| Biochar was widely used in environmental Teatment because of its huge surface area and rich surface functional groups.However,the use of biochar in the study of heavy metal Pb-Cd complex in red soil is reported.(HTT = 300 ?,400 ?,500 ?),different residence time(2h,5h)and 18 ?/min heating rate were used to study the biochar and the application of bio-carbon to lead-cadmium pollution of red soil stabilization technology research,the test soil samples for the kaolinite type red soil.The basic mechanism of the biochar was prepared by analyzing the characterization of biochar and treated soil samples.The stabilization mechanism of biochar on the simultaneous stabilization of Pb-Cd complex in red soil was explained.The main results show that:(1)The shaddock peel pyrolysis stage was 180~430?,the mass loss was 60%;the carbonization stage was 420~500?,the quality loss was 20%.The pyrolysis stage of chaff was 260~355? and the mass loss was 45%;the carbonization stage was 350~630?,and the mass loss was 30%.When the temperature exceeds the carbonization temperature,only 10% of the remaining ashes were left.(2)As the pyrolysis temperature increase,the surface structure of the biochar is more complex,and the surface functional groups began to aromatize by simple hydrocarbon alkyl groups,hydroxyl groups,carboxyl groups and ester groups until 500 ° C.These surface functional groups could provide a large number of chemical adsorption sites,contribute to the stability of lead and cadmium adsorption.The effect of pyrolysis residence time on surface structure was not obvious.(3)The stabilization effect of biochar on soil Pb and Cd was higher than that of HTT 500?.The biochar stabilization group with 5h carbonation residence time had a longer stabilization advantage than 2h.The stabilization effect of soil carbon and grapefruit soil was better than that of the chaff,and the short-term(stabilization time <16 days)showed obvious fluctuation,and steady growth after 16 days.The stabilization effect of soil bio-treated group on soil lead was significantly increased after 16 ~ 32 days.(3)Simulated lead addition stability test can be obtained,the bio-charcoal in the lower lead concentration(Group C added)have a better stabilization effect on lead,more than Group D the increase is the performance of the activation.The stabilization rate of lead and cadmium was 57.6% and 48.6%,respectively.The optimal stabilization effect of P5 group was group A of treatment,and the stability of lead and cadmium was the rate of lead and cadmium stabilization was 55.9% and 32.6%,respectively.The optimal stability of the C5 group was 55.2% and 32.6% respectively.With the increase of lead content in soil,the effect of cadmium on red soil was not significant.The short-term and stable effects of Pb-Cd and C5 in red soil were not significant,but the long-term effect was not significant.The bio-charcoal of grapefruit was fluctuated in the short term,and the medium and long term had some potential for stability.(4)The the highest average stable capacity of Pb was in group C: C5 group,13.01 mg/g,P5 group 17.78 mg/g and P10 group8.93 mg/g.The average stable capacity of biochar to cadmium in red soil was 0.012 mg/g in group C5,0.026 mg/g in group B of P5 and 0.017 mg/g in group P10 The The stability of the grapefruit biochar on the Pb and Cd in the red soil was greater than that in the P5 group,and the optimum dosage was 5%(w: w).(6)According to the analysis of each characterization,the stabilization of soil lead and cadmium mainly depends on the surface physical adsorption,but the chemical adsorption of functional groups such as-OH,methyl,methylene,-C=O and R-C-O.(C36H70O4Pb),L-phenylalanine disulfide(C18H20CdN2O4)and other metal-organic complexes,as well as difficult to form a metal-organic complex of lead and cadmium and biochar on the hydroxyl,carboxyl ester and other functional groups.Dissolved lead arsenate(PbAs2O6)and other chemical precipitation,so as to achieve the purpose of stabilizing soil heavy metals. |
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