砖窑烧结固体废物中镍的迁移转化机理分析

Migration and Transformation Mechanism of Nickel in Solid Waste Sintered in Brick Kilns

为探究砖窑协同处置固体废物时,固体废物中重金属镍(Ni)的迁移转化机理,以Ni(OH)_(2)和NiCl_(2)·6H_(2)O两种重金属试剂为研究对象,模拟砖窑烧结固体废物中重金属Ni可能存在的方式,并通过TG、高温原位XRD图谱、SEM图像和EDS能谱分析,表征样品的热解过程、物相变化和形貌特征。结果表明:Ni(OH)_(2)和NiCl_(2)·6H_(2)O加热至1000℃时总失重量分别为21%和77%;Ni(OH)_(2)从300℃逐渐转化为NiO,NiCl_(2)·6H_(2)O在加热至200℃的过程中逐渐失去结晶水,自400℃开始逐渐转化为NiO;模拟烧结砖中Ni元素多数以NiO形式存在,极少数为NiAl_(2)O_(4);工程试验中显示Ni元素同时存在NiO和NiAl_(2)O_(4),多数Ni元素主要以NiO形式存在于烧结砖中;固体废物经砖窑协同处置后,其内Ni元素的浸出毒性降低。

In order to explore the migration and transformation mechanism of nickel in the co-processing of solid waste in brick kilns,this paper uses two heavy metal reagents,namely Ni(OH)_(2) and NiCl_(2)·6 H_(2)O,to simulate the possible phase of nickel in the sintered solid waste in brick kilns.Then the paper utilizes TG,in-situ HT-XRD pattern,SEM image and EDS analysis to characterize the pyrolysis process,phase change and morphological characteristics of the samples.The results are as follows:the total weight loss of Ni(OH)_(2) and NiCl_(2)·6 H_(2)O during heating to 1000℃is 21%and 77%,respectively,and Ni(OH)_(2) is gradually transformed to NiO from 300℃;NiCl_(2)·6 H_(2)O gradually loses the crystalline water in the process of heating to 200℃,and converts into NiO from 400℃;most nickel in simulated sintered bricks exist in the phase of NiO,and few are NiAl_(2)O_(4);engineering experiments show that nickel exists in both NiO and NiAl_(2)O_(4) phases,most of which exists in sintered brick mainly in the phase of NiO.The leaching toxicity of Ni element in solid waste is reduced after it is disposed by co-processing in brick kilns.