Activation of hydrogen peroxide via bicarbonate, sulfate, phosphate and urea in the oxidation of methyl phenyl sulfide

Oxygen doped graphitic carbon nitride nanosheets for the degradation of organic pollutants by activating hydrogen peroxide in the presence of bicarbonate in the dark

The development of novel wastewater treatment processes that use heterogeneous catalysts to activate hydrogen peroxide (H2O2) with bicarbonate (HCO3 -) has been a subject of great interest in recent years; however, significant challenges remain, despite research into numerous metal-based catalysts. The work presented herein employed oxygen-doped graphitic carbon nitride (O/g-C3N4) as a non-metal catalyst for activating H2O2 in the presence of HCO3 -, and this method represented the first system capable of removing organic pollutants in the dark, to our knowledge. The catalysts were characterized using several microscopic imaging, spectroscopic, electrochemical, and crystallographic techniques, as well as N2-physorption procedures. Analysis of the results revealed that the O/g-C3N4 catalyst possessed a high specific surface area and many defect sites. Various operational parameters, including the relative amounts of HCO3 -, H2O2, and O/g-C3N4, were systemically investigated. A clear performance enhancement was observed in the degradation of organic contaminants when subjected to the HCO3 --H2O2-O/g-C3N4 system, and this result was ascribed to the synchronous adsorption and chemical oxidation processes. The novel system presented herein represented a new water treatment technology that was effective for removing organic contaminants.

Rapid activation of basic hydrogen peroxide by borate and efficient destruction of toxic industrial chemicals (TICs) and chemical warfare agents (CWAs)

The activation process of the B(OH)₃-activated H₂O₂ solution and its performance toward toxic industrial chemicals (TICs) and chemical warfare agents (CWAs) were investigated to find an efficient way to destroy TICs and CWAs. ¹¹B NMR analysis proved that B(OH)₃ reacted rapidly with basic H₂O₂ to produce peroxoborates ([B(OH)_(4-x)(OOH)_x]^-), and the proportional contents were closely related to the pH and temperature. ¹O₂ and ·O₂^- were generated, and their production increased exponentially with pH. TICs thioanisole and paraoxon were used as simulants of CWAs to investigate the decontamination performance and nucleophilic/oxidizing reactivity of the B(OH)₃-activated H₂O₂. Batch experiments proved that peroxoborates acted as the oxidants for the primary oxidation of the sulfide at a pH range of 8-12 and that ·O₂^- was responsible for the further oxidation of sulfoxide. Paraoxon degraded through OOH^--mediated S_N2 displacement with high stereo-selectivity, and the degradation rate increased exponentially with pH. Mustard gas, soman, and VX degraded effectively into nontoxic products in the B(OH)₃-activated H₂O₂ solution. A pH of 9-11 was recommended as the suitable acidity for developing the B(OH)₃-activated H₂O₂ solution to be a candidate for nucleophilic/oxidizing decontaminant, with advantages in rapid activation and low loss rate of reactive oxygen species.

Stability of dissolved percarbonate and its implications for groundwater remediation

Efforts to improve the understanding of oxidant stability are of great practical significance to the design of an in-situ chemical oxidation (ISCO) system for soil and groundwater remediation. In this study, the stability of an emerging ISCO oxidant sodium percarbonate (SPC) was investigated. Although the dry solid form of SPC is relatively stable, dissolved SPC decomposes much faster than H₂O₂. SPC had higher oxidation efficiency for the dye Orange G than inactivated or alkaline-activated H₂O₂. Both OH^- and HCO₃^-/CO₃^a2-, generated from SPC dissolution, activated the peroxide content of SPC and thus promoted its decomposition and pollutant oxidation. Higher incubation temperature and longer incubation period lead to faster SPC decomposition. Decomposed SPC had lower pollutant oxidation capability.

Bicarbonate-activated hydrogen peroxide and efficient decontamination of toxic sulfur mustard and nerve gas simulants

¹³C NMR spectra showed that peroxymonocarbonate (HCO₄^-) was generated in the NaHCO₃-activated H₂O₂ solution and pH was a key factor in its production. A cycle for the bicarbonate anion was proposed as HCO₃^-→HCO₃ → (CO₂)₂*→CO₂(aq)→HCO₄^- (H₂CO₄)→HCO₃^- (HCO₃) basing on the results of NMR, electron paramagnetic resonance, chemiluminescence analysis. In this cycle, (CO₂)₂* was the key intermediate and (CO₂)₂*→2CO₂+hv was the rate controlling step. Thioanisole and paraoxon, the simulants of sulfur mustard gas and nerve gas, respectively, were efficiently decontaminated by the NaHCO₃-activated H₂O₂ solution. While HCO₄^- was the primary oxidant for the oxidation of thioanisole, O₂^- generated during the decomposition of HCO₄^- or H₂O₂ led to the secondary oxidation of the sulfide. Paraoxon was degraded in the NaHCO₃-activated H₂O₂ solution via nucleophilic substitution by OOH^- and OH^-, and the degradation rate increased exponentially with increasing pH. Alkali metal ions had a catalytic effect on the degradation of paraoxon. Mustard gas and soman degraded efficiently into nontoxic products in NaHCO₃-activated H₂O₂. A pH range of 9-10 was found to be optimum for the broad-spectrum decontamination of chemical warfare agents and other eco-toxicants using NaHCO₃-activated H₂O₂.

Kinetic investigation on the highly efficient and selective oxidation of sulfides to sulfoxides and sulfones with t-BuOOH catalyzed by La2O3

An efficient and highly selective methodology for the oxidation of various sulfides with 70% t-BuOOH as oxidant in the presence of catalytic amounts of La₂O₃ is described.