硅藻土基多孔吸附填料的制备及其对Pb2+的吸附

以硅藻土为主要原料,添加超细碳粉、烧结助剂和粘结剂,按一定比例混合、搅拌、造粒,在设定程序下煅烧,制备了硅藻土基多孔吸附填料(DBPAF),探讨了烧成温度、造孔剂添加量、硅藻土粉体粒径对DBPAF孔隙特征的影响,运用扫描电子显微镜(SEM)和X射线衍射仪(XRD)对DBPAF的微观形貌和物相组成进行了观察和分析,采用动态吸附实验研究了DBPAF的可操作性,采用静态吸附实验研究了DBPAF吸附Pb2+的性能和机制.结果表明,最适烧成温度范围为900~1000℃,最适造孔剂添加量为7.0%,最适硅藻土粉体粒径为2.40μm;与硅藻土原土(粉体)相比,DBPAF的可操作性明显提高,孔隙结构得到了明显改善,物相组成以方石英相为主.研究还表明,烧制过程升温速率以2~5℃/min为宜以保证DBPAF气孔分布均匀;DBPAF对Pb2+吸附容量较硅藻土原土(粉体)提高了78.0%,吸附过程速率控制步骤为Pb2+与DBPAF孔道内的基团发生的化学反应,吸附动力学符合拟二级动力学模型.

Preparation of diatomite-based porous adsorption filler and adsorption on Pb2+

Diatomite-based porous adsorption filler (DBPAF) was prepared by the addition of superfine carbon, sintered additive and binder into the diatomite through a established process in which these materials above were mixed, stirred and granulated with a particular ratio. In this paper, the effects of sintering temperature, carbon dose and diatomite particle size on the porosity characteristic of DBPAF were studied. Micro-morphology and phase composition of DBPAF were observed and analyzed by SEM and XRD. Further more, DBPAF’s maneuverability, adsorption property and relative adsorption mechanism of Pb2+ were studied by dynamic and static adsorption experiment, respectively. As the results indicated, the optimal value of sintering temperature, carbon addition and diatomite particle size were 900~1000℃, 7.0%, 2.40μm, respectively. The maneuverability of DBPAF was significantly improved compared with natural diatomite and the porosity characteristic of DBPAF, whose the main phase was cristobalite, also obtained a certain degree of improvement. The results also illustrated that the optimum rate of temperature increase should be 2-5℃/min to ensure the pores distributing uniformly in DBPAF. In other side, the adsorption capacity of DBPAF increased by 78.0% compared with natural diatomite. Elementary mechanism studies implied that the key procedure of adsorption on Pb2+ of DBPAF was the chemical reaction happened in the channels of DBPAF where Pb2+ and active groups might react mutually. Further, the kinetic mode of Pb2+ adsorption on DBPAF followed Pseudo-second-order.