Usability study of spent black tea leaves and pomegranate peel in adsorption of tetracycline hydrochloride antibiotic

Adsorption of tetracycline hydrochloride (TCH) from aqueous solutions by using spent black tea leaves (SBTL) and pomegranate peel (PP) wastes as low cost and available adsorbents are studied in this paper. Batch adsorption experiments were Investigated to study the sorption behaviour of (SBTL) and (PP) towards TCH as a function of initial concentration, reaction time, dosage of (SBTL) and (PP) wastes, pH and temperature. Time dependent experiments showed that adsorption reached equilibrium at 180 and 30 min for both (SBTL) and (PP) respectively. The adsorption of TCH is found to be better in acidic pH for both wastes. Equilibrium isotherms were tested by applying Freundlich, Langmuir, Tempkin and Dubinin–Radushekevich (D-R) models and it was found that the equilibrium data could be well described by Tempkin for the adsorption process on (SBTL) wastes and by (D-R) for the adsorption on (PP) wastes. Four kinetics models including simple - first - order pseudo – first – order, second – order, pseudo – second – order models were employed and the experimental results were found to be follow Pseudo - second-order equation for both wastes with a good correlation coefficients (R2 > 0.99). Thermodynamic parameters such as ∆Hᵒ, ∆Sᵒ and ∆Gᵒ have been determined and the findings data suggested that the physisorption is predominant. The positive values of ∆Hᵒ and ∆Sᵒ confirm that the adsorption process is endothermic and increased the randomness of the system interface. The negative value of ∆Gᵒ indicates the adsorption process is spontaneous and favourable. In order to support that Physisorption is the predominant the values of activation energy Ea and sticking probability S were calculated, the values of S and Ea indicates the applicability of (SBTL) and (PP) to be used as an effective pharmaceutical adsorbents of TCH from aqueous solutions and of TCH overdose.