Study on the Chemical Oxygen Demand of Liquid after Reduction of Silver Hydrazine Hydrate
At present,formaldehyde is commonly used as a reducing agent for silver reduction,but formaldehyde has high storage requirements,is easy to crystallize,and the COD value of the reduced solution is high,which has high requirements for wastewater treatment.Taking silver chloride as the intermediate material in the treatment process of copper anode slime as the research object,hydrazine hydrate reduction was used with an initial alkalinity of 100 g/L;Liquid solid ratio 4∶1;the amount of hydrazine hydrate is 1.2 times the theoretical amount,and the main grade of silver in the prepared coarse silver powder cast into the anode plate is 99.8%,which meets the requirements for the grade of the silver electrolysis anode plate.The average COD of the silver reduction solution is 4 510 mg/L,which was much smaller than the existing formaldehyde reduction solution.Hydrazine hydrate reduction replacing formaldehyde can effectively reduce the COD value of wastewater,which is of great significance for promoting the ecological and environmental protection work of factories.
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