The invention discloses a passivator for treating Cd / Pb-polluted soil. The passivator is proportionally composed of
biochar,
red mud and monoammonium
phosphate. When the passivator is in use, a TCLP (
toxicity characteristic leaching procedure) process is utilized to evaluate the heavy
metal pollution conditions in soil, the weight of the passivator is determined according to the
mass ratio of the soil, and the passivator is applied into the soil many times at appropriate time intervals, thereby effectively improving the soil microenvironment. In the slightly alkaline high-reducibility soil, the mobility of Cd and Pb is greatly lowered, and the
biochar can absorb abundant Cd and Pb in the soil. The nano
red mud has fine particles, contains rich iron aluminum oxides, and can effectively combine Cd-Pd; the applied monoammonium
phosphate and
red mud further enhance the Cd / Pb adsorptivity, thereby obviously lowering the bioavailable-state Cd / Pb content in the soil, and greatly lowering the Cd / Pb content in crops. Meanwhile, the passivator has high soil environment friendliness, can not generate secondary
pollution, and thus, has popularization and application values.