Dynamic behavior of hydroxyl radical in sono-photo-Fenton mineralization of synthetic municipal wastewater effluent containing antipyrine

Monitoring Photo-Fenton and Photo-Electro-Fenton process of contaminants emerging concern by a gas diffusion electrode using Ca10-xFex-yWy(PO4)6(OH)2 nanoparticles as heterogeneous catalyst

The catalytic performance of modified hydroxyapatite nanoparticles, Ca10-xFex-yWy(PO4)6(OH)2, was applied for the degradation of methylene blue (MB), fast green FCF (FG) and norfloxacin (NOR). XPS analysis pointed to the successful partial replacement of Ca by Fe. Under photo-electro-Fenton process, the catalyst Ca4FeII1·92W0·08FeIII4(PO4)6(OH)2 was combined with UVC radiation and electrogenerated H2O2 in a Printex L6 carbon-based gas diffusion electrode. The application of only 10 mA cm-2 resulted in 100% discoloration of MB and FG dyes in 50 min of treatment at pH 2.5, 7.0 and 9.0. The proposed treatment mechanism yielded maximum TOC removal of ∼80% and high mineralization current efficiency of ∼64%. Complete degradation of NOR was obtained in 40 min, and high mineralization of ∼86% was recorded after 240 min of treatment. Responses obtained from LC-ESI-MS/MS are in line with the theoretical Fukui indices and the ECOSAR data. The study enabled us to predict the main degradation route and the acute and chronic toxicity of the by-products formed during the contaminants degradation.

Insights into the adsorption of CO2 generated from synthetic urban wastewater treatment on olive pomace biochar

In this investigation, a sustainable and low-cost method to capture CO₂ generated from the treatment of urban wastewater was evaluated. We studied the adsorption of CO₂ on olive pomace biochar. The experiments of degradation of synthetic wastewater mimicking effluents of municipal wastewater treatment plant (WWTP) with an initial Total Organic Carbon (TOC) concentration of 10 mg L^-1 were conducted by using the UV-C/H₂O₂ process in the absence or presence of biochar. The biochar was placed in a fixed bed column through which air from the UV reactor was circulated. First, the effects of different parameters such as H₂O₂ initial concentration and pH on wastewater mineralization efficiency were determined. Total Organic Carbon (TOC) removal was 87% in 2 h under optimal degradation conditions. The maximal concentration of CO_2(gas) in air, in a closed system (air volume: 7.3 10^-4 m³), after 11 h was 12,500 μmol mol^-1 in the absence of biochar and only 150 μmol mol^-1 when 10 g biochar were used. The results proved that by combining biochar with oxidative degradation of organic compounds, it is possible to mineralize organic compounds and reduce the requisite CO₂ emissions by about 99%. The experimental equilibrium results were fit well with both Langmuir and Freundlich isotherms models concluding that CO₂ adsorption on biochar followed both chemisorption and physisorption and both monolayer and multi-layer CO₂ adsorption could occur. The total desorption of CO₂ from biochar was reached in 120 min by simultaneously increasing the temperature to 150 °C and introducing a purge N_2(gas).

An optimized sono-heterogeneous Fenton degradation of olive-oil mill wastewater organic matter by new magnetic glutarlaldehyde-crosslinked developed cellulose

The present study highlights the olive mill wastewater (OMW) treatment characteristics through a sono-heterogeneous Fenton process using new designed [GTA-(PDA-g-DAC) @Fe₃O₄] and characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), magnetic properties measurements, and point of zero charge (pH pzc) analysis. A preliminary removal study showed significant degradation efficiency (75%) occurred combining the magnetic synthesized catalyst [GTA-(PDA-g-DAC)@Fe3O4] ([catalyst] = 2 g/L) with US /H₂O₂ and maintaining 500WL^-1 ultrasonic power (US). The values obtained by US only were (13%), H₂O₂/US (18%), US/Fe₃O₄ (28%), and US /Fe₃O₄/H₂O₂(35%). The catalytic findings have shown that [GTA-(PDA-g-DAC)@Fe₃O₄] exhibited good properties for OMW compound's degradation. The sonocatalytic process coupling and extra oxidant addition resulted in the degradation substantial levels. For instance, the concomitant effect of degradation optimized parameters; H₂O₂ 10 mM, [GTA-(PDA-g-DAC) @Fe₃O₄] nanocomposites 2.5 g/L, at pH 3, and T 35 °C for 70 min resulted in an almost complete mineralization of aqueous OMW solution followed by a significant decolorization. Oxidation results exhibited efficient degradation rates in total phenolic compounds (TPC), total amino compounds (TAC), and chemical oxygen demand (COD) oxidation rate were 89.88, 92.75, and 95.66 respectively following the optimized sono-heterogeneous catalytic Fenton process. The prepared magnetic catalyst exhibited a good stability during repeated cycles. The gathered findings gave the evidence that sono-heterogeneous catalytic Fenton process is a promising treatment technology for OMW effluents.

Decontamination of toxic Malathion pesticide in aqueous solutions by Fenton-based processes: Degradation pathway, toxicity assessment and health risk assessment

This study evaluates the degradation efficiency of Malathion using Fenton (Fe²⁺/H₂O₂: F), photo-Fenton (UV/Fe²⁺/H₂O₂: PF), and sono-photo Fenton (US/UV/Fe²⁺/H₂O₂: SPF) processes as well as determines the toxicity of the byproducts of degradation. The effect of various operational parameters on the Malathion degradation rate, including pH, Fe²⁺ concentration, Malathion concentration, and H₂O₂ were studied. The removal efficiency was determined to be 98.79% for the SPF, > 70.92% for the PF, and > 55.94% for the F processes under the following optimal conditions: pH = 3, [H₂O₂]₀ = 700 mg/L, [Fe²⁺]₀ = 20 mg/L, and [Malathion]₀ = 20 mg/L. The operating costs (USD/kg_{Malathion-removed}) were acquired as SPF > PF > F. Moreover, Malaoxon, diethyl maleate, diethyl malate, ethyl 2-hydroxysuccinate, and D-malate were among the detected byproducts from the Malathion degradation in the SPF process. Both the non-carcinogenic risk and the carcinogenic risk were assessed to establish the quality of the effluent from all three processes. The toxicity of the treated effluents, determined by Vibrio fischeri luminescence, indicated that the toxicity depends on the selected treatment process. The high degradation efficiency of the Fenton-based processes is not equivalent to achieving detoxification of the effluents. As such, the SPF process was determined to be the most effective for the Malathion degradation, total organic carbon (TOC) removal, and health risk assessment.

Efficient purification of wastewater by applying mechanical force and BaCO3/TiO2 and BaTiO3/TiO2 piezocatalysts

In typical advanced oxidation catalysis, a semiconductor should have a robust capacity to generate separated electron-hole pairs on a material's surface under irradiation of photons with energy more than the material's bandgap. However, rapid charge carrier recombination and low photon to current yield of semiconductor photocatalysts and low percentages of UV light in sunlight leads to a low level of photocatalytic efficiency for practical application. Mechanical energy is a natural energy that can be considered as a form of rich, clean and renewable energy which can be harvested by using piezoelectric materials. Here, we developed BaCO₃/TiO₂ and BaTiO₃/TiO₂ composites as mechanical harvesting materials to decontaminate pollutants. Results showed that BaCO₃ has a great effect on the piezocatalytic activity of products. The control sample (sample without Ba) only degraded 11.2% of Acid Red 151 (AR151) , while the sample containing Ba degraded 96.7% of AR151. Besides, the effects of several parameters, including the natural surfactant, reaction time and temperature, calcination, and ultrasonic power and pulse on the catalytic activity of the as-prepared piezocatalysts were studied. Results showed that it is possible to degrade 99.1% of AR151 by controlling ultrasonic parameters during 2 h of mechanical energy force.

Capture of ambient air CO2 from municipal wastewater mineralization by using an ion-exchange membrane

The capture of ambient air CO_2(gas) from synthetic urban wastewater mineralization reaction was studied. An ion exchange membrane was used as sorbent, which adsorbs CO₂ when dry and releases it when wet. The UV/H₂O₂ degradation process was chosen to convert Total Organic Carbon (TOC) to carbon dioxide due to its advantages of convenience and fast kinetics over the conventional biological treatment that is usually used in urban wastewater treatment plants. In the first phase, experiments combining UV-C light and H₂O₂ were carried out to select the optimal values of the following parameters: pH, the dose of H₂O₂ and temperature. In the second stage, the CO_2(gas) emission into the air from the degradation of organic compounds present in wastewater during UV/H₂O₂ process in the absence or presence of ion exchange membranes was evaluated. The effects of parameters such as temperature or air humidity were studied. A qualitative study of desorption was carried out to check the viability of reuse CO₂ captured in the membrane. Finally, a similar CO_2(gas) adsorption capacity after five cycles of adsorption and regeneration of the membranes was observed, being percentage loss of around 4%.

A comparative study on phenazone degradation by sulfate radicals based processes

In this paper, a comparative study on removal of the emerging pollutant phenazone (PNZ) by two treatment processes UVA/Fe(II)/persulfate (PS) and UVA/Fe(II)/peroxymonosulfate (PMS) was conducted. The two processes showed high efficiency in PNZ degradation, followed by a reasonable mineralization. The treatment system with PMS was found to be more efficient for PNZ degradation than that with PS due to the larger amounts of radicals generated. While the treatment process UVA/Fe(II)/PS showed higher ΔTOC/ΔSMX (TOC removal per unit of PNZ decay) than UVA/Fe(II)/PMS process. The sulfate and hydroxyl radicals played dominant roles in PNZ degradation in the UVA/Fe(II)/PS and UVA/Fe(II)/PMS process, respectively. Six and seven intermediates during PNZ degradation by UVA/Fe(II)/PS and UVA/Fe(II)/PMS process were detected, respectively. Among the detected intermediates, six of them are found for the first time. It takes shorter time for toxicity elimination by UVA/Fe(II)/PS process than UVA/Fe(II)/PMS, possibly due to the lower Kow values of hydroxylated products. The results demonstrate that UVA/Fe(II)/PMS process is more efficient in PNZ degradation, while UVA/Fe(II)/PS is more efficient in detoxification of PNZ. The two sulfate radicals based processes have good potentials in degradation, mineralization and detoxification of the emerging contaminants such as PNZ.

Enhanced removal of basic violet 10 by heterogeneous sono-Fenton process using magnetite nanoparticles

The removal of basic violet 10 (BV10), which is known as a cationic dye, from aqueous solution was studied by employing a heterogeneous sono-Fenton process over the nano-sized magnetite (Fe₃O₄) which had been prepared by the milling of magnetite mineral using a high-energy planetary ball milling process. The magnetite samples were characterized using the X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), and inductively couple plasma mass spectrometer (ICP-MS). It was found that the catalytic activity of the ball-milled magnetite sample was enhanced along with the improvement in its physicochemical properties; also, the ball-milled magnetite of 6 h displayed the highest catalytic activity in BV10 removal by the heterogeneous sono-Fenton process as compared with that for 4 h (66.12% after 120 min) and 2 h (48% after 120 min).The effect of operational parameters, namely, pH solution, catalyst dosage, the initial H₂O₂ concentration, ultrasonic power and the initial BV10 concentration, on the removal efficiency (RE%) of BV10 was investigated. The optimum conditions for the BV10 RE% were: the pH value of 3, the catalyst dosage of 1.5 g L^-1, the initial H₂O₂ concentration of 36 mM, the ultrasonic power of 450 W L^-1, and the initial BV10 concentration of 30 mg L^-1. The RE% of BV10 was 75.94% at these conditions after the reaction time of 120 min. The trapping experiments revealed that OH radicals were the dominant oxidative species, but O₂^-/HO₂ radicals also had a partial role in the removal of BV10.The reusability of the magnetite nanoparticles revealed about 28% decrease in the removal efficiency within five consecutive runs. The results obtained through GC-MS analysis also confirmed the efficient removal of BV10 molecules in the aqueous solution during the process.

Study of the intensification of solar photo-Fenton degradation of carbamazepine with ferrioxalate complexes and ultrasound

The intensification of the solar photo-Fenton system with ferrioxalate photoactive complexes and ultrasound applied to the mineralization of 15mg/L carbamazepine aqueous solution (CBZ) was evaluated. The experiments were carried out in a solar compound parabolic collector (CPC) pilot plant reactor coupled to an ultrasonic processor. The dynamic behavior of hydroxyl radicals generated under the different studied reaction systems was discussed. The initial concentrations of hydrogen peroxide and ferrous/oxalic acid and pH were found to be the most significant variables (32.79%, 25.98% and 26.04%, respectively). Under the selected optimal conditions ([H₂O₂]₀=150mg/L; [Fe²⁺]₀=2.5mg/L/[(COOH)₂]₀=12.1mg/L; pH=5) CBZ was fully degraded after 5min and 80% of TOC was removed using a solar photo-Fenton system intensified with ferrioxalate (SPFF). However, no improvement in the mineralization using SPFF process combined with ultrasound was observed. More mild pH conditions could be used in the SPFF system if compared to the traditional photo-Fenton (pH 3) acidic systems. Finally, a possible reaction pathway for the mineralization of CBZ by the SPFF system was proposed and therein discussed.

Enhanced decolorization of methyl orange in aqueous solution using iron-carbon micro-electrolysis activation of sodium persulfate

Reactivity of sodium persulfate (PS) in the decolorization of methyl orange (MO) in aqueous solution using an iron-carbon micro-electrolysis (ICE) method was investigated. The effects of sodium persulfate doses, pH, Fe-to-C mass ratios, initial MO concentration as well as the reaction temperature were comprehensively studied in batch experiments. The ICE-PS coupled process was more suitable for wide ranges of pH, initial MO concentration and reaction temperature, accompanied by the reduction of Fe compared ICE. The MO removal efficiency improved substantially by ICE-PS technique, 76.03% for ICE and 91.27% for ICE-PS at experimental conditions of pH 3.0, Fe-to-C mass ratio 3:1, PS addition 10 mM and initial MO concentration 0.61 mM. Furthermore, the biodegradability index (BI) dramatically increased from 0.26 to 0.65. The binary hydroxyl and sulfate radicals that non-selectively degrade MO to the derivatives with small molecules are ascribed to ICE-PS method as detected by the UV-vis spectra. The PS activation resource was Fe²⁺ through the hydroxyl radical quenching reaction by the additive tert-butanol (TBA). This study provides an in-depth theoretical understanding of the development and wide commercial application of the ICE technology to refractory industrial dye wastewater treatment.