Adsorption site-dependent transport of diclofenac in water saturated minerals and reference soils

Fate, transformation and toxicological implications of environmental diclofenac: Role of mineralogy and solar flux

Diclofenac is an emerging surface water contaminant, yet the environmental impact of its degradation products remains elusive. The current study focuses on mineralogy-controlled diclofenac photo-degradation and its potential health impacts. Under irradiated conditions, we studied the effects of kaolinite, hematite, and anatase on diclofenac degradation. Our results showed that kaolinite doubled the diclofenac degradation rate, which can be attributed to the high catalytic effect, mediated via increased surface area and pore size of mineral surface in the low pH. Conversely, anatase, a crystal phase of titanium dioxide (TiO₂), diminished the diclofenac degradation compared to treatments without TiO₂. Hematite, on the other hand, showed no effect on diclofenac degradation. Photo-degradation products also varied with the mineral surface. We further assessed in vitro toxicological effects of photo-degraded products on two human cell lines, HEK293T and HepG2. Biological assays confirmed that photo-degraded compound 6 (1-(2,6-dichlorophenyl)indolin-2-one) decreased HEK293T cell survival significantly (p < 0.05) when compared to diclofenac in all concentrations. At lower concentrations, inhibition of HEK293T cells caused by compounds 4 (2-(8-chloro-9H-carbazol-1-yl)acetic acid), and 5 (2-(9H-carbazol-1-yl)acetic acid) was greater than diclofenac. Compound 7 (1-phenylindolin-2-one) was toxic only at 250 µM. Additionally, compound 6 decreased HepG2 cell viability significantly when compared to diclofenac. Overall, our data highlighted that mineralogy plays a vital role in environmental diclofenac transformation and its photo-degraded products. Some photo-degraded compounds can be more cytotoxic than the parent compound, diclofenac.

Green Blends Based on Ionic Liquids with Improved Performance for Membrane Technology: Perspectives for Environmental Applications

Present research was directed towards the development of new high-performance and cost-effective polysulfone membranes (PSFQ) by introducing ionic liquids (ILs—Cyphos 101 IL and Aliquat 336) into their matrix. Variation of ILs was performed with the aim to find the one that brings new properties and improves the functionality and selectivity of PSFQ membranes in ultrafiltration processes. Based on the obtained results of the rheological study, we established the compatibility of compounds and optimal content of the used ILs, namely 3 wt% and 15 wt% Cyphos 101 IL and compositions varying between 3 and 15 wt % Aliquat 336. Results indicated that the ILs acted as plasticizers when they were added to the system, a helpful aspect in processing membranes used in water decontamination. The efficiency and performance of the membranes were evaluated by their use in the treatment of diclofenac (DCF)-containing waters. Membranes obtained from PSFQ/Aliquat 336 solution containing 15 wt% IL exhibited a 97% removal degree of DCF in the treatment process of 50 mL solution containing 3 mg/L DCF. The separation efficiency was kept constant for four filtration/cleaning cycles. The results indicated an improvement in membrane performance as the amount of IL in their structure increased, which confirms the potential for application in water treatment processes.

Effects of Al substitution on sorption of diclofenac to Fe(III) (hydr)oxides: roles of phase transition and sorption mechanisms

Fe(III) (hydr)oxides commonly contained many metal impurities such as Al. The incorporation of Al might change the properties of minerals and consequently affect sorption behaviors of pollutants with polar functional groups (e.g., diclofenac (DCF)). In this study, batch experiments and microscale characterization were conducted to investigate the DCF sorption mechanisms to goethite and Al-substituted minerals. Goethite and Al-substituted products (including Al-goethite, Al-goethite-hematite, and Al-hematite) were synthesized with different Al contents (i.e., 0%, 5%, 10%, and 15% (in mol)) by co-precipitation method. Due to difference of ionic radius between Al and Fe and formation of excessive -OH, Al substitution resulted in deviation of cell parameters from the Vegard line. Al substitution caused increasing -OH in Al-goethite and phase transformation caused decreasing -OH in Al-hematite. The total -OH in minerals was positively related to DCF sorption capacity. In the lower initial concentration range (0.4-9 mg/L), the sorption distribution coefficient (Kd) values of goethite, Al-goethite, and Al-hematite were 21.98, 22.25, and 21.18 L/kg, respectively. Desorption characteristics and ion strength effects indicated that DCF sorption to minerals occurred mainly through outer-sphere complexation. Fourier transform infrared analyses revealed that H-bonds could be formed through -OH of minerals and -COOH of DCF, and the H-bond strength on Al-hematite was stronger than that on goethite/Al-goethite. In the normal environmental pH (e.g., 6.0 to 8.0), Kd values of DCF decreased linearly with increasing pH. These findings are helpful for understanding of DCF migration in environment involving Al-substituted minerals.

Diclofenac degradation based on shape-controlled cuprous oxide nanoparticles prepared by using ionic liquid

Persulfate oxidation technology is widely used in wastewater treatment, but there are still many disadvantages, such as high energy consumption, side reaction and narrow pH applicability. Copper oxides can activate persulfate steadily with higher efficiency. In this paper, a novel preparation method of shape-controlled cuprous oxide (Cu₂O) nanoparticles featured with high catalytic performance was explored. It was found that adding ionic liquid 1-butyl-3-methylimidazolium bromide ([BMIM]Br) during preparation of Cu₂O can improve the degradation rate of diclofenac (DCF). Cu₂O nanoparticles possess good stability in consecutive cycling tests, which was confirmed by X-ray photoelectron spectroscopy. The possible mechanism of Cu₂O activating persulfate at different initial pH conditions was discussed based on electron paramagnetic resonance spin-trapping experiment. It was found that DCF was efficiently degraded in the Cu₂O/peroxydisulfate (PDS) system within a broad pH range from 5 to 11. It proved via a quenching experiment that the activation process of PDS mainly occurs on the surface layer of Cu₂O nanoparticles. As a result, shape-controlled Cu₂O nanoparticles prepared by ionic liquid are expected to be used for in situ chemical oxidation, which is an effective oxidation processes to degrade DCF remaining in surface water and ground water.

Approach to the Dynamic of Carbamazepine and its Main Metabolites in Soil Contamination through the Reuse of Wastewater and Sewage Sludge

The release of pharmaceutically active compounds to the soils through the application of sewage sludge and the irrigation with wastewater, or even with surface water, is constant. The adsorption of these compounds onto the soil is one of the key factors affecting their fate in the environment and their potential environmental risks. In this work, the adsorption of carbamazepine (CBZ) and its metabolites, 3-hydroxy-carbamazepine (3OH-CBZ), carbamazepine-10,11-dihydro-10,11-epoxide (EP-CBZ), and 10,11-dihydro-10-hydroxycarbamazepine (10OH-CBZ), in three Mediterranean soils was evaluated using single-solute and four-solute experiments. The highest adsorptions were measured for 3OH-CBZ, followed by CBZ, EP-CBZ, and 10OH-CBZ, in that order. A high influence of the physicochemical characteristics of the compounds, pH, and soil characteristics in the adsorption of the studied compounds was observed and corroborated by the statistical analysis of the results. Moreover, a good fit was observed in the three isotherm models evaluated (linear, Freundlich, and Langmuir) in single-solute experiments (R² > 0.90). However, a decrease of the measured adsorptions and a worse fit to the isotherm models were observed in the case of multiple-solute experiments. This could be mainly due to the competition established between the studied compounds for the active sites of the soils.

Adsorption, Bioavailability and Microbial Toxicity of Diclofenac in Agricultural Soil

Persistence and environmental implication of pharmaceuticals in agricultural soil is determined depending on adsorption, bioavailability and toxicity. This study aims to assess adsorption/partitioning behaviour of diclofenac (DCF) and its impact on microbial activity in four agricultural soils, differing in pH, organic carbon content, and cation exchange capacity. Results from batch studies suggests that soil/water partition coefficients of DCF are essentially nonlinear, i.e. depends on drug amount (p = 0.001), and positively correlated with soil organic carbon (p = 0.008). The adsorption data can effectively be modelled using Freundlich isotherm (regression coefficients between 0.84 and 0.90). In soil incubation studies, DCF could not be detected after 6 days of spiking (20 µg/g) in all soil types, including abiotic control. This suggests an interplay of combined biotic/abiotic process in DCF removal. Though microbial activity (based on tetrazolium reduction) declined with incubation time, but was not correlated with DCF exposure, particularly in soils rich in organic carbon.