Experimental Study On Immobilization Of Lead In Soil By Amino Modified Biochar

Soil heavy metal pollution has always been a pain and difficulty in environmental governance.Biochar can not only improve the physical and chemical properties of soil.but also reduce the migration efficiency and bioavailability of heavy metals in soil.In this paper,straw biochar pyrolyzed at 500℃was used as raw material to modify the amino group.The amino group modification of biochar was verified and evaluated by means of element analysis,Fourier transform infrared spectroscopy,zero potential and other methods.The adsorption characteristics of amino modified biochar were analyzed by adsorption experiments.Different amounts of biochar and modified biochar were applied to treat Pb polluted simulated soil,and the effects of modified biochar on soil physical and chemical properties,nitrogen and phosphorus content,Pb available state and chemical form in soil were investigated.The main conclusions are as follows:（1）The adsorption process of amino modified biochar is mainly controlled by the process of quasi-second-order kinetics model.The equilibrium adsorption capacity calculated from the fitting results is also close to the equilibrium adsorption capacity measured by experiment.At 25℃,the maximum adsorption capacity is 45.8mg/g,and the adsorption capacity is increased by 145%compared with that before modification.The thermodynamic study shows that the adsorption of Pb²⁺by amino modified biochar is a spontaneous and chaotic process,and the adsorption process is more consistent with Langmuir model,indicating that the adsorption process is monolayer adsorption.When the solution p H was less than 5,the adsorption capacity of amino modified biochar was inhibited with the increase of the solution p H.When the p H was between 5 and 6,the change range of biochar adsorption capacity was small.When the p H is greater than 7,a precipitation reaction occurs.（2）Amino biochar improved the physical and chemical properties of soil.After biochar remediation,the cation exchange capacity in soil increased by 3.11%-4.61%.Soil organic matter content also increased significantly.Ammonia nitrogen in soil treated with amino modified biochar increased by 83.75%～146.28%.After adding biochar,the content of available P and available K in soil increased by 12.79%～40.47%and 28.9%～127.2%respectively.（3）After the addition of amino modified biochar,the content of available lead in soil decreased significantly.The available lead of BC-1%in the experimental group was 11.7%more than that of NBC-1%,and the available lead of BC-3%in the experimental group was 15.1%more than that of NBC-3%.The proportion of extractable heavy metals in the soil treated with modified biochar decreased significantly,and the proportion of residue Pb in the soil treated with amino modified biochar increased by 75%～375%compared with the control group.The results showed that the amino modified biochar had a fixed effect on Pb in soil.There are 32 figures,9 tables and 94 references in this thesis.