Adsorption of Naproxen Sodium from Aqueous Solutions on Commercial Activated Carbons

The pollution of surface and drinking water with pharmaceuticals is one of the growing problems. One of the groups used in large quantities involves nonsteroidal anti-inflammatory drugs which can be bought without a prescription. This group includes naproxen, which was identified in wastewater, surface water and even drinking water all over the world. The aim of the study was to assess the opportunities for the removal of naproxen sodium from water using carbon sorbents. The measurements were carried out for three commercial microporous (WG-12 and F-300) and micro-mesoporous (ROW 08 Supra) activated carbons. The kinetics and statics of adsorption were studied. The adsorption from solutions with pH from 6 to 10 and temperature from 20°C to 40°C was analysed. It was found that the higher the pH, the lower the adsorption and the higher the temperature, the greater the adsorption of naproxen sodium. The highest adsorption of naproxen sodium was obtained for the F-300 activated carbon, whereas the lowest – for the ROW 08 Supra activated carbon. It was found that the adsorption results depend on many factors, the most important of which include hydrogen bonds between carboxyl groups of naproxen sodium and phenolic groups on the surface of activated carbons and electrostatic repulsion between the anions of naproxen sodium and negatively charged the surface of the activated carbon. The results of adsorption kinetics were described with the following models: pseudo-first order and pseudo-second order, intraparticle diffusion, and Elovich. The highest values of correlation coefficient R² were obtained for the pseudo-second order and Elovich model. The results of adsorption statics were described using the Freundlich, Langmuir, and Temkin models. A good match between isotherms and the obtained results was obtained for the Freundlich and Temkin equations. It was found based on the adsorption intensity 1/n and distribution coefficient R_L that this process was beneficial for all the considered activated carbons and the investigated adsorption conditions.