羟基磷灰石-四氧化三铁-沸石复合材料制备及去除水中刚果红研究

采用可溶性磷酸盐、钙离子、二价铁离子、三价铁离子和天然沸石等材料制备了羟基磷灰石-四氧化三铁-沸石(HAPFe3O4-沸石)复合材料,对该复合材料进行了表征,并考察了该复合材料对水中刚果红的吸附作用.结果表明,HAP-Fe3O4-沸石复合材料对水中的刚果红具备良好的吸附能力.当pH由3增加到4或由7增加到11时,HAP-Fe3O4-沸石复合材料对水中刚果红的去除能力下降;当pH由4增加到7时,对刚果红的吸附能力基本保持不变.HAP-Fe3O4-沸石复合材料对水中刚果红的去除率随吸附剂投加量的增加而增加,而对水中刚果红的单位吸附量则随吸附剂投加量的增加而降低.HAP-Fe3O4-沸石复合材料对水中刚果红的吸附动力学过程可以较好地采用准二级动力学模型加以描述,对刚果红的吸附平衡数据可以采用Langmuir和Freundlich等温吸附模型加以描述.根据Langmuir模型确定的最大吸附容量为117 mg·g-1.(pH 7和303 K).HAP-Fe3O4-沸石复合材料对水中刚果红的吸附是自发吸热并伴随熵增加的过程.当pH为7时,HAP-Fe3O4-沸石复合材料吸附水中刚果红的主要机制包括表面配位作用、氢键作用以及路易斯酸碱反应.采用热再生的方法可以使吸附刚果红后的HAP-Fe3O4-沸石复合材料得到再生,热再生后的复合材料可以循环使用并且对水中刚果红的吸附性能良好.X射线衍射分析结果表明HAP-Fe3O4-沸石复合材料含Fe3O4,磁滞回线结果表明HAP-Fe3O4-沸石复合材料具备较高的磁饱和强度,复合材料吸附刚果红后可以很容易地通过外加磁场的作用快速地与水溶液分离.结果表明,HAP-Fe3O4-沸石复合材料适合作为一种吸附剂去除废水中的刚果红.

Synthesis of Hydroxyapatite/Magnetite/Zeolite Composite for Congo Red Removal from Aqueous Solution

In this study, a novel hydroxyapatite/magnetite/zeolite (HAP/Fe₃O₄/Zeo) composite was prepared, characterized and used as an adsorbent to remove Congo red (CR) from aqueous solution. The adsorption characteristics of CR from aqueous solution on the HAP/Fe₃O₄/Zeo composite were investigated using batch experiments. Results showed that the HAP/Fe₃O₄/Zeo composite was effective for the removal of CR from aqueous solution. The CR adsorption capacity for the HAP/Fe₃O₄/Zeo composite decreased with solution pH increasing from 3 to 4 or solution pH increasing from 7 to 11, and remained basically unchanged with pH increasing from 4 to 7. The CR removal efficiency of the HAP/Fe₃O₄/Zeo composite increased with increasing adsorbent dosage, while the amount of CR adsorbed on the HAP/Fe₃O₄/Zeo composite decreased with increasing adsorbent dosage. The adsorption kinetic data of CR on the HAP/Fe₃O₄/Zeo composite well fitted a pseudo-second-order model. The equilibrium adsorption data of CR on the HAP/Fe₃O₄/Zeo composite could be described by the Langmuir and Freundlich isotherm models. The maximum monolayer adsorption capacity for CR derived from the Langmuir isotherm model was determined to be 117 mg·g^-1 at pH 7 and 303 K. The adsorption process of CR on the HAP/Fe₃O₄/Zeo composite was spontaneous and endothermic. The main mechanisms for the adsorption of CR on the HAP/Fe₃O₄/Zeo composite at pH 7 included surface complexation, hydrogen bonding and Lewis acid-base reaction. Thermal regeneration showed that the HAP/Fe₃O₄/Zeo composite could be used for five desorption-adsorption cycles with high removal efficiency for CR in each cycle. X-ray diffraction (XRD) analysis revealed that the HAP/Fe₃O₄/zeolite composite contained Fe₃O₄, and this composite had relatively high saturation magnetization. The HAP/Fe₃O₄/Zeo composite adsorbed with CR could be collected from aqueous solution under an external magnetic field quickly. Results of this study suggested that the HAP/Fe₃O₄/Zeo composite should be applicable for the removal of CR from wastewater.