Study on the risk of heavy metals in coking sludge carbon and its application in coking wastewater treatment
Coking sludge carbon was prepared from coking sludge.Afterwards,the form transformation and risk assessment of heavy metals in the process of carbonization and modification with nitric acid were studied,and the efficiency of modified coking sludge carbon for coking wastewater treatment was explored.The contents of Cr and Ni in coking sludge(CWS)were much higher than other heavy metals.Coking sludge carbon(CWS-C)was obtained after carbonization and then the modified coking sludge carbon(CWS-C)was obtained after activation.The ecological risk factor(RI)was decreased from 122.79(CWS)to 33.70(CWS-N),indicating the low risk of heavy metal pollution in CWS-N.In comparison with CWS-C,CWS-N contained a variety of iron phases(i.e.,FeO,Fe2Al2O4,Fe3O4 and Fe0.95C0.005)which was in favor of the Fe(Ⅱ)/Fe(Ⅲ)cycle;thus,CWS-N could effectively catalyze H2O2 to produce·OH,and the removal rate of TOC in coking wastewater was as high as 66.3％.The iron leaching rate of iron,the active component,on CWS-N was less than 0.5％,indicating its superior catalytic stability.The dissolved organic compounds in coking wastewater were mainly lignin,lipids and condensed nucleus compounds,while the compounds contained N or S accounted for 81.1％.Most organic compounds could be removed after catalytic degradation with CWS-N.
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