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.