Experimental study and quantum-chemical simulation of piroxicam adsorption on the coal sorbent from walnut shells

Abstract

The aim of this work was to study the sorption of piroxicam on the surface of activated carbon obtained by heat treatment from walnut shells. The objects of study are piroxicam (a) and model clusters of the sorbent. The quantitative determination and study of the sorbability of piroxicam is based on photometric recording of spectra at λ 400 nm. The most complete sorption of piroxicam occurs at pH 6,8–7,3, where the maximum difference in the optical density of the solutions was observed before and after sorption, which indicates the formation of a stable state of piroxicam. The results obtained from three series before and after sorption were subjected to statistical processing. The dependences “sorption – equilibrium concentration” presented at various temperatures made it possible to attribute the obtained curves to the Langmuir solution. Based on the obtained thermodynamic indicators, the following conclusions can be made: the reaction proceeds spontaneously, exothermally. Saturation of the surface of activated carbon with a monomolecular layer of piroxicam does not depend much on temperature changes, which is confirmed by close values of thermodynamic parameters at three temperatures. Quantum chemical calculations of the starting materials and model adsorption complexes in the “piroxicam – activated carbon surface” system were performed using the GAMESS US and MOPAC software. As a result of the work done, it was found that activated carbon obtained by heat treatment of walnut shells is a good and quite promising material for concentrating piroxicam and other drugs with the aim of subsequent determination from water and various biological environments.