Enhanced conversion of superoxide radical to singlet oxygen in peroxymonosulfate activation by metal-organic frameworks derived heteroatoms dual-doped porous carbon catalyst

Enhanced humic acid removal by sludge activated carbon/Fe2+ composite in peroxymonosulfate activation: mechanism and performance

In subsurface water, humic acid (HA) can react with active chlorine to form carcinogenic compounds, posing ecological issues and health risks. This study aims to create sludge activated carbon (SAC), combine it with Fe2+, and activate peroxosulfate (PMS) to remove HA from water. To verify the successful modification of SAC, the physicochemical properties were characterized using various methods such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer Emmett Teller (BET) analysis, and X-ray photoelectron spectroscopy (XPS). Moreover, in the Fe2+/SAC/PMS system, the removal rate of HA rose significantly, peaking at 96%. The removal of HA conformed to the first-order reaction kinetic equation, with a reaction rate constant of 0.048 min-1, showing that activated PMS generates potent oxidative radicals or non-radicals, boosting reaction efficiency. After four repeated cycles of use, the removal rate of HA remained above 90%, demonstrating its excellent stability and reusability. The results of three-dimensional fluorescence spectroscopy (3D-EEM) indicated that the Fe2+/SAC/PMS system could effectively degrade dissolved organic matter (DOM) in water. Quenching experiments and electron paramagnetic resonance (EPR) analysis further confirmed that singlet oxygen (1O2) is the primary oxidative species for degrading HA. Therefore, the Fe2+/SAC/PMS reaction system presented promising application prospects to remove HA from water.

Efficient activation of peroxymonosulfate by N-doped waste herb senna obtusifolia biochar for degrading NPX: Synergistic effect of carbonyl and nitrogen sites

In this work, waste herb senna obtusifolia was utilized as the biochar precursor, and a N-doped biochar (NSOBC-6) was prepared to activate peroxymonosulfate (PMS) for degrading Naproxen (NPX). NSOBC-6 exhibited superior catalytic performance in activating PMS, which could degrade NPX completely within 60 min. The NSOBC-6/PMS system also had good reusability and effectiveness under a wide range of pH values and high salinity conditions. The significant contribution of singlet oxygen (1O2) and superoxide radicals (O2•-) in NPX degradation was revealed. The results of XPS and DFT calculations indicated C=O, pyridinic-N and graphitic-N participated as catalytic sites in the degradation of NPX. The differences in electron density and the ELUMO-EHOMO (ΔELUMO-HOMO) gap were induced by N doping, enhancing the PMS activation capacity of NSOBC-6. This work presented a strategy to convert waste herbal into functional biochar materials, which was of great significance for the development of green and efficient catalysts.

Multi-chamber membrane capacitive deionization coupled with peroxymonosulfate to achieve simultaneous removal of tetracycline and peroxymonosulfate reaction byproducts

Advanced oxidation technologies based on peroxymonosulfate (PMS) have been extensively applied for the degradation of antibiotics. However, the degradation process inevitably introduces SO42- and other sulfur-containing anions, these pollutants pose a huge threat to the water and soil environment. Addressing these concerns, this study introduced PMS oxidation into a multi-chamber membrane capacitive deionization (MC-MCDI) device to achieve simultaneous tetracycline (TC) degradation and removal of PMS reaction byproduct ions. The experimental results demonstrated that when the TC solution (40 mg L-1) was pre-adsorbed for 10 min, the voltage was 1.2 V and the concentration of PMS solution added was 4 mg mL-1, the removal efficiency of TC and ion can reach 77.4 % and 46.5 % respectively. Furthermore, the activation process of PMS in MC-MCDI/PMS system and the reactive oxygen (ROS) that mainly produce degradation were deeply investigated. Finally, liquid chromatography-mass spectrometry (LC-MS) was employed to identify intermediates of TC degradation, propose potential degradation pathways, and analyze the toxicities of the intermediates. In addition, in five cycles, the MC-MCDI/PMS system demonstrated excellent stability. This study provides an effective strategy for treating TC wastewater and a novel approach for simultaneous TC degradation and desalination.

Defective nitrogen doped carbon material derived from nano-ZIF-8 for enhanced in-situ H2O2 generation and tetracycline hydrochloride degradation in electro-Fenton system

Tetracycline hydrochloride (TC) accumulates in large quantities in the water environment, causing a serious threat to human health and ecological environment safety. This research focused on developing cost-effective catalysts with high 2e- selectivity for electro-Fenton (EF) technology, a green pollution treatment method. Defective nitrogen-doped porous carbon (d-NPC) was prepared using the metal-organic framework as the precursor to achieve in-situ H2O2 production and self-decomposition into high activity ·OH for degradation of TC combined with Co2+/Co3+. The d-NPC produced 172.1 mg L-1 H2O2 within 120 min, and could degrade 96.4% of TC in EF system. The self-doped defects and graphite-nitrogen in d-NPC improved the oxygen reduction performance and increased the H2O2 yield, while pyridine nitrogen could catalyze H2O2 to generate ·OH. The possible pathway of TC degradation was also proposed. In this study, defective carbon materials were prepared by ball milling, which provided a new strategy for efficient in-situ H2O2 production and the degradation of pollutants.

Peroxymonosulfate activation by iron-cobalt bimetallic phosphide modified nickel foam for efficient dye degradation

Novel catalysts with multiple active sites and rapid separation are required to effectively activate peroxymonosulfate (PMS) for the removal of organic pollutants from water. Therefore, an integrated catalyst for PMS activation was developed by directly forming Co-Fe Prussian blue analogs on a three-dimensional porous nickel foam (NF), which were subsequently phosphorylated to obtain cobalt-iron bimetallic phosphide (FeCoP@NF). The FeCoP@NF/PMS system efficiently degraded dye wastewater within 20 min. The system exhibited excellent catalytic degradation over a broad pH range and at high dye concentrations due to the presence of unique asymmetrically charged Coa+ and Pb- dual active sites formed by cobalt phosphides within FeCoP@NF. These active sites significantly enhanced the catalytic activity of PMS. The activation mechanism of PMS involves phosphorylation that accelerates electron transfer from FeCoP@NF to PMS, to generate SO4·-, ·OH, O2·-, and 1O2 active species. Three-dimensional FeCoP@NF could be readily recycled and showed good stability for PMS activation. In this study, a highly efficient, stable, and readily recyclable integrated catalyst was developed. This catalyst system effectively resolves the separation and recovery issues associated with conventional powder catalysts and has a wide range of potential applications in wastewater treatment.

Bimetallic iron-nickel phosphide as efficient peroxymonosulfate activator for tetracycline hydrochloride degradation: Performance and mechanism

Sulfate radical-based advanced oxidation processes with (SR-AOPs) are widely employed to degrade organic pollutants due to their high efficiency, cost-effectiveness and safety. In this study, a highly active and stable FeNiP was successfully prepared by reduction and heat treatment. FeNiP exhibited high performance of peroxymonosulfate (PMS) activation for tetracycline hydrochloride (TC) removal. Over a wide pH range, an impressive TC degaradation efficiency 97.86% was achieved within 60 min employing 0.1 g/L FeNiP and 0.2 g/L PMS at room temperature. Both free radicals of SO4·-, ·OH, ·O2- and non-free radicals of 1O2 participated the TC degradation in the FeNiP/PMS system. The PMS activation ability was greatly enhanced by the cycling between Ni and Fe bimetal, and the active site regeneration was achieved due to the existence of the negatively charged Pn-. Moreover, the FeNiP/PMS system exhibited substantial TC degradation levels in both simulated real-world disturbance scenarios and practical water tests. Cycling experiments further affirmed the robust stability of FeNiP catalyst, demonstrating sustained degradation efficiency of approximately 80% even after four cycles. These findings illuminate its promising potential across natural water bodies, presenting an innovative catalyst construction approach for PMS activation in the degradation of antibiotic pollutants.

Role of biochar in superoxide-dominated dye degradation in catalyst-activated peroxymonosulphate process

In recent times, the application of biochar (BC) as an upcoming catalyst for the elimination of recalcitrant pollutants has been widely explored. Here, an iron loaded bamboo biochar activated peroxymonosulphate (PMS) process was tested for removing Congo red (CR) dye from water medium. The catalyst was synthesized using a green synthesis method using neem extracts and characterized using SEM, FTIR, and XRD. The effects of various operating parameters, including solution pH, catalyst dosage, and pollutant dosage, on dye degradation efficiency were examined. The results showed that at the optimized conditions of 300 mg L-1 PMS concentration, 200 mg L-1 catalyst dosage, and pH 6, about 89.7% of CR dye (initial concentration 10 ppm) was removed at 60 min of operation. Scavenging experiments revealed the significant contribution of O2•-, •OH, and 1O2 for dye degradation, with a major contribution of O2•-. The activation of PMS was mainly done by biochar rather than iron (loaded on biochar). The catalyst was highly active even after four cycles.

Ultra-high flux mesh membranes coated with tannic acid-ZIF-8@MXene composites for efficient oil-water separation

Oil/water separation has become a global concern due to the increasing discharge of multi-component harmful oily wastewater. Super wetting membranes have been shown to be an effective material for oil/water separation. Ultra-high flux stainless-steel meshes (SSM) with superhydrophilicity and underwater superoleophobicity were fabricated by tannic acid (TA) modified ZIF-8 nanoparticles (TZIF-8) and two-dimensional MXene materials for oil/water separation. The TZIF-8 increased the interlayer space of MXene, enhancing the flux permeation (69,093 L m-2h-1) and rejection of the composite membrane (TZIF-8@MXene/SSM). The TZIF-8@MXene/SSM membrane showed an underwater oil contact angle of 154.2°. The membrane maintained underwater superoleophobic after stability and durability tests, including various pH solutions, organic solvents, reusability, etc. In addition, the oil/water separation efficiency of TZIF-8@MXene/SSM membranes was higher than 99% after treatment in harsh conditions and recycling. The outstanding anti-fouling, stability, durability, and recyclability properties of TZIF-8@MXene/SSM membrane highlight the remarkable potential of membranes for complex oil/water separation process.

Peroxymonosulfate activation by nanocomposites towards the removal of sulfamethoxazole: Performance and mechanism

Heterogeneous activation of peroxomonosulfate (PMS) has been extensively studied for the degradation of antibiotics. The cobalt ferrite spinel exhibits good activity in the PMS activation, but suffers from the disadvantage of low PMS utilization efficiency. Herein, the nanocomposites including FeS, CoS2, CoFe2O4 and Fe2O3 were synthesized by hydrothermal method and used for the first time to activate PMS for the removal of sulfamethoxazole (SMX). The nanocomposites showed superior catalytic activity in which the SMX could be completely removed at 40 min, 0.1 g L-1 nanocomposites and 0.4 mM PMS with the first order kinetic constant of 0.2739 min-1. The PMS utilization efficiency was increased by 29.4% compared to CoFe2O4. Both radicals and non-radicals contributed to the SMX degradation in which high-valent metal oxo dominated. The mechanism analysis indicated that sulfur modification, on one hand, enhanced the adsorption of nanocomposites for PMS, and promoted the redox cycles of Fe2+/Fe3+ and Co2+/Co3+ on the other hand. This study provides new way to enhance the catalytic activity and PMS utilization efficiency of spinel cobalt ferrite.

Palladium nanospheres-embedded metal-organic frameworks to enhance the ECL efficiency of 2,6-dimethyl-8-(3-carboxyphenyl)4,4'-difluoroboradiazene in aqueous solution for ultrasensitive Cu2+ detection

Nowadays, organic emitters suffer from insufficient electrochemiluminescence (ECL) efficiency in aqueous solutions, and their practical applications are severely restricted in the bio-sensing field. In this work, palladium nanospheres-embedded metal-organic frameworks (Pd@MOFs) were exploited to enhance the ECL efficiency of 2,6-dimethyl-8-(3-carboxyphenyl)4,4'-difluoroboradiazene (BET) prepared by a one-pot method in aqueous environment. First, the Pd@MOFs were generated via in situ reduction of Pd nanospheres anchored onto the MOFs, and fabricated by orderly coordination of palladium chloride (PdCl2) with 1,2,4,5-benzenetetramine (BTA) tetrahydrochloride. Then, the influence of protons on the ECL response of BET was studied in detail to obtain stronger ECL emission using potassium persulfate (K2S2O8) as co-reactant in aqueous environment. As a result, a 1.47-fold ECL efficiency enlargement of BET/K2S2O8 was harvested at the Pd@MOFs/GCE, where Ru(bpy)32+ behaved as a standard. Based on the fact that the ECL signals of the BET-covered Pd@MOFs modified glassy carbon electrode (simplified as BET/Pd@MOFs/GCE) can be quenched by Cu2+, the as-built ECL sensor showed a wide linear range (1.0-100.0 pM) and a limit of detection (LOD) as low as 0.12 pM. Hence, such research offers huge potential to promote the development of organic emitters in ECL biosensors and environmental monitoring.