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.

The principal objective of the present research involved the achievement of high biodegradation degrees of perfluorooctanoic acid (PFOA) and perfluorosulfonic acid (PFOS) using pure individual bacterial strains. The use of such microorganisms can contribute to the improvement of the wastewater treatment process in sewage treatment plants through bioaugmentation or other bioremediation processes. Thus, in this study, we investigated the biodegradation potential of PFOA and PFOS. Bacterial strains tested in this study were from the Pseudomonas genus, namely: Pseudomonas aeruginosa and Pseudomonas putida, due to their known capacity to degrade xenobiotic compounds. The results indicated that Pseudomonas aeruginosa was able to transform 27.9% of PFOA and 47.3% of PFOS in 96 h, while Pseudomonas putida managed to transform 19.0% of PFOA and 46.9% of PFOS in the same time frame. During the biodegradation tests, PFHxA was recognized as the principal biotransformation product of PFOA in the presence of Pseudomonas aeruginosa, and PFPeA, PFPxA and PFHpA were recognized as the biotransformation products in the presence of Pseudomonas putida. For PFOS, only two biotransformation products (PHHxA and PFHpA) were observed as a consequence of biodegradation by both bacterial strains.

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.