Equilibrium, thermodynamics and kinetics study of doxycycline adsorption from aqueous solution using spent black tea leaves and pomegranate peel wastes

Pharmaceutical antibiotics also known anti-bacteria, which inhibit the growth of bacteria and various infections. Doxycycline (DOC) is a member of the tetracycline antibiotics which is frequently used to treat many different bacterial infection such as Chronic Prostitutes, Pelvic inflammatory disease and etc. Also Doxycycline has been demonstrated to reduce the invitro. growth of human breast and Prostate cancer cell, but at the sometime they have a negative effect on the environment when its presence in the industrial waste water . Adsorption of Doxycycline from aqueous solutions by Spent Black Tea Leaves (SBTL) and Pomegranate Peel (PP) wastes asl low- cost and available adsorbents has been studied in this work. Batch adsorption experiment were investigated to study the sorption behaviour of (SBTL) and (PP) towards DOC as a function of initial concentration, reaction time, adsorbent dosage, pH and temperature. Time dependent showed that the adsorption process reached equilibrium at 150 and 90 min. for both (SBTL) and (PP) respectively. Four adsorption isotherms equations were employed including Freundlich, Langmuir, Tempkin and Dubinin–Radushekevich (D-R) equations. The equilibrium data could be well described by D-R equation for the adsorption process on (SBTL) waste and by freundlich for the adsorption on (PP) waste . Also four kinetics equations. including simple - first - order pseudo – first – order, second – order, pseudo – second –order were applied and the resulting data were found to be follow pseudo – second –order equation for both wastes. Findings therrmodynamics data suggested that the physical adsorption is predominant, and the negative value of ∆Hᵒ and ∆Sᵒ confirm that the adsorption process is exothermic and decreased the randomness of the system interface. The positive values of ∆Gᵒ indicates the adsorption process is non-spontaneous. Furthermore the value of activation energy (Ea) and sticking probability (S) were calculated to assess the applicability of (SBTL) and (PP) as an effective adsorbents of DOC from aqueous solutions.