强化氯化焙烧梯级分离电镀污泥中铬镍铜机制研究

Study on the Mechanism of Enhanced Chlorination Roasting Step Separation of Cr,Ni and Cu from Electroplating Sludge

电镀污泥是一种具有资源和危害双重特性的人造富矿典型危险废物。采用NH_(4)Cl和CaCl_(2)为复合氯化剂,同时引入FeSO_(4)·7H_(2)O为强化剂,采用强化氯化焙烧的方式,通过控制调节温度场梯级分离电镀污泥中的Cr、Ni、Cu,并探究其梯级分离机制。热力学计算表明,电镀污泥中Ni、Cr、Cu的主要物相(Cr_(2)O_(3)除外)均能被HCl或Cl_(2)氯化成相应金属氯化物。试验结果表明:NH4Cl在大约400℃分解产生HCl,首先将电镀污泥中Ni、Cr、Cu的主要物相进行氯化,生成的少量CrCl_(3)在500℃左右挥发;在700℃时,FeSO_(4)·7H_(2)O分解产生SO_(2)和O_(2)促进CaCl_(2)分解生成Cl_(2)进行二次氯化;生成的NiCl_(2)在800℃时大量挥发,挥发过程可采用零级化学反应动力学模型即属相边界反应控制来描述;而生成的CuCl_(2)在900℃左右开始挥发,1100℃时挥发完全,且该温度下收集到的CuCl_(2)(H_(2)O)_(2)晶体纯度达到94%,高温挥发过程可用1级反应动力学模型和1/2级反应动力学模型共同描述。因此,在可控的温度场下,通过氯化剂的定向相变,可以实现Cr、Ni、Cu的逐步分离和高效回收。该研究为电镀污泥中有价金属资源化回收提供了新的方法和重要的理论依据,同时对其他多金属固废的资源化利用具有借鉴意义。

Electroplating sludge is a typical hazardous waste with both resources and hazards.NH_(4)Cl and CaCl_(2)were used as compound chlorination agents,and FeSO_(4)·7H_(2)O was introduced as the fortifying agent.By using the method of enhanced chlorination roasting,Cr,Ni and Cu in electroplating sludge were separated in steps by controlling and adjusting temperature field,and the step separation mechanism was explored.Thermodynamic calculation shows that the main phases of Ni,Cr and Cu in electroplating sludge(except Cr_(2)O_(3))can be chlorinated by HCl or Cl_(2)into corresponding metal chlorides.The experimental results show that NH_(4)Cl is decomposed to produce HCl at about 400℃.First,the main phases of Ni,Cr and Cu in the electroplating sludge are chlorinated,and a small amount of CrCl_(3)is volatilized at about 500℃.At 700℃,the decomposition of FeSO_(4)·7H_(2)O produces SO_(2)and O_(2),which promotes the decomposition of CaCl_(2)to produce Cl_(2)for secondary chlorination.The generated NiCl_(2)volatilized in large quantities at 800℃,and the volatilization process can be described by zero-order chemical reaction kinetics model,namely the phase boundary reaction control.The volatilization of CuCl_(2)begins at about 900℃and completes at 1100℃.The purity of CuCl_(2)(H_(2)O)2 crystals collected at this temperature is 94%and the volatilization process at high temperature can be described by the first-order reaction kinetics model and the 12 order reaction kinetics model.Therefore,the phase separation and efficient recovery of Cr,Ni and Cu can be realized by directional phase transformation of chlorinated agent under controlled temperature field.This study provides a new method and an important theoretical basis for the recovery of valuable metals from electroplating sludge and has significant reference for the recycling of other polymetallic solid wastes.