Effect of LDH platelets on the transport properties and carbonation of anion exchange membranes

Preparation and characterization of CS/PAT/ MWCNT@MgAl-LDHs nanocomposite for Cd2+ removal and 4-nitrophenol reduction

The present study evaluated the performance of multiwalled carbon nanotube (MWCNT)@MgAl-layered double hydroxide (LDH) nanoparticles loaded on poly-2 aminothiazole (PAT)/chitosan (CS) matrix (CPML) to remove Cd2+ ions from aqueous solution. The removal efficiency of modified CS/PAT with MWCNT@MgAl-LDHs was increased significantly compared to pure CS/PAT. The influence of heavy metal ion concentration, pH, temperature, adsorbent dosage, and contact time on the adsorption was examined. The optimum conditions for the adsorption of Cd2+ ions were 25 0C with the adsorbent dosage of 0.06 g and initial concentration for adsorption of the Cd2+ 100 mg/L at pH = 8. The maximum adsorption capacity was measured to be 1106.19 mg/g. The values of thermodynamic parameters namely Gibbs free energy (ΔG°), entropy change (ΔS°), and enthalpy change (ΔH°) indicated the feasibility, spontaneity and the endothermic nature of the adsorption process, respectively. The pseudo-second-order kinetics and the Langmuir model were selected as the best models for the adsorption process. Also, CPML nanocomposite (NC) was successfully tested for p-nitrophenol (p-NP) reduction in the presence of NaBH4. The reaction was nearly completed in 6 min. The fabricated CPML-NC could be reused for three consecutive cycles.

MWCNTs Decorated with TiO2 as Highly Performing Filler in the Preparation of Nanocomposite Membranes for Scalable Photocatalytic Degradation of Bisphenol A in Water

Bisphenol A (BPA), an endocrine-disrupting compound with estrogenic behavior, is of great concern within the scientific community due to its high production levels and increasing concentration in various surface aquifers. While several materials exhibit excellent capacity for the photocatalytic degradation of BPA, their powdered nature and poor chemical stability render them unsuitable for practical application in large-scale water decontamination. In this study, a new class of nanocomposite membranes based on sulfonated polyethersulfone (sPES) and multiwalled carbon nanotubes decorated with TiO2 nanoparticles (MWCNTs-TiO2) were investigated as efficient and scalable photocatalysts for the photodegradation of BPA in aqueous solutions. The MWCNTs-TiO2 hybrid material was prepared through a facile and inexpensive hydrothermal method and extensively characterized by XRD, Raman, FTIR, BET, and TGA. Meanwhile, nanocomposite membranes at different filler loadings were prepared by a simple casting procedure. Swelling tests and PFG NMR analyses provided insights into the impact of filler introduction on membrane hydrophilicity and water molecular dynamics, whereas the effectiveness of the various photocatalysts in BPA removal was monitored using HPLC. Among the different MWCNTs-TiO2 content nanocomposites, the one at 10 wt% loading (sP-MT10) showed the best photoactivity. Under UV irradiation at 254 nm and 365 nm for 240 min, photocatalytic oxidation of 5 mg/L bisphenol A by sP-MT10 resulted in 91% and 82% degradation, respectively. Both the effect of BPA concentration and the membrane regenerability were evaluated, revealing that the sP-MT10 maintained its maximum BPA removal capability over more than 10 cycles. Our findings indicate that sP-MT nanocomposite membranes are versatile, scalable, efficient, and highly reusable photocatalysts for the degradation of BPA, as well as potentially for other endocrine disruptors.

Multifunctional Cross-Linked Shrimp Waste-Derived Chitosan/MgAl-LDH Composite for Removal of As(V) from Wastewater and Antibacterial Activity

This work synthesized a novel chitosan-loaded MgAl-LDH (LDH = layered double hyroxide) nanocomposite, which was physicochemically characterized, and its performance in As(V) removal and antimicrobial activity was evaluated. Chitosan-loaded MgAl-LDH nanocomposite (CsC@MgAl-LDH) was prepared using cross-linked natural chitosan from shrimp waste and modified by Mg-Al. The main mechanisms predominating the separation of As(V) were elucidated. The characteristic changes confirming MgAl-LDH modification with chitosan were analyzed through Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis-differential thermal analysis, and Brunauer-Emmett-Teller measurements. Porosity and the increased surface area play an important role in arsenic adsorption and microbial activity. Adsorption kinetics follows the general order statistically confirmed by Bayesian Information Criterion differences. To understand the adsorption process, Langmuir, Freundlich, and Liu isotherms were studied at three different temperatures. It was found that Liu's isotherm model was the best-fitted model. CsC@MgAl-LDH showed the maximum adsorption capacity of 69.29 mg g^-1 toward arsenic at 60 °C. It was observed that the adsorption capacity of the material rose with the increase in temperature. The spontaneous behavior and endothermic nature of adsorption was confirmed by the thermodynamic parameters study. Minimal change in percentage removal was observed with coexisting ions. The regeneration of material and adsorption-desorption cycles revealed that the adsorbent is economically efficient. The nanocomposite was very effective against Staphylococcus aureus and Bacillus subtilus.

Nanocomposite Membranes for PEM-FCs: Effect of LDH Introduction on the Physic-Chemical Performance of Various Polymer Matrices

This is a comparative study to clarify the effect of the introduction of layered double hydroxide (LDH) into various polymer matrices. One perfluorosulfonic acid polymer, i.e., Nafion, and two polyaromatic polymers such as sulfonated polyether ether ketone (sPEEK) and sulfonated polysulfone (sPSU), were used for the preparation of nanocomposite membranes at 3 wt.% of LDH loading. Thereafter, the PEMs were characterized by X-ray diffraction (XRD) and dynamic mechanical analysis (DMA) for their microstructural and thermomechanical features, whereas water dynamics and proton conductivity were investigated by nuclear magnetic resonance (PFG and T1) and EIS spectroscopies, respectively. Depending on the hosting matrix, the LDHs can simply provide additional hydrophilic sites or act as physical crosslinkers. In the latter case, an impressive enhancement of both dimensional stability and electrochemical performance was observed. While pristine sPSU exhibited the lowest proton conductivity, the sPSU/LDH nanocomposite was able to compete with Nafion, yielding a conductivity of 122 mS cm-1 at 120 °C and 90% RH with an activation energy of only 8.7 kJ mol-1. The outcome must be ascribed to the mutual and beneficial interaction of the LDH nanoplatelets with the functional groups of sPSU, therefore the choice of the appropriate filler is pivotal for the preparation of highly-performing composites.