Effect Of Washing On The Adsorption Of Lead And Atrazine By Biochar

Biochar is a stable carbonaceous product derived from thermal pyrolysis of organic wastes under oxygen-limited and low-temperature?<700??conditions.Because of its rich surface oxygen-containing functional groups,developed pore structure and high surface aromatization,as well as low cost and high efficiency,it has a good application prospect in environmental pollution control.Pyrolysis temperature and raw materials have a significant impact on the physicochemical properties of biochar,and then affect its function.Therefore,it is very important to select suitable raw materials and optimize pyrolysis conditions for obtaining the optimal biochar.Although biochar materials have good stability,the physical and chemical properties of biochar can be changed by long-term natural environmental effects?such as leaching from rainwater scouring or river irrigation?or human factors?such as water washing?,which in turn affect its adsorption properties to pollutants.In this paper,peanut shell,corn stover and corn cob were used as raw materials to prepare biochar through different pyrolysis temperatures?450°C,650°C?,and the biochar was washed with water to characterize and compare the effect of washing on the physical and chemical properties of different kinds of biochars.Aiming at the pollution problems of lead and atrazine in some regions of China,the effect of washing on the adsorption performance and the competitive adsorption of coexisting pollutants as well as mechanism of pollutants by biochar was clarified.The main results of this thesis are as following:1)the elemental composition,pore structure and mineral composition of biochar prepared by different pyrolysis temperatures and raw materials are different,and the water washing treatment only has a significant effect on ash content and pH.2)high temperature?650??biochar is more conducive to the adsorption of Pb²⁺,and the water washing treatment significantly reduces the adsorption capacity of biochar to Pb²⁺.The adsorption of coexisting ions Cd²⁺is affected by Pb²⁺,while the adsorption of Pb²⁺was weakly affected by Cd²⁺.3)Low temperature?450??biochar was more beneficial to the adsorption of atrazine.Washing treatment significantly promoted the adsorption of atrazine by biochar except BCps650.The presence of Pb²⁺significantly inhibited the adsorption of atrazine by BCcs450 and BCcs650,while the presence of atrazine had little effect on the adsorption of Pb²⁺by BCcs450 and BCcs650.The washing treatment changes the competition relationship between coexisting pollutants.4)The mechanism for Pb²⁺sorption by biochar mainly includes precipitation with minerals,complexation with functional groups and Pb²⁺-?interaction.The mechanism of biochar adsorbing atrazine mainly includes partition into uncarbonized fraction,hydrogen bond,?-??EDA?interaction,pore-filling and hydrophobic effect.