Sonochemical degradation of antibiotics from representative classes-Considerations on structural effects, initial transformation products, antimicrobial activity and matrix

In this work, the sonochemical treatment (at 354 kHz and 88 W L-120 ) of six relevant antibiotics belonging to fluoroquinolones (ciprofloxacin and norfloxacin), penicillins (oxacillin and cloxacillin) and cephalosporins (cephalexin and cephadroxyl) classes was evaluated. Firstly, the ability of the process to eliminate them was tested, showing that sonodegradation of these antibiotics is strongly chemical structure25 dependent. Thus, correlations among initial degradation rate of pollutants (Rd), solubility in water (Sw), water-octanol partition coefficient (Log P) and topological polar surface area (TPSA) were tested. Rd exhibited a good correlation with Log P (i.e., the hydrophobicity degree of antibiotics). The considered penicillins had the fastest elimination and from the constitutional analysis using Lemke method was clear that the functional groups arrangement on these antibiotics made them highly hydrophobics. The penicillins were degraded closer at cavitation bubble than the fluoroquinolones or cephalosporins. The investigation of degradation products showed that sonogenerated hydroxyl radical primary attacked the β-lactam ring of cloxacillin and cephalexin, whereas on norfloxacin induced a decarboxylation. On the other hand, the evolution of antimicrobial activity was also followed. It was evidenced the process capacity to remove antimicrobial activity from treated solutions, which was associated to the transformations of functional groups on antibiotics with important role for interaction with bacteria. Additionally, degradation of antibiotics having the highest (the most hydrophobic, i.e., cloxacillin) and lowest (the most hydrophilic, i.e., cephadroxyl) Rd, was performed in synthetic matrices (hospital wastewater and seawater). Ultrasound degraded both antibiotics; for cloxacillin in such waters higher eliminations than in distilled water were observed (probably due to a salting-out effect exerted by matrix components). Meanwhile, for cephadroxyl a moderate inhibition of degradation in hospital wastewater and seawater respect to distilled water was found, this was related to competition by hydroxyl radical of the other substances in the matrices. These results show the quite selectivity of high frequency ultrasound to eliminate antibiotics form different classes even in complex matrices

Degradation of seventeen contaminants of emerging concern in municipal wastewater effluents by sonochemical advanced oxidation processes

The simultaneous degradation of seventeen emerging concern pollutants in effluent from the municipal wastewater treatment plant (MWTP) of Bogotá-Colombia was studied using high frequency ultrasound (375 kHz). The considered compounds in the effluent corresponded to pharmaceuticals (diclofenac, carbamazepine, venlafaxine, ciprofloxacin, norfloxacin, valsartan, losartan, irbesartan, sulfamethoxazole, clarithromycin, azithromycin, erythromycin, metronidazole, trimethoprim and the high potentiality of the sono-photo-Fenton/oxalic acid system for the pollutants elimination in real-world wastewater matrices. clindamycin); cocaine and its major metabolite benzoylecgonine. Due to limitation of the MWTP for the pollutants elimination, ultrasound was applied to remove these compounds. Interestingly, ultrasonic physical action led to releasing of ciprofloxacin, norfloxacin, diclofenac and sulfamethoxazole from suspended solids, whereas the chemical effects induced degradation of the rest of compounds. For the latter ones, an interesting correlation between the sonodegradation and arithmetic multiplication between hydrophobicity and concentration of pollutants was established. Afterwards, the sonochemical process was complemented with ferrous ions (sono-Fenton), ferrous ions plus light (sono-photo-Fenton) or ferrous ions plus light in presence of oxalic acid (sono-photo-Fenton/oxalic acid). Additionally, to clarify fundamental aspects of the different systems, individual treatments in distilled water of a model pollutant (valsartan) were performed. The complemented processes significantly enhanced all compounds degradation, following the order: sono-photo-Fenton/oxalic acid > sono-photo-Fenton ~ sono-Fenton > sonochemistry. The Fe2+ addition improved the pollutants elimination by generation of more hydroxyl radicals in the solution bulk. Meanwhile, oxalic acid avoided Fe3+ precipitation favoring the iron catalytic cycle. Thus, the work demonstrate

Optimization and application of a continuous flow photo-electro-Fenton system for the removal of pharmaceutical active compounds detected in irrigation water of Bogotá – Savanna (Colombia) Crops

In this study, a continuous flow photo-electro-Fenton (PEF) system was evaluated for its ability to remove pharmaceutically active compounds (PhACs) from irrigation water used in Bogotá-savanna crops. The PEF system consisted of dimensionally stable anode and graphite diffusion gas cathode, which were irradiated with LEDs. Firstly, the system was optimized using response surface methodology (RSM) in ultrapure water. The most favorable conditions for efficient generation of oxidants (the response variable) were found to be a flow rate of 210 mL/min, a current density of 15 mA/cm2, and an electrolyte concentration of 0.1 mol NaCl/L. Subsequently, model compounds of PhACs, including losartan (LOS), sulfamethoxazole (SMX), and diclofenac (DCF), were eliminated after only 10 min of treatment under the previously established conditions. After demonstrating the potential of the PEF system to eliminate PhACs, the system was applied to real irrigation water to evaluate the degradation of seven PhACs, namely carbamazepine (CBZ), sulfamethoxazole (SMX), ciprofloxacin (CIP), clarithromycin (CLR), diclofenac (DCF), valsartan (VAL), and trimethoprim (TMP). The results showed that after 30 min of treatment with the PEF system, the concentration of these compounds was drastically reduced remaining undetected. This demonstrates the high potential of the PEF system to reduce the presence of PhACs in irrigation water and associated environmental and food health risks

Exploring the applicability of solar driven photocatalytic processes to control inestation by zebra mussel

Dreissena polymorpha (zebra mussel) is an invasive freshwater bivalve mollusc that causes important technical and environmental problems. Titanium dioxide solar photocatalysis was checked for disinfestation of veligers of zebra mussel. Approximately 70% damaged larvae were observed after 2h of solar irradiation with 0.2 and 0.5g/l of TiO 2. Neutral photo-Fenton could be a promising alternative as ca. 80% damaged larvae were detected in only 3h irradiation in the presence of H 2O 2 (10mg/l). This process was clearly more effective than sunlight irradiation, H 2O 2, or dark Fenton. The performance of the process was slightly improved when a pH value of 5.5 was employed, although further research is needed to explore the compatibility of this medium with irrigation. Finally, the process was scaled up to 4l using a solar photo-reactor; again in this case, 90% of the veligers were damaged after 3h of irradiation. © 2011 Elsevier B.V.We want to acknowledge the financial support of Spanish Ministerio de Medio Ambiente, Medio Rural y Marino (Project 100/RN08/03.4) and Confederacion Hidrografica del Ebro for providing water samples infested with zebra mussel.Bernabeu García, A.; Vicente Candela, R.; Peribañez Lopez, MA.; Arques Sanz, A.; Amat Payá, AM. (2011). Exploring the applicability of solar driven photocatalytic processes to control inestation by zebra mussel. Chemical Engineering Journal. 171(2):490-494. https://doi.org/10.1016/j.cej.2011.04.009S490494171

Photo-electro-Fenton process applied to the degradation of valsartan: Effect of parameters, identification of degradation routes and mineralization in combination with a biological system

In this work, the oxidation of the antihypertensive drug valsartan by the Electro-Fenton (EF) and photo-electro-Fenton (PEF) processes was studied using a Ti/IrO2 doped with SnO2 as anode, and a carbon felt air diffusion electrode as cathode. Initially, the influence of variables such as supporting electrolyte type, current density, and pH on EF and/or PEF processes was evaluated. The processes were carried out in batch mode, in an open and undivided cell of 200 cm3. The efficiency of the systems was evaluated in terms of the removal of the initial contaminant and rate of mineralization. When NaCl was used as a supporting electrolyte at pH 3.0 and current density 3.46 mA/cm2 adding 3.6 × 10−5 mol/L of Fe2+, total valsartan (20 mg/L) degradation was observed after 45 min. After 120 min, even if total removal of valsartan was reached, only 25% of mineralization was obtained. Thus, valsartan degradation tests at near neutral pH in presence of oxalic acid (4.6 × 10−5 mol/L) lead to comparable results with those obtained at pH 3.0. Primary aromatic intermediates were identified by high resolution mass spectrometry (HRMS) using hybrid quadrupole- time-of-flight (QTOF) MS, from which an initial degradation pathway was proposed. At the end of the PEF system, several aliphatic acids were accumulated and observed, which were effectively removed in a subsequent aerobic biological system. The results demonstrate the feasibility of PEF and biological coupling process to completely mineralize emerging pharmaceutical pollutants, such as valsartan, at natural pH

Comparative evaluation of polymer surface functionalization techniques before iron oxide deposition. Activity of the iron oxide-coated polymer films in the photo-assisted degradation of organic pollutants and inactivation of bacteria

The preparation of iron oxide-coated polymer films and their photocatalytic activity in organic pollutants degradation and bacterial inactivation is described. Polyvinyl fluoride (PVF), polyethylene (PE) and polyethylene terephtalate (PET) films were used as catalyst supports. Polymer surfaces were functionalized by vacuum-UV radiation (V-UV) and radio-frequency plasma (RF-P); and also by photo-Fenton oxidation (P-FO) and TiO2 photocatalysis (Ti-PC) in solution. These pre-treatments were performed to improve iron oxide adhesion on the commercial polymer surface. The functionalized polymers films (P-f) were afterward immersed in an aqueous solution for the deposition of iron oxide layer by hydrolysis of FeCl3. The photocatalytic activities of iron oxide-coated functionalized polymers films (P-f-Fe oxide) prepared by different methods were compared during hydroquinone degradation in presence of H2O2. RF-P and Ti-PC pre-treated polymers showed significantly higher photocatalytic activity and long-term stability during processes leading to pollutant abatement, if compared with not treated ones (NT), although similar leaching of iron was observed for all the materials. PET bottles (PETb) were used as reactor and catalyst supports. The produced PETbf-Fe oxide surfaces were efficient in photo-assisted bacterial inactivation in the presence of H2O2, and no dissolved iron species were detected in solution. (C) 2010 Elsevier B.V. All rights reserved

Comparative degradation of two highly consumed antihypertensives in water by sonochemical process. Determination of the reaction zone, primary degradation products and theoretical calculations on the oxidative process

This work compares the sonochemical degradation of losartan and valsartan (antihypertensives) in water. Initially, the suitable operational conditions of ultrasonic power density and frequency were established. Under such conditions, losartan was eliminated in a higher percentage than valsartan, which was associated to differences in their hydrophobicities. Additionally, degradations in presence of isopropanol and ferrous ions confirmed that losartan was closer to cavitation bubble than valsartan. The structures of primary products indicated that sonogenerated hydroxyl radical attacked biphenyl tetrazole moiety (common nucleus of both pharmaceuticals). Then, theoretical calculations were applied to the products to estimate the toxicity, degree of oxidation and probable routes of aerobic biodegradation suggesting a beneficial action of sonodegradation. Finally, the sonochemical degradation of the antihypertensives was carried out in two simulated complex matrices (i.e., seawater and hospital wastewater) and an actual wastewater. Interestingly, the losartan and valsartan eliminations in such waters were similar to the observed in distilled water. This fact indicates the high potentiality of ultrasound to degrade losartan or valsartan in waters containing other substances, even at higher concentrations than these pollutants

Elimination of contaminants of emerging concern and their environmental risk in world-real municipal wastewaters by electrochemical advanced oxidation processes

In this study, sixteen contaminants of emerging concern (CECs), present in the effluent of the wastewater treatment plant (WWTP) “Salitre” (Bogotá – Colombia), were subjected to several electrochemical advanced oxidation processes (EAOPs). Thus, the elimination of the pharmaceuticals diclofenac, carbamazepine, venlafaxine, Irbesartan, losartan, metronidazole, sulfamethoxazole, trimethoprim, clindamycin, norfloxacin, ciprofloxacin, clarithromycin, erythromycin, and azithromycin, the illicit drug cocaine, and its major metabolite benzoylecgonine was assessed by electro-Fenton (EF), photo-electro-Fenton (PEF), and photo-electro-Fenton in the presence of added oxalic acid (PEFox). A boron-doped diamond and a gas diffusion electrode were used as anode and cathode. After 1 h of treatment, the total concentration of CECs decreased by 36% when PEFox was applied. In the case of EF and PEF, the degradation percentages were lower (29% and 19%, respectively). The highest degradation by using PEFox was due to the enhanced availability of soluble iron ions by forming Fe(III)-oxalate complexes at near-neutral pH values. This allows the Fenton reaction to yield additional HO• radicals. Finally, the effect of EAOPs to reduce the environmental risk associated with the CECs in the WWTP was evaluated. The best system, PEFox, lowered by more than ten times the environmental hazard of the tested CECs in the effluent. This work shows the high potential of PEFox, as tertiary treatment, to eliminate emerging pollutants and reduce their risk in effluents from WWTP. In this system, the added oxalic acid, which has a biodegradable character, could be eliminated in a subsequent biological step

Effective elimination of fifteen relevant pharmaceuticals in hospital wastewater from Colombia by combination of a biological system with a sonochemical process

This work presents the treatment of selected emerging concern pharmaceuticals in real hospital wastewater (HWW) from Tumaco-Colombia by combination of a biological system with a sonochemical process. Fifteen compounds, commonly present in HWW, were considered: acetaminophen, diclofenac, carbamazepine, venlafaxine, loratadine, ciprofloxacin, norfloxacin, valsartan, irbesartan, sulfamethoxazole, trimethoprim, clarithromycin, azithromycin, erythromycin and clindamycin. Initially, HWW was characterized in terms of global parameters and the pharmaceuticals content. HWW contained a moderate amount of organic matter (i.e., total organic carbon: 131.56 mg L−1 (C)) mainly associated to biodegradable components. However, the most of pharmaceuticals were found at levels upper than their predicted no effect concentration (PNEC). Then, a conventional biological treatment was applied to the HWW. After 36 h, such process mainly removed biodegradable substances, but had a limited action on the pharmaceuticals. The resultant biotreated water was submitted to the sonochemical process (375 kHz and 88 W L−1, 1.5 h), which due to its chemical (i.e., radical attacks) and physical (i.e., suspended solids disaggregation) effects induced a considerable pharmaceuticals degradation (pondered removal: 58.82%), demonstrating the complementarity of the proposed combination. Afterwards, Fe2+ (5 ppm) and UVC light (4 W) were added to the sonochemical system (generating sono-photo-Fenton process), which significantly increased up to 82.86% the pondered pharmaceuticals removal. Subsequently, to understand fundamental aspects of the pharmaceuticals degradations, a model compound (norfloxacin) in distilled water was treated by sonochemical system, sono-photo-Fenton process and their sub-systems (i.e., sono-Fenton and UVC alone). This allowed proving the hydroxyl radical action in sonochemical treatment, plus the contribution of Fenton reaction and direct photodegradation in the pharmaceuticals removal by sono-photo-Fenton. Finally, it was found that 91.13% of the initial pharmaceuticals load in HWW was removed by the biological/sono-photo-Fenton combination. The high pollutants abatement evidenced that this combination is a powerful alternative for removing pharmaceuticals from complex-matrix waters, such as raw HWW

Treatment of two sartan antihypertensives in water by photo-electro-Fenton using BDD anodes: Degradation kinetics, theoretical analyses, primary transformations and matrix effects

Degradation of two representative antihypertensives, losartan (LOS) and valsartan (VAL) in water by photo-electro-Fenton (PEF), using a BDD anode in presence of sulfate anion was evaluated. PEF showed a fast elimination of these pollutants (>95% at 30 and 60 min of treatment for LOS and VAL, respectively). The main elimination route was the attacks of radicals produced in the system, having pseudo-first-order rate constants of 0.154 and 0.054 min−1 for LOS and VAL, correspondingly. Theoretical analyses of atomic charges were performed to rationalize the antihypertensives reactivity toward the electrogenerated degrading agents. Afterwards, the primary transformation products were assessed. The transformation products revealed that the degrading species attack the biphenyl-tetrazole, imidazole, and alcohol moieties on LOS. Meanwhile, carboxylic and amide groups, plus the central nucleus, were modified on VAL. These moieties corresponded well with the electron-rich sites indicated by the theoretical calculations. Also, the PEF process removed between 33 and 38% of total organic carbon after 5 h of electrolysis. Finally, it was considered LOS treatment in presence of oxalic acid (a typical organic waste of pharmaceutical industry), in addition to the pollutant degradation in effluents from municipal sewage treatment plants by PEF at pH ∼5. Oxalic acid accelerated LOS degradation. Meanwhile, in the effluent, the process led to 64% of LOS removal after 120 min of treatment, indicating the high potentiality of PEF to degrade antihypertensives in water containing organic and inorganic substances