Directional Extraction Of Copper From Electroplating Sludge Based On Phase Change Regulation Of Chlorides

Copper is a strategic metal resource that is involved in many aspects of the national economy.China,as the world’s largest copper consumer,consumes nearly 50%of copper in the world annually,but its reserves are less than 3%of the world.So we have to pay more attention to the recycling of secondary copper resources.On the other hand,because the electroplating sludge generated from the electroplating industry is rich in heavy metals with high toxicity,it is recognized worldwide as a hazardous solid waste.The research on the separation and extraction of heavy metals from electroplating sludge is considered as the key to solving environmental problems and recovering heavy metal resources.Since the copper grade of electroplating sludge is much higher than the average grade of the world’s annual mined copper ore,and the annual discharge of sludge is huge,it is of great significance to recover the copper.However,the sludge composition is complex,so it is difficult to balance the separation efficiency and reaction energy consumption by the existing extraction methods.Therefore,it is urgent to research how to reasonably reduce energy consumption and extract copper from electroplating sludge efficiently and selectively.Due to metal chloride is characterized by easy solubility and volatility,it can effectively reduce the metal recovery temperature by chloritizing roasting.But the direct recovery of copper in the form of chloride has rarely been reported in the field of electroplating sludge disposal.Based on the principle of phase regulation,this work extracted the copper directionally and selectively in the form of chloride from the separation copper-containing electroplating sludge and the copper-nickel mixed electroplating sludge respectively,which not only reasonably reduced the energy consumption of the smelting extraction method,but also overcame the non-selectivity of leaching method.The main research contents are as follows:（1）The chlorination-volatilization method was used to treat separation copper-containing electroplating sludge to extract copper in the form of Cu Cl₂·2H₂O in one step.Furthermore,the effects of chlorination agent type,holding time,reaction temperature and agent addition ratio on the copper recovery were investigated.The main components in this sludge were Ca CO₃,Si O₂,Mg₃Si O₁₀（OH）₂,Cu（OH）₂,Fe（OH）₂,and Fe（OH）₃.After treatment,97%of the copper in the sludge was volatilized as chloride,while the remaining metal impurities were transformed into stable metal salts（Ca SO₄,Ca Mg Si₂O₆）and oxides（Fe₂O₃,Fe₃O₄）.The purity of the products obtained was 95%.And the mechanism of copper volatilization process was explained thermodynamically.Finally,the feasibility of this method was evaluated from the economic,technical,and environmental perspectives.（2）The copper-nickel mixed electroplating sludge was treated by the chlorination-volatilization method,and the copper in the mixed electroplating sludge was selectively recovered in the form of Cu Cl_2·2H₂O through thermal regulation or the regulator Si O₂.The effects of reaction temperature,holding time,addition of chlorinating agent and Si O₂on the selective extraction of copper were investigated.The raw sludge mainly contained Ca,P,Cu,Ni,Fe and Al,among which the contents of heavy metals Cu and Ni were 6.9wt%and 5.5 wt%,respectively.Under the optimal conditions,the extraction rate of Cu could reach 93%,while the volatilization rate of Ni was stably controlled to below 5%.And,the mechanism of selective separation of copper from copper-nickel mixed sludge was analyzed from the thermodynamic perspective.（3）Based on the studies in the first two chapters,we know that the separation process of copper was mainly based on the volatilization of chloride.In order to deeply understand the mechanism of copper volatilization process and to provide more theoretical support for the optimization and application of chlorination-volatilization method,we introduced the method of thermal analysis kinetics to analyze the kinetic process of copper chloride volatilization.As shown by the results,with the increase of the heating rate,the TG curve shifted toward higher temperatures and the copper volatilization rate also increased,providing research ideas for rising the recovery rate of copper from low copper content.The average value of apparent activation energy₍（6） for copper chloride volatilization is94.20 k J/mol.This process followed a single kinetic mechanism,which could be described by the Power Law,the mechanism function is（）=^1/15,belonging to theα-t accelerated curve.