 131.58, 150.64 and 179.28 mg/g for GO, GO/MnO2, and GO/MnO2/CS respectively, at pH 2. The adsorption behavior of Cr (VI) onto the synthesized nanocomposites followed the Freundlich isotherm model, indicating multilayer adsorption on a heterogeneous surface. Kinetic studies revealed that the process followed a pseudo-second-order model, suggesting chemisorption as the dominant mechanism.

CB[6]/ZnO chelated superoleophobic-hydrophilic PVDF membranes for one-step remediation of multi-contaminant in wastewater

Industrial wastewater, despite undergoing primary and secondary treatments with conventional methods, continues to pose challenges due to the presence of multiple contaminants. Membrane separation has emerged as an effective solution to streamline the treatment process, yet it often results in surface fouling. This study introduces a single platform designed for simultaneous removal of dyes, oils, and proteins during the tertiary treatment stage, thereby eliminating the need for multiple separation steps. To enhance membrane robustness and address common fouling issues, polyvinylidene fluoride-montmorillonite-cucurbit[6]uril/zinc oxide (PV-M-CB[6]ZnO) mixed-matrix membranes have been developed. The incorporation of montmorillonite (M), cucurbit[6]uril (CB[6]) host-guest encapsulation, and zinc metal chelation significantly improves the membrane's capability in eliminating cationic dyes, treating oil-water emulsions, and separating bovine serum albumin. With an optimal CB[6]/ZnO loading of 1.6 wt%, the PV-M-CB[6]ZnO membranes exhibit superior performance with high water permeability (4114 L/m2.h.bar) and exceptional separation efficiencies: 95.5% for malachite green, 93.2% for methylene blue, and 98.2% for crystal violet, compared to pristine PVDF membranes. Additionally, these membranes demonstrate an impressive oil-water rejection rate of 97.6% and a bovine serum albumin rejection rate of 76%, with a flux recovery ratio exceeding 86% after seven filtration cycles. Thus, the PV-M-CB[6]ZnO membranes offer enhanced hydrophilicity, improved antifouling properties, and increased efficiency for the removal of multiple contaminants from industrial wastewater, providing a promising solution for sustainable environmental remediation.

Polymer-assisted synthesis of ternary magnetic graphene oxide nanocomposite for the adsorptive removal of Cr(VI) and Pb(II) ions

The presence of chromium [Cr(VI)] and lead [Pb(II)] ions in the water bodies have adverse effects on humans and aquatic life. Graphene oxide-based magnetic nanocomposites synthesized in the presence of chitosan (mGO/CS) or polyaniline (mGO/PA) as potential adsorbents for the removal of Cr(VI) and Pb(II) ions. The FTIR (Fourier transform infrared spectroscopy), EDX (Energy dispersive X-ray), XRD (X-ray diffraction) and SEM (Scanning electron microscopy) were employed to investigate the chemical composition, structural, elemental analysis, crystalline size and morphology of the nanocomposites. The FTIR results confirmed the synthesis of the nanocomposites by detecting peaks of specific functional groups. The average crystallite sizes of the mGO, mGO/CS, and mGO/PA nanocomposites were 17, 25, and 23 (nm), respectively, as determined by the Debye-Scherrer equation from the XRD data. Batch adsorption experiments were conducted for Pb(II) and Cr(VI) removal by varying the variables like pH, concentration of metal ions and contact time. The Box Behnken design (BBD) was used to optimize the adsorption parameters. Under the optimum conditions, mGO/CS and mGO/PA showed maximum removal percentages (%R) of 92.36 and 98.7 for Pb(II), and 85.25 and 93.08 for Cr(VI), respectively. The adsorption capacities were 110.84 and 118.44 mg/g for Pb(II), and 87.74 and 111.7 mg/g for Cr(VI) were obtained for mGO/CS and mGO/PA, respectively. The pseudo-second-order kinetic model and Langmuir isotherm fitted well to the experimental data and explain the adsorption mechanism of the nanocomposite materials for both metal ions.

Multifunctional Ternary NLP/ZnO@l-cysteine-grafted-PANI Bionanocomposites for the Selective Removal of Anionic and Cationic Dyes from Synthetic and Real Water Samples

The development of competent adsorbents based on agro-waste materials with multifunctional groups and porosity for the removal of toxic dyes from aqueous solutions is still a challenge. Herein, a bionanocomposite made up of neem leaf powder (NLP), zinc oxide (ZnO), and amino acid (l-cysteine)-functionalized polyaniline (PANI), namely, NLP/ZnO@l-cysteine-grafted-PANI (NZC-g-PANI), has been prepared by an in situ polymerization method. The as-prepared bionanocomposite was tested for the adsorptive removal of three anionic dyes, namely, methyl orange (MO), amido black 10B (AB 10B), and eriochrome black T (EBT), as well as three cationic dyes, namely, brilliant green (BG), crystal violet (CV), and methylene blue (MB), from synthetic aqueous medium. The morphological and structural characteristics of the NZC-g-PANI nanocomposite were examined with the help of HR field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman spectroscopy. FTIR and Raman studies show that the formulated NZC-g-PANI have an ample number of functional moieties such as carboxyl (-COOH), hydroxyl (-OH), amines (-NH₂), and imines (-N=), thus demonstrating outstanding dye removal capacity. C-S linkage helps to attach l-cysteine with polyaniline. Moreover, the predominance of chemisorption via ionic/pi-pi interaction and hydrogen bonding between the NZC-g-PANI nanocomposite and dyes (BG and MO) has been realized by FTIR and fitting of kinetics data to the PSO model. For both BG and MO dyes, the biosorption isotherm was precisely accounted for by the Langmuir isotherm with q _max values of up to 218.27 mg g^-1 for BG at pH 6 and 558.34 mg g^-1 for MO at pH 1. Additionally, thermodynamic studies revealed the endothermic and spontaneous nature of adsorption. NZC-g-PANI showed six successive regeneration cycles for cationic (MO: from 96.3 to 90.4%) and anionic (BG: from 94.7 to 88.7%) dyes. Also, batch adsorption operations were validated to demonstrate dye biosorption from real wastewater, such as tap water, river water, and laundry wastewater. Overall, this study indicates that the prepared NZC-g-PANI biosorbent could be used as an effective adsorbent for the removal of various types of anionic as well as cationic dyes from different aqueous solutions.

Experimental Insights into Mesoporous Polyaniline-Based Nanocomposites for Anionic and Cationic Dye Removal

This work presents the preparation of inorganic-organic hybrid nanocomposites, namely three-dimensional polyaniline (Pani)/activated silica gel (ASG) (3D Pani@ASG), their characterization, and in removing application as a potential adsorbent for cationic brilliant green (BG), crystal violet (CV), and anionic Congo red (CR), and methyl orange (MO) dyes. Pani@ASG nanocomposites have been prepared by the in situ polymerization method and characterized using various techniques such as Fourier transform infrared (FTIR), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) with selected area electron diffraction, thermogravimetric analysis with derivative thermogravimetry, zeta potential analyses, and Brunauer-Emmett-Teller (BET). The scanning electron microscopy (SEM) study confirms the average particle size of the Pani@ASG nanocomposite is in the range of 5 nm. FESEM, TEM, FTIR, and XRD analysis proved the successful decoration of ASG over Pani. The BET result of Pani@ASG shows a mesoporous nature with a pore diameter of less than 3 nm and a surface area of 423.90 m² g^-1. Both SEM and TEM analyses show the proportional distribution of ASG over Pani's surface. The adsorption trend of BG and MO on the studied materials at pH 7 was found as follows: Pani@ASG > Pani > ASG. The highest sorption capacities of MO and BG on Pani@ASG were 161.29 and 136.98 mg/g (T = 298.15 K, and Pani@ASG dose: 0.04 g for MO and 0.06 g for BG), which were greater compared with bare Pani and bare ASG, respectively. The interaction mechanism behind the adsorption of BG and MO dyes onto the Pani@ASG nanocomposite includes electrostatic interaction, π-π interaction, and hydrogen bonding. The mechanistic pathway and the interactions between the targeted dyes and Pani@ASG were further studied using adsorption isotherm, adsorption kinetics, and thermodynamics.