Removal of Rifampicin from Wastewater Using Acid-Modified Tea Leaves as an Eco-Friendly Domestic Waste-Based Biosorbent: Regeneration and Isotherm Studies

Waste black tea powder (WBT) was used in the present study as a low-cost adsorbent for the removal of rifampicin (RF) from aqueous solutions. The adsorbent surface was characterized using FESEM and TEM morphological techniques to confirm its suitability for pharmaceutical contaminant removal. The effects of contact time (۵–۱۲۰ min), initial RF concentration (۱۰–۵۰ mg/L), solution pH (۳–۱۱), and adsorbent dosage (۰.۱–۱.۰ g/۱۰۰ mL) were systematically investigated through batch adsorption experiments. The results showed that adsorption efficiency increased with increasing contact time and pH, reaching equilibrium after ۶۰ min. Higher removal efficiency was observed at lower RF concentrations (۱۰–۳۰ mg/L), while the removal percentage decreased at concentrations above ۳۰ mg/L due to saturation of adsorption sites. The removal efficiency also increased with increasing adsorbent dosage due to the greater availability of active sites, although the adsorption capacity per unit mass decreased at higher dosages. The maximum adsorption capacity of WBT was calculated to be ۶۴.۶۳ mg/g, while ۱۰۰% removal efficiency was achieved under optimal conditions of pH ۹, contact time of ۶۰ min, RF concentration of ۳۰ mg/L, and adsorbent dosage of ۰.۰۵ g/۱۰۰ mL. Isotherm analysis revealed that the adsorption equilibrium was better fitted by the Freundlich model (R² > ۰.۹۸۶۴) than the Langmuir model, indicating heterogeneous adsorption behavior. The Langmuir maximum adsorption capacity was found to be ۶۶.۳۱۶ mg/g. Regeneration studies using ۰.۱ M NaOH demonstrated that WBT retained over ۸۶% of its initial adsorption performance after five adsorption–desorption cycles. These findings suggest that WBT is an environmentally friendly, sustainable, and efficient adsorbent for the treatment of pharmaceutical wastewater.

کلیدواژه ها:

Adsorption ، Waste black tea ، Rifampicin (RF) ، Isotherm ، Regeneration