次氯酸钙/氧化钙对高砷污泥的氧化稳定化处理

针对某硫酸厂废水处理后产生的高浓度含砷(As)污泥,开展氧化稳定化处理技术研究。以浸出毒性作为评价指标,探讨次氯酸钙和氧化钙联合使用对污泥中As的稳定化处理效果,结合XPS和XRD表征探讨了稳定化机制。结果表明:原始污泥中As主要以As(Ⅲ)形式存在,次氯酸钙能将As(Ⅲ)氧化成As(Ⅴ)；加入氧化钙能同时提高Ca/As摩尔比和pH,Ca与As(Ⅴ)结合形成稳定的砷酸钙盐。依次加入质量比为5%的次氯酸钙和10%的氧化钙,使Ca/As摩尔比达到2.4以上,As的稳定化率达到99%以上,浸出浓度从181 mg·L-1降低至1.5 mg·L-1,且浸出液pH小于12,达到《危险废物填埋污染控制标准》(GB 18598-2001)要求。

Oxidization/stabilization of high concentration arsenic containing sludge using calcium hypochlorite and calcium oxide

A strategy for oxidation and stabilization of sludge with high arsenic concentration, produced by a sulfuric plant was proposed. Calcium hypochlorite and calcium oxide were utilized and the stabilization effect was evaluated by toxicity characteristic leaching procedure (TCLP). The stabilization mechanism was discussed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). As(Ⅲ) dominated in untreated sludge was oxidized into As(Ⅴ) by calcium oxide. The calcium oxide addition increased the Ca/As mole ratio and pH, then Ca reacted with As(Ⅴ) to produce calcium arsenate. With the addition of 5% calcium hypochlorite and 10% calcium oxide (weight ratio), the stabilization ratio of As reached 99% with Ca/As molar ratio of 2.4, and the leaching concentration of As decreased from 181 mg·L-1 to 1.5 mg·L-1 at pH less than 12. The result meets the Standard for Pollution Control on the Security Landfill Site for Hazardous Wastes (GB 18598-2001).