| Summary: | 碩士 === 國立中興大學 === 土壤環境科學系所 === 100 === Burning crop residues, such as rice straw, is a common post-harvest practice on farmland, leading to the accumulation of biochars in the soil. To understand the role of biochar in determining the mobility and bioavailability of heavy metals in soil, this study investigated the adsorptions of Cu(II), Zn(II), Ni(II), Cd(II) and Pb(II) ions by two biochars derived from rice straw. Batch adsorption experiments were performed as a function of pH, contact time, initial concentration and ionic strength. The results showed that the adsorptions of metal ions on the biochars were strongly dependent on pH and ionic strength. The biochars exhibited affinity toward the metal ions in the order of : Pb(II)>Cu(II)>Cd(II)≅Zn(II)≅Ni(II). The adsorption isotherms of these metal ions were all fitted well to the Langmuir isotherm. Desorption hysteresis was observed for Cu(II) and Pb(II), indicating that their adsorptions were not reversible.
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