Removal of some pharmaceutical compounds from aqueous solution by using activated carbon prepared from agricultural waste mixtures

New molecules are synthesized day by day to be used in many industrial areas including pharmaceutical, cosmetics, food and agriculture sectors. Among these group molecules synthesized, pharmaceuticals are the most widely used species. Some part of the pharmaceuticals taken in the body for treatment, control and preventive purposes are bound by metabolism and used in the body for beneficial purposes while others are excreted through body excretions. Therefore, they are found at very low concentrations in domestic wastewaters and in receiving environments. These molecules, which are extremely dangerous even in their micro-concentrations, have to remove from the wastewaters of industrial plants where they are produced and even from domestic wastewaters without being supplied to the receiving medium. Advanced treatment technologies such as adsorption, advanced oxidation processes (IOP) and membrane processes are widely used for removal of these resistant organic compounds which can not be removed from the water by biological treatment methods. Among these processes, IOPs are considered as the most advantageous method because they provide complete mineralization controlled and do not create a secondary waste risk. It is more suitable for treatment of highly concentrated wastewater and is a rather expensive method. The most common method for low-concentration pollutants is adsorption. Activated carbons having large surface area and pore volume are the most commonly used adsorbents in industrial applications. However, they are relatively expensive depending on raw materials and production methods. Lately, highly advantageous activated carbons have been produced using agricultural wastes to reduce production costs. In this thesis study; removal of amoxicillin (C16H19N3O5S) and tetracycline (C22H24N2O8), paracetamol (C8H9NO2), and naproxen (C8H9NO2) from aqueous solution by using a new activated carbon prepared from almond, apricot and peach kernel shell mixtures by ZnCl2 chemical activation has been investigated. For this purpose; the effects of parameters such as active carbon dose, contact time, temperature, and initial pharmaceutical concentration on each molecule removal were investigated. The obtained data was applied to first and second order kinetics equations and Freundlich and Langmuir adsorption isotherms to calculate the maximum adsorption capacity of the activated carbon for each molecule. In a system containing four molecules under conditions optimized in a single system, the competitive adsorption of the molecules was investigated and the selectivity of the activated carbon for each molecule was demonstrated. In addition, desorption of the molecules from adsorption residue was investigated in the methanol solutions having different concentrations. According to the results obtained; In a single system, amoxycillin, paracetamol, tetracycline and naproxenin with an initial concentration of 500 ppb were found to be removed by 98-99 % after 60 min contact time at 20°C with 0.66 g/L activated carbon. It has been found that the recovery efficiencies did not change in a distinctive range depending on the temperature increase. it has been found that the adsorption of the molecules onto the activated carbon fits to the pseudo second order kinetic and the Langmuir adsorption isotherm and the maximum adsorption capacities of the activated carbon were found to be 100, 50, 50 and 100 mg/g for amoxicillin, paracetamol, tetracycline and naproxen, respectively. Although the removal efficiencies were partially reduced with the increasing initial concentration, over 87 % of all the molecules investigated could successfully be removed up to 20.000 ppb in the presence of activated carbon with a low dose of 0.66 g/L. It has been determined that the activated carbon can remove the molecules investigated in quadruple system in the order of naproxen, paracetamol, amoxicillin and tetracycline. It has been found that the molecules adsorbed from the adsorption residue are partly desorbed in the pure methanol solution.