高炉渣酸解液的絮凝脱硅研究

Study on flocculation and desilication of acid hydrolysate of blast furnace slag

为回收利用高炉渣中的有效元素,以高镁炼铁炉渣的硫酸酸解液为原料,采用絮凝脱硅法分离回收硅元素。研究絮凝剂种类、絮凝温度、絮凝时间、絮凝剂质量分数和絮凝剂加入量等因素对脱硅效果的影响,并利用X射线衍射(XRD)与扫描电镜-能谱分析(SEM-EDS)对脱硅渣的物相和结构进行分析。研究结果表明:阳离子高分子絮凝剂能有效脱除酸解液中带负电的硅酸分子。在反应初期,随絮凝温度、时间、絮凝剂质量分数和絮凝剂加入量的增大,脱硅率增大;絮凝温度继续增大,絮凝剂聚合氯化铝和PDADMAC自身受到温度影响,脱硅效果下降;絮凝剂质量分数继续增大,聚丙烯酰胺发生“架桥保护”,脱硅效果下降。最佳反应条件如下:脱硅絮凝剂为聚丙烯酰胺,絮凝温度为50℃,絮凝时间为1.5 h,脱硅絮凝剂质量分数为1%,每50 mL酸解夜中,脱硅絮凝剂加入量为8 g。在最佳反应条件下,有效脱除了高炉渣酸解液中的硅元素,硅元素质量浓度由1 366 mg/L降低到235 mg/L,脱硅渣中硅氧含量(质量分数)达95.8%,可用于制备水玻璃、硅肥等产品。

In order to recover the effective elements in blast furnace slag, the sulfuric acid hydrolysate of high magnesium iron making slag was used as raw materials, and the silicon element was separated and recovered by flocculation desilication method. The effects of different factors such as flocculant type, flocculating temperature,flocculating time, flocculant mass fraction and flocculant dosage on desilication effect were studied, and the phase and structure of desilication slag were analyzed by X-ray diffraction(XRD) and scanning electron microscope-energy dispersive spectrometer(SEM-EDS). The results show that the cationic polymer flocculant can effectively remove the negatively charged silicic acid molecules from the acidolysis solution. At the initial stage of the reaction, the desilication rate increased with the increase of flocculation temperature, time, flocculant mass fraction and flocculant dosage. As the flocculation temperature continues to increase, the flocculants polyaluminium chloride and PDADMAC themselves are affected by temperature, and the desilication effect decreases. With the increase of flocculant mass fraction, the polyacrylamide is bridge-protected, and the desilication effect decreases. The optimum reaction conditions are as follows: the desilication flocculant is polyacrylamide, the flocculation temperature is 50 ℃, the flocculation time is 1.5 h, the desilication flocculant mass fraction is 1%, and the desilication flocculant addition is 8 g in every 50 mL acidolysis solution. The content of silicon in the acid hydrolysis solution is reduced from 1 366 mg/L to 235 mg/L under the optimum reaction conditions, which effectively removes the silicon in the acid hydrolysis solution of blast furnace slag. The content of silicon and oxygen in the desilication slag reaches 95.8%, which can be used to prepare sodium silicate, silicon fertilizer and other products.