羟基磷灰石/蔗渣炭复合吸附剂的制备及其对As(Ⅴ)的吸附机理

以甘蔗渣为原料，采用水热合成法制备羟基磷灰石/蔗渣炭复合吸附剂--HBA，通过静态吸附试验研究HBA对As（Ⅴ）的吸附特性，并采用红外光谱和X射线光电子能谱对吸附前后的HBA进行表征，探讨其吸附As（Ⅴ）的机理.结果表明:HBA的比表面积为89.52 m2/g，pH_zpc（零点电荷）=7.2，HBA上的羟基磷灰石的分子式为Ca₁₀（PO₄）₆（OH）₂.HBA吸附As（Ⅴ）的效果最佳pH为5.0~9.0.Langmuir等温吸附模型适合拟合HBA对As（V）的吸附等温线，25℃时Langmuir最大吸附量为6.76 mg/g，是蔗渣炭对As（Ⅴ）最大吸附量的20多倍.红外光谱分析表明，HBA含有的＝C＝O、─OH、─COOH等含氧官能团，可为化学吸附提供充足的吸附位点和提高HBA的吸附能力.XPS分析表明，HBA表面的含氧官能团如羧基（─O─C＝O，532.2 eV）、羟基（─OH，530.6 eV）]参与了吸附反应，羟基磷灰石能提高HBA吸附As（Ⅴ）的能力，被吸附到HBA表面上的As主要以AsO₄3-和HAsO₄2-形态存在. 

Preparation of Hydroxylapatite/Bagasse Biochar Composite Adsorbent and Its Adsorption Mechanism of As(V) from Aqueous Solution

Hydroxylapatite/bagasse biochar composite adsorbent(HBA) was prepared from sugarcane bagasse by using the hydrothermal synthesis method.The adsorption capacity for As(V) on HBA was measured through a series of batch adsorption experiments.The adsorption mechanism of As(V) from aqueous solution onto HBA was investigated using Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS).The results showed that the specific surface area of HBA was 89.52 m2/g, and the point of zero charge values of HBA was 7.2.The molecular formula of hydroxylapatite in HBA was Ca₁₀(PO₄) ₆(OH) ₂.The pH range for the optimal As(V) adsorption was between 5.0 and 9.0.The As(V) adsorption isotherm could be well fitted with the Langmuir model.The maximum As(V) adsorption capacity for HBA was 6.76 mg/g at 25℃, which is 23 times that of the bagasse biochar.FTIR analysis indicated that oxygen-containing functional groups presented abundantly on the external and internal surfaces of HBA, which provided numerous chemical sorption sites and thereby increased the adsorption capacity of HBA.XPS analysis showed that the oxygen-containing functional groups, carboxyl oxygen─O─C＝O, 532.2 eV] and hydroxyl-OH, 530.6 eV], were involved in adsorption.Hydroxylapatite in HBA played the key role in the As(V) adsorption process.The As(V) adsorbed on the HBA surface existed mainly as AsO₄3- and HAsO₄2-.