Selective Catalytic Reduction Of Nitric Oxide Emission Via Electroplating Sludge

Electroplating sludge is the sludge waste from wastewater treatment in platingindustry, which contains heavy metals. Though its quantity is much less thanwastewater, but the Cu, Ni, Cr, Zn, Fe and other heavy metals are transferred to thesludge, in a way, electroplating sludge is more harmful than electroplating wastewaterto the environment. If no disposal would been done, it is the most serious destructionof the environment, on the other hand, high concentration heavy metals fromelectroplating sludge not to be recycled also means the enormous waste of resources.In the "Twelve-Five" period, nitrogen oxides （NOx） is included in a binding indicatorsystem for the first time, total emissions need to be reduced10%. At present, thenational NOx emissions are about10Mt/a, according to estimates, domestic emissionswill reach20Mt/a by2015. Explore an effective cheap NOx catalyst is looming. Thisarticle studied the feasibility on catalytic decomposition of NO pollution gas viaelectroplating sludge, on a scientific basis for selective catalytic reduction of NOx.The effect on the sludge content by washing, acid leaching and precipitationpretreatment method had been studied. The result shows that: the optimal washingcondition is under the room temperature, liquid to solid ratio is200:1and5%NaClsolution for washing; the remove quality percentage of sulfate is up to100%, acidleaching and precipitation method can also remove the sulfate, but can not removethem completely; metal content in the sludge showed an upward trend. This paperfurther explored the actual catalytic properties of the two pretreatment methods ofelectroplating sludge catalysts in conditions of low concentration and highconcentration of NO. The result shows that: washing and acid leaching precipitationpretreatment both improve the catalytic performance of electroplating sludge, theeffect of washing pretreatment is better,5%NaCl washing is better than tap waterpretreatment, mainly due to5%NaCl can remove more calcium and sulfate. Catalytictempreture has a great influence on NO removal, the optimum temperature is500°C.This paper studied the effect of the catalytic temperature and electroplating sludge dosage on the NO catalyzing through the establishment of electroplatingsludge catalyst calcined at700°C for2h at Ar atmosphere preparation and NOcatalytic system. NO removal rate has remained at more than99%under750-650-550-450-350°C continuous catalytic experiments, indicating that theelectroplating sludge has good catalytic thermal stability. The NO removedstabilization time is amounted to222,694,733min under300°C,450°C and550°C,the catalytic effect is maintained at above99%.0.64g8#electroplating sludgecatalytic time is similar at450°C and750°C, NO removal amount is3.35mmol/g and3.04mmol/g, respectively, illustrating that the increase in the amount of electroplatingsludge does not affect the temperature effect on NO Catalytic. Catalytic removal ofNO last for853min and1509min and3.79mmol/g and3.35mmol/g NO removalcapacity under0.32g and0.64g electroplating sludge dosage, indicating electroplatingsludge catalyst amount is proportional to the catalytic removal of NO.The papar measured the C content before and after catalyting, C consumption is1.9mmol/g, the molar ratio of C consumption and NO decomposition is close to1:2,CO2is generated in the reaction process as measured by the GC, inferring catalyticreactions may occur similar to C+2NO=CO²⁺ N2reaction mechanism. From thesolid-phase product analysis, the electroplating sludge catalytic has no nitrogendeposition and NO3-cumulative phenomenon, the main phase comes into FeNiOmixture from FeNi mixture, indicating the FeNi in electroplating sludge has a certainreaction with NO and the oxygen in NO comes into FeNi mixture structure.Based on the concept of “waste treatment by waste”, and the system aboutmultiple metal loading of carbon, this paper used electroplating sludge to remove NOfor the first time, providing a new method for the degradation of NO and achievingthe purpose of recycle of electroplating sludge.