Fenton-超声联合处理金刚烷胺制药废水

近年来,流感常用药盐酸金刚烷胺的产量不断增大,然而,其生产过程中产生的废水由于得不到有效处理,引起较大污染。以盐酸金刚烷胺生产过程中产生的胺化废水和溴化废水为原水,利用Fenton-超声联合工艺进行处理,主要研究反应时间、初始pH、H2O2投加量和H2O2/Fe2+的投加比和声能密度等操作条件对于金刚烷胺制药废水处理效果的影响。实验结果表明,优化处理条件下,Fenton-超声联合工艺对金刚烷胺制药废水中TOC去除效果最高达到65.6%。超声和Fenton的联合产生了良好的协同效果,Fenton-超声联合工艺对金刚烷胺制药废水的处理效果比单独超声和单独Fenton处理效果之和高18%,大大提高了废水中有机物的去除效果。     

Fenton-like degradation of nalidixic acid with Fe3+/H2O2

The Fenton-like degradation of nalidixic acid was studied in this work. The effects of Fe³⁺ concentration and initial H₂O₂ concentration were investigated. Increasing the initial H₂O₂ concentration enhances the degradation and mineralization efficiency for nalidixic acid, while Fe³⁺ shows an optimal concentration of 0.25 mM. A complete removal of nalidixic acid and a TOC removal of 28 % were achieved in 60 min under a reaction condition of [Fe³⁺]?=?0.25 mM, [H₂O₂]?=?10 mM, T?=?35 °C, and pH?=?3. LC–MS analysis technique was used to analyze the possible degradation intermediates. The degradation pathways of nalidixic acid were proposed according to the identified intermediates and the electron density distribution of nalidixic acid. The Fenton-like degradation reaction of nalidixic acid mainly begins with the electrophilic attack of hydroxyl radical towards the C₃ position which results in the ring-opening reaction; meanwhile, hydroxyl radical attacking to the branched alkyl groups of nalidixic acid leads to the oxidation at the branched alkyl groups.     

4种高级氧化法处理高浓度正丙醇废水的动力学比较

研究了1%和10%(V/V)模拟正丙醇废水在UV/TiO2体系、UV/H2O2体系、Fe2+/H2O2体系和UV/TiO2/Fe2+/H2O2体系等4种工艺条件下的降解动力学过程,对比了降解动力学特点及工艺参数对动力学常数的影响,优化工艺参数。结果表明,UV/TiO2体系和Fe2+/H2O2体系的降解过程可分为零级反应阶段和一级反应阶段,转折点分别在反应开始后2 h和氧化剂浓度为6.7 g/L,UV/H2O2体系和UV/TiO2/Fe2+/H2O2体系分别符合零级反应和一级反应规律;相同工艺参数条件下,6 h反应后,组合工艺UV/TiO2/Fe2+/H2O2体系在处理效率达85%,比前3个体系分别高52.0%、8.3%和32.0%,与UV/TiO2体系和Fe2+/H2O2体系的处理效率之和持平,其协同效应提高了速率常数,在目标物浓度降低时依然可维持较高降解速率。而目标物浓度提高10倍后,UV能量利用率提高35.5倍,氧化剂用量是Fe2+/H2O2体系的1/7.1。     

Degradation of diethyl phthalate (DEP) by vacuum ultraviolet process: influencing factors,oxidation products,and toxicity assessment

The vacuum ultraviolet (VUV) process, which can directly produce hydroxyl radical from water, is considered to be a promising oxidation process in degrading contaminants of emerging concern, because of no need for extra reagents. In this study, the influencing factors and mechanism for degradation of diethyl phthalate (DEP) by the VUV process were investigated. The effects of irradiation intensity, inorganic anions, natural organic matter (NOM), and H₂O₂ dosage on the performance of VUV process were evaluated. The results showed that DEP could be more efficiently degraded by the VUV process compared with ultraviolet (UV)-254-nm irradiation. The presence of HCO₃^?, NO₃^? and NOM in the aqueous solutions inhibited the degradation of DEP to a different degree, mainly by competing hydroxyl radicals (HO^?) with DEP. Degradation rate and removal efficiency of DEP by VUV process significantly enhanced with the addition of H₂O₂, while excess H₂O₂ dosage could inhibit the DEP degradation. Moreover, based on the identified seven oxidation byproducts and their time-dependent evolution profiles, a possible pathway for DEP degradation during the VUV process was proposed. Finally, the ecotoxicity of DEP and its oxidation byproducts reduced overall according to the calculated results from Ecological Structure Activity Relationships (ECOSAR) program. The electrical energy per order (EE/O) was also assessed to analysis the energy cost of the DEP degradation in the VUV process. Our work showed the VUV process could be an alternative and environmental friendly technology for removing contaminants in water.

     

UV-C-activated persulfate oxidation of a commercially important fungicide: case study with iprodione in pure water and simulated tertiary treated urban wastewater

Recently, the European Food Safety Authority (EFSA) has banned the use of iprodione (IPR), a common hydantoin fungicide and nematicide that was frequently used for the protective treatment of crops and vegetables. In the present study, the treatment of 2 mg/L (6.06 μM) aqueous IPR solution through ultraviolet-C (UV-C)-activated persulfate (PS) advanced oxidation process (UV-C/PS) was investigated. Baseline experiments conducted in distilled water (DW) indicated that complete IPR removal was achieved in 20 min with UV-C/PS treatment at an initial PS concentration of 0.03 mM at pH?=?6.2. IPR degradation was accompanied with rapid dechlorination (followed as Cl^? release) and PS consumption. UV-C/PS treatment was also effective in IPR mineralization; 78% dissolved organic carbon (DOC) was removed after 120-min UV-C/PS treatment (PS?=?0.30 mM) compared with UV-C at 0.5 W/L photolysis where no DOC removal occurred. LC analysis confirmed the formation of dichloroaniline, hydroquinone, and acetic and formic acids as the major aromatic and aliphatic degradation products of IPR during UV-C/PS treatment whereas only dichloroaniline was observed for UV-C photolysis under the same reaction conditions. IPR was also subjected to UV-C/PS treatment in simulated tertiary treated urban wastewater (SWW) to examine its oxidation performance and ecotoxicological behavior in a more complex aquatic environment. In SWW, IPR and DOC removal rates were inhibited and PS consumption rates decreased. The originally low acute toxicity (9% relative inhibition towards the photobacterium Vibrio fischeri) decreased to practically non-detectable levels (4%) during UV-C/PS treatment of IPR in SWW.

     

Degradation of methylparaben in water by corona plasma coupled with ozonation

The degradation of methylparaben (MeP) in water was investigated using a pulsed corona discharge generated in oxygen, above the liquid. A comparison was made between results obtained in semi-batch corona (SBC) configuration (stationary solution, continuous gas flow) and results obtained in a semi-batch corona with recirculation combined with ozonation (SBCR?+?O₃), where the liquid is continuously circulated between a solution reservoir and the plasma reactor and the effluent gas containing ozone is bubbled through the solution in the reservoir. It was found that MeP was completely degraded after 10–15 min of treatment in both configurations. Oxidation by ozone alone, in the absence of plasma, was a slower process. The energy efficiency for MeP removal (Y _MeP) and for mineralization (Y _TOC) was significantly higher in the SBCR?+?O₃ configuration (Y _MeP?=?7.1 g/kWh at 90 % MeP removal and Y _TOC?=?0.41 g/kWh at 50 % total organic carbon (TOC) removal) than in the SBC configuration (Y _MeP?=?0.6 g/kWh at 90 % MeP removal and Y _TOC?=?0.11 g/kWh at 50 % TOC removal).     

Decolourization and removal of some organic compounds from olive mill wastewater by advanced oxidation processes and lime treatment

Background Olive mill wastewater (OMW) generated by the olive oil extracting industry is a major pollutant, because of its high organic load and phytotoxic and antibacterial phenolic compounds which resist biological degradation. Mediterranean countries are mostly affected by this serious environmental problem since they are responsible for 95% of the worldwide oliveoil production. There are many methods used for OMW treatment, such as adsorption, electro coagulation, electro-oxidation, biological degradation, advanced oxidation processes (AOPs), chemical coagulation, flocculation, filtration, lagoons of evaporation and burning systems, etc. Currently, there is no such economical and easy solution. The aim of this study was to evaluate the feasibility of decolourization and removal of phenol, lignin, TOC and TIC in OMW by UV/H₂O₂ (AOPs). The operating parameters, such as hydrogen peroxide dosage, times, pH, effect of UV and natural sunlight were determined to find the suitable operating conditions for the best removal. Moreover, there is no study reported in the literature related to the use of UV/H₂O₂ and lime together in OMW treatment. Methods OMW was obtained from an olive-oil producing plant (Muğla area of Turkey) which uses a modern production process. No chemical additives are used during olive oil production. This study was realised by using two different UV sources, while taking the time and energy consumption into consideration. These two sources were mercury lamps and natural sunlight. Before starting AOPs experiments, one litre of OMW was treated by adding lime until a pH of 7.00. Then, 100 ml was taken from each sample, and 1 to 10 ml of a 30% H₂O₂ (Riedel-deHaen) solution was added. These solutions in closed vessels were laid in the natural sunlight for a week and their compositions and colour changes were analysed daily by UV-Vis spectrophotometer. At the end of the one-week period, they were treated with lime. In this study, the effect of changes in the initial pH, times and H₂O₂ concentrations on removal was investigated. At the end of all experiments, changes in colour, phenol, lignin, TOC and TIC concentrations were analysed according to standard methods. Results and Discussion In the samples exposed to natural sunlight and having an H₂O₂/OMW ratio of 3 ml/100 ml, a significant colour removal was achieved approximately 90% of the time at the end of 7 days. When the same samples were treated with lime (pH: up to 7), 99% efficiency was achieved. When phenol and lignin removals were examined in the same concentration, phenol and lignin removal were found 99.5%, 35%, respectively. However, for maximum lignin removal, more use of H₂O₂ (10 ml H₂O₂/100 ml OMW) was found to be necessary. Under these conditions, it was found that lignin can be removed by 70%, but to 90% with lime, at the end of a seven-day period. Rate constants obtained in the experiments performed with direct UV were found to be much higher than those of the samples exposed to natural sunlight (k^a _lignin = 0.3883 ≫ k^b _lignin = 0.0078; k^a _phenol = 0.5187 ≫ k^b _phenol = 0.0146). Moreover, it should be remembered in this process that energy consumption may induce extra financial burden for organisations. Conclusions It was found, in general, that colour, lignin, total organic carbon and phenol were removed more efficiently from OMW by using H₂O₂ UV and lime OMW. Moreover, in the study, lime was found to contribute, both initially and after radical reactions, to the efficiency to a great extent. Recommendations and Perspectives Another result obtained from the study is that pre-purification carried out with hydrogen peroxide and lime may constitute an important step for further purification processes such as adsorption, membrane processes, etc.     

Fenton氧化活性深蓝染料B-2GLN的动力学

为了考查H2O2/Fe2+的摩尔比和H2O2的初始剂量、pH值以及活性深蓝染料B-2GLN(RDB B-2GLN)的初始浓度对活性深蓝染料B-2GLN降解过程的影响,采用在线分光光度法对活性深蓝染料B-2GLN的Fenton氧化过程进行了研究,探讨了其动力学过程,并利用气相色谱-质谱联用分析降解中间产物。结果显示,采用Fenton氧化降解水溶液中活性深蓝染料B-2GLN,在H2O2的剂量为2.635 mmol/L,pH值为2.7,H2O2/Fe2+的摩尔比为37.80和活性深蓝染料B-2GLN的初始浓度16 mg/L的条件下,得到300 s后活性深蓝染料B-2GLN的最大色度去除率为85.04%。水溶液中活性深蓝染料B-2GLN与·OH的反应速率常数为2.62×1011L/(mol·s)。活性深蓝B-2GLN染料的分子结构被Fenton试剂分解而未被完全矿化,同时对活性深蓝染料降解产物进行了分析。在线分光光度法是研究染料色度去除率的一种精确、快速与可行的方法。     

电-Fenton法预处理干法腈纶生产废水

以Ti金属网为阴极,Ti基RuO2涂层形稳电极为阳极,采用外加H2O2和Fe2+的方式,研究了电-Fenton氧化预处理干法腈纶生产废水的工艺,考察了H2O2投加量、Fe2+投加量、pH值和电流强度等因素对污染物降解过程的影响,分析了废水可生化性和污染物变化规律。结果表明,电-Fenton法可以有效降解废水中有机污染物,使废水COD迅速降低,在初始pH值为3.0,Fe2+投加量为5.0 mmol/L,H2O2投加量为60.0 mmol/L,电流强度0.2 A的条件下,反应120 min后COD去除率可以达到44.0%以上;反应过程中H2O2的投加方式对电-Fenton法的处理效果具有明显影响,H2O2分6次投加可以使COD去除率由一次性投加时的44.8%提高至54.1%;处理后废水的BOD5/COD由0.29升高至0.68;GC-MS结果表明,经电-Fenton法预处理后,废水中多数芳香族化合物和特征污染物能被有效降解。     

Comparison of Fenton and Photo-Fenton Processes for Livestock Wastewater Treatment

In this study, the photochemical degradation of livestock wastewater was carried out by the Fenton and Photo-Fenton processes. The effects of pH, reaction time, the molar ratio of Fe^{2 +}/H₂O₂, and the Fe^{2 +} dose were studied. The optimal conditions for the Fenton and Photo-Fenton processes were found to be at a pH of 4 and 5, an Fe^{2 +} dose of 0.066 M and 0.01 M, a concentration of hydrogen peroxide of 0.2 M and 0.1 M, and a molar ratio (Fe^{2 +}/H₂O₂) of 0.33 and 0.1, respectively. The optimal reaction times in the Fenton and Photo-Fenton processes were 60 min and 80 min, respectively. Under the optimal conditions of the Fenton and Photo-Fenton processes, the chemical oxygen demand (COD), color, and fecal coliform removal efficiencies were approximately 70–79, 70–85 and 96.0–99.4%, respectively.     

Degradation of bisphenol A in aqueous solution by persulfate activated with ferrous ion

Degradation of bisphenol A (BPA) in aqueous solution was studied with high-efficiency sulfate radical (SO₄ ^?·), which was generated by the activation of persulfate (S₂O₈ ^2?) with ferrous ion (Fe²⁺). S₂O₈ ^2? was activated by Fe²⁺ to produce SO₄ ^?·, and iron powder (Fe⁰) was used as a slow-releasing source of dissolved Fe²⁺. The major oxidation products of BPA were determined by liquid chromatography-mass spectrometer. The mineralization efficiency of BPA was monitored by total organic carbon (TOC) analyzer. BPA removal efficiency was improved by the increase of initial S₂O₈ ^2? or Fe²⁺ concentrations and then decreased with excess Fe²⁺ concentration. The adding mode of Fe²⁺ had significant impact on BPA degradation and mineralization. BPA removal rates increased from 49 to 97 % with sequential addition of Fe²⁺, while complete degradation was observed with continuous diffusion of Fe²⁺, and the latter achieved higher TOC removal rate. When Fe⁰ was employed as a slow-releasing source of dissolved Fe²⁺, 100 % of BPA degradation efficiency was achieved, and the highest removal rate of TOC (85 %) was obtained within 2 h. In the Fe⁰–S₂O₈ ^2? system, Fe⁰ as the activator of S₂O₈ ^2? could offer sustainable oxidation for BPA, and higher TOC removal rate was achieved. It was proved that Fe⁰–S₂O₈ ^2? system has perspective for future works.     

Fenton-混凝法处理苯胺废水

农药生产过程中产生的苯胺废水,COD浓度高、生物毒性强、可生化性差,一般生化方法很难处理。研究了Fenton与PAC联用处理苯胺废水。结果表明,Fenton氧化处理苯胺废水在最佳条件为pH=6、m（H2O2）/m（COD）=1.8、n（H2O2）/n（Fe2＋）=8时,COD和色度去除率分别为78.4%和92.3%。Fenton氧化后废水B/C值由0.037提高到0.324。最佳条件下联用PAC,在投加量为320 mg/L时COD与色度去除率分别为83.6%和94.8%,并且处理时间显著缩短,实际应用中可减少水力停留时间和构筑物体积。     

Electro-oxidation of the dye azure B: kinetics,mechanism, and by-products

In this work, the electrochemical degradation of the dye azure B in aqueous solutions was studied by electrochemical advanced oxidation processes (EAOPs), electro-Fenton, and anodic oxidation processes, using Pt/carbon-felt and boron-doped diamond (BDD)/carbon-felt cells with H₂O₂ electrogeneration. The higher oxidation power of the electro-Fenton (EF) process using BDD anode was demonstrated. The oxidative degradation of azure B by the electrochemically generated hydroxyl radicals (^?OH) follows a pseudo-first-order kinetics. The apparent rate constants of the oxidation of azure B by ^?OH were measured according to pseudo-first-order kinetic model. The absolute rate constant of azure B hydroxylation reaction was determined by competition kinetics method and found to be 1.19?×?10⁹ M^?1 s^?1. It was found that the electrochemical degradation of the dye leads to the formation of aromatic by-products which are then oxidized to aliphatic carboxylic acids before their almost mineralization to CO₂ and inorganic ions (sulfate, nitrate, and ammonium). The evolution of the TOC removal and time course of short-chain carboxylic acids during treatment were also investigated.     

活性炭纤维上4-氯酚及焦化废水尾水的O3催化氧化降解实验研究

选择YT-1000型活性炭纤维（ACF）作为催化剂,考察ACF与O₃协同作用催化降解水溶液中4-氯酚的最佳反应条件,并将该条件应用于焦化废水生物处理尾水中难降解有机污染物的催化氧化。ACF表面具有丰富的微孔结构,对4-氯酚有良好的吸附作用,在动力学上提高了其与O3反应的起始浓度,并且在ACF表面含氧、含氮等基团的催化作用下发生氧化反应,1 L浓度为100 mg/L的4-氯酚水样中投加2 g ACF反应6 min时,吸附作用对TOC的去除率为43.4%,而ACF协同O₃作用时的TOC去除率提高到72.5%,协同增效作用为67.1%;在选定的反应条件下,ACF协同O₃降解焦化废水生物处理尾水,60 min时的TOC与色度的去除率分别达到56.8%和96.3%。上述研究过程证明了吸附作用与催化作用的协同能有效降解生物过程不能降解的焦化废水中惰性有机污染物。     

Application of Fenton, photo-Fenton, solar photo-Fenton, and UV/H2O2 to degradation of the antineoplastic agent mitoxantrone and toxicological evaluation

In the present study, selected advanced oxidation processes (AOPs)—namely, photo-Fenton (with Fe²⁺, Fe³⁺, and potassium ferrioxalate—FeOx—as iron sources), solar photo-Fenton, Fenton, and UV/H₂O₂—were investigated for degradation of the antineoplastic drug mitoxantrone (MTX), frequently used to treat metastatic breast cancer, skin cancer, and acute leukemia. The results showed that photo-Fenton processes employing Fe(III) and FeOx and the UV/H₂O₂ process were most efficient for mineralizing MTX, with 77, 82, and 90 % of total organic carbon removal, respectively. MTX probably forms a complex with Fe(III), as demonstrated by voltammetric and spectrophotometric measurements. Spectrophotometric titrations suggested that the complex has a 2:1 Fe³⁺:MTX stoichiometric ratio and a complexation constant (K) of 1.47 × 10⁴ M^–1, indicating high MTX affinity for Fe³⁺. Complexation partially inhibits the involvement of iron ions and hence the degradation of MTX during photo-Fenton. The UV/H₂O₂ process is usually slower than the photo-Fenton process, but, in this study, the UV/H₂O₂ process proved to be more efficient due to complexing of MTX with Fe(III). The drug exhibited no cytotoxicity against NIH/3T3 mouse embryonic fibroblast cells when oxidized by UV/H₂O₂ or by UV/H₂O₂/FeOx at the concentrations tested.     

Fenton氧化法深度处理抗生素废水二级出水

采用Fenton氧化法对青霉素和土霉素混合废水二级处理出水进行深度处理,通过正交和单因素实验研究了废水初始反应pH值、H2O2投加量、Fe2+/H2O2摩尔比及反应时间等因素对废水处理效果的影响。实验结果表明,Fenton氧化法处理的最佳反应条件为:初始pH值4、H2O2(30%)投加量50 mL/L、Fe2+/H2O2摩尔比1/20和反应时间60 min,处理后出水COD小于120 mg/L,COD去除率在75%以上,急性毒性(HgCl2毒性当量)小于0.07 mg/L,满足《发酵类制药工业水污染物排放标准》(GB21903-2008)表2标准要求。     

超声-Fenton联用技术深度处理皮革综合废水生化出水

针对皮革综合废水生化处理出水中存在COD和色度偏高等问题,提出采用超声-Fenton联用技术对生化后的皮革综合废水进行深度处理。通过单因素实验考察了超声功率、H2O2投加量、Fe2+投加量(即H2O2/Fe2+比)、溶液pH和反应时间对水样中COD和色度去除率的影响;正交实验结果表明,当溶液初始pH值为4.0时,各因素影响显著性的先后顺序为H2O2>超声功率>反应时间>Fe2+;其优化的实验条件为:H2O2为24.0 mL/L、超声功率为85 W、反应时间为45min、Fe2+为2.2 g/L,经超声-Fenton联用技术深度处理后COD的去除率可达85.4%。在最佳实验条件下,对超声-Fenton联用技术深度处理皮革综合废水生化出水的动力学研究发现,水样中的COD降解反应符合表观一级反应动力学,速率常数增强因子可达8.64,表明存在显著的协同效应。     

Influence of operational key parameters on the photocatalytic decolorization of Rhodamine B dye using Fe2+/H2O2/Nb2O5/UV system

The present research deals with the development of a new heterogeneous photocatalysis and Fenton hybrid system for the removal of color from textile dyeing wastewater as Rhodamine B (RhB) solutions by using Fe²⁺/H₂O₂/Nb₂O₅ as a photocatalytic system. The application of this photocatalytic system for the decolorization of dye contaminants is not reported in the literature yet. Different parameters like dye concentration, Nb₂O₅/Fe²⁺ catalyst amount, pH, and H₂O₂ concentration have been studied. The optimum conditions for the decolorization of the dye were initial concentration of 10 mg L^?1 of dye, pH 4, and Nb₂O₅/Fe²⁺ catalyst concentration of 0.5 g L^?1/50 mg L^?1. The optimum value of H₂O₂ concentration for the conditions used in this study was 700 mg L^?1. Moreover, the efficiency of the Nb₂O₅/photo-Fenton hybrid process in comparison to photo-Fenton alone and a dark Fenton process as a control experiment to decolorize the RhB solution has been investigated. The combination of photo-Fenton and Nb₂O₅ catalysts has been proved to be the most effective for the treatment of such type of wastewaters. The results revealed that the RhB dye was decolorized in a higher percent (78 %) by the Nb₂O₅/photo-Fenton hybrid process (Fe²⁺/H₂O₂/Nb₂O₅/UV) than by the photo-Fenton process alone (37 %) and dark Fenton process (14 %) after 120 min of treatment. Moreover, the Nb₂O₅ catalyst as a heterogeneous part of the photocatalytic system was demonstrated to have good stability and reusability.     

A novel application of H2O2-Fe(II) process for arsenate removal from synthetic acid mine drainage (AMD) water

Batch experiments were carried out to investigate the influences of H₂O₂/Fe(II) molar ratio, pH, sequence of pH adjustment, initial As(V) concentration, and interfering ions on As(V) removal in H₂O₂-Fe(II) process from synthetic acid mine drainage (AMD). The optimum H₂O₂/Fe(II) molar ratio was one for arsenate removal over the pH range of 4-7. Arsenate removal at pH 3 was poor even at high Fe(II) dosage due to the high solubility of Fe(III) formed in situ. With the increase of Fe(II) dosage, arsenate removal increased progressively before a plateau was reached at pH 5 as arsenate concentration varied from 0.05 to 2.0 mg L⁻¹. However, arsenate removal was negligible at Fe/As molar ratio <3 and then experienced a striking increase before a plateau was reached at pH 7 and arsenate concentration ≥1.0 mg L⁻¹. The co-occurring ions exerted no significant effect on arsenate removal at pH 5. The experimental results with synthetic AMD revealed that this method is highly selective for arsenate removal and the co-occurring ions either improved arsenate removal or slightly depressed arsenate removal at pH 5-7. The extended X-ray absorption fine structure (EXAFS) derived As-Fe length, 3.27-3.30 Å, indicated that arsenate was removed by forming bidentate-binuclear complexes with FeO(OH) octahydra. The economic analysis revealed that the cost of the H₂O₂-Fe(II) process was only 17-32% of that of conventional Fe(III) coagulation process to achieve arsenate concentration below 10 μg L⁻¹ in treated solution. The results suggested that the H₂O₂-Fe(II) process is an efficient, economical, selective and practical method for arsenate removal from AMD.     

Effectiveness evaluation of glyphosate oxidation employing the H2O2/UVC process: Toxicity assays with Vibrio fischeri and Rhinella arenarum tadpoles

The H₂O₂/UVC process was applied to the photodegradation of a commercial formulation of glyphosate in water. Two organisms (Vibrio fischeri bacteria and Rhinella arenarum tadpoles) were used to investigate the toxicity of glyphosate in samples M_1, M₂, and M₃ following different photodegradation reaction times (120, 240 and 360 min, respectively) that had differing amounts of residual H₂O₂. Subsamples of M₁, M₂, and M₃ were then used to create samples M_1,E, M_2,E and M_3,E in which the H₂O₂ had been removed. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were measured in tadpoles to determine possible sub-lethal effects. In V. fischeri, M_1,E, which was collected early in the photodegradation process, caused 52% inhibition, while M_3,E, which was collected at the end of the photodegradation process, caused only 17% inhibition. Survival of tadpoles was 100% in samples M₂, M₃, and in M_1,E, M_2,E and M_3,E. The lowest percentages of enzymatic inhibition were observed in samples without removal of H₂O₂: 13.96% (AChE) and 16% (BChE) for M₂, and 24.12% (AChE) and 13.83% (BChE) for M₃. These results show the efficiency of the H₂O₂/UVC process in reducing the toxicity of water or wastewater polluted by commercial formulations of glyphosate. According to the ecotoxicity assays, the conditions corresponding to M₂ (11 ± 1 mg a.e. L^?1 glyphosate and 11 ± 1 mg L^?1 H₂O₂) could be used as a final point for glyphosate treatment with the H₂O₂/UV process.