Roasting And Leaching Experiment Of The Electroplating Sludge

At Present, Polymer heavy metal chelating agent depends on its strong complex ability for metals and become the best ideal choice for the end of treatment the electroplating wastewater.The biggest drawback of the process is to produce the degrade complex electroplating sludge containing copper, nickel, chromium,zinc and other metals to be difficult treated. So, recovery of the valuable metal elements from this sludge must be an urgent problem to be solved now.On the basis of analyzing the physical and chemical properties of the sludge in some park, aiming at containing a certain amount of organic matter and high metals, its combustion characteristics and the released gas compositions were studied under air atmosphere by TG–FTIR. The results show that the combustion process of organic matter in the sludge has four stages and the organic matter pyrolysis and combustion occur at 230?~450?; CO2, water vapor and traces of NH3 and SO2 are released during combustion. Considering the full combustion of organic, the decomposition of Cr(OH)3,Fe(OH)3 and Al(OH)3 and the metals volatilization, the best incineration temperature should be controlled at about 500?.Electroplating sludge roasting experiments in the tube furnace shows that the loss weight rate of the sludge is about 17% after it roastes at 500? for 1.5h, the metal content enriches the maximum in ash and the metals mainly exist as the metal oxide.But the amphoteric oxide Al2O3?Cr2O3?ZnO can not be separated from the ash by high temperature leaching.Electroplating sludge sodium roasting experiments in the tube furnace shows thatAl, Cr and Zn in the sludge are converted to a water-soluble NaAlO2, Na2CrO4 and Na2ZnO2, when the 1.0 to 1.1 times of the oretical amount of Na2CO3 was added to the sludge and the sludge was roasted at 700? for 1.5h. The ash is leached by water and the leaching rates of aluminum, chromium and zinc are 70%, 50% and 50%,respectly.But the condition of the roasting and the leaching process need to optimize in order to further improve the leaching rate of Al, Cr and Zn.