Degradation of pharmaceuticals in different water matrices by a solar homo/heterogeneous photo-Fenton process over modified alginate spheres

A review toward contaminants of emerging concern in Brazil: Occurrence, impact and their degradation by advanced oxidation process in aquatic matrices

This work presents data regarding the occurrence and treatment of Contaminants of Emerging Concern (CECs) in Brazil in the past decade. The literature review (2011-2021) revealed the detection of 87 pharmaceutical drugs and personal care products, 58 pesticides, 8 hormones, 2 illicit drugs, caffeine and bisphenol A in distinct matrices (i.e.: wastewater, groundwater, sea water, rainwater, surface water, drinking water and hospital effluent). Concentrations of CECs varied from ng-μg L^-1 depending on the location, compound and matrix. The inefficiency of conventional wastewater treatment methods on the removal of CECs and lack of basic sanitation in some regions in the country aggravates contamination of Brazilian aquatic environments and poses potential environmental and health risks. Advanced oxidation processes (AOPs) are pointed out as viable and efficient alternatives to degrade CECs and prevent environmental contamination. A total of 375 studies involving the use of AOPs in Brazilian aqueous matrices were published in the last decade. Fenton and photo-Fenton processes, photo-peroxidation, ozonation, electrochemical advanced oxidation and heterogeneous photocatalysis are some of the AOPs applied by Brazilian research groups. Although many works discuss the importance of applying these technologies for CECs removal in real treatment plants, most of these studies assess the treatment of distilled water or simulated effluent. Therefore, the conduction of studies applying AOPs in real matrices are critical to drive the implementation of these processes coupled to conventional water and wastewater treatment in real plants in order to prevent the contamination of environmental matrices by CECs in Brazil.

Miniaturized Method for Chemical Oxygen Demand Determination Using the PhotoMetrix PRO Application

The analysis of chemical oxygen demand (COD) plays an important role in measuring water pollution, but it normally has a high ecological price. Advances in image acquisition and processing techniques enable the use of mobile devices for analytical purposes. Here, the PhotoMetrix PRO application was used for image acquisition and multivariate analysis. Statistical analysis showed no significant difference in the results compared to the standard method, with no adverse effect of the volume reduction. The cost of analysis and waste generation were reduced by one third, while the analysis time was reduced by one fifth. The miniaturized method was successfully employed in the analysis of several matrices and for the evaluation of advanced oxidation processes. The AGREE score was improved by 25% due to miniaturization. For these reasons, the miniaturized PhotoMetrix PRO method is a suitable option for COD analysis, being less hazardous to the environment due to reductions in the chemicals used and in waste generation.

Heterogeneous Advanced Oxidation Processes: Current Approaches for Wastewater Treatment

Nowadays, water pollution is one of the most dangerous environmental problems in the world. The presence of the so-called emerging pollutants in the different water bodies, impossible to eliminate through conventional biological and physical treatments used in wastewater treatment plants due to their persistent and recalcitrant nature, means that pollution continues growing throughout the world. The presence of these emerging pollutants involves serious risks to human and animal health for aquatic and terrestrial organisms. Therefore, in recent years, advanced oxidation processes (AOPs) have been postulated as a viable, innovative and efficient technology for the elimination of these types of compounds from water bodies. The oxidation/reduction reactions triggered in most of these processes require a suitable catalyst. The most recent research focuses on the use and development of different types of heterogeneous catalysts, which are capable of overcoming some of the operational limitations of homogeneous processes such as the generation of metallic sludge, difficult separation of treated water and narrow working pH. This review details the current advances in the field of heterogeneous AOPs, Fenton processes and photocatalysts for the removal of different types of emerging pollutants.

Antibiotics in Aquaculture Wastewater: Is It Feasible to Use a Photodegradation-Based Treatment for Their Removal?

Aquacultures are a sector facing a huge development: farmers usually applying antibiotics to treat and/or prevent diseases. Consequently, effluents from aquaculture represent a source of antibiotics for receiving waters, where they pose a potential threat due to antimicrobial resistance (AMR) induction. This has recently become a major concern and it is expectable that regulations on antibiotics’ discharge will be established in the near future. Therefore, it is urgent to develop treatments for their removal from wastewater. Among the different possibilities, photodegradation under solar radiation may be a sustainable option. Thus, this review aims at providing a survey on photolysis and photocatalysis in view of their application for the degradation of antibiotics from aquaculture wastewater. Experimental facts, factors affecting antibiotics’ removal and employed photocatalysts were hereby addressed. Moreover, gaps in this research area, as well as future challenges, were identified.

Effective treatment of hospital wastewater with high-concentration diclofenac and ibuprofen using a promising technology based on degradation reaction catalyzed by Fe0 under microwave irradiation

Real hospital wastewater was effectively treated by a promising technology based on degradation reaction catalyzed by Fe⁰ under microwave irradiation in this work. Fe⁰ powders were synthesized and characterized by different techniques, resulting in a single-phase sample with spherical particles. Optimum experimental conditions were determined by a central composite rotatable design combined with a response surface methodology, resulting in 96.8% of chemical oxygen demand reduction and 100% organic carbon removal, after applying MW power of 780 W and Fe⁰ dosage of 0.36 g L^-1 for 60 min. Amongst the several organic compounds identified in the wastewater sample, diclofenac and ibuprofen were present in higher concentrations; therefore, they were set as target pollutants. Both compounds were completely degraded in 35 min of reaction time. Their plausible degradation pathways were investigated and proposed. Overall, the method developed in this work effectively removed high concentrations of pharmaceuticals in hospital wastewater.

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.

An overview of homogeneous and heterogeneous photocatalysis applications for the removal of pharmaceutical compounds from real or synthetic hospital wastewaters under lab or pilot scale

The last few decades, Pharmaceutical Active Compounds (PhACs) have been considered as emerging contaminants due to their continuous release and persistence to aquatic environment even at low concentrations. A growing number of research articles have shown the occurrence of numerous PhACs in various wastewater treatment plant influents, hospital effluents, and surface waters all over the world. The rising concern regarding PhACs, which present high recalcitrance towards conventional treatment methods, has provoked extensive research in the field of their effective remediation. This review provides a comprehensive assessment of homogeneous and heterogeneous photocatalytic applications for the removal of PhACs, from real or artificial hospital wastewater effluents. These two representative advanced oxidation processes (AOPs) are assessed in terms of their efficiency to remove PhACs, reduce the COD and toxicity as well as increase the biodegradability of the effluent. Simultaneously with their efficiency the operational costs of the processes are considered. Their potential combination with other processes is critically discussed, as this option seems to enhance the treatment efficiency and simultaneously overcome the limitations of each individual process. Moreover, the type of reactors as well as the main parameters that should be considered for the design and the development of photoreactors for wastewater treatment are reviewed. Finally, based on the literature survey, indications for future work are provided.

Reducing toxicity and antimicrobial activity of a pesticide mixture via photo-Fenton in different aqueous matrices using iron complexes

This is the first study to investigate ethylenediamine-N,N'-disuccinic acid (EDDS)/photo-Fenton process to polish real wastewater containing pesticides for possible water reuse. To this end, simultaneous degradation of pesticides ametrine, atrazine, imidacloprid and tebuthiuron was evaluated in distilled water (DW) and in sewage treatment plant (STP) effluent at initial pH 6.0. Several operational parameters (Fe³⁺-EDDS concentration, Fe³⁺-EDDS molar ratio, EDDS addition patterns and radiation source) were evaluated. 80-98% removal of target pesticides were obtained in DW using 30 μmol L^-1 of Fe³⁺-EDDS with a molar ratio of 1:2 (300 μmol L^-1 of H₂O₂). In addition, the proposed Fe³⁺-EDDS photo-Fenton at pH 6 was more efficient than classic photo-Fenton at pH 2.7 (30-84% removal). Experiments conducted in the presence of radical trapping agents (2-propanol or chloroform) revealed that HO^• was the most active radical during treatment. Matrix composition strongly affected the degradation of target pesticides as a six-fold higher concentration of reagents (180 μmol L^-1 of Fe³⁺-EDDS and 1800 μmol L^-1 of H₂O₂) was needed to reach the same efficiency in STP compared to DW. Even so, first order rate constants corresponding to the degradation of pesticides in DW (k = 0.098-0.85 min^-1) were nearly two-fold higher than in STP (k = 0.079-0.49 min^-1) under the same radiation source (black-light or solar radiation). Finally, acute toxicity towards Vibrio fischeri and Drosophila melanogaster flies, and antibacterial activity assessed for Escherichia coli were eliminated after the application of the proposed treatment, thus indicating environmental safety for either discharge or reuse of treated wastewater for crop irrigation in agriculture.

Combination of solar photo-Fenton and adsorption process for removal of the anticancer drug Flutamide and its transformation products from hospital wastewater

The anti-cancer drug Flutamide (FLUT) is widely used and is of great environmental concern. The solar photo-Fenton (SPF) process can be an effective treatment for the removal of this type of micropollutant. The use of a single addition of 5 mg L^-1 of Fe²⁺ and 50 mg L^-1 of H₂O₂ achieved 20% primary degradation and only 3.05% mineralization. By using three additions of 5 mg L^-1 Fe²⁺, with an initial H₂O₂ concentration of 150 mg L^-1, 58% primary degradation was achieved, together with 12.07% mineralization. Consequently, thirteen transformation products (TPs) were formed. The SPF process was further combined with adsorption onto avocado seed activated carbon (ASAC) as an environmentally friendly approach for the removal of remained FLUT and the TPs. Doehlert design was used to assess the behavior of 13 TPs by optimizing the contact time and the adsorbent mass load. The optimal conditions for removal of FLUT and the TPs were 14 mg of ASAC and a contact time of 40 min. Remained FLUT and the TPs were totally removed using the adsorption process. The mechanisms of adsorption of FLUT and the TPs were strongly influenced by their polarity and π-π interactions of the TPs onto ASAC.

Photoreaction characteristics of ferrous oxalate recovered from wastewater

Photoreaction with the Fe(III)-oxalate complex has been reported to play an important role in various photochemical reactions in the natural atmospheric environment, and are applicable to treat various recalcitrant compounds in wastewater. We previously showed that a Fe(II) oxalate (FeOx) crystal can be recovered from the wastewater generated from soil washing, which can then be applied to the photoreaction for degradation of recalcitrant pollutants; however, photoreactions with FeOx compounds have not been fully reported yet. Therefore, this study aims to investigate the photoreaction characteristics of FeOx recovered from wastewater, to demonstrate the feasibility of its application to wastewater treatment. The physical and chemical properties of FeOx were characterized with X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy analyses. The photoreaction of FeOx showed high methylene blue (MB) removal efficiencies similar to the reaction with TiO₂, indicating that FeOx is applicable to the photoreaction for degradation of pollutants. Furthermore, the photodegradation of MB with FeOx was observed under visible light, as opposed to TiO₂. MB could be removed by the photoreaction of FeOx under both basic and acidic pH conditions. Under basic pH conditions, MB could be removed by FeOx via both photoreaction and surface adsorption. The concentration of FeOx affected light penetration and Fe and oxalate levels in the solution, resulting in different MB removal kinetics. The photoreaction efficiency of FeOx could be affected by both photoreaction of Fe and oxalate in the solution and photoreaction and adsorption reaction of the FeOx surface.

Degradation of the anticancer drug flutamide by solar photo-Fenton treatment at near-neutral pH: Identification of transformation products and in silico (Q)SAR risk assessment

Flutamide (FLUT) is a non-steroidal drug mainly used in the treatment of prostate cancer and has been detected in the aquatic environment at ng L^-1 levels. The environmental fate and effects of FLUT have not yet been studied. Conventional treatment technologies fail to completely remove pharmaceuticals, so the solar photo-Fenton process (SPF) has been proposed as an alternative. In this study, the degradation of FLUT, at two different initial concentrations in ultra-pure water, was carried out by SPF. The initial SPF conditions were pH₀ 5, [Fe²⁺]₀ = 5 mg L^-1, and [H₂O₂]₀ = 50 mg L^-1. Preliminary elimination rates of 53.4% and 73.4%. The kinetics of FLUT degradation could be fitted by a pseudo-first order model and the k_obs were 6.57 × 10^-3 and 9.13 × 10^-3 min^-1 t_30W and the half-life times were 95.62 and 73.10 min t_30W were achieved for [FLUT]₀ of 5 mg L^-1 and 500 μg L^-1, respectively. Analysis using LC-QTOF MS identified thirteen transformation products (TPs) during the FLUT degradation process. The main degradation pathways proposed were hydroxylation, hydrogen abstraction, demethylation, NO₂ elimination, cleavage, and aromatic ring opening. Different in silico (quantitative) structure-activity relationship ((Q)SAR) freeware models were used to predict the toxicities and environmental fates of FLUT and the TPs. The in silico predictions indicated that these substances were not biodegradable, while some TPs were classified near the threshold point to be considered as PBT compounds. The in silico (Q)SAR predictions gave positive alerts concerning the mutagenicity and carcinogenicity endpoints. Additionally, the (Q)SAR toolbox software provided structural alerts corresponding to the positive alerts obtained with the different mutagenicity and carcinogenicity models, supporting the positive alerts with more proactive information.

Modeling and optimization of fixed mode dual effect (photocatalysis and photo-Fenton) assisted Metronidazole degradation using ANN coupled with genetic algorithm

The study presents the novel concept of application of fixed bed-batch mode in-situ dual effect of degradation of photo-Fenton and photocatalysis using composite material composed of fuller's earth and foundry sand for the removal of antibiotic Metronidazole. The composite material was involved in the subsequent leaching of iron prompting to in-situ photo-Fenton reactions while TiO₂ layer immobilized upon the support involved in photocatalysis. Dual process facilitated the significant reduction in treatment time as 80% of the compound degraded with 30 min of the reaction. Both the processes almost took 180 min for 50% degradation, when applied individually. No doubt, there was an astonishing increase in the rate constant. An artificial neural network model coupled with the genetic algorithm was employed for the optimization of various parameters like H₂O₂ dose, treatment time, number of beads, pH, etc. Various characterizations have been performed to confirm the novelty of the process. Extended recyclability up to 70 recycles of these composite beads really confirmed the feasibility of this technology for field-scale applications.