Hydroxyapatite composite humic acid and its removal of Mn(Ⅱ)
Hydroxyapatite(HAP)was successfully synthesized by chemical precipitation method using calcium nitrate and ammonium hydrogen phosphate as raw materials,and HAP-HA composite adsorbent was prepared by combining HAP with humic acid(HA).The samples were characterized by Fourier transform infrared spectroscopy(FT-IR),specific surface area and pore size analysis,differential thermal-thermogravimetric analysis(TG-DSC)and scanning electron microscopy(SEM).The results showed that humic acid was successfully loaded onto hydroxyapatite.The pore size of HAP-HA was mainly dis-tributed in 3～5 nm,the specific surface area was large,and it had good stability.The surface of HAP-HA was rough and po-rous,which increased the specific surface area and provided a large number of active sites for heavy metal ions.Taking Mn(Ⅱ)as the target pollutant and the removal rate of Mn(Ⅱ)as the index,the adsorption performance of HAP-HA on pollutants was investigated by adsorption experiments.The results showed that the removal rate of Mn(Ⅱ)by HAP-HA was the highest at room temperature,pH of 8.0,dosage of 0.15 g and adsorption time of 150 min,which could reach more than 99.0%.The adsorption process conformed to the Freundlich isothermal adsorption model.At the same time,the desorption and regeneration adsorption experiments were carried out on the adsorbent after the adsorption experiment.The NaOH solu-tion was used as the eluent to obtain better desorption effect,and the desorption efficiency could reach 78.1%.HAP-HA still had good adsorption performance after 6 regeneration cycles.
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