Study On Preparation And Adsorption Properties Of Sludg-based Biochar

The disposal and treatment of sewage sludge become key issue in the environmental filed.Sludge pyrolysis is an important technology,which can not only reduce the amount of sludge but also produce new materials,such as biochar,gas and oil.This thesis mainly focuses on the resource utilization of sludge through pyrolysis protocol.The effects of different reactors and pyrolysis atmosphere on the physical and chemical properties of sludge biochar were investigated by direct pyrolysis of sludge in pure nitrogen gas and low oxygen baking coupled pyrolysis in rotary tube furnace and fixed bed tube furnace.Furthermore,the co-pyrolysis of sludge and camellia oleifera shell was carried out to explore the influence of co-pyrolysis on the physical and chemical properties of the biochar.Then,the adsorption behavior and kinetics properties of tetracycline on the biochar were investigated.The adsorption mechanism of tetracycline on biochar was explored by FTIR and XPS.The main results are as follows:(1)Compared with the sludge biochar pyrolyzed in rotating tube furnace at the same temperature,the biochar prepared in the fixed-bed tube furnace has lower O/C ratio and higher H/C ratio,indicating that the biochar pyrolyzed in the fixed-bed tube furnace has lower hydrophilicity and higher stability.BET results show that the specific surface area of the sludge biochar prepared in the fixed bed tube furnace is larger than that prepared in the rotating tube furnace when the pyrolysis temperature is higher than 700 ℃.The calorific value of sludge biochar pyrolyzed in fixed bed tube furnace is lower than that in rotary tube furnace.Compared with that of biochar pyrolyzed in pure nitrogen gas,the calorific values of biochar pyrolyed in nitrogen gas with low oxygen gas are increased.(2)The addition of camellia camellia oil shell reduced the ash content of biochar and increased the calorific value of biochar.However,the pore volumes and the contents of inorganic components are reduced by the addition of camellia oil hull.(3)According to the kinetic and isotherm anlysis,the adsorption of tetracycline on biochar mainly follows chemical adsorption mechanism.The dried sludge biochar pyrolyzed at 700 ℃ exhibits the highest adsorption capacity towards tetracycline,which reaches to 238.58 mg/g.The adsorption capacity of tetracycline on biochar obtained by co-pyrolysis of dehydrated sludge and camellia oil hull is 197.03 mg/g.More importantly,the drying process of sludge is omitted through co-pyrolysis of camellia oil hull and dehydrated sludge which can greatly reduce energy consumption.Although the biochar synthesized in this thesis has a relatively low adsorption capacity for tetracycline compared with the commercial activated carbon(336 mg/g),the preparation protocol has the advantages of low cost simple process and convenient operation.Therefore,the sludge based biochar developed in this thesis is a cheap adsorption material with a relatively high application prospect and is expected to be used for the removal of volatile organic compounds(VOCs)in automobiles.