Analytical methods for selectively determining hydrogen peroxide, peroxymonosulfate and peroxydisulfate in their binary mixtures

Sustainability-Inspired Upcycling of Organophosphorus Pollutants into Phosphatic Fertilizer in a Continuous-Flow Reactor

With the increasing requirement for phosphorus resources and their shortage in nature, cyclic utilization of organophosphorus pollutants into phosphatic fertilizer might offer a sustainable approach to achieve the recycling of phosphorus. Herein, we first report the selective degradation of organophosphorus pollutants, via the synergistic effect of peroxymonosulfate (PMS) and sodium percarbonate (SPC), into phosphates (o-PO4 3-), which are continually converted into phosphatic fertilizer by struvite precipitation on the continuous-flow reactor. Quenching experiments, electron paramagnetic resonance (EPR) results, electrochemical analysis, and density functional theory (DFT) calculation suggest that the transfer of electrons from SPC to PMS results in the synthesis of catalytically active species (i.e., ·OH, ·O2 -, 1O2, and CO3·-) for hydroxyethylidene-1,1-diphosphonicacid (HEDP) degradation. For the real glyphosate wastewater, the PMS/SPC system exhibits excellent catalytic activity with 69.20% decrease in chemical oxygen demand (COD) and 37.80% decrease in the total organic carbon (TOC) after 90 min. Indeed, high performance liquid chromatography (HPLC) confirms that glyphosate is completely degraded in 90 min with the formation of 271.93 µmol/L of o-PO4 3-, which is further converted into phosphatic fertilizer by the precipitation of struvite with 87.20% yield on continuous-flow reactor. Finally, biotoxicity of glyphosate to zebrafish and wheat seeds are significantly deceased after treatment of PMS/SPC system by zebrafish toxicology assays and germination tests of wheat seeds.

Nickel Ion Induced Multistage Assembly of Th13 Cluster

Clusters have proven useful models to elucidate the correlation between macroscopic properties and microstructures. However, the actinide clusters still remain much less developed compared to the splendid and systematic works of other members of this family. Here we show the synthesis of a tetra-shell mixed-metal cluster [ThO8@Th12(OH)24@Ni6(H2O)18@(sba)12] (IHEP-25, H2sba: 2-sulfobenzoic acid) with the strategic introduction of competitive Ni2+ ions. A cluster-based framework (IHEP-28), featuring a 2D honeycomb network and demonstrating excellent stability, has been constructed through the multistage assembly of IHEP-25, facilitated by the introduction of cationic cluster [Na4(OH)3(H2O)3]+. IHEP-28 acts as a highly effective visible light-driven photocatalyst for CO2 reduction. This study demonstrates that the incorporation of heterometal ions not only alters the hydrolysis patterns of actinide metal ions, resulting in the formation of new actinide clusters, but also broadens their potential applications.

Treatment of cationic red X-GRL in high-salt printing and dyeing wastewater by an electrocatalytic ozonation system: treatment efficiency and degradation mechanism

High salt concentrations in printing and dyeing wastewaters significantly influence pollutant removal. The function of the electrocatalytic ozonation (MgMn x O y -GAC/EP) system in removing pollutants from high-salt printing and dyeing wastewater was investigated. Under high NaCl concentration, the H2O2 yield in the electrochemical system was maintained at approximately 53 mg L-1. Under optimal treatment conditions, the degradation efficiency of cationic red X-GRL in the MgMn x O y -GAC/EP system reached 100% within 16 min, and the mineralization efficiency achieved 90.8% within 60 min. The specific energy consumption of the MgMn x O y -GAC/EP system was 0.027 kW h per gCOD. The SF of the MgMn x O y -GAC/EP system was 13.04, indicating that MgMn x O y -GAC, EO and O3 had a remarkable synergistic effect in the removal of cationic red X-GRL. The existence of ˙OH, ˙Cl, ˙O2 - and 1O2 in the MgMn x O y -GAC/EP system was demonstrated by quenching and electron paramagnetic resonance experiments. Based on these outcomes, the degradation mechanism of cationic red X-GRL in the MgMn x O y -GAC/EP system under high salt conditions was proposed, which was the action mechanism of multiple free radicals mainly dominated by ˙O2 - and 1O2. After repeated experiments, the MgMn x O y -GAC/EP system accomplished a COD removal efficiency of 84%, which signified its relatively high stability. The MgMn x O y -GAC/EP system achieved a COD removal efficiency of approximately 86% for diverse pollutants. Overall, this study revealed that the MgMn x O y -GAC/EP system has novel prospects for the treatment of organic pollutants in high-salt wastewater.

Reconsideration of the role of hydrogen peroxide in peroxymonocarbonate-based oxidation system for pollutant control

Advanced oxidation processes that utilize peroxymonocarbonate (HCO4-), generated in-situ through the reaction of HCO3- and H2O2, are employed for the removal of pollutants in water. Nevertheless, the precise role of H2O2 in these processes remains a subject of debate. This study established a HCO4--based oxidation system using NaHCO3 and H2O2 for the degradation of acetaminophen and investigated the activation mechanisms of coexisting oxidants. Under thermal activation conditions, the OO bond in HCO4- (HOOCOO-) was more readily cleaved than the OO bond in the co-existing oxidant H2O2 (HOOH), leading to the generation of reactive oxygen species (ROS). Based on kinetics and ROS evaluation, H2O2 primarily served to form HCO4- rather than converting to ·OH or O2, with HCO4- acting as the primary oxidant for degradation through the formation of CO3·-and ·OH. In this oxidation system, H2O2 utilization efficiency for ·OH production reached 27.34 %, ·OH yield reached 24.15 % and acetaminophen degradation efficiency realized 83 % at 60 °C with 20 mM HCO3- and 20 mM H2O2. The apparent activation energy of acetaminophen degradation and HCO4- activation were calculated as 90.83 kJ mol-1 and 18.81 kJ mol-1, respectively. Moreover, a novel CO2-derived HCO4--based system led to a comparable acetaminophen degradation efficiency of 82 % and a higher kobs of 0.028 min-1. The system optimization and ROS evaluation suggest that high concentration of H2O2 inhibited the degradation and quenched CO3·- and ·OH to yield ·O2- and 1O2. Furthermore, EPR analysis and quenching experiments indicate that CO3·- was mainly responsible for acetaminophen degradation. This work provides fundamental understanding of the HCO4--based oxidation system.

Hydrogen Peroxide-Assisted Alkaline Defluorination of the Fumigant and Potent Greenhouse Gas, Sulfuryl Fluoride: Hydrogen Peroxide as a Nucleophilic Reagent

Sulfuryl fluoride (SO2F2, SF) is an effective and increasingly popular fumigant for treating buildings and commodities in international trade but has come under scrutiny as a potent greenhouse gas. Passage of vent gases through an alkaline spray has been proposed for scrubbing SF, but base hydrolysis is insufficiently fast and generates equal yields of fluoride and fluorosulfate, the latter of unknown environmental hazard. We report here that alkaline hydrogen peroxide (H2O2) markedly accelerates SF removal and gives nearly quantitative yield of fluoride, with fluorosulfate produced in less than 3.5% yield. The other major products are sulfate, peroxymonosulfate, and oxygen. The oxidation state of S was unchanged. Hydroxyl and superoxide radical scavengers had no effect on the rate. The reaction proceeds by sequential nucleophilic displacement of fluoride by hydroperoxide ion (HO2-) to form a transient diperoxysulfate species that rapidly undergoes intramolecular redox rearrangement to give sulfate and singlet oxygen. Peroxymonosulfate, produced through side reactions, can fully defluorinate SF as well, although more slowly. Two new peaks were detected in the 19F-NMR spectrum corresponding to intermediates. Fluoride can be removed conventionally, and the other products are innocuous or short-lived. Thus, H2O2-assisted alkaline defluorination promises to be an effective method for scrubbing spent SF fumes and preventing SF from reaching the atmosphere. This study highlights the benefits of H2O2 and peroxymonosulfate as nucleophiles in remediation chemistry.

Can Rice Growth Substrate Substitute Rapeseed Growth Substrate in Rapeseed Blanket Seedling Technology? Lesson from Reactive Oxygen Species Production and Scavenging Analysis

Rapeseed (Brassica napus L.) seedlings suffering from inappropriate growth substrate stress will present poor seedling quality. However, the regulatory mechanism for the production and scavenging of reactive oxygen species (ROS) caused by this type of stress remains unclear. In the current study, a split plot experiment design was implemented with two crop growth substrates-a rice growth substrate (RIS) and rapeseed growth substrate (RAS)-as the main plot and two genotypes-a hybrid and an open-pollinated variety (Zheyouza 1510 and Zheyou 51, respectively)-as the sub-plot. The seedling quality was assessed, and the ROS production/scavenging capacity was evaluated. Enzymatic and non-enzymatic systems, including ascorbic acid and glutathione metabolism, and RNA-seq data were analyzed under the two growth substrate treatments. The results revealed that rapeseed seedling quality decreased under RIS, with the plant height, maximum leaf length and width, and aboveground dry matter being reduced by 187.7%, 64.6%, 73.2%, and 63.8% on average, respectively, as compared to RAS. The main type of ROS accumulated in rapeseed plants was hydrogen peroxide, which was 47.8% and 14.1% higher under RIS than under RAS in the two genotypes, respectively. The scavenging of hydrogen peroxide in Zheyouza 1510 was the result of a combination of enzymatic systems, with significantly higher peroxidase (POD) and catalase (CAT) activity as well as glutathione metabolism, with significantly higher reduced glutathione (GSH) content, under RAS, while higher oxidized glutathione (GSSH) was observed under RIS. However, the scavenging of hydrogen peroxide in Zheyou 51 was the result of a combination of elevated oxidized ascorbic acid (DHA) under RIS and higher GSH content under RAS. The identified gene expression levels were in accordance with the observed enzyme expression levels. The results suggest that the cost of substituting RAS with RIS is a reduction in rapeseed seedling quality contributing to excessive ROS production and a reduction in ROS scavenging capacity.

Influence of microplastics and environmentally persistent free radicals on the ability of biochar components to promote degradation of antibiotics by activated peroxymonosulfate

Microplastics (MPs) in sludge can affect the ability of biochar-activated peroxymonosulfate (PMS) to degrade antibiotics. In this work, biochar was prepared by mixing sludge and polystyrene (PS) through hydrothermal carbonization (HTC) and high-temperature pyrolysis processes. The resulting biochar was used to activate PMS to degrade ofloxacin (OFX), levofloxacin (LEV), and pefloxacin (PFX). The addition of PS significantly enhanced the ability of biochar/PMS to degrade antibiotics and the levels of environmentally persistent free radicals (EPFRs, 4.59 × 1020 spin/g) due to the decomposition of PS. The addition of PS resulted in a slight decrease in the specific surface area of biochar (2-3 m2/g on average), but a significant increase in the concentration of EPFRs increased the removal efficiency. The activation of PMS by biochar is dominated by free radicals, accounting for about 70%, in which SO4•- and •OH contribute the most and O2•- the least. However, 1O2 contributes 15-20% to the degradation of antibiotics in non-free radical processes. Overall, the process of biochar/PMS degradation of antibiotics is mainly dominated by free radicals, and the effect of non-free radicals is not obvious. Both hydrochar and pyrocarbon samples showed good hydrophilicity, and this property should improve the ability of active sites on biochar to degrade antibiotics. In the HTC process, PS can decompose during hydrochar preparation, with a maximum reduction value of 40.09%. The three-dimension excitation emission matrix fluorescence spectroscopy (3D-EEM) and total organic carbon (TOC) results show that the protein content in sludge plays a major role in reducing PS, with little effect of polysaccharide and SiO2. There are six to seven degradation intermediates of quinolone antibiotics, which are eventually degraded into CO2, H2O, and inorganic substances. The regeneration experiment showed good reusability of hydrochar and pyrocarbon, further demonstrating the suitability of biochar for the degradation of antibiotics.