Display omitted
•High rates of Valproate and TOC removal were obtained using low concentration of iron.•Photo-Fenton degradation products of Valproate were identified.•Electrical cost estimation ...demonstrated that both BLB and UVC are profitable options for degrading VA via photo-Fenton.
The abatement of valproic acid sodium salt (VA) via photo-Fenton process was investigated to evaluate the effect of irradiation type. Three different light sources have been used: UVA (black light blue lamps, BLB reactor), UVC (UVC reactor) and simulated sunlight in a Solarbox (SB). Using the highest concentrations of Fe2+ (10mgL−1) and H2O2 (150mgL−1), 100% of VA degradation was observed in BLB and UVC devices, and 89.7% in Solarbox. Regarding mineralization, 67.4% and 76.4% of TOC conversion were achieved in BLB and UVC, respectively. In Solarbox, mineralization was negligible. Treated solutions under UVA or UVC radiation became biodegradable (BOD5/COD≥0.25), which was not observed in Solarbox where BOD5/COD achieved was only 0.20. Regarding to toxicity (Vibrio Fischeri method), all processes have promoted the overall toxicity reduction of VA solution. Transformation products were identified by a LC-ESI-TOF mass spectrometer, and degradation pathways were proposed. Operating costs and the energy needed by mg of VA removed were estimated and compared, for the different installations, showing that UVA can remove around 3 times more VA than SB and 2 times more VA than UVC, under the same conditions.
Electro-oxidation with electrogenerated H2O2 (EO-H2O2) was applied to treat acidic aqueous solutions of 4-aminoantipyrine (4-AA), a persistent drug metabolite of dipyrone, in sulfate medium. Trials ...were made using a boron-doped diamond anode in the presence of H2O2 electrogenerated on site. A 24 central composite design (CCD) was employed to evaluate the effect of four independent variables, namely current density (j), pH, 4-AA concentration and electrolysis time, on the percentages of degradation and mineralization, as well as on mineralization current efficiency (MCE). Predicted responses agreed with observed values, showing linear trendlines with good R2 and R2adj values. The degradation was optimum at j=77.5mAcm−2, pH3.5 and 62.5mgL−1 4-AA, leading to 63% and 99% removal after 3 and 7min, respectively. For those solutions, the largest mineralization was found at j=77.5mAcm−2, attaining 45% abatement at 175min. Low MCE values were obtained in all electrolyses. An initial route for 4-AA degradation is proposed based on one dimer and eleven aromatic and aliphatic intermediates detected in the treated solutions at pH3.5 by LC-MS. The initial 62.5mgL−1 solution at pH3.5 presented acute toxicity on Artemia salina larvae, with LC50=13.6mgL−1, being substantially reduced after 3 and 7min of EO-H2O2 at j=77.5mAcm−2 due to the formation of less toxic derivatives.
Display omitted
•Electro-oxidation of 4-aminoantipyrine (4-AA) optimized by a 24 CCD•Total removal of 62.5mgL−1 4-AA at pH3.5 after 7min at j=77.5mAcm−2•Almost total mineralization with 91% TOC removal after 510min at j=77.5mAcm−2•Hydroxylated derivatives and dimer formed upon attack of BDD(•OH)•Acute toxicity on Artemia salina substantially reduced after 7min of treatment
A solution with 0.38 mM of the pesticide propoxur (PX) at pH 3.0 has been comparatively treated by electrochemical oxidation with electrogenerated H
2
O
2
(EO-H
2
O
2
), electro-Fenton (EF), and ...photoelectro-Fenton (PEF). The trials were carried out with a 100-mL boron-doped diamond (BDD)/air-diffusion cell. The EO-H
2
O
2
process had the lowest oxidation ability due to the slow reaction of intermediates with
•
OH produced from water discharge at the BDD anode. The EF treatment yielded quicker mineralization due to the additional
•
OH formed between added Fe
2+
and electrogenerated H
2
O
2
. The PEF process was the most powerful since it led to total mineralization by the combined oxidative action of hydroxyl radicals and UVA irradiation. The PX decay agreed with a pseudo-first-order kinetics in EO-H
2
O
2
, whereas in EF and PEF, it obeyed a much faster pseudo-first-order kinetics followed by a much slower one, which are related to the oxidation of its Fe(II) and Fe(III) complexes, respectively. EO-H
2
O
2
showed similar oxidation ability within the pH range 3.0–9.0. The effect of current density and Fe
2+
and substrate contents on the performance of the EF process was examined. Two primary aromatic products were identified by LC-MS during PX degradation.
Solutions with 0.65 mM of the antituberculosis drug isoniazid (INH) in 0.050 M Na
2
SO
4
at pH 3.0 were treated by electro-Fenton (EF) and UVA photoelectro-Fenton (PEF) processes using a cell with a ...BDD anode and a carbon-PTFE air-diffusion cathode. The influence of current density on degradation, mineralization rate, and current efficiency has been thoroughly evaluated in EF. The effect of the metallic catalyst (Fe
2+
or Fe
3+
) and the formation of products like short-chain linear aliphatic carboxylic acids were assessed in PEF. Two consecutive pseudo-first-order kinetic regions were found using Fe
2+
as catalyst. In the first region, at short time, the drug was rapidly oxidized by
●
OH, whereas in the second region, at longer time, a resulting Fe(III)-INH complex was much more slowly removed by oxidants. INH disappeared completely at 300 min by EF, attaining 88 and 94% mineralization at 66.6 and 100 mA cm
−2
, respectively. Isonicotinamide and its hydroxylated derivative were identified as aromatic products of INH by GC-MS and oxalic, oxamic, and formic acids were quantified by ion-exclusion HPLC. The PEF treatment of a real wastewater polluted with the drug led to slower INH and TOC abatements because of the parallel destruction of its natural organic matter content.
Greywater presents great potential for reuse; if treated correctly and efficiently, it can be used for several residential uses. The objective of this work was to test advanced oxidation for ...greywater disinfection through UV/TiO
, UV/TiO
/H
O
, photo-Fenton, UV/H
O
and photolysis (UV) processes, using Pseudomonas aeruginosa as an alternative indicator. In general, the processes with hydrogen peroxide (150 mg.L
) mixed in the pretreated greywater and exposed to solar radiation or artificial radiation from UV lamps were the most efficient in the disinfection experiments, with total inactivation of P. aeruginosa. These processes (UV/H
O
and photo-Fenton) were better fitted to the log-linear/caudal decay model with remaining microorganism for the hydrogen peroxide concentration of 25 mg.L
. The use of P. aeruginosa as an alternative indicator for the greywater disinfection was very promising due to its high resistance and high natural concentration in the effluent used in the experiments. The treatment applied with the UV/H
O
process with the hydrogen peroxide concentration at 150 mg.L
was the only one that showed acute toxicity, even though it removed a good part of the surfactant concentration from the pre-treated greywater.
Display omitted
•95 % Ketoprofen degradation with wetland and solar photo-Fenton at near neutral pH.•39 % of the organic matter was removed from the effluent.•Reduction of toxicity in Artemia sp. and ...Lactuca sativa to UT < 0.4.•Effluent treated and classified as water for reuse with combined system.•Lower treatment cost for the CW + solar photo-Fenton process at pH 6.0.
Emerging contaminants in the environment are a matter of concern due to their widespread use and continuous disposal without proper treatment. Conventional treatments in sewage treatment plants (STPs) are not able to completely eliminate them, resulting in the presence of these compounds in several environmental matrices. Therefore, exploring and adding technologies to reduce or avoid the disposal of these compounds in the environment is necessary. This study aimed to use the solar photo-Fenton process combined with a partially saturated bottom vertical flow constructed wetland (VFCW) to remove ketoprofen (KET) from anaerobic effluent (sewage + landfill leachate) post-treated by a real-scale upflow anaerobic sludge blanket (UASB) reactor. The combined constructed wetland + solar photo-Fenton in pH 3.0 (CW + SPF3) and constructed wetland + solar photo-Fenton in pH 6.0 (CW + SPF6) systems showed high efficiency in degrading KET, achieving removal rates of 97% and 95%, respectively. The systems also showed efficiency in removing conventional parameters such as COD, BOD5,20, and turbidity. In addition to having a lower cost, only the combined CW + SPF6 system was able to eliminate toxicity for Artemia sp. and Lactuca sativa (TU < 0.4). The solar photo-Fenton process and constructed wetlands have proven to be compatible technologies. This combination resulted in an innovative and effective method for wastewater treatment systems containing emerging contaminants. The use of new technological arrangements for the treatment of sewage and effluents, such as constructed wetlands (CWs), which are nature-based solutions, and environmentally sustainable advanced solar oxidation processes, establish a NEXUS concept, promoting the circular economy.
This article reports the synthesis and characterization of pure and N-, B-, and Ag-doped TiO2 and the ability of these oxides to photodegrade methylene blue (MB) under sunlight or UV-ABC radiation. ...The compounds were synthesized using the sol-gel method and characterized by scanning electron microscopy, X-ray diffraction, diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. Photocatalytic efficiency was significantly increased by N-doping, resulting in 98% MB decomposition under UV-ABC irradiation for 180 min. Ag- and B-doped TiO2 lowered MB degradation rates to 52 and 73%, respectively, compared with pure TiO2. The same behavior was observed with exposure to UV-Vis, with 88, 65, 60, and 42% MB removal with N-doped, pure, B-doped, and Ag-doped TiO2, respectively. Under visible light alone, N-doped TiO2 exhibited higher photocatalytic efficiency than commercial P25-type TiO2. Photocatalysis with N-doped TiO2 proved to be a promising alternative for MB degradation, given the potential of employing solar energy, thus minimizing operating costs.
This paper reports the degradation of 10 mg L
−1
Ametryn solution with different advanced oxidation processes and by ultraviolet (UV
254
) irradiation alone with the main objective of reducing acute ...toxicity and increase biodegradability. The investigated factors included Fe
2+
and H
2
O
2
concentrations. The effectiveness of the UV
254
and UV
254
/H
2
O
2
processes were investigated using a low-pressure mercury UV lamp (254 nm). Photo-Fenton process was explored using a blacklight blue lamp (BLB, λ = 365 nm). The UV
254
irradiation process achieved complete degradation of Ametryn solution after 60 min. The degradation time of Ametryn was greatly improved by the addition of H
2
O
2
. It is worth pointing out that a high rate of Ametryn removal was attained even at low concentrations of H
2
O
2
. The kinetic constant of the reaction between Ametryn and HO
●
for UV
254
/H
2
O
2
was 3.53 × 10
8
L mol
−1
s
−1
. The complete Ametryn degradation by the Fenton and photo-Fenton processes was observed following 10 min of reaction for various combinations of Fe
2+
and H
2
O
2
under investigation. Working with the highest concentration (150 mg L
−1
H
2
O
2
and 10 mg L
−1
Fe
2+
), around 30 and 70% of TOC removal were reached within 120 min of treatment by Fenton and photo-Fenton processes, respectively. Although it did not obtain complete mineralization, the intermediates formed in the degradation processes were hydroxylated and did not promote acute toxicity of
Vibrio fischeri
. Furthermore, a substantial improvement of biodegradability was obtained for all studied processes.
PDF
