Remediation of heavy metal pollution in farmland soil is very important to protect human health and ecological security, and biochar has a certain adsorption and fixation effect on soil heavy metals. In this paper, three kinds of biochar (unmodified biochar, acid modified biochar and biochar from pyrolysis of alkali modified rice straw, abbreviated as RBC, HRBC and KRBC, respectively) were prepared from rice straw, the surface morphology characteristics of RBC, HRBC and KRBC were characterized with SEM scanning, BET specific surface area measurement and porosity measurement and the adsorption characteristics of Zn in/on the three kinds of biochar and the in-situ immobilization effect for the soil Zn were investigated through the laboratory simulation. The results showed that KRBC had larger specific surface area, richer porosity, more oxygen-containing functional groups on the surface, as well as higher aromaticity and carbonization degree than that of RBC and HRBC; the adsorption kinetic characteristics of Zn in RBC, HRBC and KRBC were fitted well with the quasi second-order kinetic model and the adsorption thermodynamic characteristics of Zn in RBC, HRBC and KRBC could be described well with both the models of Langmuir and Freundlich, the maximum adsorption capacity of Zn was the order of KRBC>RBC>HRBC; KRBC had the strongest immobilization ability for Zn in soil, which was related to the strongest ability of KRBC to improve soil pH and soil organic carbon. Therefore, biochar from pyrolysis of alkali modified rice straw (KRBC) was being of the significant immobilization remediation effect on soil Zn pollution. This study can provide theoretical and technical support basis for remediation of Zn contaminated soil.

农田土壤中重金属污染的修复对保护人类健康和生态安全非常重要，生物炭对土壤重金属具有一定的吸附和固定作用。本文从稻草中制备了三种生物炭（未改性生物炭，酸改性生物炭和碱改性稻草热解制得的生物炭，分别简称为RBC，HRBC和KRBC），RBC，HRBC和RBC的表面形态特征。通过SEM扫描，BET比表面积测量和孔隙率测量对KRBC进行了表征，并通过室内模拟研究了三种生物炭中锌在三种生物炭中的吸附特性以及对土壤锌的原位固定作用。结果表明，KRBC的比表面积更大，孔隙率更高，与RBC和HRBC相比，表面含氧官能团更多，芳香性和碳化度更高。Zn在RBC，HRBC和KRBC中的吸附动力学特性与拟二阶动力学模型吻合得很好，并且可以用Langmuir和Freundlich模型很好地描述Zn在RBC，HRBC和KRBC中的吸附热力学特性。锌的最大吸附量为KRBC> RBC> HRBC。KRBC对土壤中锌的固定能力最强，这与KRBC改善土壤pH和土壤有机碳的最强能力有关。因此，碱改性稻草（KRBC）热解产生的生物炭具有固定化修复土壤锌污染的作用。