镉在黏土烧结过程中的固化机理

Solidification Mechanism of Cadmium in Clay Sintering

以黏土为原料,通过控制化学成分和烧结温度对Cd进行烧结固化,测试其对Cd的固化率和浸出浓度的影响,通过XRD、SEM、XPS、FTIR和重金属形态分析探讨黏土烧结过程中Cd的固化机理。结果表明:提高Fe_(2)O_(3)含量有利于赤铁矿的生成,Cd在750℃时的残渣态占比高于其他样品;提高铝硅比后,样品中CdAl_(2)Si_(2)O_(8)含量增多,当铝硅比为0.3、温度为1 050℃时,Cd的固化率最高可达99.64%;CaO含量提高至3%(质量分数)后,浸出浓度低于1 mg/L,钙长石的形成可提高浸出液的pH值进而抑制Cd的浸出。黏土经烧结后可形成更致密的结构,将Cd包裹在液相内,同时Cd^(2+)可取代Ca^(2+)进入晶体中生成稳定的CdAl_(2)Si_(2)O_(8),使得Cd在黏土中被固定。

The effects of chemical composition and sintering temperature on the solidification rate and leaching concentration of Cd in clay sintering material were studied.And the solidification mechanism of Cd during clay sintering was investigated by XRD,SEM,XPS,FTIR and heavy metal speciation analysis.The results show that the increasing content of Fe_(2)O_(3) is beneficial to the formation of hematite,and the residue proportion of Cd sintering at 750 ℃ is higher than that of other samples.The content of CdAl_(2)Si_(2)O_(8) increases after increasing the Al/Si ratio.When the Al/Si ratio is 0.3 at the sintering temperature of 1 050 ℃,the solidification rate of Cd can reach 99.64%.When the CaO content increases to 3%(mass fraction),the leaching concentration is lower than 1 mg·L^(-1).The formation of anorthite increases the pH value of the leaching solution and inhibits the leaching of Cd.The clay can form a denser structure after sintering,which can wrap Cd in the liquid phase.At the same time,Cd^(2+) can replace Ca^(2+) in the crystal to generate stable CdAl_(2)Si_(2)O_(8),as a result,Cd is fixed in the sintered clay material.