锡冶炼含砷烟尘低温陶瓷固化技术

以锡冶炼过程中排放的含砷烟尘为研究对象,对浸出特性和低温陶瓷胶凝材料对其的固化效果进行了研究。结果表明,含砷烟尘As、Cu和Zn毒性浸出浓度分别为6 783、167和224 mg/L,严重超过国家毒性浸出鉴别标准值。其经低温陶瓷胶凝材料固化处理,当含砷烟尘掺量小于40%,自然养护3 d,As、Cu和Zn毒性浸出浓度急剧降低,且低于国家标准值。XRD和SEM分析表明,低温陶瓷胶凝材料在复合化学激发剂作用下,反应生成类沸石水化铝硅酸盐矿物(Al-O-Si);固化体中Ca-Fe-As-O盐是As固化的主要矿物相。Cu2+、Zn2+替换铝硅酸盐聚合物结构中的Na+、K+保持平衡电荷。胶凝材料水化产物填充于材料颗粒间,使其连接成一致密整体,有效降低了有害物质的毒性浸出浓度。

Solidification/stabilization of arsenic-bearing fly ash from a tin refining process with chemically bonded ceramics cement

An industrial fly ash, originating from a metallurgical process in which tin is refined and containing large amounts of arsenic (48.61 wt%), was studied. Chemically bonded ceramics cement(CBCC) prepared with industrial wastes was used to solidify arsenic-bearing fly ash. The leachability of As, Cu and Zn in the fly ash determined with the solid waste extraction procedure for leaching toxicity horizontal vitration method (HJ 557-2010), were 6 783, 167 and 224 mg/L, respectively. After 3 days of curing with 40 wt% CBCC, the concentrations of As, Cu and Zn leached from the solidification samples dramatically decreased, lower than the national standards. It was indicated from XRD and SEM patterns that hydration products of CBCC were calcium aluminium silicate gel under the alkaline conditions, which have a polymeric Al-O-Si three-dimensional framework structure similar to the zeolites. The calcium ferric arsenate (Ca-Fe-As-O) hydrate were present in the CBCC-treated samples as the key phases responsible for As immobilization. The Na⁺, K⁺ could be substituted by Cu²⁺ and Zn²⁺ to keep charge balance at calcium aluminium silicate gel. The hydration products (calcium aluminium silicate gel) were filled in the spare space between materials particles and became a stable part. Thus, the addition of CBCC was effective to decrease the As, Cu and Zn leachability.