IMMOBILIZATION EFFECT OF SLUDGE BIOCHAR ON HEAVY METALS IN CONTAMINATED DREDGED SEDIMENT IN RIVER CHANNELS IN MINING REGION
To clarify the immobilization effect of sludge biochar on Cu,Pb,and Cd in dredged sediment contaminated by river channel in a mining region,this study used the municipal sludge as raw material to prepare sludge biochar under anoxic condition at 500 ℃,analyzed the influences of addition ratios of different sludge biochar on the distribution and immobilization effect of three heavy metals in dredged sediment,combining with characterization methods of scanning electron microscopy,FTIR and XPS.The results showed that the addition of sludge biochar could improve the stabilization forms of heavy metals in dredged sediment.When the addition ratio was 1.0％,the proportion of Cu,Pb,and Cd in the stable(oxidizable and residual)in dredged sediment increased by 37.7％,42.9％,and 42.4％,respectively.Sludge biochar mainly immobilizes heavy metals through complexation reaction and precipitation.The leaching concentration of Cu,Pb,and Cd in the dredged sediment after sludge biochar immobilized decreased from 0.876 mg/L,0.057 mg/L and 0.018 mg/L to 0.253 mg/L,0.011 mg/L and 0.001 mg/L,respectively.Meanwhile,the leaching concentration was lower than the limit of the Class Ⅲstandard of Environmental Quality Standard for Surface Water(GB 3838-2002).The immobilized dredged sediment can be reused as resources with no risk of secondary dissolution of heavy metals.
sludge derived biocharrivers in mining regiondredged sedimentheavy metalimmobilization effects
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