磷矿硅渣合成NaA型分子筛及应用于湿法磷酸脱氟的研究
Synthesis of NaA-Type Molecular Sieves from Silica Slag of Phosphate Ore and Its Application to Defluorination of Wet Process Phosphoric Acid

湿法磷酸中氟的存在会影响磷酸的品质，需要将其脱除。而磷矿硅渣如果不加以处理，会造成严重污染。采用磷矿硅渣为原料合成NaA型分子筛，探究硅源溶液pH对分子筛合成的影响，通过X射线粉末衍射(XRD)和扫描电镜(SEM)对NaA型分子筛进行表征，对NaA型分子筛的晶型结构和表面形貌进行了讨论分析；以分子筛为脱氟剂，对湿法磷酸脱氟，考察了分子筛颗粒大小、过柱时间和次数对脱氟效果的影响。结果表明，将磷矿硅渣制成硅源溶液和铝源溶液后，添加铝酸钠使凝胶混合物组成为Si:Na:Al:F = 1:5.1~7.4:1~2.3:4.27水热晶化合成NaA型分子筛，硅源溶液的pH降低时会得到冰晶石(Na₃AlF₆)。使用NaA型分子筛对湿法磷酸脱氟，分子筛颗粒大小为1~1.6 mm，过柱时间为30 min，过柱3次时脱氟率最高达到47.21%。
The presence of fluorine in wet process phosphoric acid affects the quality of phosphoric acid and needs to be removed. Phosphate silica residue can cause serious pollution if not treated. The NaA-type molecular sieves were synthesized from phosphate silica dregs, and the effect of pH of silica source solution on the synthesis of molecular sieves was investigated. The NaA-type molecular sieves were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), and the crystalline structure and surface morphology of the NaA-type molecular sieves were discussed and analyzed; the molecular sieves were used as a defluorinating agent for defluorination of wet process phosphoric acid, and the effects of the sieves’ particle size, time and frequency on the effect of defluorination were examined. The effects of molecular sieve particle size, time and number of times on the defluorination effect were investigated. The results showed that after the silicon and aluminum source solutions were made from phosphate silica residue, sodium aluminate was added to make the gel mixture composed of Si:Na:Al:F = 1:5.1~7.4:1~2.3:4.27 NaA-type molecular sieves were synthesized by hydrothermal crystallization, and cryolite (Na₃AlF₆) was obtained when the pH of the silicon source solution was lowered. The defluorination of wet process phosphoric acid was carried out using NaA-type molecular sieves with the particle size of 1~1.6 mm, the column passing time was 30 min, and the highest defluorination rate of 47.21% was achieved when the column was passed for three times.