Removal of the pharmaceutical microcontaminant cyrofloxacin with activated carbon from rice husk

Pollution of surface and groundwater is becoming an increasingly serious problem worldwide as the use of chemicals increases with the development of technology and population growth. Water pollution is caused by chemicals from sources such as industrial wastes, agricultural activities, domestic wastes, petroleum products and pharmaceutical wastes. Pharmaceutical micropollutants such as ciprofloxacin are excreted from the body after consumption and end up in wastewater systems. Activated carbon is an effective material for removing water pollution. Especially in wastewater treatment plants, it can reduce the mixing of pharmaceuticals and other chemicals into water systems. In our thesis study, activated carbon (PAC) was prepared from rice husk for the removal of ciprofloxacin from aqueous solution and investigated by batch adsorption method. The effect of pH, adsorbent dose, contact time, concentration were investigated to find the optimum adsorption conditions. Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherms were applied. Freundlich model was found to be the most appropriate adsorption isotherm model under experimental conditions. The good fit of the Freundlich isotherm to the experimental data indicates the multilayer coverage of ciprofloxacin on the PAC surface as well as the heterogeneous distribution of active sites on the activated carbon surface. Thermodynamic parameters such as enthalpy (ΔH°), Gibbs' free energy (ΔG°) and entropy (ΔS°) were calculated. Negative ΔG° values indicate that ciprofloxacin adsorption on activated carbon is spontaneous. Positive values of ΔH° indicate that the process is endothermic. The positive value of ΔS indicates increased randomness at the solid-liquid interface during adsorption of ciprofloxacin on adsorbents. The adsorption of ciprofloxacin on PAC showed that the adsorbent was multilayered and heterogeneous and the process was endothermic, physical and spontaneous.