Comparative adsorption of tetracycline by acid-modified silicomanganese fumes: kinetic and process modelling

In this novel study, we treated silicomanganese fumes with HNO₃ and HCl to produce high-performance adsorptive materials, namely SMF-HN and SMF-HC. These acid-modified materials were then subjected to morphology, crystallinity, thermal, and spectroscopic analysis. The prepared materials were then tested for their efficacy in removing tetracycline antibiotics from wastewater. Surface analysis, a key property in the adsorption process, revealed BET surface areas of 178.14, 154.1, and 7.73 m²/g for SMF-HC, SMF-HN, and SMF, respectively. The adsorption performance was further analysed with respect to various parameters such as pH, dosage, pollutant concentration, and contact time. The adsorption isotherms models in agreement with the Langmuir, Redlich-Peterson, and Sips models, with high R² values for all the samples. The SMF-HN and SMF-HC show a comparable adsorption capacity at 111.17 and 93.32 mg/g, respectively. The kinetics models indicated that the reaction follows pseudo-second-order kinetics. This study suggests that the adsorption mechanism occurs via chemisorption methods. The regeneration studies demonstrated that SMF-HN and SMF-HC adsorbents maintained a high removal percentage of TC after undergoing five cycles of adsorption-desorption experiments. Specifically, both adsorbents maintained 100% removal of TC in the first three cycles and a slight drop in the fourth (~96%) and fifth cycles (~90%).