The increasing presence of plastics in the environment has raised concerns about their potential impact, especially as carriers of heavy metals such as Cd, Ni, and Pb. However, the adsorption mechanism of heavy metals on microplastics remains poorly understood. In this study, we investigated the adsorption behavior of Cd, Ni, and Pb by polystyrene (PS) and polypropylene (PP) microplastics to better comprehend their interaction and potential environmental implications. Our results revealed that equilibrium adsorption of microplastics with different heavy metals was achieved within a 6-h contact time. The FTIR analysis findings, which suggest that physical interactions play a significant role in the adsorption of heavy metals onto microplastics, are further supported by the observed changes in surface morphology after adsorption. We explored the influence of solution pH, contact duration, and initial concentration on the adsorption capacity and found significant effects on the adsorption behavior. To model the adsorption process, we applied Langmuir and Freundlich adsorption isotherm models and observed that the Langmuir model better fit the experimental data. Furthermore, we compared the pseudo-first and pseudo-second-order kinetic models and found that the pseudo-second-order model provided a more accurate description of the adsorption kinetics. Notably, the adsorption percentages varied depending on the type of microplastic and experimental conditions. Overall, this study enhances our understanding of the adsorption mechanism of heavy metals on microplastics and provides valuable insights into their behavior in aquatic environments. These findings have implications for the development of effective strategies for mitigating pollution caused by microplastics and heavy metals in aquatic ecosystems.

This research investigates commercial activated carbon (AC) potential to remove methyl orange (MO) dye removal from aqueous solution using a batch process. The AC material was characterized using FTIR spectroscopy and SEM analysis. The effect of the main operating parameters, such as the pH, adsorbent dosage, contact time, and initial dye concentration, was studied. MO removal could be accomplished within 30 min at a pH value of 3. The calculated maximum MO adsorption capacity onto activated carbon was 129.3 mg/g, while the removal efficiency was 97.8%. Adsorption results were analyzed by studying the Langmuir and Freundlich isotherm models. The MO adsorption data on activated carbon were better explained by the Langmuir isotherm than by the Freundlich isotherm. The pseudo-second-order kinetic model may have had an effect on the MO dye adsorption on AC material. This research showed that the commercial activated carbon can be used as an effective sorbent for MO removal from wastewater sample. Moreover, the AC material has good reusability and practical utilization capacities.

This paper is aimed at assessing the occurrence, fate, transport and ecological risk of ten organic UV filters in the aquatic environment of Romania. In influents, the highest concentration levels were determined for benzophenone-1 and 2,3,4-trihydroxybenzophenone with values of thousands of ng L⁻¹ (up to 2787 and 1108 ng L⁻¹, respectively). In the sewage sludge samples, the predominant contaminants were those with high hydrophobicity, namely benzyl salicylate, homosalate and ethylhexyl salicylate (up to 1395, 1035 and 688 ng g⁻¹ dw, respectively). Although the removal efficiency of these organic micropollutants in the WWTPs proved to be quite high, over 60% of the UV filters monitored, some of them were also detected in effluents, in relatively high concentrations. Thus, the effluents were dominated by ethylhexyl salicylate and benzophenone-1 with concentrations up to 219 and 181 ng L⁻¹, respectively. In surface waters, the most abundant compounds were found to be benzophenone-1, benzophenone-8 and 4-hydroxybenzophenone, with values up to 206, 108 and 159 ng L⁻¹ respectively. On calculating the risk coefficient of the organic UV filters investigated on various aquatic species, it was observed that for fish, benzophenone-2 presents a medium risk both in effluents and in samples taken downstream of the WWTPs, while benzophenone-1 presents a high risk also in effluents as well as in surface waters taken upstream and downstream of the WWTPs. Among the salicylate derivatives, homosalate was found to present a medium risk for Daphnia magna in both effluents and samples taken downstream of the WWTPs, while ethylhexyl salicylate posed a high risk for freshwater algae in all three types of analyzed samples.

Pharmaceuticals are emerging contaminants in waste waters from where they are discharged into surface water, so they may be harmful to aquatic organisms. Beta-blockers are consumed in high tonnage every year owing to the rise in cardiovascular disease of the population, and are incompletely metabolized. They are eliminated from the body as the parent drugs or as metabolites into wastewater. A sensitive method using off-line solid-phase extraction (SPE) and liquid chromatography coupled with mass spectrometry (LC-MS/MS) has been developed for the determination of 6 beta-blockers (bisoprolol, nadolol, betaxolol, atenolol, propranolol, pindolol) and one metabolite (4-hydroxy propranolol) in the influents and effluents of three urban waste water treatment plants (WWTPs). Extraction of the compounds was performed on Oasis C18 cartridges at pH 10 adjusted with ammonium hydroxide. As the LC mobile phase, formic acid 0.1% in water and methanol in gradient elution was used to separate the analytes in 13 minutes on a Luna C18 column kept at 45 °C. A linear response was obtained for all substances in the range of 1–100 ng mL⁻¹ with determination coefficients >0.99. The parameters of the SPE procedure and of the LC-MS method were optimized to obtain the best results. The method was validated and beta-blocker recoveries after SPE in waste water were in the range of 71.2–103.3% with satisfactory intra-day and inter-day precision (RSD%) being located between 4.7 and 8.4%, and 8.1 and 14.4%, respectively. Optimization of LC-MS parameters generated low LOQ values between 0.34 and 7.37 ng mL⁻¹. Atenolol was detected in all samples at higher average concentrations which ranged between 94.6 ng L⁻¹ and 208.6 ng L⁻¹ (effluent samples, influents). The other 3 beta-blockers: bisoprolol, betaxolol and propranolol were detected in influents in mean concentrations of 100.1 ng L⁻¹, 44.9 ng L⁻¹ and 26.8 ng L⁻¹ and in effluents in mean concentrations of 51 ng L⁻¹, 16.9 ng L⁻¹ and 19.4 ng L⁻¹. Propranolol was eliminated with the lowest average yields ranging from 25.19% to 31.78%, whereas atenolol, bisoprolol and betaxolol were eliminated from WWTPs with average yields ranging from 44.97 to 60.96%, 46.8 to 52.9% and 47.05 to 69.08%, respectively. Results obtained suggest that the adopted wastewater treatment processes are not efficient to remove these compounds and by penetrating into surface waters through evacuated effluents they can adversely affect aquatic organisms.

This study investigated the occurrence and transport of four isothiazolinone-type biocides from commercial products to wastewater treatment plants (influents, sludges, and effluents) and to natural emissaries (upstream and downstream the wastewater treatment plants) in Romania. All four biocides were determined in personal care and household products, with the highest concentration of 76.4 µg/L OIT (2-octyl-4-isothiazolin-3-one). For environmental samples, three of the four isothiazolinones were determined, CMI (5-chloro-2-methyl-4-isothiazolin-3-one) being the prominent compound for water samples. The maximum concentration of 84.0 µg/L in influent, 122 µg/L upstream, and 144 µg/L downstream the wastewater treatment plants were obtained for CMI. Unlike water samples, in the sewage sludge samples, OIT proved to be the dominant compound, with concentration up to 5.80 µg/g d.w. The extremely high levels of isothiazolinone determined in different WWTPs from Romania may be due to the COVID-19 pandemic situation, during which a much larger amount of cleaning, hygiene, and personal care products was used. The isothiazolinone-type biocides were readily removed from the influents of the five WWTPs, with the mean removal rate up to 67.5%. The mean mass loading value for the targeted biocides based on influent was 20.4 μg/day/1000 people, while the average environmental emissions were 6.93 μg/day/1000 people for effluents. The results obtained for riverine water combine with statistical analysis showed that the anthropogenic activities are the major contamination sources of the surface waters. Preliminary ecological risk evaluation showed that BIT (1,2-benzisothiazol-3(2H)-one), OIT, and CMI could pose a very high risks to different aquatic species living in the receiving aquatic environments.