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.

No 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.