Removal of Mefenamic acid from aqueous solutions by oxidative process: Optimization through experimental design and HPLC/UV analysis

Enhanced photocatalytic activity of hydrozincite-TiO2 nanocomposite by copper for removal of pharmaceutical pollutant mefenamic acid in aqueous solution

Nanocomposites based on hydrozincite-TiO₂ and copper-doped HZ-xCu-TiO₂ (x = 0.1; 0.25; 0.35) were synthesized in a single step using the urea method. The samples were characterized by XRD, FTIR, SEM/TEM, and DRS. The study of adsorption capacity and photocatalytic efficiency of these nanocomposites have been tested on a pharmaceutical pollutant, mefenamic acid (MFA). Kinetic study of removal of MFA indicates that this pollutant was adsorbed on the surface of the synthesized phases, according to Langmuir's model. Such adsorption proved to be well adapted in a kinetic pseudo-second-order model with capacity of 13.08 mg/g for HZ-0.25Cu-TiO₂. Subsequently, the kinetics of photocatalytic degradation under UV-visible irradiation was studied according to several parameters, which allowed us to optimize our experimental conditions. The nanocomposite HZ-0.25Cu-TiO₂ showed significant removal efficiency of MFA. Elimination rate reached 100% after 20 min under UV-vis irradiation, and 77% after 7 h under visible light irradiation. Repeatability tests have shown that this nanocomposite is extremely stable after six photocatalytic cycles. By-products of MFA were detected by LC/MS. These photoproducts was produced by three types of reactions of hydroxylation: cyclization and cleavage of the aromatic ring. MFA underwent complete mineralization after 22 h of irradiation in the presence of the HZ-0.25Cu-TiO₂.

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.

A Review on Biological Processes for Pharmaceuticals Wastes Abatement-A Growing Threat to Modern Society

Over the last decades, the production and consumption of pharmaceuticals and health care products grew manifold, allowing an increase in life expectancy and a better life quality for humans and animals, in general. However, the growth in pharmaceuticals production and consumption comes with an increase in waste production, which creates a number of challenges as well as opportunities for the waste management industries. The conventional current technologies used to treat effluents have shown to be inefficient to remove or just to reduce the concentrations of these types of pollutants to the legal limits. The present review provides a thorough state-of-the-art overview on the use of biological processes in the rehabilitation of ecosystems contaminated with the pharmaceutical compounds most commonly detected in the environment and eventually more studied by the scientific community. Among the different biological processes, special attention is given to biosorption and biodegradation.

Electro-transformation of mefenamic acid drug: a case study of kinetics, transformation products, and toxicity

Poor removal of many pharmaceuticals and personal care products in sewage treatment plants leads to their discharge into the receiving waters, where they may cause negative effects for aquatic environment and organisms. In this study, electrochemical removal process has been used as alternative method for removal of mefenamic acid (MEF). For our knowledge, removal of MEF using electrochemical process has not been reported yet. Effects of initial concentration of mefenamic acid, sodium chloride (NaCl), and applied voltage were evaluated for improvement of the efficiency of electrochemical treatment process and to understand how much electric energy was consumed in this process. Removal percentage (R%) was ranged between 44 and 97%, depending on the operating parameters except for 0.1 g NaCl which was 9.1%. Consumption energy was 0.224 Wh/mg after 50 min at 2 mg/L of mefenamic acid, 0.5 g NaCl, and 5 V. High consumption energy (0.433 Wh/mg) was observed using high applied voltage of 7 V. Investigation and elucidation of the transformation products were provided by Bruker software dataAnalysis using liquid chromatography-time of flight mass spectrometry. Seven chlorinated and two non-chlorinated transformation products were investigated after 20 min of electrochemical treatment. However, all transformation products (TPs) were eliminated after 140 min. For the assessment of the toxicity, it was impacted by the formation of transformation products especially between 20 and 60 min then the inhibition percentage of E. coli bacteria was decreased after 80 min to be the lowest value.

Application of Oxides Electrodes (Ru, Ti, Ir and Sn) for the Electrooxidation of Levofloxacin

Background:

The main sources of antibiotic pollution are industries, hospitals, and urban effluents, as well as wastewater from farms that use antibiotics for veterinary purposes. Fluoroquinolones are very useful as antimicrobial agents and are probably among the most important classes of synthetic antibiotics in veterinary and human medicines worldwide. Despite this relevance, studies on the analysis of fluoroquinolones in wastewaters and alternative processes to degrade these compounds, and their effects on human health and environment are scarce. Here, we prepared different oxide electrodes (Ti/Ru0.3Ti0.7O2, Ti/Ru0.3Sn0.7O2, Ti/Ir0.3Ti0.7O2, and Ti/Ir0.3Sn0.7O2) and used them in the electrochemical oxidation of levofloxacin, an antibiotic belonging to the class of fluoroquinolones.

Methods:

The oxide electrodes with nominal compositions: Ti/Ru0.3Ti0.7O2, Ti/Ru0.3Sn0.7O2, Ti/Ir0.3Ti0.7O2, and Ti/Ir0.3Sn0.7O2 were prepared by the traditional method. Briefly, the precursor solution was dissolved in isopropanol and applied by brushing on both sides of the titanium substrate. The resulting material was thermally decomposed at 400°C for 5 min in a preheated oven, which was followed by cooling. This procedure was repeated until the desired oxide thickness was achieved (2 mm). Using the electrochemical cell, the electrolysis experiments were carried out by applying current densities of 25, 50, and 100 mA cm-2 on the oxide electrodes for 60 min. During this experiment, aliquots were removed at times: 5, 10, 15, 20, 30, 45 and 60 min for quantification. Levofloxacin was quantitatively determined by High-Performance Liquid Chromatography (HPLC).

Results:

The catalytic efficiency of different electrodes is measured as the yield of levofloxacin degradation, which in most cases reaches 50% within 1 h of electrolysis, regardless of the applied current. The electrodes bearing ruthenium afford the same % residual levofloxacin (18%) after 1 h of electrolysis under 100 mA cm-2. The electrodes that contain iridium provide similar results at all the applied currents, being less efficient as compared to the ruthenium-based electrodes. The electrode Ti/Ru0.3Sn0.7O2 presented the highest levofloxacin degradation value (levofloxacin residual is 8% at 50 mA cm-2) and levofloxacin removal rate was calculated considering order 1 kinetics (-lnC/Co=kt), for each of the applied current densities reaching 4.4, 4.9 and 4.5 mg L-1min-1 for the experiments at 25, 50, 100 mA cm-2. Therefore, the Ti/Ru0.3Sn0.7O2 electrode affords the highest yield and the best cost/benefit ratio.

Conclusion:

In this work, electrodes were prepared with different compositions to study the catalytic efficiency in the degradation of levofloxacin, an antibiotic belonging to the class of fluoroquinolones. The mixed oxide electrodes prepared herein have proven to be an efficient alternative to treat effluents contaminated with organic compounds. The electrode containing RuO2 and SnO2 oxidizes levofloxacin the most efficiently, reaching a removal efficiency of 92% (4.9 mg L-1 min-1) under 50 mA cm-2. Hence, the substitution of Ti for Sn generates better degradation efficiency.

Response Surface Methodology Optimization for Photodegradation of Methylene Blue in a ZnO Coated Flat Plate Continuous Photoreactor

In this paper, a continuous flat plate photoreactor with ZnO coating was studied in the photodegradation of methylene blue. The structural properties of catalyst were characterized by means of X-ray diffraction, Field emission scanning electron microscopy (FESEM), and energy dispersive X-ray (EDX). The XRD results indicate that high crystalline ZnO particles with average size of 13.5 nm were coated on the glass plate. The thickness of ZnO layer was 39.67 μm and the coating was uniform and crack free. The EDX showed clear border between glass and ZnO layer which confirmed no material transfer between glass and ZnO layer during thermal treatment. The influence of reactor parameters such as the slope of the glass plate, number of UV lamps, distance between lamp and ZnO coated glass plate and flow rate of wastewater was investigated using optimal custom design which is a subset of response surface methodology (RSM). The results indicated that the maximum photodegradation of methylene blue was achieved under the following conditions: plate slope of 9, 3 UVA lamps, 12 ml/s wastewater flow rate and 10 cm distance between lamp and glass plate. The response of surface methodology at optimum conditions was 65.05% while experimental value was 64.66%, showing good agreement between the experimental values and those predicted by the models, with relatively small errors which were only 0.64. The kinetic study was also performed for methylene blue photodegradation at optimum conditions.