Effect Of Tea Polyphenols On Cu(?) Adsorption By Two Variable-charge Soils

The effect of tea polyphenols on adsorption capacity of Cu(?) by variable-charge soils and the release of cations from these soil base on batch equilibrium experiments. Influence conditions including dose of tea polyphenols, initial concentration of copper ions and the pH of the suspension system.The adsorption capacity of Cu(?) by two variable charge soils(Oxisol and Ultisol) was increased with dose of tea polyphenols increasing. The extent influence of Oxisol was greater than the Ultisol. With the dose of tea polyphenols continue increased, the adsorption capacity of Cu(?) was declined, especially Ultisol. In the presence of tea polyphenols, the release capacity of Mn2+ was increased greatly and the release capacity of Mn2+ from Oxisol was much than from Ultisol. With the dose of tea polyphenols increasing, the release capacity of Mn2+ from Oxisol and Ultisol were decreased. Tea polyphenols which with a large amount of negative charge increased the soil surface negative charge. The Ca2+ and Mg2+ were decreased to reach the soil surface charge balance.The Cu(?) adsorption capacity of Oxisol and Ultisol were increased with the concentration of Cu(?) increasing. Tea polyphenols increased the Cu(?) adsorption capacity by two Variable-charge Soils. Both Langmuir and Freundlich equations fitted the adsorption isotherms of Cu(?) by the two soils well. Tea polyphenols increased the maximum Cu(?) adsorption capacity of Oxisol and Ultisol, from 38.6 mmol kg-1 to 76.9 mmol kg-1 and form 49.1 mmol kg-1 to 117 mmol kg-1, respectively. The KL was also increased, especially for Oxisol. With the concentration of Cu(?) increasing, the release capacity of Mn2+ also increased.Tea polyphenols enhance adsorption capacity of Cu(?) highest at pH 4.5. Tea polyphenols increased electrostatic adsorption of Cu(?) in low pH and decreased electrostatic adsorption at high pH. Manganese oxides were reduced by tea polyphenols and then released Mn2+ to the suspension. Hydrogen ion activity decreased as pH increasing, thus the release of Mn2+ decreased. In the presence of Tea polyphenols increased release of Mn2+, because of tea polyphenols can be reduced from manganese oxides. Tea polyphenols can increase negative charge on surface of soil, thereby reduced Ca2+ and Mg2+ release from Variable-charge Soil The release capacity of Fe3+/Fe2+ and Al3+ was related to free tea polyphenols in the suspension. At low pH or high pH condition, much free tea polyphenol in suspension, so the release capacity of Fe3+/Fe2+ and Al3+ least at pH 4.5.In Conclusion, tea polyphenols can increase the Cu(?) adsorption capacity by two Variable-charge Soils, mainly to increase as non-electrostatic adsorption. With the increase of initial concentration of Cu(?), the adsorption capacity of Cu(?) was also increased. Cu(?) and tea polyphenols can be synergistic adsorbed on surface of soil. Tea polyphenols enhance adsorption capacity of Cu(?) highest at pH 4.5. Manganese oxides were reduced by tea polyphenols and then released Mn2+ to the suspension. The Mn2+ release in from Oxisol was significantly higher than that from Ultisol. Tea polyphenols can increase negative charge on surface of soil, thereby reduced Ca2+ and Mg2+ release from Variable-charge Soil The release capacity of Fe3+/Fe2+ and Al3+ was related to free tea polyphenols in the suspension.