Laura Bulgariu

This study examines the potential of physically activated PET fibers (PA-PET) as an adsorbent for adsorption of two antibiotics (rifampicin (RIF) and rifaximin (RIX)) from aqueous solution. To evaluate the performance of PA-PET, the effects of the initial antibiotic concentration and the contact time were experimentally investigated at pH 2.0 and an adsorbent dosage of 0.4 g/L. While no notable differences were observed regarding the contact time, equilibrium being reached after 180 min, similar to raw PET fibers, a significant increase in adsorption capacity was recorded across the entire range of initial antibiotic concentrations. The highest increases in adsorption capacity were obtained at RIF concentrations of 68 mg/L, where the adsorption capacity increased by more than 107%, and at RIX concentrations of 4.28 mg/L, where the increase reached approximately 84%, compared with the raw PET fibers. To further highlight the performance of PA-PET in the adsorption of RIF and RIX, the isotherm and kinetic data were modeled. Desorption of RIF and RIX from PA-PET was carried out using a medical-grade polyelectrolyte solution (SL) as the desorbing agent. Although the desorption efficiency is relatively modest (below 33% for RIF and 26% for RIX, after 360 min), the molecular structure of RIF and RIX does not change after desorption, and antibiotics can be reintroduced into the technological circuit. These results demonstrate that PA-PET is as a promising, low-cost, and efficient adsorbent for antibiotic removal, offering a practical solution for pollution reduction and more sustainable waste management.

This study examines the potential of physically activated PET fibers (PA-PET) as an adsorbent for the removal of two antibiotics (rifampicin (RIF) and rifaximin (RIX)) from aqueous solution. To evaluate the performance of PA-PET, the effects of the initial antibiotic concentration and the contact time were experimentally investigated at pH 2.0 and an adsorbent dose of 0.4 g/L. If in the case of contact time there are no notable differences (equilibrium being reached after 180 min., similar to raw PET fibers), in the case of the initial concentration of antibiotics a significant increase in adsorption capacity was observed. The highest increases in adsorption capacity were obtained at RIF concentrations of 68 mg/L, where the adsorption capacity increased by more than 107%, and at RIX concentrations of 4.28 mg/L, where the increase reached approximately 84%, compared with the raw PET fibers. To further highlight the performance of PA-PET in the adsorption of RIF and RIX, the isotherm and kinetic data were modeled. Desorption of RIF and RIX from PA-PET was carried out using a medical-grade polyelectrolyte solution (SL) as the desorbing agent. Although the desorption efficiency is relatively modest (below 33% for RIF and 26% for RIX, after 360 min), the molecular structure of RIF and RIX does not change after desorption, and antibiotics can be reintroduced into the technological circuit. These results demonstrate that PA-PET is as a promising, low-cost, and efficient adsorbent for antibiotic removal, offering a practical solution for pollution reduction and more sustainable waste management.

The synthesis of precious metal nanoparticles (PM-NPs) is an important field of research that has expanded significantly in recent decades due to their numerous applications. Therefore, research has been directed toward developing green methods for the synthesis of such nanoparticles that are simple, safe, eco-friendly, efficient, and sustainable. In this context, the use of marine algae biomass for the green synthesis of PM-NPs can be a viable large-scale alternative, as algae are easy to cultivate, have a rapid growth rate, and are widely distributed across many regions of the globe. The reduction of precious metal ions takes place at the surface of algae biomass particles, and the characteristics of the resulting precious metal nanoparticles depend on the experimental conditions (pH, amount of algae biomass, contact time, etc.), as well as on the type of algae biomass and the speciation form of the metal ions in the solution. All these factors significantly influence the properties of precious metal nanoparticles, and their understanding allows the development of synthesis strategies that can be applied on a large scale. The aim of this review is to provide a comprehensive overview of the way in which PM-NPs can be synthesized using algae biomass. The importance of experimental conditions (such as pH, contact time, amount of biomass, type of algal biomass, temperature, etc.) on the synthesis efficiency, as well as the elementary steps involved in the synthesis, is also discussed in this study. Particular attention has been paid to the analytical methods used for characterizing PM-NPs, as they provide crucial data regarding their structure and composition. These aspects are essential for identifying the practical applications of PM-NPs.

The synthesis of precious metal nanoparticles (PM-NPs) is an important field of research that has expanded significantly in recent decades due to their numerous applications. Therefore, research has been directed toward developing green methods for the synthesis of such nanoparticles that are simple, safe, eco-friendly, efficient and sustainable. In this context, the use of marine algae biomass for the green synthesis of PM-NPs can be a viable large-scale alternative, as algae are easy to cultivate, have a rapid growth rate, and are widely distributed across many regions of the globe. The reduction of precious metal ions takes place at the surface of algae biomass particles, and the characteristics of the resulting precious metal nanoparticles depend on the experimental conditions (pH, amount of algae biomass, contact time, etc.), as well as on the type of algae biomass and the speciation form of the metal ions in the solution. All these factors significantly influence the properties of precious metal nanoparticles, and their understanding allows the development of synthesis strategies that can be applied on a large scale. The aim of this review is to provide a comprehensive overview of how PM-NPs can be synthesized using algae biomass. The importance of experimental conditions (such as pH, contact time, amount of biomass, type of algal biomass, temperature, etc.) on the synthesis efficiency, as well as the elementary steps involved in the synthesis, are also discussed in this study. Particular attention has been paid to the methods used for characterizing PM-NPs, as they provide crucial data regarding their structure and composition. These aspects are essential for identifying the practical applications of PM-NPs.

The removal of antibiotics from aqueous media along with their recovery is still an open research topic, due to their practical and economical importance. Adsorption allows these two objectives to be achieved, provided that the adsorbent used is chemically and mechanically stable and has a low preparation cost. In this study, PET (polyethylene terephthalate) fibers, obtained by mechanically processing PET waste, were used for the adsorption of rifampicin (RIF) and rifaximin (RIX) antibiotics from aqueous media. The experimental adsorption capacity of PET fibers for the two antibiotics (RIF and RIX) was determined at different pH values (2.0–6.5), adsorbent dose (0.4–20.0 g/L), contact time (5–1440 min), initial antibiotic concentration (4.0–67.0 mg/L), and temperature (10, 22, and 50 °C); the experimental values of these parameters were analyzed using a neuro-evolutive technique (ANE) combining sequential deep learning (DL) models with a differential evolution algorithm. The obtained optimal ANN-DL algorithm was then used to obtain the optimal models for the adsorption of RIF and RIX on PET fibers, which should adequately describe the adsorption dynamics for both antibiotics. The adsorption processes are spontaneous and endothermic (ΔG < 0, ΔH > 0) and are described by the Langmuir model (R² > 0.97) and the pseudo-second order kinetic model (R² > 0.99). The retention of RIF and RIX on the surface of PET fibers occurs through physicochemical interactions, and the FTIR spectra and microscopic images support this hypothesis. The presence of inorganic anions in the aqueous solution leads to an increase in the adsorption capacities of RIF (max. 7.6 mg/g) and RIX (max. 3.6 mg/g) on PET fibers, which is mainly due to the ordering of water molecules in the solution. The experimental results presented in this study allowed for the development of the adsorption mechanism of RIF and RIX on PET fibers, highlighting the potential practical applications of these adsorption processes.

The removal of antibiotics from aqueous media along with their recovery is still an open research topic, due to their practical and economical importance. Adsorption allows these two objectives to be achieved, provided that the adsorbent used is chemically and mechanically stable and has a low preparation cost. In this study, PET (polyethylene terephthalate) fibers, obtained by mechanically processing of PET waste, were used for the adsorption of rifampicin (RIF) and rifaximin (RIX) antibiotics from aqueous media. The experimental adsorption capacity of PET fibers for the two antibiotics (RIF and RIX) was determined at different pH values (2.0-6.5), adsorbent dose (0.4-20.0 g/L), contact time (5-1440 min), initial antibiotic concentration (4.0-67.0 mg/L) and temperature (10, 22, and 50°C), and the experimental values of these parameters were analyzed using a neuro-evolutive technique (ANE) combining sequential deep learning (DL) models with Differential Evolution algorithm. The obtained optimal ANN-DL algorithm was then used to obtain the optimal models for the adsorption of RIF and RIX on PET fibers, which should adequately describe the adsorption dynamics for both antibiotics. The adsorption processes are spontaneous and endothermic (ΔG < 0, ΔH > 0), and are described by the Langmuir model (R2 > 0.97) and the pseudo-second order kinetic model (R2 > 0.99). The retention of RIF and RIX on the surface of PET fibers occurs through physicochemical interactions, and the FTIR spectra and microscopic images support this hypothesis. The presence of inorganic anions in the aqueous solution leads to an increase in the adsorption capacities of RIF (max. 7.6 mg/g) and RIX (max. 3.6 mg/g) on PET fibers, which is mainly due to the ordering of water molecules in the solution. The experimental results presented in this study allowed the development of the adsorption mechanism of RIF and RIX on PET fibers, and highlight the potential practical applications of these adsorption processes.

In this study, kaolinite-based clay (Ka-Clay) was used as an adsorbent for the efficient removal of Pb(II), Cd(II) and Hg(II) ions from aqueous media. The selection of Pb(II), Cd(II) and Hg(II) ions for experimental studies took into account their high toxicity, while the choice of Ka-Clay, the ease of preparation and high availability of this material were the most important arguments. Ka-Clay exhibits high adsorption performance, with removal percents over 98% for Pb(II) and 93% for Cd(II), even at high concentrations of metal ions (over 150 mg/L, pH = 6.5, 4 g adsorbent/L, 21 ± 1 °C). For Hg(II) ions, the adsorption percent does not exceed 55%, and this moderate value is mainly due to the significant change in pH. The adsorption behavior was in accordance with the Langmuir model (R² > 0.95) and the pseudo-second order kinetic model (R² > 0.99), indicating an adsorption process that occurs mainly through chemical interactions at the adsorbent surface between the metal ions and the functional groups. Adsorption processes are spontaneous (ΔG = −8.66 ÷ −15.76 kJ/mol) and endothermic (ΔH = 7.09 ÷ 21.81 kJ/mol), and the adsorption mechanism is the results of elementary processes of electrostatic attraction, ion exchange and superficial complexation. The insignificant effect of other ions (Ca(II), Mg(II), Na(I), K(I)) present in real wastewater samples as well as the desorption behavior of exhausted adsorbent highlight the practical utility of this adsorbent on a large scale. The experimental results included in this study suggest that Ka-Clay can be used as a promising adsorbent for the removal of high concentrations of toxic heavy metals with low cost and high efficiency, and this can contribute to the design of a sustainable wastewater treatment method.

The discharge of industrial effluents containing toxic heavy metals in water sources has serious consequences for human health and the environment, and biosorption appears to be an environmentally-friendly and cost-effective alternative that can be used for wastewater treatment. The use of different types of agricultural waste as biosorbents for the removal of toxic heavy metals, although an alternative, is quite difficult to apply in practice because these wastes have many other uses. Based on these considerations, in this study, soybean biomass (SB), soybean waste biomass obtained from oil extraction (SBW), and biochar obtained from soybean waste pyrolysis (BC-SBW) were tested as biosorbents for removing Pb(II) and Cd(II) ions, in batch systems. Under optimal conditions (pH = 5.4, 4.0 g biosorbent/L, room temperature (25 ± 1 °C), contact time = 180 min), the biosorption capacity increases in the order SB < SBW < BC-SBW for both metal ions (Pb(II) ions (69.43 mg/g < 99.81 mg/g < 116.83 mg/g) and Cd(II) ions (25.63 mg/g < 36.12 mg/g < 49.10 mg/g)), indicating that BC-SBW has the highest efficiency in removing toxic heavy metals. In addition, experiments on wastewater samples have shown that, in addition to significantly reducing the content of heavy metals, BC-SBW also significantly improved other quality indicators (such as pH, TSM (total suspended matter), COD (chemical oxygen demand), BOD5 (biochemical oxygen demand)), compared to the other biosorbents (SB and SBW). Quantitative evaluation of the biosorption performance of each biosorbent (SB, SBW, and BC-SBW) shows that BC-SBW has a real chance of being used on an industrial scale for wastewater treatment. All these aspects allowed the development of a circular approach for the use of soybean biomass in the removal processes of toxic heavy metals. This approach minimizes the shortcomings of using biomass as a biosorbent and increases the chance of using these materials in industrial practice.