THE REMOVAL OF PHENAZOPYRIDINE FROM CONTAMINATED WATER USING MONTMORILLONITE THROUGH THE PROCESS OF ADSORPTION FOLLOWED BY THE THERMOLYSIS TECHNIQUE

Abstract

In this study, phenazopyridine hydrochloride (Phz) and tetracycline (TC) were efficiently removed from aqueous solutions using modified montmorillonite (MOT) as an adsorbent. The modification process involved dispersing raw montmorillonite in hot water at 80 °C, followed by calcination at 700 °C to improve surface activation, porosity, and adsorption efficiency. The effects of key operational parameters, including initial adsorbate concentration, adsorbent dosage, solution pH, and temperature, were systematically investigated. The adsorption capacity increased with increasing MOT dosage until equilibrium was achieved, whereas it decreased with increasing initial adsorbate concentration. The optimal pH values were determined to be 5 for Phz and 4 for TC, with equilibrium times of less than 14 min for both systems. An increase in temperature from 20 to 50 °C led to a decrease in adsorption capacity, indicating an exothermic adsorption process. Kinetic modeling demonstrated that the adsorption data for both compounds were best described by the pseudo-second-order model. Equilibrium analysis revealed that the Langmuir isotherm provided a better fit than the Freundlich model, suggesting monolayer adsorption on a homogeneous surface. Based on the calculated activation energy values, the adsorption mechanism was predominantly physical in nature. The presented research demonstrated that Mont material maintained its adsorption ability after four cycles of thermal decomposition at 700 °C during removal processes involving Phenazopyridine and Tetracycline. The montmorillonite material showed very good reusability in adsorption applications when treated by thermal decomposition at various temperatures starting from 400 °C. The research introduced thermal regeneration as a novel approach for the activation of spent Mont materials and provided a greener alternative to conventional chemical activation methods. The gases resulting from the thermal decomposition process were environmentally benign and may have further value in subsequent chemical processes. Captured gases using chemical trapping could create further process value due to the possibility of subsequent chemical conversions.