Individual and simultaneous degradation of sulfamethoxazole and trimethoprim by ozone, ozone/hydrogen peroxide and ozone/persulfate processes: A comparative study.

This study investigates the individual and simultaneous degradation and mineralization of the antibiotics, sulfamethoxazole (SMX) and trimethoprim (TMP) in aqueous solution by ozonation, ozone-activated persulfate (PS) and hydrogen peroxide (H2O2) processes. The trials were carried out in a semi-continuous column bubble reactor with an ozone diffuser located at the bottom of the column for a period of 2 h. Furthermore, the efficiency of studied processes were evaluated at two different initial pH and various doses of oxidants. The target compounds degradation observed pseudo-first-order rate constants (kobs) and removal of total organic carbon (TOC) using ozone-based oxidation processes were compared. Irrespective of the applied processes, the mineralization of target compounds was less effective than their degradation in both individual and simultaneous systems. The highest antibiotics degradation rate constants were observed for individual oxidation of TMP (kobs = 0.379 min-1) and SMX (kobs = 0.367 min-1) at alkaline initial pH (pH0) in the O3/H2O2 system at an [antibiotic]/H2O2 molar ratio of 1/1. Irrespective of the antibiotic studied, the most effective TOC removal (~44%) was observed after a 2-h treatment with the O3/H2O2 system at an [antibiotic]/H2O2 molar ratio of 1/5 (pH0 10.9). The O3/PS system at an [antibiotic]/PS molar ratio of 1/5 (pH0 10.9) proved the most effective system for both mineralization and degradation (kobs values of 0.294 min-1 and 0.266 min-1) of TMP and SMX, respectively, during the simultaneous oxidation of SMX-TMP. The decomposition by-products of SMX and TMP in studied ozone-based processes were identified using LC-MS analysis. The results of this study strongly suggest that using the O3/PS process is a promising solution to reduce SMX-TMP contamination in water matrices.

UV-assisted chemical oxidation of antihypertensive losartan in water.

Population growth and deteriorating health issues have led to an increase in the consumption of angiotensin receptor blockers (ARBs), such as losartan (LOR), for treating high blood pressure and, as a result, to the frequent detection of these drugs in water and wastewater. The present study focuses on the oxidation of LOR by UV photolysis, UV(/Fe2+)-activated persulfate (PS) and hydrogen peroxide (H2O2) systems. The effects of operating parameters including pH value, reaction time, concentration of oxidant and activator on the efficacy of treatment were studied. The target compound degradation by direct UV photolysis, UV/PS and UV/H2O2 systems proved to be efficient and followed a pseudo-first-order kinetic model. The application of UV/oxidant systems even at lower PS or H2O2 concentrations resulted in more than 95% of LOR degradation in 10 min. In addition, the use of UV/Fe2+-activated oxidant systems led to a further increase in the kobs by improving the LOR oxidation in aqueous solution. The effectiveness of LOR mineralization based on total organic carbon (TOC) removal was also considered. The optimized results of the studied systems obtained in ultrapure water were used in groundwater to assess the effectiveness of LOR decomposition in more complex environmental matrix. Moreover, the acute toxicity of LOR solutions before and after the UV/Fe2+-activated PS and H2O2 oxidation to luminous bacteria (Vibrio fischeri) was investigated.

Photochemical degradation of nonylphenol in aqueous solution: the impact of pH and hydroxyl radical promoters.

The degradation of nonylphenol (NP) in aqueous solution with UV, H2O2/UV, and Fenton/photo-Fenton processes was studied. The efficacy of direct and hydrogen peroxide photolysis proved to be dependent on the pH value. The addition of H2O2 to UV treatment improved NP degradation. The application of UV photolysis and the H2O2/UV system at pH 7 resulted in low pseudo first-order rate constants at 10-4 sec-1. In the experiments at elevated pH values the pseudo-first order rate constants increased to 10-3 sec-1. The efficacy of the Fenton process was lower in comparison with UV and hydrogen peroxide photolysis. The addition of UV irradiation to the H2O2/Fe2+ system substantially improved NP degradation efficacy. In terms of performance, the photo-Fenton process was similar to the H2O2/UV process. The most favourable process for complete nonylphenol degradation considering both operational cost and treatment efficacy was H202/UV at pH 11 and 250 micromol/L H2O2.

Catalytic degradation of picric acid by heterogeneous Fenton-based processes.

The efficiency of goethite, magnetite and iron powder (Fe0) in catalysing the Fenton-based oxidation of picric acid (PA) in aqueous solution was studied. The effect of pH, hydrogen peroxide concentration, and catalyst type and dosage on treatment efficacy was investigated. The adsorption of PA from aqueous solution by heterogeneous catalysts was also examined. The results demonstrated negligible PA removal in H2O2/alpha-FeOOH and H2O2/Fe3O4 systems independent of process pH, and hydrogen peroxide and catalyst dosage. The PA adsorption effects of both iron oxides turned out to be insignificant for all studied pH values and catalyst dosages. The H2O2/Fe0 system proved efficient at degrading PA, but only under acidic conditions (pH 3). The results indicated that, due to rather fast leaching of ferrous ions from the iron powder surface, PA degradation was carried out mainly by the classic Fenton oxidation mechanism in the bulk solution. The adsorption of PA onto the iron powder surface may also contribute to the overall efficiency of PA degradation.

Insights into nonylphenol degradation by UV-activated persulfate and persulfate/hydrogen peroxide systems in aqueous matrices: a comparative study.

Nonylphenol ethoxylates are widely used industrial surfactants. Once released into environment compartments, these chemicals undergo degradation and generate more toxic short chain artificial compound nonylphenol (NP). The latter is a known endocrine disrupting compound and persistent micropollutant. In the present study, the performance of NP degradation in UV-induced PS, PS/Fe2+, PS/H2O2, and PS/H2O2/Fe2+ systems was examined. The effect of concentration of oxidant and activators on the efficiency of target compound decomposition was studied. The trials were conducted in ultrapure water and groundwater to assess the influence of matrix composition. The obtained results indicated that NP degradation by all the systems studied followed a pseudo-first-order kinetics. The application of UV-activated PS at lower concentrations of the oxidant improved NP oxidation in both water matrices. The addition of iron activator at a cost-effective concentration showed slight improvement in the studied PS-based systems. The application of UV-induced dual oxidant PS/H2O2 system demonstrated promising results in NP oxidation. In turn, the addition of Fe2+ to the UV/PS/H2O2 system accelerated the target compound oxidation at an optimized dose of iron activator. The radicals scavenging studies indicated that HO• was the predominant radical in all UV-induced PS-based systems. The results of this research could provide significant information for the removal of NP from different water matrices by means of UV-induced persulfate-based oxidation processes.

Persulfate-based photodegradation of a beta-lactam antibiotic amoxicillin in various water matrices.

Amoxicillin (AMX), a widely used beta-lactam antibiotic, belongs to the World Health Organization's list of essential medicines. This subsequently causes its long-term presence in the environment and therefore, affects different environmental compartments. In this research, the degradation and mineralisation of AMX by UVC-activated persulfate-based treatment in various aqueous media was assessed. The degradation of the target compound was in accordance with the pseudo-first-order reaction kinetics in all the UVC-induced systems. The results indicated that AMX degradation in any real water matrices is notably inhibited by the matrix properties. The trials with radical scavengers in ultrapure water proved the existence of [Formula: see text] and HO., but mainly [Formula: see text] contributed to the degradation of AMX in the UVC/[Formula: see text] and UVC/[Formula: see text]/Fe2+ systems. It was shown that the parent compound disappeared during the treatment, but the mineralisation extent referred to the formation of transformation products the main of which were identified. The findings of this study could provide valuable information about the elimination of beta-lactam antibiotics from various environmental and processed waters.

Photo-induced oxidation of ceftriaxone by persulfate in the presence of iron oxides.

The present study focuses on degradation and mineralization of a third generation cephalosporin antibiotic ceftriaxone (CTA) in UVA- and UVC-induced persulfate (PS) system combined with heterogeneous (α-FeO(OH) and Fe3O4) activators. The CTA oxidation efficiency was investigated in buffered solution (pH 7.4) to stimulate the inhibitory properties of environmental and processed water matrices. Irrespective of the studied UV-induced persulfate system, the mineralization was less effective than CTA degradation. In turn, UVC-induced systems proved to be more effective than UVA-induced processes for decomposition of the target compound and removal of TOC. Accordingly, 2-h oxidation in UVA-induced systems resulted in partial decomposition and negligible mineralization of CTA. While the application of UVC-activated persulfate processes resulted in complete CTA degradation during the first 15 min of oxidation with the most efficient kobs of 0.53 min-1 and 38.3% TOC removal obtained in the UVC/PS system at [PS]0 = 500 µM. Groundwater (GW) trials results clearly indicated the inhibitory effect of the GW composition on the effectiveness of CTA degradation in the studied UV-induced PS-based systems, while the potential treatment efficacy in GW proved predictable based on the results obtained in the buffered UW trials. Adjusting the pH to 3 considerably improved the removal of TOC and the use of PS in both of the water matrices studied. The results of radicals scavenging experiments indicated that both SO4- and HO contributed to the CTA decomposition efficacy in the UV-induced persulfate systems, but the former was the predominant radical in all studied processes. The findings of the study strongly suggest that the UV-induced PS systems are promising treatment technologies for the abatement of cephalosporin antibiotics pollution in natural aqueous matrices.

Ferrous ion-activated persulphate process for landfill leachate treatment: removal of organic load, phenolic micropollutants and nitrogen.

The innovative [Formula: see text] treatment technology based on sulphate radicals induced oxidation was applied for the treatment of landfill leachate. The performance of chemical oxygen demand (COD) and dissolved organic carbon (DOC) removal in the Fe2+-activated persulphate system was moderate; however, the results of dissolved nitrogen (DN) and total phenols removal showed significant efficacy (≤39% and ≥87%, respectively). [Formula: see text] addition to the [Formula: see text] system enhanced the treatment efficacy and resulted in supplementary 15% of COD and 5% of DN removal. Hydroxyl radical-based H2O2/Fe2+ treatment of the landfill leachate was performed as well; the results indicated higher removal efficacy of COD and DOC compared to the [Formula: see text] system. However, practical application of the H2O2/Fe2+ system is considerably influenced by temperature rise and excessive foam formation. Generally, the ferrous ion-activated persulphate treatment could be a promising technology for ex situ as well as in situ landfill leachate treatment applications.

Oxidative degradation of emerging micropollutant acesulfame in aqueous matrices by UVA-induced H2O2/Fe2+ and S2O82-/Fe2+ processes.

In the present study, UVA/H2O2/Fe2+ and UVA/S2O82-/Fe2+ processes were applied to degrade the artificial sweetener, acesulfame (ACE) in ultrapure water (UW), groundwater (GW), and secondary effluent (WW). The degradation time and mineralization of 75 µM of ACE determined the efficacy of the procedures. The results indicated that the UVA-induced H2O2/Fe2+ and S2O82-/Fe2+ systems are a promising alternative for the removal of ACE from different aqueous matrices as both studied processes completely degraded the target compound at an ACE/oxidant/Fe2+ molar ratio of 1/10/1 and pH 3. In the case of UVA-induced systems application without pH adjustment, the ACE decomposition was achieved only in ultrapure water. The maximum mineralization of ACE in ultrapure water by the UVA/H2O2/Fe2+ system (molar ratio of 1/10/1) at pH 3 resulted in residual TOC of 18.3%. The oxidative effectiveness of the UVA/S2O82-/Fe2+ system was proved to be mainly formed by the hydroxyl radicals. The obtained results indicate that UVA light can be successfully used for the oxidation of the studied artificial sweetener in various aqueous matrices with carefully adjusted process conditions.