Sustainable water purification through the adsorptive removal of tetracycline via modified clay and regeneration via controlled thermolysis: a reusable and environmentally friendly approach for contaminant mitigation

Abstract

Pharmaceutical pollutants such as tetracycline (TC) are environmentally dangerous because of their persistence in aquatic bodies. This work introduces a unique and sustainable treatment approach by combining modified natural clay (MC) adsorption with controlled thermolysis regeneration to eliminate TC from wastewater in a reusable system. Batch adsorption experiments revealed an optimum TC removal of 93% at pH 3.5, 25 °C, and 40 mg/L TC, with an equilibrium time of 45 min. Adsorption followed the Langmuir isotherm (R² = 0.9713), indicating monolayer adsorption with a capacity of 85.54 mg/g, whereas kinetic modeling was pseudo-second order, suggesting chemisorption. The integration of thermolysis at 550 °C for 120 min not only decomposed TC into CO₂ and H₂O but also preserved the structural integrity of the MC for reuse over five cycles. Continuous-flow column trials corroborated the effectiveness of the approach under real conditions in practical applications. Structural characterization techniques (XRD, SEM, TGA, and FT-IR) were used to validate the thermal stability, porous structure, and high adsorption capacity of MC. This adsorption‒thermolysis approach with combined adsorption presents an economically viable and environmentally friendly alternative to traditional water treatment processes, which effectively destroys secondary waste and facilitates sustainable pollutant removal. This closed-loop, eco-friendly method not only eliminates secondary waste but also demonstrates scalable potential for industrial wastewater treatment.