钙铝黄长石晶体的形成机制及应用研究

Formation Mechanism and Application of Gehlenite Crystal

摘要: 以碳酸钙、氧化铝和氧化硅为原料，通过高温烧结法制备钙铝黄长石晶体。采用TG-DSC、XRD、SEM和TEM探究了煅烧温度对钙铝黄长石合成的影响；利用静态浸出实验检测了钙铝黄长石的供碱释钙能力，并将其用于废水中$P{O}_4^{3-}$ 和Cd²⁺的吸附去除。结果表明：四方短柱状钙铝黄长石晶体可在1400℃下经固相反应合成，硅灰石、硅酸二钙和铝酸钙是其合成的中间产物，并且高温下液相的形成和饱和析晶是其主要形成机制。20 g/L的投加量下，钙铝黄长石可向水溶液中释放252.91 mg/L的Ca²⁺，并将溶液pH提升至9.1，具有良好的供碱释钙能力。钙铝黄长石可以作为理想的水处理用吸附剂，对初始浓度为50 mg/L的$P{O}_4^{3-}$ 去除率达到99.25%，对初始浓度为20 mg/L的Cd²⁺去除率达到83.26%。

Abstract: Calcium carbonate, silica and alumina were used as raw materials to prepare gehlenite by sintering. The influence of sintering temperature on the synthesis of gehlenite was analyzed by TG-DSC, XRD, SEM and TEM. The alkali and calcium releasing capacity of gehlenite was tested by static leaching experiment. Gehlenite was also used to remove $P{O}_4^{3-}$ and Cd²⁺ from aqueous solutions by adsorption. The results showed that gehlenite crystals were tetragonal short columnar and could be synthesized by solid phase reaction at 1400˚C. Wollastonite, larnite and calcium aluminate were generated as intermediates for gehlenite. The formation of liquid phase and saturation crystallization at high temperature were the main formation mechanisms of gehlenite. At the dosage of 20 g/L, gehlenite could release 252.91 mg/L of Ca²⁺, and increase the solution pH to 9.1, which had a good alkali and calcium releasing capacity. Moreover, the removal efficiency of $P{O}_4^{3-}$ (50 mg/L) and Cd²⁺ (20 mg/L) reached 99.25% and 83.26%, respectively, so gehlenite was an ideal adsorbent for wastewater treatment.