Adsorption of some Fluoroquinolones on Selected Adsorbents

The adsorption of some fluoroquinolones (antibiotics) such as: Gemifloxacin Mesylate and Levofloxacin Hemihydrate using selected adsorbents such as charcoal, kaolin, silica gel and alumina was carried out in terms of initial pH, residence time, initial concentration of drug (adsorbate), weight of adsorbent, temperature and affinity of the solute to the adsorbent. The adsorption was determined by measuring concentration of the drug both before and after the attainment of equilibrium, with the aid of UV-visible spectrophotometer. Gemifloxacin absorbs at 343nm and at 340nm, where Levofloxacin absorbs at 294nm and at 288nm, in acidic and basic pH respectively. For equilibrium studies, two adsorption isotherms were used, Freundlich and Langmuir,the later fitted most data very well. Maximum adsorption capacity for Gemifloxacin into charcoal was 137mg/g compared to 0.04 mg/g with kaolin. For Levofloxacin with charcoal was 87mg/g more than that with kaolin which was 0.26mg/g. The amount adsorbed at equilibrium decreases as adsorbate's concentration increases and as the weight of adsorbent increases the amount of drug adsorbed increases. pH played a significant role in the adsorption especially with silica and alumina. Maximum amount of Gemifloxacin adsorbed onto silica occurred at pH=7 and with alumina at pH=6 respectively. With charcoal adsorption of GEMX was more in the acidic medium than in basic and the maximum adsorption was at pH=6 and at neutral pH for kaolin. LEVX adsorption with charcoal and kaolin was at about pH=7 and was in acidic pH more than basic pH. Thermodynamics parameters showed that adsorption process was exothermic and spontaneous as ΔGo and ΔHo had negative values, ΔSo was positive.