Electrochemical degradation of ciprofloxacin through a DoE-driven optimization in a filter-press type reactor under batch recirculation mode.

In this work, the electrochemical degradation of ciprofloxacin (CIP) was studied in a filter-press-type reactor without division in a batch recirculation manner. For this purpose, two boron-doped diamond (BDD) electrodes (as cathode and anode) were employed. Also, the optimal operating conditions were found by response surface methodology (RSM) following a central composite face-centered design with three factors, namely current intensity (i), initial pH (pH0), and initial concentration ([C]0) with two responses, namely remotion efficiency (η) and operating cost. Optimal operating conditions were i = 3 A, pH0 = 8.49, and [C]0 = 33.26 mg L-1 within an electrolysis time of 5 h, leading to a maximum removal efficiency of 93.49% with a minimum operating cost of $0.013 USD L-1. Also, a TOC analysis shows an 80% of mineralization extent with an energy consumption of 5.11 kWh g-1 TOC. Furthermore, the CIP degradation progress was followed by mass spectrometry (LC/MS) and a degradation pathway is proposed.

Convex optimization for maximizing the degradation efficiency of chloroquine in a flow-by electrochemical reactor.

The degradation efficiency of chloroquine phosphate (CQ), an anti-COVID-19 drug, was investigated in a flow-by electrochemical reactor (FBER) provided with two boron-doped diamond (BDD) electrodes (as cathode and anode) under batch recirculation mode. A central composite rotatable design (CCRD) was run down to model and assess the influence of initial pH in an interval of 3.71 to 11.28, the current density in an interval of 34.32 to 185.68 mA cm-2, and liquid volumetric flow rate in an interval of 0.58 to 1.42 L min-1, and conduct the convex optimization to obtain the maximum degradation efficiency. Experimental results were modeled through a second-order polynomial equation having a determination coefficient (R2) of 0.9705 with a variance coefficient of 1.1%. Optimal operating conditions found (initial pH of 5.38, current density (j) of 34.4 mA cm-2, and liquid flow rate (Q) of 1.42 L min-1) led to a global maximum degradation efficiency, COD removal efficiency, and mineralization efficiency of 89.3, 51.6 and 53.1%, respectively, with an energy consumption of 0.041 kWh L-1 within 9 h of treatment. Additionally, a pseudo-zero-order kinetic model was demonstrated to fit the experimental data and the calculated pseudo-zero-order kinetic constant (kapp) was 13.14 mg L-1 h-1 (2.54 × 10-5 mol dm-3 h-1). Furthermore, the total operating cost was of 0.47 US$ L-1. Finally, this research could be helpful for the treatment of wastewater containing an anti-COVID-19 drug such as CQ. Supplementary Information: The online version contains supplementary material available at 10.1007/s10008-023-05452-7.

Al/Cu-PILC as a Photo-Fenton Catalyst: Paracetamol Mineralization.

Pillared clays have shown to effectively catalyze the photo-Fenton process without the necessity of acidic conditions, which is a very attractive feature from the perspective of environmentally friendly processes, especially when high natural abundance of chemical elements are incorporated. In this work, the catalytic activity of Al/Cu interlayered pillared clays for the degradation and mineralization of paracetamol through a photo-Fenton-like process was investigated. Al/Cu-pillared clays were prepared by adding ane Al/Cu pillaring solution to a bentonite suspension. X-ray diffraction (XRD) confirmed the enlargement of the interlayer space of the clay provoked by the pillaring process and Al and Cu species in the prepared samples were verified by atomic absorption spectroscopy (AAS). The specific surface area of pure bentonite was 2-fold increased after the Al/Cu pillaring process. A synthetic paracetamol solution with an initial concentration of 100 ppm was prepared for the assessment of the activity of the prepared materials. Different catalyst concentrations were tested (0.2, 0.5, 0.75, and 1 g L-1) and the complete removal of paracetamol was achieved in all cases, but the highest mineralization rate (69.8 mg total organic carbon (TOC) gcat -1 h-1) corresponds to the catalyst loading of 0.5 g L-1. An ultraviolet-C (UVC) light source was employed, and no adjustment of the pH to acidic conditions was needed to achieve these results. Liquid chromatography coupled to mass spectroscopy (LC-MS) was employed to identify the reaction intermediates of paracetamol degradation. A proposed pathway for the oxidation of paracetamol molecule is presented. The effect of Cu content in the pillared clay and the stability and reusability of the catalyst were also assessed. The kinetic constants of paracetamol removal were 0.2318 and 0.0698 min-1, under photo-Fenton and UV + H2O2 processes, respectively.

Biodiesel Production from Waste Cooking Oil Catalyzed by a Bifunctional Catalyst.

The objective of this study was to prepare bifunctional catalysts based on iron and CaO and test them in the biodiesel production using waste cooking oil (WCO) as feedstock. Two iron precursors were studied, Fe2O3 and Fe(NO3)3·9H2O. The identified crystalline phases were Ca2Fe2O5 and CaFeO3. Surface morphology and textural properties (distribution of active species, specific surface area, size, and pore volume) were also analyzed. Additionally, thermal stability was studied and 800 °C was established as the optimum calcination temperature. The density of both acidic and basic sites was higher with the catalyst prepared with Fe2O3 than with that prepared with Fe(NO3)3·9H2O. The latter, however, leads to reach equilibrium in half of the time than with the former. This was ascribed to the ratio of acidic to basic sites, which is higher with the catalyst prepared with the precursor salt. This ratio not only affects the overall cost of the process by affecting the time at which equilibrium is reached but also by dictating the methanol/oil molar ratio at which the equilibrium is reached sooner. The prepared bifunctional catalyst allowed us to produce biodiesel with 90% of methyl ester content at atmospheric pressure, reaction temperature of 60 °C, reaction time of 2 h, with 12:1 M ratio of methanol/WCO, 10 wt % of Fe over CaO, and a catalyst loading of 5 wt %. This catalyst can be used at least 3 times. The so-obtained biodiesel met the European norm EN-14214 regarding viscosity and density.

Bionanotechnology: Silver Nanoparticles Supported on Bovine Bone Powder Used as Bactericide.

Bionanotechnology is a relatively new term that implies the use of some biological material or organisms in order to prepare nanosystems or nanoparticles. This work presents the preparation and bactericide application of a sustainable nanometric system (silver nanoparticles) using a waste biological support (bovine bone powder). This system was prepared by the method of metallic salt reduction, using NaBH4 as reducing agent and AgNO3 as metallic salt. Two silver contents were analyzed, 1% and 5% weight. The latter was found to be more efficient than the former. Transmission electronic microscopy shows an average size of 10.5 ± 3.3 nm and quasi-sphere morphology. The antimicrobial assay shows that a 5% weight content of silver had a bactericide effect for Escherichia coli at 46.8 min of exposure. The minimum inhibitory concentration (MIC) of silver nanoparticles supported on bovine bone powder for Escherichia coli was 7.5 µg/mL. The biocomposite exhibits a specific antibacterial kinetics constant (k) of 0.1128 min-1 and decimal reduction time (DRT) of 20.39 min for Escherichia coli. Thus, it was concluded that a biocomposite was prepared with a biodegradable, waste, and low-cost support, under mild conditions (room temperature and atmospheric pressure) and using water as solvent.

17-ß-Estradiol: Significant reduction of its toxicity in water treated by photocatalysis.

The aim of this study was to assess the efficiency of photocatalysis by TiO2 on the removal of 17-ß-estradiol (E2) (at environmentally relevant concentrations) and the toxicity caused by this emerging pollutant. After 60min of TiO2/UV treatment at pilot scale (14L), E2 was removed from water approximately 85%. The toxicity was established by using Cyprinus carpio as bioindicator organism and oxidative stress biomarkers (OSB): [lipid peroxidation level (LPX), hydroperoxide content (HPC) and protein carbonyl content (PCC)] and enzymes [superoxide dismutase (SOD) and catalase (CAT)]. It was found that the photocatalytic treatment led to significantly reduce OSB in approximately 85-95%. Thus, it can be concluded that heterogeneous photocatalysis by TiO2 is an efficient process to eliminate the toxicity caused by E2 and thus to remediate water polluted with this molecule.

17ß-Estradiol induces cyto-genotoxicity on blood cells of common carp (Cyprinus carpio).

17ß-Estradiol, a natural hormone present at high concentrations in aquatic ecosystems, affects and modifies endocrine function in animals. In recent years research workers have expressed concern over its potential effects on aquatic organisms; however, little is known about its capacity to induce genetic damage or the pro-apoptotic effects of such damage on fish. Therefore, this study aimed to evaluate 17ß-estradiol-induced cyto-genotoxicity in blood cells of the common carp Cyprinus carpio exposed to different concentrations (1 ng, 1 µg and 1 mg L-1). Peripheral blood samples were collected and evaluated by comet assay, micronucleus test, determination of caspase-3 activity and TUNEL assay at 12, 24, 48, 72 and 96 h of exposure. Increases in frequency of micronuclei, TUNEL-positive cells and caspase-3 activity were observed, particularly at the highest concentration. In contrast, the comet assay detected significant increases at 24 and 96 h with the 1 µg and 1 ng L-1 concentrations respectively. The set of assays used in the present study constitutes a reliable early warning biomarker for evaluating the toxicity induced by this type of emerging contaminants on aquatic species.

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.