Effects of pyrolysis temperature on physicochemical properties and cadmium adsorption of wetland plant-based biochar

LI Xinyi; LU Lifang; MA Chunya; LEI Mingjing; ZHU Jian

doi:10.13732/j.issn.1008-5548.2023.01.006

Abstract：The biochar was prepared by thermal decomposition method at 300,500,and 700℃using wetland plants as raw materials including Canna indica L(MBC),Thalia dealbata Fraser(ZBC)and Cyperus involucratus Rottboll(HBC).The physicochemical properties of the biochar were characterized by automatic elemental analyzer,scanning electron microscope and infrared spectroscopy,and the adsorption characteristics of cadmium on the biochar were systematically studied by static adsorp-tion method.The results show that the pyrolysis temperature has a great influence on the physicochemical properties,surface morphology and mineral composition of biochar.The biochar that prepared at medium temperature(500℃)and high tempera-ture(700℃)pyrolysis temperature has better cadmium adsorption capacity than the low temperature(300℃).The pyrolyzed biochar on 500℃has the highest adsorption capacity,its average adsorption capacity for Cd2+ reaches 96.00 mg·g-1,the extreme value reaches 108.28 mg·g-1,and the adsorption capacity from large to small is ZBC,MBC,HBC.The adsorption equilibrium time of pyrolyzed plant-based biochar on 500℃to Cd2+ is about 30 mins.The appropriate dosage and larger solution pH,initial ion concentration and reaction temperature have positive effects on the Cd2+ adsorption.The adsorption process of Cd2+ by biochar is in line with the Freundlich isothermal adsorption model and quasi-two-stage kinetic model,and it belongs to preferential adsorption.The higher pyrolysis temperature can promote the aromatization of biochar,improve the pore structure and increase the specific surface area,which in turn enhances the activity of biochar.The biochar pyrolyzed at medium and high temperature has better adsorption capacity for cadmium.