New carbon-silica adsorbents enriched with Fe and Mn metals were synthesized. They were characterized in terms of porous structure, surface properties, as well as electrokinetic and stability behavior. These carbon-based materials were used for the adsorptive removal of diclofenac – the over-the-counter nonsteroidal anti-inflammatory drug, also in the presence of poly(acrylic acid).

Abstract

Diclofenac is one of the most popular over-the-counter non-steroidal anti-inflammatory drug and poly(acrylic acid) is a frequently used as thickener, filler or stabilizer. For these reasons, they are common organic contaminants in raw wastewater. The purpose of the presented studies was to compare the adsorption capacity of three carbon-silica composites – metal-free C/SiO₂, iron-enriched C/Fe/SiO₂ and manganese-enriched C/Mn/SiO₂ towards diclofenac. The studies were carried out in single, and mixed systems in the presence of poly(acrylic acid) polymer. Adsorption, desorption and kinetics of the adsorption process were investigated. The concentration of diclofenac in the supernatants was determined using high-performance liquid chromatography. The solids were also characterized with an ASAP apparatus using low-temperature nitrogen desorption adsorption isotherms at liquid nitrogen temperature. In addition, potentiometric titrations and electrophoretic mobility measurements, as well as stability tests of the studied suspensions were carried out. The most efficient composite among investigated ones proved to be C/Fe/SiO₂ removing diclofenac at the level of 46.68 mg/g for its initial concentration of 90 ppm. The results obtained clearly demonstrated that the carbon-silica composites are effective in separation of drugs from aqueous solutions and can be successfully used in the future for the removal of organic pollutants from water environment.