Pyrite-activated persulfate to degrade 3,5,6-trichloro-2-pyridyl in water: Degradation and Fe release mechanism.

TCP (3,5,6-trichloro-2-pyridinol), the main recalcitrant degradation product of chlorpyrifos, poses a high risk to human health and ecological systems. This study provided a comprehensive exploration of the pyrite-activated persulfate (PS) system for the removal of TCP in water and placed particular emphasis on the pyrite oxidation process that releases Fe. The results showed that the pyrite-activated PS system can completely degrade TCP within 300 min at 5.0 mmol/L PS and 1000 mg/L pyrite at 25 °C, wherein small amounts of PS (1 mmol/L) can effectively facilitate TCP removal and the oxidation of pyrite elements, while excessive PS (>20 mmol/L) can lead to competitive inhibitory effects, especially in the Fe release process. Aimed at the dual effects, the evident positive correlation (R2 > 0.90) between TCP degradation (kTCP) and Fe element release (kFe), but the value of k (0.00237) in the pyrite addition variable experiment was less than that in the PS experiment (k = 0.00729), further indicating that the inhibition effect of excessive addition consists of PS but not notably pyrite. Moreover, the predominant free radicals and non-free radicals produced in the pyrite/PS system were tested, with the order of significance being •OH < Fe (Ⅳ) < SO4•- < â€¢O2- < 1O2, wherein 1O2 emerged as the principal player in both TCP degradation and Fe release from the pyrite oxidation process. Additionally, CO32- can finitely activate PS but generally slows TCP degradation and inhibit pyrite oxidation releasing Fe process. This study provides a theoretical basis for the degradation of TCP using pyrite-activated PS.

Optimizing soil tetrabromobisphenol A remediation through iron-based activation of persulfate: A comparative analysis of homogeneous and heterogeneous systems.

Tetrabromobisphenol A (TBBPA) that widely exists in soil and poses a potential threat to ecological environment urgently needs economically efficient remediation techniques. This study utilized both homogeneous Fe2⁺ solution and heterogeneous iron-based nanomaterials (chemically synthesized nano zero-valence iron (nZVI) and green-synthesized iron nanoparticles (G-Fe NPs)) to activate persulfate (PS) and assess their efficacy in degrading TBBPA in soil. The results demonstrate the superior performance of heterogeneous catalytic systems (WG-Fe NPs/PS (82.07%) and WnZVI/PS (78.32%)) over homogeneous catalytic system (WFe2+/PS (71.69%)), In addition, G-Fe NPs and nZVI effectively controlled the slow release of Fe2+. The optimization analysis using response surface methodology (RSM) reveal the remarkable significance of the experimental model based on the box-behnken design. RSM show that G-Fe NPs/PS exhibited optimal process parameters and predicted the maximum soil TBBPA degradation efficiency reaching 98.77%. The results of density functional theory calculations suggest that C-Br are the primary targets for electrophilic substitution reactions. Based on the f0 value and △G, the degradation pathway of TBBPA is inferred to involve a sequential debromination process, followed by the cleavage of intermediate carbon-carbon bonds and subsequent oxidation reactions. Hence, G-Fe NPs/PS not only facilitate waste resource utilization but also hold significant application potential.

Persulfate activation with sodium alginate/sulfide coated iron nanoparticles for degradation of tetrabromobisphenol a in soil.

The accumulation of tetrabromobisphenol A (TBBPA) in soil posed a serious threat to ecosystem and human health. Sodium alginate/sulfide coated iron nanoparticles (SA@S-Fe NPs) was synthesized by a two-step modification of Fe NPs prepared with tung tree leaves extracting solution, and utilized as a persulfate (PS) activator to degrade TBBPA in soil. Response surface methodology (RSM) optimization showed a theoretical maximum TBBPA degradation reaching 99.79% at the 34.28 °C, SA@S-Fe NPs and PS additions of 3.57 g kg-1 and 36.35 mM, respectively. The degradation mechanism of TBBPA suggested that the main reactive species produced in the SA@S-Fe NPs/PS system were •OH, SO4•-, and O2•-. Proposed mechanisms for the degradation of TBBPA in soil involved debromination, benzene rings split, hydroxylation, demethylation, and complete mineralization to CO2 and H2O. We also further studied the effect to soil physicochemical properties and morphology structure during TBBPA degradation in SA@S-Fe NPs/PS system, which showed that SOM, TN, C/N and TOC slightly reduced, the heavy metals Fe, Cu and Zn still existed in stable residue form, and the soil morphology showed a certain degree of aggregation. Therefore SA@S-Fe NPs/PS technology can effectively degrade soil TBBPA, maintain soil fertility, curb the migration of heavy metals, and environmental risks.