| As an important secondary resource,electroplating sludge is highly valued by people.In its comprehensive utilization process,the key technology is the efficient leaching of incineration ash and the separation and recovery of valuable metals in the leaching solution.In this paper,copper,nickel and zinc were leached from the sludge by H2SO4 and NH3·H2O-?NH3?2CO3 system and the separation and recovery of the valuable metals in the leaching solution were studied.When the sludge is leached using 5.5 mol·L-11 H2SO4 at 85?for 65min under the optimal conditions,the leaching liquid-solid ratio is 3.5,the leaching rate of copper,nickel,zinc and iron was up to 91.37%,90.10%,91.24%and 91.37%respectively.When the sludge is leached using 4.5 mol·L-11 NH3·H2O-?NH3?2CO3 at 65?for 90min under the optimal conditions,the leaching liquid-solid ratio is 6:1,the leaching rate of copper,nickel and zinc can reach 85.55%?82.66%and 90.93%respectively.Using NH3·H2O-?NH3?2CO3 system leaching sludge,copper,nickel and zinc leaching rate is not as good as that of sulfuric acid,but the leaching selectively is better,there are few kinds of impurity metals in the solution,it is advantageous to the separation and recovery of metals from the leaching liquid.The recovery of metals in the NH3·H2O-NH4HCO3 leaching solution was carried out by Na2S precipitation and HCHO reduction-Na2CO3 precipitation nickel and zinc-precipitation calcination-Na OH solution dissolving zinc.The better conditions for recovery metals using Na2S precipitation is that the 1.0 times theory amount Na2S,the precipitation temperature for 30?,the precipitation time for 10 min,copper,nickel and zinc precipitation rate can reach 99.90%,97.44%and 99.90%respectively.In the step by step recycling process,the reduction Cu?NH3?42+using HCHO,the optimal conditions are the pH value for 11,25%HCHO concentration,the reduction temperature for 50?,the reduction time for 20 min,the copper precipitation rate can reach 99.7%.the precipitation nickel and zinc better conditions with Na2CO3 is 100g·L-1of Na2CO3 concentration,75?of the precipitation temperature,30 min of the precipitation time,9 of the precipitation pH value,nickel precipitation rate is up to 91%.Although the recycling process of Na2S precipitation has advantages,the process is rather simple and the precipitated liquid can be returned to leach for comprehensive utilization.However,these metals in the leaching solution are recovered in the form of mixed metal sulfide,and it is not separated effectively.The research results provide some theoretical and technical support for the recovery of copper,nickel and zinc in electroplating sludge. |
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