铬渣中铬的赋存形态表征和酸浸出特性

Characterization of chromium-bearing mineral species in the chromite ore processing residue and leaching characteristics

摘要:

为研究铬渣在湿法解毒技术无害化处理过程中重金属污染物铬的浸出特性,对铬渣进行了酸中和能力实验,分析了不同pH条件下铬渣中总铬和6价铬及其他主要金属元素的溶出特性,并采用X射线荧光仪、X射线衍射仪、扫描电子显微镜以及热重分析对铬渣中的元素组成和矿物物相组成进行表征.得出硫酸硝酸法和TCLP法毒性浸出实验中浸出液中Cr主要以Cr6+形式存在.铬渣的强碱性且在碱性范围内有较大的缓冲能力以及复杂的物相组成是制约湿法还原铬渣处理效果的两个主要因素,因此,优选工艺pH条件来提高铬渣中铬的溶出率是提高湿法还原处理效率的关键,浸出pH在8.0左右时,能够获得较高的6价铬浸出率且处理成本相对较低.

Abstract:

In order to investigate the leachability of chromium from chromite ore processing residue (COPR) during the detoxification process, the leaching behavior of total chromium, hexavalent chromium and other main metal elements in the COPR samples under different pH were evaluated. The chemical compositions and mineral phases of COPR were analyzed by X-ray fluorescence spectrometry (XRF), X-ray power diffraction (XRPD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The results indicated that Cr6+ exist as the major fraction in both leachates of the sulfuric acid/nitric acid extraction and the toxicity characteristic leaching procedure (TCLP) extraction. Strong alkaline properties of COPR and its large alkaline buffer capacity were the two main factors affected the detoxification process using reduction method. Therefore, the chosen of an optimum pH is the key process to enhance the leachability of hexavalent chromium from COPR. High leachability of hexavalent chromium from COPR can be achieved under pH8.0, with a relatively low operational cost.