Vis LED Photo-Fenton Degradation of 124-Trichlorobenzene at a Neutral pH Using Ferrioxalate as Catalyst

Solar-assisted oxidation of organochlorine pesticides in groundwater using persulfate and ferrioxalate

The oxidation of hexachlorocyclohexane isomers in the aqueous phase (Milli-Q and groundwater) was studied using persulfate activated by ferrioxalate and solar light at circumneutral pH. The experiments were conducted in a solar simulator reactor with local radiation fluxes qw= 1.12·10-7 E cm-2s-1 and in compound parabolic collectors with solar light (qw≈10-7 E cm-2s-1) for 390 min. The effect of activator dosage (18-125 μM ferrioxalate) and persulfate concentration (520-2600 μM) on hexachlorocyclohexane conversion and oxalate and oxidant consumption was analyzed. Conversion of about 95% of β isomer was achieved at 390 min using 1300 μM of initial persulfate and 63 μM of Fe3+ concentration despite this β isomer being the most recalcitrant to oxidation (XHexachlorocyclohexanes=0.98). Dechlorination above 80% was achieved under these conditions, analyzing the chlorides released into the water. The influence of chloride and bicarbonate on hexachlorocyclohexanes degradation was analyzed in milli-Q water and in groundwater. Hexachlorocyclohexane conversion at 390 min decreases from 98% to 83, 75 and 65% in the presence of chloride, bicarbonate or groundwater, respectively. Results obtained with compound parabolic collectors and solar light using 2600 μM Na2S2O8 and 63 μM Fe for removing hexachlorocyclohexanes agreed with those from the solar simulator reactor, supporting using solar light to activate persulfate for sustainable abatement of persistent organic pollutants in aqueous matrixes.

Improvement of ferrioxalate assisted Fenton and photo-Fenton processes for paracetamol degradation by hydrogen peroxide dosage

This work aimed to investigate the impact of hydrogen peroxide (HP) punctual dosage on paracetamol (PCT) degradation, through Fenton and photo-Fenton processes under near-neutral pH conditions, using ferrioxalate and artificial sunlight. The assays were performed using a D-optimal experimental design, to statistically evaluate the influence of radiation (ON or OFF), HP concentration (94.5-756 mg L-1), and HP dosage (YES or NO), on PCT conversion. The optimal conditions determined from the study were: HP = 378 mg L-1, DOS = YES, and RAD = ON, achieving a predicted PCT conversion of 99.68% in 180 min. This result obtained from the model was very close to the experimental one (98.80%). It was verified that HP dosage positively influenced the iron catalytic cycle since higher Fe2+ concentrations were reached at shorter reaction times, accelerating not only PCT conversion but also its by-products hydroquinone and 1,4-benzoquinone, leading to better performances of Fenton and photo-Fenton reactions. Under optimal conditions and employing real water matrices (an artificial matrix with inorganic anions, a real groundwater sample, and a synthetic industrial wastewater), HP dosage demonstrated the ability to mitigate the negative effects caused by the content of different ions and other organic compounds and significantly improve HP consumption in challenging wastewater conditions.

Current status and future challenges of chlorobenzenes pollution in soil and groundwater (CBsPSG) in the twenty-first century: a bibliometric analysis

The global industrial structure had undertaken significant changes since the twenty-first century, making a severe problem of chlorobenzene pollution in soil and groundwater (CBsPSG). CBsPSG receives increasing attention due to the high toxicity, persistence, and bioaccumulation of chlorobenzenes. To date, despite the gravity of this issue, no bibliometric analysis (BA) of CBsPSG does exist. This study fills up the gap by conducting a BA of 395 articles related to CBsPSG from the Web of Science Core Collection database using CiteSpace. Based on a comprehensive analysis of various aspects, including time-related, related disciplines, keywords, journal contribution, author productivity, and institute and country distribution, the status, development, and hotspots of research in the field were shown visually and statistically. Moreover, this study has also delved into the environmental behavior and remediation techniques of CBsPSG. In addition, four challenges (unequal research development, insufficient cooperation, deeply mechanism research, and developing new technologies) have been identified, and corresponding suggestions have been proposed for the future development of research in the field. Afterwards, the limitations of BA were discussed. This work provides a powerful insight into CBsPSG, enabling to quickly identify the hotspot and direction of future studies by relevant researchers.

Sustainable reuse of toxic spent granular activated carbon by heterogeneous fenton reaction intensified by temperature changes

A common strategy for removing highly toxic organic compounds, such as chlorinated organic compounds, is their adsorption on granular activated carbon. Spent granular activated carbon results in a toxic residue to manage; therefore, the regeneration and reuse of granular activated carbon on the site would be advisable. This work studies the regeneration of a granular activated carbon saturated in 1,2,4-trichlorobenzene, chosen as the model chlorinated organic compounds, by heterogeneous Fenton, where iron was previously immobilised on the granular activated carbon surface. This methodology avoids the addition of iron to the aqueous phase at concentrations above the allowable limits and the need for acidification. Three successive cycles of adsorption-regeneration were carried out batchwise (5 gGAC·L-1) with a granular activated carbon saturated with 300 mg124-TCB·gGAC-1. The recovery of the adsorption capacity after regeneration was studied with H2O2 (166 mM, 1.5 the stoichiometric dosage), at different concentrations adsorbed with iron adsorbed concentrations (0-12 mgFe·gGAC-1) and temperatures (20-80 °C). Stable recovery of the adsorption capacity values of 65% were obtained at 180 min with 12 mgFe·gGAC-1 and 60 °C. The porosity and surface chemistry of the adsorbent remained very similar after different adsorption-regeneration cycles without iron leaching into the aqueous phase. The oxidant consumption was close to the stoichiometric value for the mineralization of 1,2,4-trichlorobenzene, with a low unproductive consumption of H2O2 with granular activated carbon. In addition, no aromatic or chlorinated by-products were detected in the aqueous solution obtained in the regeneration process. The negligible toxicity of the aqueous phase with the Microtox bioassay confirmed the absence of toxic oxidation by-products.

Study on Degradation of 1,2,4-TrCB by Sugarcane Cellulose-TiO2 Carrier in an Intimate Coupling of Photocatalysis and Biodegradation System

1,2,4 trichlorobenzene (1,2,4-TrCB) is a persistent organic pollutant with chemical stability, biological toxicity, and durability, which has a significant adverse impact on the ecological environment and human health. In order to solve the pollution problem, bagasse cellulose is used as the basic framework and nano TiO₂ is used as the photocatalyst to prepare composite carriers with excellent performance. Based on this, an intimate coupling of photocatalysis and biodegradation (ICPB) system combining photocatalysis and microorganisms is constructed. We use the combined technology for the first time to deal with the pollution problem of 1,2,4-TrCB. The biofilm in the composite carrier can decompose the photocatalytic products so that the removal rate of 1,2,4-TrCB is 68.01%, which is 14.81% higher than those of biodegradation or photocatalysis alone, and the mineralization rate is 50.30%, which is 11.50% higher than that of photocatalysis alone. The degradation pathways and mechanisms of 1,2,4-TrCB are explored, which provide a theoretical basis and potential application for the efficient degradation of 1,2,4-TrCB and other refractory organics by the ICPB system.