Development of Hydroxyapatite Nanocomposites for Waste Water Treatment

Abstract

Development of porous materials for treating contaminated water is of paramount importance. Porous composites materials based on Hydroxyapatite and cellulose, graphene, CNTs are prepared in laboratory. These composites are utilized for removal of (i) metallic impurities (Cobalt), (ii) organic pollutant (phenol) and (iii) dye pollutant (Rhodamine 6G) from synthetic waste water. Different characterizations techniques have been successfully utilized for assessing their suitability for adsorption properties. Structural and morphological characterizations are performed using X-Ray Diffraction (XRD), Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX), contact angle measurements. Thermal stability of adsorbents is seen by means of TGA while zeta potentials measurements have been carried out to know surface charge of adsorbents. Various adsorption parameters have been evaluated which include (i) effect of variation in adsorbate concentration, (ii) effect of adsorbent doses, (iii) effect of pH of solution, (iv) effect of contact time of adsorbents with adsorbate solution, etc. Synthesis of Hydroxyapatite in presence of Cellulose nanofibres (CNF), Graphene and CNT shows significant change in morphology of hydroxyapatite formation with respect to pure hydroxyapatite. Synthesized composites adsorbents show increase in the adsorption capacities for different contaminants compared to their HAp counterpart. Synthesized cellulose nanofibrils films with different mass percentages are used for phenol adsorption; the maximum adsorption capacity obtained is about 64 mgg-1 at lower pH (and#8776;2) which follows the pseudo second order kinetic model. The adsorption repeatability tests show its efficiency of adsorbents film for phenol adsorption even after 3 successive cycles of its use. Moreover, with negligible swelling property of CNF-HAp makes it a probable candidate for membrane applications. Other composites such as CNF-HAp and TEMPO CNF-HAp composite powder adsorbent are synthesized