Simultaneous degradation of phenol and paracetamol during photo-Fenton process: Design and optimization

Optimization of the Photo-Fenton process for the effective removal of chemical oxygen demand and phenols in portable toilet wastewater: A treatment study under real world conditions

Wastewater from portable toilets (WWPT) is characterized by a high content of organic matter and a variety of chemical compounds that retain bad odors, especially phenols, a type of pollutant that is difficult to degrade by conventional treatments; in addition, it is persistent, toxic, and accumulates in the aquatic environment. Although different successful experiences with the use of Photo-Fenton are reported in the scientific domain, its application in WWPT is scarce and warrants study due to the wide use of portable toilets. The objective of this study was to evaluate the Photo-Fenton oxidation process in the removal of organic matter expressed as COD in a WWPT, as well as the reduction of phenols and BOD5. The experimental runs were carried out in a 0.50 L batch reactor to evaluate the effect of the factors (H2O2: 0.019, 25.56, 40.67, 87.24, 148.91, 174.45 g L-1 and pH: 2.80, 3.00, 3.27, 4.40, 5.53, 6.00 UNT) on COD removal and sludge production. It was found that the optimum operating conditions of pH 4.72 and H2O2 dosage of 174.45 g L-1 reduced the concentration of phenols by 97.83 % and 95.49 % of COD. In addition, 98.01 % of BOD5 was reduced, resulting in a biodegradability ratio (BOD5/COD) of 0.23 compared to the untreated wastewater of 0.53. From a cost perspective, the use of Photo-Fenton to treat wastewater under these conditions would be US$ 1.15 per liter.

Magnetic biosensors for identification of SARS-CoV-2, Influenza, HIV, and Ebola viruses: a review

Infectious diseases such as novel coronavirus (SARS-CoV-2), Influenza, HIV, Ebola, etc kill many people around the world every year (SARS-CoV-2 in 2019, Ebola in 2013, HIV in 1980, Influenza in 1918). For example, SARS-CoV-2 has plagued higher than 317 000 000 people around the world from December 2019 to January 13, 2022. Some infectious diseases do not yet have not a proper vaccine, drug, therapeutic, and/or detection method, which makes rapid identification and definitive treatments the main challenges. Different device techniques have been used to detect infectious diseases. However, in recent years, magnetic materials have emerged as active sensors/biosensors for detecting viral, bacterial, and plasmids agents. In this review, the recent applications of magnetic materials in biosensors for infectious viruses detection have been discussed. Also, this work addresses the future trends and perspectives of magnetic biosensors.

A critical review on paracetamol removal from different aqueous matrices by Fenton and Fenton-based processes, and their combined methods

Paracetamol (PCT), also known as acetaminophen, is a drug used to treat fever and mild to moderate pain. After consumption by animals and humans, it is excreted through the urine to the sewer systems, wastewater treatment plants, and other aquatic/natural environments. It has been detected in trace amounts in effluents of wastewater plant treatments, sewage sludge, hospital wastewaters, surface waters, and drinking water. PCT can cause genetic code damage, oxidative degradation of lipids, and denaturation of protein in cells, and its toxicity has been well-proven in bacteria, algae, macrophytes, protozoan, and fishes. To avoid its harmful health problems over living beings, powerful Fenton and Fenton-based treatments as pre-eminent advanced oxidation processes (AOPs) have been developed because of the inefficient treatment by conventional treatments. This paper presents a comprehensive and critical review over the application of such Fenton technologies to remove PCT from natural waters, synthetic wastewaters, and real wastewaters. The characteristics and main results obtained using Fenton, photo-Fenton, electro-Fenton, and photoelectro-Fenton are described, making special emphasis in the oxidative action of the generated reactive oxygen species. Hybrid processes based on the coupling with ultrasounds, gamma radiation, photocatalysis, photoelectrocatalysis, zero-valent iron-activated persulfate, adsorption, and microbial fuel cells, are analyzed. Sequential treatments involving the initiation with plasma gliding arc discharge and post-biological process are detailed. Comparative results with other available AOPs are also described and discussed. Finally, 13 aromatic by-products and 9 short-linear aliphatic carboxylic acid detected during the PCT removal by Fenton and Fenton-based processes are reported, with the proposal of three parallel pathways for its initial degradation.

Towards an Efficient Generalization of the Online Dosage of Hydrogen Peroxide in Photo-Fenton Process to Treat Industrial Wastewater

This work addresses the dosage of H2O2 in photo-Fenton processes and the monitoring of Dissolved oxygen (DO) that can be used to drive the dosage of H2O2. The objective of this work is to show that a smarter monitoring of a process variable such as DO (for which on-line measurement can be inexpensively obtained) enables the proposal and implementation of efficient dosage strategies. The work explores the application of a recent proposed strategy consisting of: (i) initial H2O2 addition, (ii) continuous H2O2 addition until a DO set up is reached, and (iii) automatic H2O2 addition by an on-off control system based on DO slope monitoring, and applies it to the treatment of different individual contaminants and their mixtures (paracetamol and sulfamethazine). The assays performed following this dosage strategy showed improved values of TOC removed per H2O2 consumed. For the case of sulfamethazine, this improvement increased up to 25-35% with respect to the efficiency obtained without dosage. Furthermore, a deeper analysis of the results allowed detecting and assessing the opportunity to redesign the dosage scheme and reduce its complexity and the number of control parameters. The promising results obtained are discussed in regard of future research into further increasing the simplicity and robustness of this generalized control strategy that improves the applicability of the photo-Fenton process by reducing its operating costs and increasing automation.

Reaction kinetics formulation with explicit radiation absorption effects of the photo-Fenton degradation of paracetamol under natural pH conditions

The degradation of paracetamol (PCT) in an aqueous medium using the Fenton and photo-Fenton reactions was investigated. The aim of this research was the development of a kinetic model based on a reaction mechanism, which includes two main intermediates of PCT degradation and the local volumetric rate of photon absorption (LVRPA). Ferrioxalate was used as a catalyst and the working pH was adjusted to 5.5 (natural pH). Experimental work was planned through a D-optimal experimental design and performed in a flat plate reactor irradiated by a solar simulator. Hydrogen peroxide (HP) concentration, reaction temperature, and radiation level were the operating parameters. The photo-Fenton reaction allowed to reach a minimum relative PCT concentration of 2.01% compared to 5.04% achieved with Fenton reaction. Moreover, the photo-Fenton system required a 50% shorter reaction time and lower HP concentration than in dark conditions (90 min and 189 mg L^-1 vs. 180 min and 334 mg L^-1, respectively). The experimental results were used to estimate the kinetic parameters of the proposed kinetic model employing a nonlinear, multi-parameter regression method. The values obtained from the normalized root-mean-square error (14.52, 1.96, 4.36, 13.16, and 8.72 % for PCT, benzoquinone, hydroquinone, HP, and oxalate, respectively) showed a good agreement between the predicted and experimental data.

Solar assisted photocatalytic degradation of organic pollutants in the presence of biogenic fluorescent ZnS nanocolloids

The main aim of this study was to ascertain the photocatalytic degradation of organic pollutants present in aqueous phase using fluorescent biogenic ZnS nanocolloids produced from an endophytic fungus Aspergillus flavus. The degradation studies were carried out using different organic pollutants such as methyl violet (MV), 2,4-dichlorophenoxyacetic acid (2,4-D) and paracetamol (PARA) for 120 min, 270 min and 240 min, respectively, at pH varying from 3.0 to 11.0. The results from this study indicate that the degradation efficiency of ZnS nanocolloids for MV, 2,4-D and PARA were 87%, 33% and 51%, respectively, at the optimum concentration of 100 mg/L of the tested organic pollutants. At different time intervals, the samples were analyzed for their chemical oxygen demand (COD) and total organic carbon (TOC) contents. The reduction of COD and TOC were 78% and 74% for MV at 120 min; 55.5% and 57.2% for 2,4-D at 270 min and 47.6% and 44.5% for PARA at 240 min, respectively. The degradation pathway was determined based on the mass spectrum and the intermediates formed; in addition, the interaction between organic pollutants and nanocolloids was also elucidated based on atomic force microscopy (AFM) and fluorescence spectrum.

A kinetic study for the Fenton and photo-Fenton paracetamol degradation in an annular photoreactor

A kinetic model describing Fenton and photo-Fenton degradation of paracetamol (PCT) and consumption of hydrogen peroxide (H₂O₂) was proposed. A set of Fenton and photo-Fenton experiments (18 runs in total) was performed by fixing the initial concentration of PCT to 40 mg L^-1 and varying the initial concentrations of H₂O₂ and ferrous ion, Fe²⁺. The experimental set-up was a well-stirred annular photoreactor equipped with an actinic BL TL-DK 36 W/10 1SL lamp. Experimental results highlighted that PCT is no more detected by HPLC analysis within a minimum reaction time of 2.5 and a maximum reaction time of 15.0 min. Besides, a maximum conversion of total organic carbon (TOC) of 68.5% was observed after 75 min of reaction in case of using UV radiation and the highest concentrations of the Fenton reagents. The experimental data were used to fit the kinetic model. The radiation field inside the reactor was taken into account through the local volumetric rate of photon absorption, evaluated by assuming a line source model with spherical and isotropic emission. The kinetic parameters were estimated by using a non-linear least-squares regression procedure and root mean square errors (RMSE) were calculated in order to validate the feasibility of the proposed model. A good agreement between experimental and predicted data was observed and the lowest values of RMSE resulted in 5.84 and 9.59% for PCT and H₂O₂ normalized concentrations, respectively.

Treatment of real benzene dye intermediates wastewater by the Fenton method: characteristics and multi-response optimization

Benzene dye intermediates (BDI) wastewater has caused major environmental concern due to its potential carcinogenic, teratogenic, and mutagenic effects.

Correlation between degradation pathway and toxicity of acetaminophen and its by-products by using the electro-Fenton process in aqueous media

The evolution of the degradation by-products of an acetaminophen (ACE) solution was monitored by HPLC-UV/MS and IC in parallel with its ecotoxicity (Vibrio fischeri 81.9%, Microtox^® screening tests) during electro-Fenton (EF) oxidation performed on carbon felt. The aromatic compounds 2-hydroxy-4-(N-acetyl) aminophenol, 1,4-benzoquinone, benzaldehyde and benzoic acid were identified as toxic sub-products during the first stage of the electrochemical treatment, whereas aliphatic short-chain carboxylic acids (oxalic, maleic, oxamic, formic, acetic and fumaric acids) and inorganic ions (ammonium and nitrate) were well identified as non-toxic terminal sub-products. Electrogenerated hydroxyl radicals then converted the eco-toxic and bio-refractory property of initial ACE molecule (500 mL, 1 mM) and subsequent aromatic sub-products into non-toxic compounds after 2 h of EF treatment. The toxicity of every intermediate produced during the mineralization of ACE was quantified, and a relationship was established between the degradation pathway of ACE and the global toxicity evolution of the solution. After 8 h of treatment, a total organic carbon removal of 86.9% could be reached for 0.1 mM ACE at applied current of 500 mA with 0.2 mM of Fe²⁺ used as catalyst.

Biological hazard evaluation of a pharmaceutical effluent before and after a photo-Fenton treatment

The aim of this study was to evaluate the biological hazard of a pharmaceutical effluent before and after treatment. For the former, the determined 96h-LC50 value was 1.2%. The photo-Fenton treatment catalyzed with an iron-pillared clay reduced this parameter by 341.7%. Statistically significant increases with respect to the control group (P<0.05) were observed at 12, 24, 48 and 72h in HPC (50.2, 30.4, 66.9 and 43.3%), LPX (22, 83.2, 62.7 and 59.5%) and PCC (14.6, 23.6, 24.4 and 25.6%) and antioxidant enzymes SOD (29.4, 38.5, 32.7 and 49.5%) and CAT (48.4, 50.3, 38.8 and 46.1%) in Hyalella azteca before treatment. Also increases in damage index were observed before treatment of 53.1, 59.9, 66.6 and 72.1% at 12, 24, 48 and 72h, respectively. After treatment the same biomarkers of oxidative stress decreased with respect to before treatment being to HPC (29.3, 22.5, 41.6 and 31.7%); LPX (14.2, 43.1, 30.7 and 35.5%); PCC (12.6, 21.3, 24.2 and 23.9%); SOD (39.2, 33.9, 49.5 and 37.9%) and CAT (28.6, 35.8, 33.7 and 31.7) at 12, 24, 48 and 72h, respectively (P<0.05). The damage index were decreased at 12, 24, 48 and 72h in 48.9, 57.8, 67.3 and 72.1%, respectively. In conclusion, the obtained results demonstrate the need of performing bioassays in order to characterize an effluent before discharge and not base such a decision only upon current normativity. In addition, it was also concluded that the heterogeneous photo-Fenton process decreases the presence of PCT, oxidative stress, genotoxic damage and LC50 in Hyalella azteca.