Study On Adsorption Properties Of Heavy Metals Lead By Preparation Of Modified Biochar Based Source Conditioning

Biochar is the solid product of biomass pyrolysis under the condition of absolute or limited oxygen,which is widely used as adsorbents for gaseous or liquid pollutants due to its special pore structure and stable physicochemical properties.Based on the biomass pyrolysis technology,the study combines source conditioning and biochar modification to prepare biochar with excellent adsorbed performance to alleviate heavy metals pollution in water.The obtained biochar was analyzed by an elemental analyzer,fourier transform infrared spectroscopy?FT-TR?,specific surface area analyzer?BET?,electron scanning electron microscopy?SEM?,X-ray photoelectron spectroscopy?XRD?,Zeta potential analyzer and so on.Then adsorption mechanism of biochar on Pb²⁺was analyzed by adsorption kinetics and isothermal adsorption.In this paper,the skin,pith and leaves of corn stalks were separately to pyrolyze,and the effects of reaction temperature and residence time on the yield and properties of biochar were investigated.When the reaction temperature was 600°C and the residence time was 30 min,the biochar with high yields and the largest specific surface areas was obtained.Under the reaction conditions,the polyethylene was mixed to co-pyrolyze with corn stalks in different proportions and the biochar was modified with potassium hydroxide.The removal of Pb²⁺from water by biochar was studied.The results strongly suggested that polyethylene played a role in promoting the physical and chemical properties of biochar and adsorptivity of biochar on heavy metals,and modified biochar by potassium hydroxide was more effective in improving the adsorption property,which was a good adsorbent for Pb²⁺.After mixed pyrolysis,the yields and oxygen content of biochar increased.When the mass ratio of biomass to polyethylene was 4:1,the yield and specific surface area of biochar were the largest.Potassium hydroxide modification made the pores of the biochar uniform which was mostly microporous structure and the specific surface area increased greatly.The adsorption capacity of biochar modified by potassium hydroxide for Pb²⁺was greatly improved with the increase of hydroxyl functional group of biochar.The adsorption amount of stem-pith biochar was the largest,reached 99.95mg/g.During the adsorbed process,the new phases were formed by the co-precipitation and complexation reactions of biochar and Pb²⁺.The Pseudo-second-order model and Langmuir adsorption isotherm model could preferably describe the adsorption process.