Synthesize of montmorillonite supported hydroxyapatite and determination of adsorption capacity by tetracycline removal

Abstract

In this study, removal of organic pollutants in wastewater using HA/MMT composite material was studied. Tetracycline (TC) antibiotic was used as an organic pollutant. HA/MMT composites were synthesized in a ball mill at different ratios (1:1, 1:2 and 2:1). The synthesis time was fixed at 5 hours. As a result of the experiments, it was concluded that 1:2 ratio of HA/MMT composite has the highest adsorption capacity (147 mg g-1) among the others. The isotherm experiments showed that the Langmuir isotherm model was compatible with the experimental data, and the maximum adsorption capacity was obtained as 150 mg g-1, which indicated that TC was adsorbed to create a monolayer coverage on HA/MMT adsorption cites. In the light of kinetic data, pseudo-second-order kinetic model was the best suitable model for TC adsorption; moreover the calculated adsorption capacity (qe = 227.27 mg g-1) was found suitable with experimental (qe = 223.47 mg g-1). In addition, it has been observed that intra-particle diffusion takes place as a rate-determining step. It has been concluded that TC adsorption of HA/MMT composite was an endothermic (ΔHo = +39.85 kJ mol-1) and spontaneous process thermodynamically. It has been concluded that the synthesized HA/MMT composite has high adsorption capacity and can be used for the removal of organic pollutants such as TC from wastewater.

Keywords

• hydroxyapatite
• montmorillonite
• clay composites
• removal of antibiotics