The Effect Of Alternanthera Philoxeroides Biochar Aging On Heavy Metal Lead Retention In Tea Garden Soil

Due to the improper use of pesticides and fertilizers and the acidity of tea plantation soil,the pollution of lead in soils is serious.The physical and chemical properties of biochar?such as elemental content,specific surface area,surface structure and other physical and chemical properties?change when biochar is applied to soil environment,thus affecting the adsorption capacity of biochar to lead and the biochar's remediation effect on lead-contaminated soil.Therefore,with the wide application of biochar,it is of great significance to study the effect of aging on biochar.In this study,two kinds of biochar with pyrolysis temperature were prepared from the Alternanthera philoxeroides weed,and then were treated with the aging method of HNO₃/H₂SO₄ mixed acid solution.The effects of different pyrolysis temperature and aging process on the biochar properties and the remediation of Pb were discussed in lead-contaminated soil.The main conclusions are as follows:?1?After the aging treatment,the O/C ratio and the?O+N?/C ratio of biochar increased,indicating an increase in the oxygen-containing functional groups;The infrared spectrum showed that the carboxyl functional group and the aromatic structure of the biochar on the surface of biochar increased after aging.Aging caused a significant increase in the specific surface area of the biochar,and the integrity of the tubular structure was broken into fragmentation.?2?The effect of biochar on lead adsorption was studied from the aspects of kinetics,the effect of Pb²⁺initial concentration on adsorption and the effect of initial pH on adsorption.The results showed that all biochar samples reached adsorption equilibrium within 24 hours,and the adsorption rate of biochar prepared at lower temperature was higher than that of biochar prepared at higher temperature.The maximum adsorption capacity of Alternanthera philoxeroides biochar to Pb was up to 286.07 mg/g,and the biochar samples all reached the best adsorption effect when the solution pH was close to 5.?3?After Pb-contaminated soil and biochar were cultured for a period of time,the available state extraction method was used to extract the available Pb and the o rder of available Pb content was 200+LB<200+HB<200+LB-20%<200+HB-20%,600+LB<600+HB<600+LB-20%<600+HB-20%.The results showed that fresh biochar wi th lower preparation temperature had better soil remediation ability than fresh bioch ar prepared with higher temperature,and the biochar holding ability of lead decreas ed after aging.