Natural chelating agents from olive mill wastewater to enable photo-Fenton-like reactions at natural pH

Sono-photo-Fenton action is improved by the addition of Passiflora edulis f. flavicarpa Degener (yellow passion fruit)

The improvement of the sono-photo-Fenton process at nearby neutral pH (~ 6.2) and high iron concentration (5 mg L-1) by the addition of the juice of Passiflora edulis f. flavicarpa Degener (yellow passion fruit) on the degradation of imipenem in water is reported for the first time. Considering that the combination of sonochemistry with photo-Fenton takes advantage of the in situ sonogeneration of H2O2, the effects of frequency and acoustic power for the H2O2 accumulation were established initially. The sonication at 578 kHz and 23.8 W favored the H2O2 generation. Using such frequency and power, the antibiotic was synergistically degraded by the sono-photo-Fenton system in distilled water, leading to ~ 90% removal at 120 min of treatment. An atomic charge analysis showed that thioether, β-lactam ring, and carboxylic acid moieties on the imipenem structure were very prone to interactions with the HO• generated in the sono-photo-Fenton process. Indeed, the primary transformation products (TPs) came from the oxidation of the thioether, the opening of the β-lactam ring, and decarboxylations. Such TPs had a lower probability than imipenem to be active against bacteria. Besides, the addition of small amounts (2.5-10 µL) of the yellow passion fruit juice to the sono-photo-Fenton system significantly improved the pharmaceutical elimination. However, a juice excess (e.g., 100 µL) caused a detrimental effect due to competing effects by radicals. The juice of the yellow passion fruit induced analogous effects to citric acid (a commercial complexing agent) on the sono-photo-Fenton process. Indeed, the degradation of imipenem in simulated hospital wastewater by sono-photo-Fenton was improved by the yellow passion fruit juice (~ 38% at 60 min), and it was similar to that with citric acid (~ 39% of removal at 60 min). Thus, the commercial reagent can be replaced by a natural and low-cost complexing agent (e.g., yellow passion fruit juice or fruit wastes containing citric acid), as an enhancer of the sono-photo-Fenton process carried out at near-neutral pH and high iron concentration for degrading imipenem in water.

Effects of Phenols from Olive Vegetation Water on Mutagenicity and Genotoxicity of Stored-Cooked Beef Patties

This explorative study aimed to assess the mutagenicity and genotoxicity of stored-cooked beef patties formulated with and without phenols (7.00 mg of phenols/80-g patty) extracted from olive vegetation water (OVW), as related to the formation of cholesterol oxidation products (COPs) and heterocyclic amines (HCAs). The patties were packaged in a modified atmosphere, sampled during cold storage (4 °C) for 9 days, and grilled at 200 °C. The genotoxicity was evaluated by the Comet assay. The patty extract was found to be genotoxic on primary peripheral blood mononuclear cells (PBMCs), while no mutagenicity was detected. The addition of OVW phenols significantly decreased the genotoxicity of the patty extract and reduced the total COPs content in stored-cooked patties (4.59 times lower than control); however, it did not affect the content of total HCAs (31.51-36.31 ng/patty) and the revertants' number. Therefore, these results demonstrate that the OVW phenols were able to counteract the formation of genotoxic compounds in stored-cooked beef patties.

Technical and economical assessment of the treatment of vinasse from Pisco production using the advanced oxidation process

The removal of organic matter from Pisco production wastewater was evaluated using coagulation/flocculation, filtration as a pre-treatment, and solar photo-Fenton, with the use of two types of photoreactors: compound parabolic collectors (CPC) and flat plate (FP), with and without utilizing the ozonation process. The overall removal efficiency for chemical oxygen demand (COD) was 63% and 15% using FP and CPC, respectively. Also, for the overall removal efficiency of polyphenols, a percentage of 73% and 43% were obtained using FP and CPC, respectively. When ozone was used in the solar photoreactors, the resulting trends were similar. COD and polyphenol removal, using an FP photoreactor in the solar photo-Fenton/O₃ process, resulted in values of 98.8% and 86.2% after the process. COD and polyphenol removal, using solar photo-Fenton/O₃ process in a CPC, resulted in values of 49.5% and 72.4%, respectively. The economic indicators of annual worth and economic treatment capacity established that FP reactors represent lower costs than CPCs. These results were corroborated by the economic analyses of the evolution of costs versus COD removed as well as by the cash flow diagrams projected for 5, 10, and 15 years.

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.

Photo-Fenton process applied for the treatment of industrial wastewaters containing diclofenac: optimization with low iron ions concentrations and without pH control

Diclofenac (DCF) can cause several adverse effects in the environment and it should be removed from industrial pharmaceutical wastewaters. Advanced oxidation processes (AOPs) are promising methods for the DCF degradation. But, in many cases, AOPs require acidic pH. However, at this condition, DCF precipitates, which may hinder its oxidation. Thus, in this work, some AOP were studied for the DCF degradation, especially the photo-Fenton process, applying the experimental design technique (Doehlert matrix), operating without and with pH control (between 6.5 and 7.0). As independent variables, the initial ferrous ion concentration ([Fe²⁺]) and the molar addition rate of H₂O₂ (F_H2O2) were evaluated. Empirical models were proposed and optimized conditions were determined without ([Fe²⁺] = 0.27 mmol L^-1 and F_H2O2 = 1.64 mmol min^-1) and with pH control ([Fe²⁺] = 1.0 mmol L^-1 and F_H2O2 = 1.64 mmol L^-1), with the following predicted mineralization percentages: 93% and 68%, respectively. So, photo-Fenton process without pH control presented the best performances. Furthermore, at this condition, iron concentration respects the limit value established by the Brazilian environmental legislation. That is, in this condition, additional processes, in order to remove iron ions, would not be necessary, that is very interesting for applications on an industrial scale.

Use of vinasse and coffee waste as chelating agent of photo-Fenton landfill leachate treatment

This research studies the use of vinasse (VS) coming from Pisco and caffeic acid (Caa) from solid coffee waste as chelating agents of this process, to carry out a photo-Fenton process using UVc lamps of 254-nm wavelength for 60 min, at the natural pH of the landfill leachate (8.9). Without the chelating agent, there was a removal of UV 254 and COD of 54.2% and 54.7%, respectively, when the photo-Fenton reaction was carried out at pH 3; at pH 6, the removal of UV 254 and COD was 13.1% and 39.2%, respectively, and at pH 8.9, the elimination of UV 254 and COD was 10.8% and 16.1%, respectively. When Caa was used in the landfill leachate (LL) for the photo-catalytic processes carried out at pH 8.9, a removal of 24.1%, 43.0%, and 47.4% of UV 254 was obtained using 5 mg/L, 50 mg/L, and 100 mg/L of Caa. The removal of UV 254 was 27.3%, 30.7%, and 36.3% using 5 mg/L, 50 mg/L, and 100 mg/L of VS, respectively, and the removal of COD was 32.2%, 35.4%, and 39.2% using 5 mg/L, 50 mg/L, and 100 mg/L of VS, respectively. When Caa was used in the LL at pH 8.9, the concentration of total Fe went from 37.5 to 33.2, from 40.2 to 36.8, and from 45.2 to 42.1, using 5 mg/L, 50 mg/L, and 100 mg/L of caffeic acid, respectively. Using VS in the LL at pH 8.9, the concentration of total Fe along the run went from 35.1 to 32.2, from 39.4 to 34.8, and from 42.1 to 40.2, using 5 mg/L, 50 mg/L, and 100 mg/L of VS, respectively. As a result of these processes, it was noted that the use of Caa and VS increases the solubility of Fe at a higher pH.

Challenges on solar oxidation as post-treatment of municipal wastewater from UASB systems: Treatment efficiency, disinfection and toxicity

The application of solar photo-Fenton as post-treatment of municipal secondary effluents (MSE) in developing tropical countries is the main topic of this review. Alternative technologies such as stabilization ponds and upflow anaerobic sludge blanket (UASB) are vastly applied in these countries. However, data related to the application of solar photo-Fenton to improve the quality of effluents from UASB systems are scarce. This review gathered main achievements and limitations associated to the application of solar photo-Fenton at neutral pH and at pilot scale to analyze possible challenges associated to its application as post-treatment of MSE generated by alternative treatments. To this end, the literature review considered studies published in the last decade focusing on CECs removal, toxicity reduction and disinfection via solar photo-Fenton. Physicochemical characteristics of effluents originated after UASB systems alone and followed by a biological post-treatment show significant difference when compared with effluents from conventional activated sludge (CAS) systems. Results obtained for solar photo-Fenton as post-treatment of MSE in developed countries indicate that remaining organic matter and alkalinity present in UASB effluents may pose challenges to the performance of solar advanced oxidation processes (AOPs). This drawback could result in a more toxic effluent. The use of chelating agents such as Fe³⁺-EDDS to perform solar photo-Fenton at neutral pH was compared to the application of intermittent additions of Fe²⁺ and both of these strategies were reported as effective to remove CECs from MSE. The latter strategy may be of greater interest in developing countries due to costs associated to complexing agents. In addition, more studies are needed to confirm the efficiency of solar photo-Fenton on the disinfection of effluent from UASB systems to verify reuse possibilities. Finally, future research urges to evaluate the efficiency of solar photo-Fenton at natural pH for the treatment of effluents from UASB systems.

Improvement of solar photo-Fenton by extracts of amazonian fruits for the degradation of pharmaceuticals in municipal wastewater

Extracts of copoazu (Theobroma gramdiflorum), canangucha (Maurita Flexuosa), and coffee (Coffea arabica) were explored as enhancers of the solar photo-Fenton process to eliminate acetaminophen, sulfamethoxazole, carbamazepine, and diclofenac in raw municipal wastewater. The process, at pH 6.2 and 5 mg L^-1 of iron without the presence of extracts, had a very limited action (~35% of the pollutants degradation at 90 min of treatment) due to the iron precipitation. Interestingly, the extract addition increased the soluble iron forms, but only copoazu extract improved the pollutant degradation (~95% of elimination at 20 min of the process action). The copoazu extract components acted as natural complexing agents, maintaining the soluble iron up to 2 mg L^-1 even after 90 min and, consequently, enhancing the pollutant degradation. The effect of copoazu extract dose on the process performance was also assessed, finding that an iron:polyphenols (from the copoazu extract) at a molar ratio equal to 1:0.16 was the most favorable condition. Then, the process improved by copoazu extract was applied to raw municipal wastewater. Remarkably, the process led to ~90% of total pharmaceuticals degradation at 20 min of treatment. This work evidenced the feasibility of amazonian fruit extracts to improve the solar photo-Fenton process to degrade pharmaceuticals in aqueous matrices at near-neutral pH.

Study of the chlorfenvinphos pesticide removal under different anodic materials and different reactor configuration

The present manuscript focuses on the study of the electrochemical oxidation of the insecticide Chlorfenvinphos (CVP). The assays were carried out under galvanostatic conditions using boron-doped diamond (BDD) and low-cost tin dioxide doped with antimony (Sb-doped SnO₂) as anodes. The influence of the operating variables, such as applied current density, presence or absence of a cation-exchange membrane and concentration of supporting electrolyte, was discussed. The results revealed that the higher applied current density the higher degradation and mineralization of the insecticide for both anodes. The presence of the membrane and the highest concentration of Na₂SO₄ studied (0.1 M) as a supporting electrolyte benefited the oxidation process of CVP using the BDD electrode, while with the ceramic anode the elimination of CVP was lower under these experimental conditions. Although the BDD electrode showed the best performance, ceramic anodes appear as an interesting alternative as they were able to degrade CVP completely for the highest applied current density values. Toxicity tests revealed that the initial solution of CVP was more toxic than the samples treated with the ceramic electrode, while using the BDD electrode the toxicity of the sample increased.

Removal of organic matter from wastewater coming from fruit juice production using solar photo-Fenton process

The grape juice production generates an industrial wastewater that has a high concentration of organic matter and several polyphenols, such as ethanol. Therefore, the discharge of this wastewater can produce environmental problems. The aim of this work was to determine the optimal concentration of the reagents involved in a solar photo-Fenton process in the treatment of wastewater coming from juice. The process was analysed in a factorial design, as a function of H2O2 (900, 1000, 1100 mg/L) and Fe2+ (90, 100, 110 mg/L) concentration. The grape juice wastewater presents high organic content (20,500 mg/L COD and 5.4 mg/L polyphenols). Also, the presence of alcohols such ethanol, ethyl acetate and 2-metil-1-propanol was confirmed. The results showed that highest COD (>27%) and polyphenols removal (>36%) were obtained in experiments with 1100 mg H2O2/L and 100 mg Fe2+/L. In treatments with higher COD removal, 2-metil-1-propanol was detected as an intermediate of ethanol oxidation. These results proved that solar photo-Fenton is a suitable approach for treating the refractory organic matter from grape juice.

Developments in the intensification of photo-Fenton and ozonation-based processes for the removal of contaminants of emerging concern in Ibero-American countries

Contaminants of emerging concern (CECs), such as pharmaceuticals, personal care products, pesticides, synthetic and natural hormones and industrial chemicals, are frequently released into the environment because of the inability of conventional processes in municipal wastewater treatment plants to remove them. Some examples of alternative options to remove such pollutants are photo-Fenton and ozone-based processes, which are two techniques widely studied in Ibero-American countries. In fact, this region has been responsible for delivering frequently publications and conferences on advanced oxidation processes. This work is a critical review of recent developments in the intensification of the two aforementioned advanced oxidation techniques for CECs elimination in the Ibero-American region. Specifically for the photo-Fenton process (pF), this study analyses strategies such as iron-complexation with artificial substances (e.g., oxalic acid and ethylenediamine-N,N'-disuccinic acid) and natural compounds (such as humic-like substances, orange juice or polyphenols) and hybrid processes with ultrasound. Meanwhile, for ozonation, the enhancement of CECs degradation by adding hydrogen peroxide (i.e., peroxone), ultraviolet or solar light, and combining (i.e., photolytic ozonation) with catalysts (i.e., catalytic ozonation) was reviewed. Special attention was paid to how efficient these techniques are for removing contaminants from water matrices, and any potentialities and weak points of the intensified processes.

Aluminized surface to improve solar light absorption in open reactors: Application for micropollutants removal in effluents from municipal wastewater treatment plants

This work proposes the evaluation of an aluminized surface on the bottom of open reactors to perform a photo-Fenton process, at circumneutral pH (using Fe III-Ethylenediamine-N,N'-disuccinic acid complex), for elimination of micropollutants (MPs) in real effluents from municipal wastewater treatment plants (EMWWTP). Firstly, the strategy was to initially investigate the real EMWWTP spiked with several MPs (acetaminophen, diclofenac, carbamazepine, caffeine, trimethoprim and sulfamethoxazole) with 20 and 100 μg L^-1 in a laboratory scale (evaluated by HPLC-UV) using a solar simulator. Finally, the removal of all MCs present in the real EMWWTP was monitored (evaluated by HPLC-MS) in a pilot-scale (90 L) in a raceway pond reactor (RPR). The treatment time required for degradation above 80% for the investigated MPs was over 30 min, and the predominant effect could be mainly associated with organics present in the real EMWWTP due to the light attenuation and scavenging of radical species. Moreover, the results confirmed that chloride and sulfate would most likely equally not affect the process. The use of an aluminized surface on the bottom of RPRs has been confirmed as a suitable option to improve the photo-Fenton reaction, enabling the use of lower doses of iron. Up to 60 different MPs found in EMWWTP have been successfully degraded using 0.1 mM of Fe at circumneutral pH with a consumption of 30 mg L^-1 H₂O₂ with less than 45 min.

Olive mill wastewater reuse to enable solar photo-Fenton-like processes for the elimination of priority substances in municipal wastewater treatment plant effluents

Olive mill wastewater (OMW) appears as an interesting and innovative natural alternative to synthetic chelating agents of iron in solar photo-Fenton processes at circumneutral pH due to its high polyphenol content, valorizing wastewater typically found in sunny countries. The aim of this work was the reuse of OMW for the elimination of other recalcitrant microcontaminants: terbutryn, chlorfenvinphos, diclofenac, and pentachlorophenol. Highly diluted OMW (1:1500) was employed to keep the iron in solution at circumneutral pH. Eighty percent degradation of microcontaminants was achieved, although the reaction rate was slow compared with conventional photo-Fenton process, due to Fe-polyphenol complex instability at neutral pH. At pH around 4 (considerable superior to the photo-Fenton optimal pH 2.8), Fe-polyphenol complex stability was promoted: solar UV energy required was 25 times lower to reach the objective of 80% microcontaminants degradation, which was attained in a single step, without coupling with other processes. Operating photo-Fenton at slightly acidic pH was proposed for the first time for possible reuse of treated wastewater in crop irrigation, requiring minimum pH adjustment by simply mixing it with natural wastewater. Graphical abstract.