Mechanistic and structure investigation of the KOH activation ZIF-8 derived porous carbon as metal-free for unprecedented peroxymonosulfate activation degradation of bisphenol A

Ultra-stable metal-organic framework-derived carbon nanocontainers with defect-induced pore enlargement for anti-corrosive epoxy coatings

Zeolitic imidazolate frameworks-8 (ZIF-8) have recently gained attention as nanocontainers for encapsulating corrosion inhibitors. However, two main challenges remain unsolved, casting doubt on their suitability as nanocontainers. The first challenge is their instability in acidic and basic environments, leading to structural decomposition and the second challenge is their mass diffusion limitation caused by micropore dominance and a small aperture size of 0.34-0.42 nm, limiting the efficient adsorption of corrosion inhibitors. To address both challenges, in this work, ZIF-8 nanostructures were transformed into nitrogen-doped ZIF-derived carbon-based nanocontainers (CZIF) via carbonization. This transformation not only stabilized the structure but also produced larger pore sizes (micro and mesopores), due to defects formed during carbonization. Benzotriazole (BTA) corrosion inhibitors were then encapsulated in CZIF structures to produce CZIF-BTA. Electrochemical impedance spectroscopy (EIS) demonstrated that the saline solution containing CZIF-BTA extract reduced the corrosion rate of steel by 50 % compared to a blank solution. The scratched epoxy (EP) coating containing 0.2 wt% of CZIF-BTA revealed an active inhibition performance with ∼100 % enhancement in the total resistance value compared to blank EP. Finally, the coating showed superior barrier properties with the impedance at the lowest frequency value of ∼2 × 1010 Ω cm2 after 71 days of immersion.

Ultrahigh Surface Area Nanoporous Carbons Synthesized via Hypergolic and Activation Reactions for Enhanced CO2 Capacity and Volumetric Energy Density

We report a family of carbon sorbents synthesized by integrating hypergolics with activation reactions on a templated substrate. The materials design leads to nanoporous carbons with a BET area of 4800 m2 g-1 with an impressive total pore volume of 2.7 cm3 g-1. To the best of our knowledge, this BET area value is the highest reported in the literature. Electron spin resonance (ESR) measurements determined the number of radicals in an effort to provide a mechanistic understanding of the formation of ultrahigh surface area carbons. In combination with XPS, we propose a mechanism based on the synergistic effect between rim-based pentagonal rings and carbon radicals, which we believe can be exploited to produce other highly porous carbons. The CO2 capture capacity of the hyperporous carbon tested under dynamic CO2 capture conditions was ∼1.25 mmol g-1 versus 0.66 mmol g-1 of a conventionally activated carbon under similar conditions. The CO2 capture kinetics were extremely fast and reached 99% of the total capacity within 120 s. Lastly, supercapacitor electrodes deliver a high volumetric energy density of ∼60 W h L-1 and a volumetric power density of 1 kW L-1, which is the highest reported value for activated carbon.

Micro-nanobubble-assisted As(III) removal from water by Ni-doped MOF materials

Micro-nanobubbles (MNBs) can form reactive oxygen species (ROS) with high oxidizing potential. In this study, nickel-doped metal-organic framework materials (MOFs) capable of activating molecular oxygen were synthesized using trivalent arsenic (As(III)) as a target pollutant and combined with peroxymonosulfate (PMS) to construct a MOF/MNB/PMS system. The results included the rapid oxidation of As(III), the successful absorption of oxidized As(V), and finally the efficient removal of As. The effects of pH, amount of PMS used, and preparation time of MNBs on the As removal performance of the MOF/MNB/PMS system were investigated experimentally. The changes in the properties of the materials before and after the reaction were analyzed by XPS, and it was found that the main active sites on the surface of the MOFs were the metal elements and the pyridine nitrogen near the carbon atom. The regular morphology and elemental composition of the MOFs were determined by TEM scanning and EDS test, which indicated the presence of nickel. XRD tests before and after the reaction showed that the MOFs were structurally stable. The results of the free radical burst experiments show that the single linear oxygen (1O2) is the main active substance in the system, and that the MNBs are key factors by which the system achieves efficient oxidation performance. In addition to providing a sustainable supply of molecular oxygen to the MOFs during the reaction process, coupling the MNBs with PMS was found to improve the oxidation capacity of the system. The results of this study thus provide a new concept for As removal and advanced oxidation in water bodies.

Peroxymonosulfate activation by CuMn-LDH for the degradation of bisphenol A: Effect, mechanism, and pathway

The remediation of water contaminated with bisphenol A (BPA) has gained significant attention. In this study, a hydrothermal composite activator of Cu3Mn-LDH containing coexisting phases of cupric nitrate (Cu(NO3)2) and manganous nitrate (Mn(NO3)2) was synthesized. Advanced oxidation processes were employed as an effective approach for BPA degradation, utilizing Cu3Mn-LDH as the catalyst to activate peroxymonosulfate (PMS). The synthesis of the Cu3Mn-LDH material was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). According to the characterization data and screening experiments, Cu3Mn-LDH was selected as the best experimental material. Cu3Mn-LDH exhibits remarkable catalytic ability with PMS, demonstrating good degradation efficiency of BPA under neutral and alkaline conditions. With a PMS dosage of 0.25 g·L-1 and Cu3Mn-LDH dosage of 0.10 g·L-1, 10 mg·L-1 BPA (approximately 17.5 μM) can be completely degraded within 40 min, of which the TOC removal reached 95%. The reactive oxygen species present in the reaction system were analyzed by quenching experiments and EPR. Results showed that sulfate free radicals (SO4•-), hydroxyl free radicals (•OH), superoxide free radicals (•O2-), and nonfree radical mono-oxygen were generated, while mono-oxygen played a key role in degrading BPA. Cu3Mn-LDH exhibits excellent reproducibility, as it can still completely degrade BPA even after four consecutive cycles. The degradation intermediates of BPA were detected by GCMS, and the possible degradation pathways were reasonably predicted. This experiment proposes a nonradical degradation mechanism for BPA and analyzes the degradation pathways. It provides a new perspective for the treatment of organic pollutants in water.

Catalytic ozonation for imazapic degradation over kelp-derived biochar: Promotional role of N- and S-based active sites

It is a feasible strategy to prepare reliable biochar catalysts for heterogeneous catalytic ozonation (HCO) processes by using inexpensive, high quality, and easily available raw materials. Here, an environmentally friendly, simple, and green biochar catalyst rich in nitrogen (N) and sulfur (S) has been prepared by the pyrolysis of kelp. Compared with directly carbonized kelp biomass (KB), acid-activated KB (KBA) and base-activated KB (KBB) have higher specific surface areas and more extensive porous structures, although only KBB displays effective ozone activation. Imazapic (IMZC), a refractory organic herbicide, was chosen as the target pollutant, which has apparently not hitherto been investigated in the HCO process. Second-order rate constants (k) for the reactions of IMZC with three different reactive oxygen species (ROS), specifically kO3, IMZC, kOH, IMZC, and k1O2, IMZC, have been determined as 0.974, 2.48 × 109, and 6.23 × 105 M-1 s-1, respectively. The amounts of graphitic N and thiophene S derived from the intrinsic N and S showed good correlations with the IMZC degradation rate, implicating them as the main active sites. OH and O2- and 1O2 were identified as main ROS in heterogeneous catalytic ozonation system for IMZC degradation. This study exemplified the utilization of endogenous N and S in biological carbon, and provided more options for the application of advanced oxidation processes and the development of marine resources.