Modification of Chlorella vulgaris carbon with Fe3O4 nanoparticles for tetracycline elimination from aqueous media

Tetracycline (TTC) is an antibiotic commonly prescribed to treat bacterial infections in animals and humans because of its low toxicity and antibacterial activity. This study focuses on the removal of TTC from an aqueous media using an activated carbon of Chlorella vulgaris modified with Fe3O4 magnetic composite (ACCV/Fe3O4 mc). The isothermal and kinetic models were studied to understand the adsorption mechanism. The Box-Behnken model was used for experimental design, and the main research parameters were ACCV/Fe3O4 mc mass (0.2–0.8 g/L), reaction time (10–60 min), TTC concentration (5–30 mg/L), and pH (3–11). The highest TTC removal rate of 90.47% was obtained at a pH of 7, a time of 60 min, an ACCV/Fe3O4 mc mass of 0.5 g/L, and an antibiotic concentration of 5 mg/L. TTC removal was fitted with the pseudo-second-order and the Langmuir model. The Langmuir adsorption capacity of TTC was computed to be 26.18 mg/g. The results show that the ACCV/Fe3O4 mc adsorbent significantly removes TTC from the aqueous solution

Aging effect on the adsorption behavior of microfibers obtained from cigarette butts in aqueous solutions

Abstract The issue of cigarette butts is an environmental crisis that has affected the world. Despite their small size, CBs are one of the most common types of solid waste found in public places, particularly in coastal areas. The aim of this study was to investigate the adsorption behavior of microfibers obtained from cigarette butts on tetracycline before and after aging. 1 g of CBs was added to 50 mL of distilled water and stirred at 220 rpm for 2 h, then filtered through Whatman 0.45 µm filter paper, and the resulting MFs were dried at 60 °C for 24 h. To simulate aging, the MFs were subjected to an ultrasonic treatment at a frequency of 80 Hz and a power of 70 W for 4 h. The adsorption behavior of aged and fresh MFs was investigated using solutions containing TTC in the range of 5–20 mg/L. This study showed that ultrasonically aged MFs had a greater tendency to adsorb TTC than fresh MFs due to an increased surface area and changes in surface chemistry. It can be concluded that as the age of MFs increases, they adsorb more concentration of pollutants. This can lead to increased contamination of MFs in the presence of contaminants

Investigating the efficiency of oak powder as a new natural coagulant for eliminating polystyrene microplastics from aqueous solutions

Abstract Polystyrene (PS) is a commonly used plastic material in disposable containers. However, it readily breaks down into microplastic particles when exposed to water environments. In this research, oak powder was used as a natural, inexpensive, and eco-friendly coagulant. The present study aims to determine the effectiveness of oak powder in removing PS from aquatic environments. The Box-Behnken model (BBD) was used to determine the optimal conditions for removal. The removal efficiency was evaluated for various parameters including PS concentration (100–900 mg/L), pH (4–10), contact time (10–40 min), and oak dosage (100–400 mg/L). The maximum removal of PS microplastics (89.1%) was achieved by using an oak dose of 250 mg/L, a PS concentration of 900 mg/L, a contact time of 40 min, and a pH of 7. These results suggest that oak powder can effectively remove PS microplastics through surface adsorption and charge neutralization mechanisms, likely due to the presence of tannin compounds. Based on the results obtained, it has been found that the natural coagulant derived from oak has the potential to effectively compete with harmful chemical coagulants in removing microplastics from aqueous solutions

Reactive red-141 removal from synthetic solutions by γ-Al2O3 nanoparticles: process modeling, kinetic, and isotherm studies

Abstract Azo dyes can cause problems such as allergies, mutagenicity, allergies, and carcinogenesis in humans in addition to having ecological effects in aquatic environments. This study emphasizes the removal of RR-141 by γ-Al2O3 NPs from the aqueous solution. To obtain the optimum conditions of RR-141 removal using the BBD model, the main factors such as the initial RR-141 level (10–70 mg/L), pH (3–9), contact time (10–70 min), and γ-Al2O3 NPs dose (0.2–0.8 g/L) were tested. According to the quadratic model, the highest removal rate (97.74%) was found at the pH of 4.81, the contact time of 51.61 min, the γ-Al2O3 NPs dose of 0.38 g/L, and the RR-141 level of 10 mg/L. The RR-141 removal follows the pseudo-second-order and Langmuir models. The highest absorption capacity for RR-141 was 40.65 mg/g. The results of this study showed that γ-Al2O3 NPs significantly removed RR-141 from aqueous solution

Removal of metronidazole antibiotic by modified red mud from aqueous solutions: process modeling, kinetic, and isotherm studies

Abstract Metronidazole is a type of antibiotic that is commonly used to treat bacterial infections in both humans and animals. The objective of this study was to eliminate MDZ from aqueous solutions using MRM. To gain a better understanding of the adsorption mechanism, we utilized kinetic and isotherm models to investigate the factors that affect the removal of MDZ. The Box–Behnken model was utilized to design experimental factors, which included the initial concentration of MDZ (ranging from 5 to 80 mg/L), MRM dose (ranging from 0.1 to 0.7 g/L), reaction time (ranging from 10 to 60 min), and pH (ranging from 4 to 10). Analysis of the adsorbent using FESEM, FTIR, EDX, DLS, and zeta potential provided valuable insights into its morphology, surface properties, functional groups, size, and electrical charge. Acid modification of red mud increased the porosity and number of pores on the adsorbent surface, thereby enhancing its ability to adsorb the MDZ antibiotic. The FTIR spectrum displays various bands corresponding to different functional groups, such as O–H, Si(Al)–O, Fe–O, and carbonate groups. EDX analysis revealed that the composition of MRM includes carbon, oxygen, and nitrogen elements. The DLS and zeta potential data demonstrate the impact of particle size and electric charge of the adsorbent on the removal of MDZ. The maximum removal of MDZ, which was 69.87%, was achieved at an MDZ concentration of 42.5 mg/L, a pH of 7, a contact time of 35 min, and an adsorbent dose of 0.4 g/L. The removal of MDZ follows both the pseudo-second-order model and the Langmuir model. The maximum adsorption capacity was found to be 6.04 mg/g. The findings of this study indicate that MRM successfully removes MDZ from aqueous solutions

Adsorption of tetracycline on polyvinyl chloride microplastics in aqueous environments

Abstract Microplastics (MPs), as carriers of organic pollutants in the environment, have become a growing public concern in recent years. Tetracycline (TTC) is an antibiotic that can be absorbed by MPs and have a harmful effect on human health. Therefore, this study was conducted with the aim of investigating the adsorption rate of TTC onto polyvinyl chloride (PVC) MPs. In addition, the adsorption mechanism of this process was studied using isothermal, kinetic, and thermodynamic models. For this purpose, experimental runs using the Box-Behnken model were designed to investigate the main research parameters, including PVC dose (0.5–2 g/L), reaction time (5–55 min), initial antibiotic concentration (5–15 mg/L), and pH (4–10). Based on the research findings, the highest TTC adsorption rate (93.23%) was obtained at a pH of 10, a contact time of 55 min, an adsorbent dose of 1.25 g/L, and an antibiotic concentration of 10 mg/L. The study found that the adsorption rate of TTC followed the pseudo-second-order and Langmuir models. Thermodynamic data indicated that the process was spontaneous, exothermic, and physical. Increasing ion concentration decreased TTC adsorption, and distilled water had the highest adsorption, while municipal wastewater had the lowest adsorption. These findings provide valuable insights into the behavior of MPs and organic pollutants, underscoring the importance of conducting additional research and implementing measures to mitigate their detrimental effects on human health and the environment

Use of Saccharomyces cerevisiae as new technique to remove polystyrene from aqueous medium: modeling, optimization, and performance

Abstract MPs are widely found in various environments. PS is the second most common microplastic in sediments, freshwater, soil, and coastal ecosystems. S. cerevisiae was studied as a biocoagulant due to its advantages such as ease of use, non-toxicity, large-scale cultivability and low cost. The aim of this study was to evaluate the efficiency of S. cerevisiae in removing PS from aqueous solutions. BBD was used to determine the optimal removal conditions. The MPs were washed, dried, crushed, sieved, and kept in a closed container to avoid exposure to light and moisture. PS removal was measured under various parameters such as the dose of S. cerevisiae (100–300 mg/L), the concentration of PS (200–900 mg/L), and the pH (4–10). The suspension of PS and S. cerevisiae was stirred and subjected to variable speeds to disperse yeast cells and contact with PS particles. The formed clots were settled under static conditions, and the suspended MPs in the aqueous solution were measured by filtering through Whatman filter paper and recording its weight after drying. The maximum PS removal efficiency was 98.81% under optimized conditions, i.e., the PS concentration of 550 mg/L, the yeast dose of 200 mg/L, and the pH of 7. With regard to the mentioned results, it can be said that S. cerevisiae can be used as a natural and environmentally friendly biocoagulant to remove PS

Biodegradation of crystal violet dye by Saccharomyces cerevisiae in aqueous medium

Crystal violet (CV) is an azo dye with cationic nature, belonging to the triphenylmethane group. This study was designed to optimize CV removal by S. cerevisiae from aqueous solutions using BBD model. Harvested cells of S. cerevisiae were locally obtained from Iran Science and Technology Research Organization (ISTRO). The decolorization tests were performed in a laboratory container containing a 100 cc of reaction solution under different variables, including yeast dose (0.5–1.5 g/L), pH (4–10), dye concentration (10–100 mg/L), and the reaction time of 24 h. After stirring with a magnetic shaker at a speed of 400 rpm, 10 cc of each sample was taken and centrifuged at 4000 rpm for 10 min to separate the biomass from dye solution. Then, the supernatant was filtered and finally the remaining CV was measured by a spectrophotometer at λmax 590 nm. After the optimization of the factors mentioned above, the removal efficiency of this dye was investigated at the reaction times of 0.5–72 h. The findings indicated that CV removal ranged from 53.92 to 84.99%. The maximum CV removal was obtained at the CV concentration of 100 mg/L, the pH of 7, and the S. cerevisiae dose of 1.5 g/L. The findings showed that the elimination efficiency is directly related to the initial CV concentration, pH, and S. cerevisiae dose. However, during the reaction time, the elimination efficiency decreased slightly. The findings of this study proved that CV can be removed from aqueous solutions with an easy and low-cost method based on the use of indigenous microorganisms