Adsorption separation of oxytetracycline hydrochloride using natural and nanostructured clay mineral of silica in synthetic solution: Integration to white and green chemistry metrics

As emerging water pollutants, oxytetracycline (OTC) and its derivatives are detrimental to humans, organisms, and aquatic ecosystems. Oxytetracycline hydrochloride (OTCH) was effectively absorbed from water by silica (SiO2) and metakaolinite (MK). In this study, we employed a unique metric known as BAGI to evaluate the suggested analytical method's suitability effectively. Blue applicability grade index (BAGI) complements green assessment tools such as the Green analytical procedure index (GAPI), Complex green analytical procedure index ComplexGAPI, Analytical GREEnness (AGREE), Analytical greenness for sample preparation (AGREEprep), and Analytical eco-scale (ESA). The BAGI metric focuses on the practical aspects of white analytical chemistry, especially those related to “blue.” The optimal parameters for adsorbing OTCH were determined by a study (pH, OTCH concentration at the beginning of the reaction, sorbent dose, and reaction duration). This study of sorbent properties was conducted via X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The highest levels of OTCH adsorption were seen at pH 5–6 for MK and at pH 7 for SiO2. The most desirable clay minerals are those with smaller quantities. The Langmuir model accurately characterizes the results, showing a strong correlation between OTCH sorption onto MK with a maximum capacity of 165.04 mg/g and a moderate correlation for SiO2 with a maximum capacity of 25.3 mg/g. Therefore, these findings regarding the effectiveness of adsorption and the analysis of properties offer supplementary insights into the potential use of clay minerals as cost-effective and eco-friendly sorbents for treating wastewater.