亚铁盐添加的矿物聚合物对Cr(Ⅵ)的解毒与固化研究

Detoxication and Immobilization of Chromium(VI) by Geopolymers Added by Ferrous Salts

中国铬盐生产量及消费量均居世界第一,铬盐生产排放的铬渣量很大,其中Cr(Ⅵ)是一种高毒性物质,是国家重点控制的重金属污染物之一,寻找经济、高效的Cr(Ⅵ)去除方法一直是研究的热点。以煤矸石为原料,以水玻璃和Na OH为碱性激发剂,合成矿物聚合物,用亚铁盐添加的矿物聚合物对Cr(Ⅵ)进行解毒与固化研究,并采用XRD、TEM/EDS、XPS对固化体进行检测。结果发现,当添加的Fe(Ⅱ)与Cr(Ⅵ)摩尔比大于3∶1时,矿物聚合物中总铬浸出的质量浓度小于1 mg·L-1,铬固化率大于99%。以亚铁盐Fe SO4·7H2O作还原剂,矿物聚合物对Cr(Ⅵ)的最大固化量为0.8%。随着Fe SO4·7H2O和Cr(Ⅵ)添加量按3∶1的摩尔比增加,矿物聚合物的抗压强度减小。XRD检测表明,Fe SO4·7H2O和Cr(Ⅵ)添加的矿物聚合物为非晶质结构。TEM/EDS检测表明,矿物聚合物的非晶质结构中含有Fe和Cr。XPS检测结果证明,矿物聚合物中Fe和Cr分别为Fe(Ⅲ)和Cr(Ⅲ)。亚铁盐添加的矿物聚合物对Cr(Ⅵ)的解毒与固化是基于氧化还原反应。在Fe(Ⅱ)和Cr(Ⅵ)添加的矿物聚合物合成过程中,Fe(Ⅱ)被氧化成了Fe(Ⅲ),Cr(Ⅵ)被还原成了Cr(Ⅲ),随后Fe(Ⅲ)和Cr(Ⅲ)被矿物聚合物中的-OAl(-)(OH)3吸引,并被固定在非晶质结构中。

Chromate production amount and consumption amount of our country are first in the world. The emission amount of Chromium residue is huge. It is well known that Cr（Ⅵ） is a highly toxic waste and one of the heavy metal pollutants controlled strictly by the country. So it is a research hot spot to look for a method in order to removal Cr（Ⅵ） economically and efficiently. In this paper, geopolymers have been synthesized using gangue as raw materials, water glass and sodium hydroxide as alkaline excitated agents. The geopolymers added by ferrous salts have been researched on detoxification and immobilization of Cr（Ⅵ）. Then curing geopolymers have been tested by XRD, TEM/EDS and XPS. When the molar ratio of Fe（Ⅱ） and Cr（Ⅵ） is more than 3∶1, the leaching concentrations of total chromium are less than 1 mg· L-1 and the fixation rates of chromium are above 99%. The best Cr（Ⅵ） fixation capacity of geopolymers is 0.8%when ferrous salt FeSO4·7H2O is used as reducing agent. The compressive strength of geopolymers decreases when the amount of FeSO4·7H2O and Cr（Ⅵ） increases accordinghe molar ratio of 3∶1. The XRD testing results show that geopolymers added by FeSO4·7H2O and Cr（Ⅵ） is non-crystaline structures. The TEM/EDS testing results show that the non-crystaline structures contain Fe and Cr. The XPS testing results show that the Fe is Fe （Ⅲ） and the Cr is Cr （Ⅲ）. The mechanism of detoxification and immobilization of Cr（Ⅵ） is oxidation-deoxidation reaction. Fe（Ⅱ） has been oxidized to Fe（Ⅲ） and Cr（Ⅵ） has been deoxidized to Cr（Ⅲ） during the synthesis of the geopolymers added by FeSO4·7H2O and Cr（Ⅵ）. Then Fe（Ⅲ） and Cr（Ⅲ） have been attracted by-OAl（-）（OH）3 in the geopolymers and fixated in the non-crystaline structures.