Treatment of oily wastewater by oily sludge-based biochar
In order to realize the harmless treatment and resource utilization of oily sludge,oily sludge was prepared into biochar by the pyrolysis and carbonization method.The mixed materials of calcium oxide,fly ash,and hexadecyltrimethylammonium bromide were used as the conditioning agent,and the corn straw was used as the carbon enhancer in the preparation of oily sludge-based biochar.The effects of ZnCl2,KOH and H2SO4 activators on the adsorption properties of biochar were compared based on the petroleum removal rate.The specific surface area,pore structure,and surface functional groups of biochar were analyzed with SEM,FTIR and BET.The adsorption and regeneration properties of biochar for oily wastewater treatment were studied by batch adsorption and regeneration experiments.The results showed that the best activator was H2SO4,and the specific surface area of biochar was 71.8069m2/g.The H2SO4 activated biochar contained a large number of pore structures with mostly mesoporous,and the surface of biochar exists—CH,C==O,—OH and C==C functional groups.When the dosage of biochar is 1.8g/L and the adsorption time is 180 min,the petroleum removal efficiency of oily wastewater(200mg/L)can reach 98.21%,and the petroleum adsorption capacity of biochar was 99.32mg/g.The process of petroleum adsorption on biochar conformed to the quasi-secondary kinetic equation and the Freundlich model,and it was a multi-molecular layer adsorption mainly controlled by chemisorption.In addition,the characteristics of the three regenerated biochars including pore structure,surface functional groups and specific surface area were not significantly different from those of the new biochar.Adsorption of different concentrations of petroleum pollutants in oily wastewater,biochar three times of regeneration efficiency reached more than 90%,which still had good adsorption performance and could meet the requirements of recycling.
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