Multivariate optimization of dispersive liquid-liquid microextraction using ionic liquid for the analysis of ultraviolet filters in natural waters.

In this work, a vortex-assisted dispersive liquid-liquid microextraction method, using an ionic liquid as the extracting solvent was developed, for the simultaneous analysis of three UV filters in different water samples. The extracting and dispersive solvents were selected in a univariate way. Then, the parameters such as the volume of the extracting and dispersive solvents, pH and ionic strength were evaluated using a full experimental design 24, followed by Doehlert matrix. The optimized method consisted of 50 µL of extracting solvent (1-octyl-3-methylimidazolium hexafluorophosphate), 700 µL of dispersive solvent (acetonitrile) and pH of 4.5. When combined with high-performance liquid chromatography, the method limit of detection ranged from 0.3 to 0.6 µg L-1, enrichment factors between 81 and 101%, and the relative standard deviation between 5.8 and 10.0%. The developed method demonstrated effectiveness in concentrating UV filters in both river and seawater samples, being a simple and efficient option for this type of analysis.

Photodegradation of oxolinic acid in aquaculture effluents under solar irradiation: is it possible to enhance efficiency by the use of TiO2/carbon quantum dots composites?

Antibiotics, such as oxolinic acid (OXA), in aquaculture effluents contribute to the dissemination of antimicrobial resistance, which makes it urgent to develop efficient and sustainable processes for their removal. Aiming a photocatalytic degradation under solar radiation, different carbon quantum dots (CQDs) were produced in this work through a bottom-up hydrothermal methodology and incorporated into TiO2 by a simple calcination method. A total of thirteen materials were synthesized and tested for OXA photocatalytic removal from synthetic and real matrices. Among them, CQDs produced with citric acid and incorporated into TiO2 at 4% (w/w) (TiO2/CQDs-CA 4% (w/w)) were the most efficient photocatalysts, providing an OXA half-life time (t1/2) decrease of 91%, 79% and 85% in phosphate buffer solution (PBS), synthetic sea salts (SSS) and brackish aquaculture effluent (BAE), respectively. Therefore, the herein synthesized TiO2/CQDs-CA 4% (w/w) composites have shown to be promising materials for a sustainable solar-driven removal of antibiotics from aquaculture effluents.

Sulfadiazine's photodegradation using a novel magnetic and reusable carbon based photocatalyst: Photocatalytic efficiency and toxic impacts to marine bivalves.

In the present study, waste-based biochar functionalized with titanium dioxide (TiO2) and afterwards magnetized by an ex-situ approach, defined as synthetic photosensitizer (SPS), was explored for the photocatalytic degradation of sulfadiazine (SDZ), an antibiotic widely used in the aquaculture industry, under solar irradiation. The use of the SPS enhanced the photodegradation efficiency, with a half-life time (t1/2) reduction from 12.2 ± 0.1 h (without SPS) to 5.6 ± 0.4 h. The applied magnetization procedure allowed to obtain a SPS with good reusability for SDZ photodegradation even after five consecutive cycles. To evaluate the effects on marine bivalves of SDZ, before and after photodegradation and in presence or absence of the SPS, a typical bioindicator species, the mussel Mytilus galloprovincialis, was used and different biochemical markers were analysed. Results obtained indicated that the exposure to SDZbefore irradiation, both in absence and presence of SPS, caused an increase in mussels' metabolism and defence mechanisms, evidencing great biochemical impacts. However, after irradiation (in the absence and presence of SPS), biochemical responses were similar to those observed in organisms exposed to control conditions, without SDZ. Therefore, this work provided a promising eco-friendly treatment for the removal of SDZ from aquaculture effluents.

Photodegradation of Aquaculture Antibiotics Using Carbon Dots-TiO2 Nanocomposites.

In this work, carbon dots (CD) were synthesized and coupled to titanium dioxide (TiO2) to improve the photodegradation of antibiotics in aquaculture effluents under solar irradiation. Oxolinic acid (OXA) and sulfadiazine (SDZ), which are widely used in aquaculture, were used as target antibiotics. To prepare nanocomposites of CD containing TiO2, two modes were used: in-situ (CD@TiO2) and ex-situ (CD/TiO2). For CD synthesis, citric acid and glycerol were used, while for TiO2 synthesis, titanium butoxide was the precursor. In ultrapure water (UW), CD@TiO2 and CD/TiO2 showed the largest photocatalytic effect for SDZ and OXA, respectively. Compared with their absence, the presence of CD@TiO2 increased the photodegradation of SDZ from 23 to 97% (after 4 h irradiation), whereas CD/TiO2 increased the OXA photodegradation from 22 to 59% (after 1 h irradiation). Meanwhile, in synthetic sea salts (SSS, 30‱, simulating marine aquaculture effluents), CD@TiO2 allowed for the reduction of SDZ's half-life time (t1/2) from 14.5 ± 0.7 h (in absence of photocatalyst) to 0.38 ± 0.04 h. Concerning OXA in SSS, the t1/2 remained the same either in the absence of a photocatalyst or in the presence of CD/TiO2 (3.5 ± 0.3 h and 3.9 ± 0.4 h, respectively). Overall, this study provided novel perspectives on the use of eco-friendly CD-TiO2 nanocomposites for the removal of antibiotics from aquaculture effluents using solar radiation.

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.

Biochar-TiO2 magnetic nanocomposites for photocatalytic solar-driven removal of antibiotics from aquaculture effluents.

Contamination of surrounding waters with antibiotics by aquaculture effluents can be problematic due to the possible increase of bacterial resistance, making it crucial the efficient treatment of those effluents before their release into the environment. In this work, the application of waste-based magnetic biochar/titanium dioxide (BC/TiO2) composite materials on the photodegradation of two antibiotics widely used in aquaculture (sulfadiazine (SDZ) and oxolinic acid (OXA)) was assessed. Four materials were synthesized: BCMag (magnetized BC), BCMag_TiO2 (BCMag functionalized with TiO2), BC_TiO2_MagIn and BC_TiO2_MagEx (BC functionalized with TiO2 and afterwards magnetized by in-situ and ex-situ approaches, respectively). SDZ half-life time (t1/2) noticeably decreased 3.9 and 3.4 times in presence of BCMag_TiO2 and BC_TiO2_MagEx, respectively. In the case of OXA, even though differences were not so substantial, the produced photocatalysts also allowed for a decrease in t1/2 (2.6 and 1.7 times, in presence of BCMag_TiO2 and BC_TiO2_MagEx, respectively). Overall, the here synthesized BC/TiO2 magnetic nanocomposites through a circular economy process are promising photocatalysts for a sustainable solar-driven removal of antibiotics from aquaculture effluents.

Solidified floating organic drop microextraction (SFODME) for the simultaneous analysis of three non-steroidal anti-inflammatory drugs in aqueous samples by HPLC.

In this work, a liquid-liquid microextraction methodology using solidified floating organic drop (SFODME) was combined with liquid chromatography and UV/Vis detection to determine non-steroidal anti-inflammatory drugs (NSAIDs) naproxen (NPX), diclofenac (DCF), and mefenamic acid (MFN) in tap water, surface water, and seawater samples. Parameters that can influence the efficiency of the process were evaluated, such as the type and volume of the extractor and dispersive solvents, effect of pH, agitation type, and ionic strength. The optimized method showed low detection limits (0.09 to 0.25 µg L-1), satisfactory recovery rates (90 to 116%), and enrichment factors in the range between 149 and 199. SFODME showed simplicity, low cost, speed, and high concentration capacity of the analytes under study. Its use in real samples did not demonstrate a matrix effect that would compromise the effectiveness of the method, being possible to apply it successfully in water samples with different characteristics.

Impact of UASB reactors operation mode on the removal of estrone and 17α-ethinylestradiol from wastewaters.

This work aims to compare the performance of the continuous operation (CO) and intermittent operation (IO) of upflow anaerobic sludge blanket (UASB) reactors for the removal of estrone (E1) and 17α-ethinylestradiol (EE2) from wastewaters. Results suggest that the IO contribute to the improvement of the overall removal of estrogens (above 95% for E1 and EE2) when compared to CO (49% for E1 and 39% for EE2). For both CO and IO, biodegradation was the main removal mechanism for E1, while for EE2, adsorption to sludge was the major removal pathway. Moreover, a higher biodegradation of estrogens was obtained with the IO compared to CO (69.4% vs. 43.3% for E1 and 21.8% vs. 8.0% for EE2). The favourable effect of IO can be justified by effluent recirculation during the feedless period which promotes the adaptation of microbial biomass to estrogens' biodegradation.

Oxolinic acid in aquaculture waters: Can natural attenuation through photodegradation decrease its concentration?

Quinolones, such as oxolinic acid (OXA), are antimicrobials commonly used in aquaculture. Thus, its presence in the aquatic environment surrounding aquaculture facilities is quite easy to understand. When present in aquatic environment, pharmaceuticals may be subjected to several attenuation processes that can influence their persistence. Photodegradation, particularly for antibiotics, can have significant importance since these compounds may be resistant to microbial degradation. OXA photodegradation studies reported in literature are very scarce, especially using aquaculture waters, but are markedly important for an appropriate risk assessment. Results hereby presented showed a decrease on photodegradation rate constant from 0.70 ± 0.02 h-1 in ultrapure water to 0.42 ± 0.01 h-1 in freshwater. The decrease on photodegradation rate constant was even more pronounced when brackish water was used (0.172 ± 0.003 h-1). In order to understand which factors contributed to the observed behaviour, environmental factors, such as natural organic matter and salinity, were studied. Results demonstrated that dissolved organic matter (DOM) may explain the decrease of OXA photodegradation observed in freshwater. However, a very sharp decrease of OXA photodegradation was observed in solutions containing NaCl and in synthetic sea salts, which explained the higher decrease observed in brackish water. Moreover, under solar radiation, the use of an 1O2 scavenger allowed us to verify a pronounced retardation of OXA decay, suggesting that 1O2 plays an important role in OXA photodegradation process.

ELISA as an effective tool to determine spatial and seasonal occurrence of emerging contaminants in the aquatic environment.

During the last two decades, studies related to the occurrence and fate of emerging contaminants in the aquatic environment have received great attention from the international scientific community. The monitoring of the presence of these compounds is particularly important since they are known to induce adverse effects in aquatic environments, even at extremely low concentrations. This work aimed to apply a simple and effective methodology, such as enzyme-linked immunosorbent assay (ELISA), in the monitoring of 17α-ethinylestradiol (EE2) and 17ß-estradiol (E2) (a synthetic and a natural hormone, respectively), carbamazepine (CBZ, an antiepileptic), cetirizine (CET, an antihistamine) and caffeine (CAF, a stimulant) in water matrices with differing salinity and organic matter contents. ELISA was proven to be a valid and practical tool, especially for screening purposes in contrast to traditional chromatographic techniques which are prohibitively expensive for an application on a broader base. The main originality of this work was to establish seasonal and spatial effects on the occurrence of the referred contaminants by using the effectiveness of ELISA to screen those compounds in samples with different characteristics. This work reports both the seasonal and spatial quantification of the referred contaminants in the aquatic environment of the central region of Portugal, with concentrations ranging as follows: 5-87 ng L-1, for E2, 2-17 ng L-1, for EE2, 10-1290 ng L-1, for CBZ, 10-190 ng L-1, for CET, and 62-6400 ng L-1, for CAF.

Biochar in soil mitigates dimethoate hazard to soil pore water exposed biota.

Soil contamination is a worldwide problem urging for mitigation. Biochar is a carbonaceous material used as soil amendment that can immobilize chemical compounds, potentially turning them unavailable for soil biota. The aim of our study was to evaluate biochar's capacity to immobilize dimethoate in soil and, therefore, decreasing the toxicity to soil organisms. Two biochar application rates (2.5% and 5% w/w) were chosen to assess dimethoate potential immobilization, looking at changes in its toxicity to the collembolan Folsomia candida and the plant Brassica rapa upon soil amendment. Complementarily, chemical analyses were performed on soil pore water. Results showed that biochar may sorb and decrease dimethoate concentrations in soil pore water, influencing dimethoate bioavailability and consequent toxicity. Contrary to dimethoate solo impact on collembolans (LC50 0.69 mg kg-1, EC50 0.46 mg kg-1), their survival rate and offspring production were not affected by dimethoate when biochar was applied, regardless of application rate (LC50 and EC50 > 1.6 mg kg-1). Shoot length, fresh and dry weights of B. rapa were less affected by dimethoate upon biochar addition (EC50 values increase for all endpoints). Our study shows that biochar may contribute to decrease dimethoate bioavailability and toxicity to soil porewater exposed organisms.

Photodegradation of sulfadiazine in different aquatic environments - Evaluation of influencing factors.

The presence of antibiotics, such as sulfadiazine (SDZ), in the aquatic environment contributes to the generation of antimicrobial resistance, which is a matter of great concern. Photolysis is known to be a major degradation pathway for SDZ in surface waters. Therefore, influencing factors affecting SDZ photodegradation in different aquatic environments were here evaluated in order to have a better knowledge about its persistence in the environment. Photodegradation of SDZ was found to be more efficient at higher pH (t1/2 = 6.76 h, at pH = 7.3; t1/2 = 12.2 h, at pH = 6.3), in the presence of humic substances (HS) (t1/2 between 1.76 and 2.42 h), as well as in the presence of NaCl (t1/2 = 1.00 h) or synthetic sea salts (t1/2 = 0.78 h). Using ˙OH and 1O2 scavengers, it was possible to infer that direct photolysis was the main pathway for SDZ photodegradation in ultrapure water. Furthermore, results under N2 purging confirmed that 1O2 was not relevant in the phototransformation of SDZ. Then, the referred observations were used for the interpretation of results obtained in environmental matrices, namely the final effluent of a sewage treatment plant (STPF), fresh and brackish water (t1/2 between 2.3 and 3.48 h), in which SDZ photodegradation was found to be much faster than in ultrapure water (t1/2 = 6.76 h).

Sulfamethoxazole exposure to simulated solar radiation under continuous flow mode: Degradation and antibacterial activity.

Among pharmaceuticals, the occurrence of antibiotics in the environment is a subject of special concern due to their environmental impact, namely the development of bacterial resistance. Sulfamethoxazole (SMX) is one of the most commonly used antibiotics and it is regularly found, not only in effluents from sewage treatment plants (STPs), but also in the aquatic environment. Photodegradation appears as an alternative process for the removal of this type of pollutants from contaminated waters. In order to be used for a remediation purpose, its evaluation under continuous flow mode is essential, as well as the determination of the final effluent antibacterial activity, which were assessed in this work. As compared with batch operation, the irradiation time needed for SMX elimination under continuous flow mode sharply decreased, which is very advantageous for the target application. Moreover, the interrelation between SMX removal, mineralization and antibacterial activity was evaluated before and during photodegradation in ultrapure water. Although mineralization was slower than SMX removal, bacterial activity increased after SMX photodegradation. Such increase was also verified in environmental water matrices. Thus, this study has proven that photodegradation is an efficient and sustainable process for both (i) the remediation of waters contaminated with antibiotics, and (ii) the minimization of the bacterial resistance.

Determination of estrone and 17α-ethinylestradiol in digested sludge by ultrasonic liquid extraction and high-performance liquid chromatography with fluorescence detection.

Estrone, 17ß-estradiol and 17α-ethinylestradiol are increasingly recognised as important micropollutants to be monitored in wastewater treatment plants. These estrogens are retained onto sludge due to their high adsorption and since they are largely used in land applications, the monitoring of these chemicals in sludge samples is of great importance. This study describes a method for the determination of estrone and 17α-ethinylestradiol in fresh sludge samples. After spiking fresh digested sludge with estrone and 17α-ethinylestradiol and maintaining in contact during 5, 30 and 60 min, the freeze-dried samples were subjected to ultrasonic liquid extraction, with methanol and acetone, and analysed by high-performance liquid chromatography with fluorescence detection. The average recoveries obtained for estrone and 17α-ethinylestradiol using the different contact times were 103 ± 3 and 97 ± 4%, respectively. Fresh sludge samples from one waste water treatment plant located in Portugal were analysed and estrone was detected in primary fresh sludge, anaerobic digested sludge and dehydrated sludge at a concentration in the range of 1-4.8 µg/g. The method here developed does not require any sample clean-up, being fast and simple, reliable and inexpensive, making possible its application for monitoring the contamination of sludge with these estrogens.

Photodegradation of sulfamethoxazole in environmental samples: The role of pH, organic matter and salinity.

Sulfamethoxazole (SMX) is the most representative antibiotic of the sulfonamides group used in both human and veterinary medicine, and thus frequently detected in water resources. This has caused special concern due to the pronounced toxicity and potential to foster bacterial resistance of this drug. Therefore, and to further understand the fate of SMX in the aquatic environment, its photodegradation under simulated solar radiation was here studied in ultrapure water and in different environmental samples, namely estuarine water, freshwater and wastewater. SMX underwent very fast photodegradation in ultrapure water, presenting a half-life time (t1/2) of 0.86 h. However, in environmental samples, the SMX photodegradation rate was much slower, with 5.4 h < t1/2 < 7.8 h. The main novelty of this work was to prove that pH, salinity and dissolved organic matter are determinant factors in the decrease of the SMX photodegradation rate observed in environmental samples and, thus, they will influence the SMX fate and persistence, potentially increasing the risks associated to the presence of this pollutant in the environment.

Optimization of a dispersive liquid-liquid microextraction method followed by UHPLC analysis for fluoxetine quantification in environmental water resources.

Fluoxetine is the most prescribed drug for treatment of depression. Recently, its presence in aquatic environment has been receiving a growing interest as several studies assessed its effects on aquatic fauna. Therefore, it's important to have an analytical method capable of monitoring these compounds at low concentrations. In this study, a new method was developed based on dispersive liquid-liquid microextraction to preconcentrate fluoxetine in a small volume of water sample (6 mL) before chromatographic analysis using ultra high performance liquid chromatography with fluorescence detection. Effect of composition and volume of extracting mixture, sample pH, vortexing time and salt addition were evaluated. Optimization of extraction conditions lead to an enrichment factor of 61 ± 18. After extraction optimization, recovery percentages of fluoxetine spiked into different water matrices between 83-110% were obtained. For the optimized method, the calibration curve was obtained in the range of 160-2500 ng/L with a limit of detection of 98.9 ng/L and a limit of quantification of 329.8 ng/L.

Dispersive liquid-liquid microextraction for the quantification of venlafaxine in environmental waters.

The present work describes a new methodology for the detection of the antidepressant venlafaxine (VEN) in aquatic environments using dispersive liquid-liquid microextraction followed by high performance liquid chromatography with fluorescence detection (DLLME-HPLC-FLD). The method developed is fast, low cost, easy to apply, uses a small volume of organic solvents and allows the simultaneous extraction of various samples. The DLLME-HPLC-FLD method presented a linearity range from 25 to 1500 ng L-1, a detection limit of 24.2 ±â€¯0.2 ng L-1, and an enrichment factor of 75 ±â€¯4. Recovery tests using solutions of NaCl and humic acids showed that ionic strength and organic matter do not influence the efficiency of the extraction, with extraction recoveries above 77%. Finally, the optimized method was applied to the analysis of water samples from different origins and VEN was only detected in one water sample obtained from a waste water treatment plant (WWTP), which had a concentration of 175 ±â€¯5 ng L-1. Recovery tests performed in environmental aquatic samples demonstrated that the developed extraction procedure is not influenced by the complex water matrices, with results ranging from 76 to 93%.

Simultaneous extraction and concentration of water pollution tracers using ionic-liquid-based systems.

Human activities are responsible for the release of innumerous substances into the aquatic environment. Some of these substances can be used as pollution tracers to identify contamination sources and to prioritize monitoring and remediation actions. Thus, their identification and quantification are of high priority. However, due to their presence in complex matrices and at significantly low concentrations, a pre-treatment/concentration step is always required. As an alternative to the currently used pre-treatment methods, mainly based on solid-phase extractions, aqueous biphasic systems (ABS) composed of ionic liquids (ILs) and K3C6H5O7 are here proposed for the simultaneous extraction and concentration of mixtures of two important pollution tracers, caffeine (CAF) and carbamazepine (CBZ). An initial screening of the IL chemical structure was carried out, with extraction efficiencies of both tracers to the IL-rich phase ranging between 95 and 100%, obtained in a single-step. These systems were then optimized in order to simultaneously concentrate CAF and CBZ from water samples followed by HPLC-UV analysis, for which no interferences of the ABS phase-forming components and other interferents present in a wastewater effluent sample have been found. Based on the saturation solubility data of both pollution tracers in the IL-rich phase, the maximum estimated concentration factors of CAF and CBZ are 28595- and 8259-fold. IL-based ABS can be thus envisioned as effective pre-treatment techniques of environmentally-related aqueous samples for a more accurate monitoring of mixtures of pollution tracers.

Salicylic acid determination in estuarine and riverine waters using hollow fiber liquid-phase microextraction and capillary zone electrophoresis.

A low-cost methodology using hollow fiber liquid-phase microextraction (HF-LPME) and capillary zone electrophoresis (CZE) with UV-Vis detector was developed to analyze the salicylic acid (SA) in estuarine and riverine waters. The technique is easy-to-use and rapid, and demands little volume of organic solvent. The extraction was carried out using a polypropylene membrane supporting into octan-1-ol. HF-LPME under optimized conditions (donor solution sample pH 2, acceptor solution pH 14, sample volume 25 mL, fiber length 10 cm, acceptor volume 25 µL, extraction time 3 h and stirring speed 350 rpm) presented high enrichment factor (407 times) and good recovery in real water samples (from 88 to 110%). A limit of detection of 2.6 µg L-1 was achieved using CZE with UV-Vis detector as quantification method. The method was applied to direct quantification of SA in environmental complex estuarine and riverine water matrices.

Photodegradation behaviour of estriol: An insight on natural aquatic organic matter influence.

Estriol (E3) is one of the steroidal estrogens ubiquitously found in the aquatic environment, photodegradation being an important pathway for the elimination of such endocrine disrupting compounds. However, it is important to understand how environmentally important components present in aquatic matrices, such as organic matter, may affect their photodegradation. The main objective of this work was to investigate the photodegradation of E3 in water, under simulated solar radiation, as well as the effect of humic substances (HS - humic acids (HA), fulvic acids (FA) and XAD-4 fraction) in E3 photodegradation. Moreover, the photodegradation behaviour of E3 when present in different environmental aquatic matrices (fresh, estuarine and waste water samples) was also assessed. Results showed a completely different E3 degradation rate depending on the aquatic matrix. In ultrapure water the half-life obtained was about 50 h, while in presence of HS it varied between 5 and 10 h. Then, half-life times between 1.6 and 9.5 h were determined in environmental samples, in which it was observed that the matrix composition contributed up to 97% for the overall E3 photodegradation. Therefore, E3 photodegradation in the considered aquatic matrices was mostly caused by photosensitizing reactions (indirect photodegradation).