Hidroxiapatitas organofuncionalizadas como sistemas para biorremediação de corante aniônico

Abstract

Between the various calcium phosphates, hydroxyapatite has been applied to remove transition cations and inorganic anions for remediation of polluted water. However, hydroxyapatite has two limitations: its low chemical stability at pH below 3.0 and its weak affinity for organic species as anionic dyes. An alternative is the organofunctionalization of the hydroxyapatite. Therefore in this work, hydroxyapatite was organofunctionalized with the silanes 3-aminepropyl- and N-3- propil ethylenediaminetrimethoxisilane in anhydrous condition. The silylated solids reacted subsequently with epichlorohydrin and ethylenediamine to increase the active sites on hydroxyapatite for the adsorption of anionic dye Remazol RN blue. The obtained materials before and after adsorption were characterized for X-ray diffratometry, infrared spectroscopy, CHN elemental analysis, UV-VIS absorption spectroscopy and termogravimetry. The obtained results suggested the proposed modifications with covalently incorporation of the organic groups on HAP surface without drastic changes in long range on inorganic structure. The maximum retentions at room temperature and pH 6.0 were 245 mg g-1 at 45 min for both silylated solids and 130 and 80 mg g-1 for the solids obtained after reaction with ethylenediaminein 90 min. The solids did not desorb the dye after Soxlet extraction with ethanol and toluene for 24 h. The systems with dye showed the characteristic absorption band of Remazol RN blue at 592 nm, which demonstrates the good performance of the organofunctionalized hydroxyapatites for use as pigment in future tests.