Effects Of Biocharon Lead Or Zinc Contaminated Soil

Currently, an effective and economic measures to get rid of heavy metal pollution of soil is the priority for environmental pollution remediation. Biochar’s characteristics such as porous structure and surface functional groups, high stability, enable it to have the capacity of immobilized heavy metals, which has great potential in the treatment of heavy metal contaminated soil. In this paper, we choose corn stalk, peanut shell as raw material to produce different biochars under 300, 500, 700℃,together with commercially Silver Fir Charcoal as research biochars, and characterized their basic physical and chemical properties. Biochars’ adsorption experiment was carried out to determine each biochar’s adsorption capacity of lead and zinc, and then we selected suitable biochars as research materials in the future. The morphological distribution and leaching toxicity of the heavy metals in the lead or zinc contaminated soil by different biochars were evaluated by waterlogged incubation experiment and leaching experiment, which can analysis the mechanism of biochar immobilized heavy metals. Finally, we conducted soybean pot experiment to research the effect of biochar on crop heavy metal toxicity. The main conclusions were as follows:(1) The characteristics of biochar are associated with raw materials and pyrolysis temperature. With the increase of pyrolysis temperature, biochar has declined production rate,higher pH value and ash content, specific surface area, whereas less surface functional groups.Biochars prepared under same pyrolysis temperature, the yield of the peanut shell biochar is greater than the yield of corn straw charcoal, whereas ash content is less than the corresponding temperature of corn straw charcoal ash content. Each biochar’s pH value is alkaline, and has a large number of pores, large surface area, hydroxyl and carboxyl, aromatic functional structure.(3) the used biochars all have strong adsorption ability for lead and zinc, and the maximum number of adsorption of Pb(II) is greater than the zinc(II) the maximum adsorption capacity; Solution pH values effect biochar’s adsorption for Pb(II), zinc(II)significantly. For Pb(II) and zinc(II) adsorption optimum pH values were 5.0 and 6.0; In general, biochar acquired by relatively high pyrolysis temperature has stronger adsorption ability for Pb(II), zinc(II). Different biochars have significant differences in the adsorption capacity of Pb(II): peanut shells biochar > corn straw charcoal > silver fir charcoal, and for zinc(II) adsorption force difference is not obvious.(3) with 1%, 1% and 5% of biochar addition amount, flooded cultivation experiment suggested that biochar can increase soil pH and organic matter content, which increased with the increased amount of biochar addition; Biochar changed the formation distribution of lead and zinc, thus reducing its biological activity, and the decrease margin increased with the more adding amount of biochar; Corn straw charcoal for soil lead pollution repair effect is best, while peanut shells biochar repair works best for zinc contaminated soil in the peanut shell biochar corn straw charcoal and silver fir charcoal,; Secondary water leaching and acid leaching experiment simulation showed that biochar can effectively fixed lead and zinc in the soil, reduced the leaching rate.(4) In the lead-contaminated soil, the amount of 3%(weight/weight) of the corn straws charcoal or silver fir charcoal short-term pot experiment showed that: biochar can promote the growth of soybeans, specifically increase the weight of the soybean plants, roots length andchlorophyll content; soybean roots, stems and leaves enrichment of lead absorption were lower than the control, which indicating that biochar can reduce the lead with crop damage.Biochar can effectively reduce the lead content in soil, Increase the pH value and organic matter content. Compared with silver fir charcoal, the effect of corn straw charcoal fixed lead in soil better.