RESEARCH PROGRESSES IN REMEDIATION OF HEAVY METAL CONTAMINATED SOILS WITH BIOCHAR

With the acceleration of the urbanization process and the rapid development of industrial production, soil heavy metal pollution is increasing seriously, which is causing serious harm to the ecological environment. Biochar is a solid material containing high fractions of aromatic functional groups and carbon. It is produced through thermal degradation under anoxic or oxygen-limited conditions. It attracts extensive attention because of significant effect in the remediation of soil contaminated with heavy metals. Based on the recent research achievements on biochar remediate heavy metals contaminated soil at home and abroad, the advances of some important aspects on, the research current situation and progress are summarized from several important aspects. They include production and properties of biochar, remediation effect and influencing factors and adsorption mechanism. The follows are shown. (1)Biochar has the advantages of low prices, high efficiency, soil improvement and friendly environment. (2)The physicochemical properties of biochar are affected by biomass materials and pyrolysis temperatures. Activation, magnetization, oxidation and digestion can improve the properties of biochar and efficiency of remediation. (3)The effect of biochar on heavy metal mobility and bioavailability includes two aspects:immobilizing heavy metals to reduce bioavailability or mobilizing heavy metals to increase bioavailability. The latter can be modified to reduce the mobility and bioavailability of heavy metals. (4)The effect of biochar on soil solidification is general, combining with other solidifying materials to improve the mechanical properties of solidified soil. (5)The effect remediation mechanism of biochar immobilized heavy metals is ranked as follows:precipitation > complexation > electrostatic interaction and ion exchange > physical adsorption. Finally, on account of research status in this field, some important research emphases and directions in the future are proposed. They mainly include establishing a uniform classification criterion of biochar, exploring the efficiency of biochar on multi-heavy metals pollution, illustrating the mechanism and contribution rate of adsorbing heavy metals by biochar, expanding the research scale, and carrying out solidification experiment and mechanical property research based on biochar.