The Curing Kinetics of Multiscale [Ni(EDTA)]-2 Intercalated Zn-Al Layered Double Hydroxides: Glass Fiber–Epoxy Composite Prepreg

In the present research, the effect of Zn2Al layered double hydroxides (LDH) and nickel (II)-EDTA complex intercalated LDH (LDH-[Ni(EDTA)]-2) on the cure kinetics of glass fiber/epoxy prepreg (GEP) was explored using nonisothermal differential scanning calorimetry (DSC). The results showed that LDH caused a shift in the cure temperature toward lower temperatures while accelerating the curing of epoxy prepregs. The use of LDH-[Ni(EDTA)]-2 more profoundly influenced the acceleration of the curing process. The curing kinetics of prepregs was assessed through the differential isoconversional Friedman (FR) technique and the integration method of Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS). A decrease was detected in the $E_{\alpha }$ value of glass fiber/LDH-[Ni(EDTA)]-2/epoxy (GELP) and glass fiber/LDH-[Ni(EDTA)]-2/epoxy (GELNiP) prepregs at small cure degrees relative to GEP, suggesting the catalytic effect of LDH or LDH-[Ni(EDTA)]-2 on the initial epoxy/amine reaction. Furthermore, LDH-[Ni(EDTA)]-2 performed better due to the catalyst role of nickel (II). Moreover, the activation energy exhibited lower reliance on the degree of conversion in the cases of GELP and GELNiP rather than pure epoxy prepregs. An autocatalytic model was used to evaluate the curing behavior of the system. Based on the results, the curing reaction of the epoxy prepreg can be described by the autocatalytic Šesták-Berggren model even after the incorporation of LDH or LDH-[Ni(EDTA)]-2. The kinetic parameters of the autocatalytic model (such as $E_{\alpha }$ , $A$ , $m$ , $n$ ) and the equations explaining the curing behavior of prepregs were introduced as well whose predictions were in line with the experimental findings.

Degradation of thiocyanate by electrochemical oxidation process in coke oven wastewater: Role of operative parameters and mechanistic study

This study presents the removal of thiocyanate (SCN^-) from coke oven wastewater by the electrooxidation (EO) process. Initially, the performances boron-doped diamond (BDD) and different DSA (Dimensionally stable anode) electrodes including Ti/IrO₂, Ti/IrO₂-RuO₂, and Ti/IrO₂-RuO₂-TiO₂ in SCN^- removal were compared. BDD anode outperformed the Ti-based mixed metal oxide (MMO) anodes achieving 96.51% SCN^- removal efficiency. The most favorable conditions for the removal of SCN^- using BDD anode were determined as follows: pH = 9, current density = 43.10 A m^-2, and the electrolyte concentration (Na₂SO₄) = 2.5 g L^-1. The strong role of ^⦁OH in the removal of SCN^- was confirmed by the addition of radical quenching agents. The evolution of the intermediates as a result of the EO of SCN^- was determined. Under the determined conditions, the EO process could remove 84.13% of SCN^- and 94.67% of phenol from a real coke oven wastewater, which was comparable to that of the simulated solution. The electrical energy consumption cost of the process to remove 1 kg of SCN^- was calculated as 0.208 US $. Overall, the study showed the EO using BDD anode is a cost-effective method for the removal of SCN^- from a coke oven wastewater.

Accelerated Redox Cycles of Fe(III)/Fe(II) and Cu(III)/Cu(II) by Photo-Induced Electron from N-CQDs for Enhanced Photo-Fenton Capability of CuFe-LDH

Layered double hydroxide (LDH) materials have shown charming photo-Fenton capability for the treatment of refractory organic wastewater. In this study, CuFe-LDH hybridized with N-doped carbon quantum dots (N-CQDs) was investigated to further enhance the photo-Fenton capability. The results showed that the assembly techniques of coprecipitation and the hydrothermal method could synthesize the target material, CuFe-LDH/N-CQDs, successfully. CuFe-LDH/N-CQDs could possess a 13.5% higher methylene blue (MB) removal rate than CuFe-LDH in 30 min due to the accelerated redox cycles of Fe(III)/Fe(II) and Cu(III)/Cu(II), resulting from the photo-induced electron transfer from N-CQDs to CuFe-LDH via a d–π conjugation electronic bridge. Moreover, CuFe-LDH/N-CQDs has excellent photo-Fenton capability in the pH range of 2–11, even after being reused five times. This study would provide an efficient and stable photo-Fenton catalyst for the treatment of refractory organic wastewater.

Outstanding chain-extension effect and high UV resistance of polybutylene succinate containing amino-acid-modified layered double hydroxides

Polybutylene succinate (PBS) nanocomposite materials were prepared using a melt compounding process. The Mg₂Al-based PBS nanocomposites, dispersed with inorganic-organic hybrid materials (layered double hydroxides, LDHs), were functionalized with the amino acids L-histidine (HIS) and L-phenylalanine (PHE). The rheological and anti-ultraviolet (anti-UV) properties were investigated and compared to filler-free PBS as well as LDH Mg₂Al/nitrate as references. Both organo-modified LDHs exhibited a remarkable chain-extension effect for PBS with an outstanding increase in the zero-shear viscosity η₀ for PBS-Mg₂Al/PHE (two order of magnitude increase as compared to filler-free PBS). These results were compared to data found in the literature. Moreover, HIS and PHE anions embedded into the LDH structure can successfully prevent the chain scission reactions that usually occur during photo-ageing of PBS under UV radiation exposure. This highlights the outstanding performance of the LDH hybrid materials, and in particular, their application as a polymer chain extender and UV stabilizer for PBS, which can likely be extended to other biodegradable polymers.

Co–Fe hydrotalcites for efficient removal of dye pollutants via synergistic adsorption and degradation

Layered double hydroxides (LDHs) with hydrotalcite-like structures containing Co(ii) and Fe(iii) were prepared and used for the removal of direct red 23 (DR23) from water solution.