AB-INITIO STUDY OF METHYLENE BLUE ADSORPTION ON HYDROXYAPATITE

Abstract

Hydroxyapatite is a naturally occurring mineral form of calcium apatite, because of the active sites on its surface, which may draw in and hold onto other molecules by a variety of mechanisms including electrostatic interactions, hydrogen bonds and van der Waals forces, hydroxyapatite has the unusual trait of being able to adsorbe a wide range of substances. In this study, we carried out first-principles (ab-initio) calculations to investigate the adsorption of the dye methylene blue on hydroxyapatite. We had focused on (001) and (010) cleaved surfaces of hydroxyapatite in order to understand the mechanism of the adsorption process using density functional theory. We have scrutinize a number of adsorption configurations that match various dye molecule orientation and different adsorption sites. As a result we have found that the (001) surface is better for the adsorption process of methylene blue on hydroxyapatite, and the adsorption process is monolayer adsorption so it is follows either Langmuir or Temkin isotherms