不同NaNO_3浓度下可变电荷土壤铜离子解吸率的分配及影响因素

研究了江西红壤和昆明铁质砖红壤在去离子水中和在0.1molL-1NaNO3溶液中吸附铜离子后,依次在包括去离子水在内,浓度由低到高的NaNO3溶液中解吸时,铜离子解吸率在不同吸附pH段的分配规律。结果表明,随着吸附pH的升高,可在去离子水中解吸的铜离子解吸率变化规律与在NaNO3溶液中者完全不同。在所研究的吸附pH范围内,大致以吸附pH3.7~4.0为界,低于此值时,吸附性铜离子基本以在去离子水中解吸为主,反之则基本为交换性解吸。土壤中氧化铁含量和吸附时溶液的NaNO3浓度越高,则能被交换解吸的铜离子所占总解吸率的比例越低。其原因与不同pH段各种铜离子吸附态在不同吸附条件下的比例分配以及解吸对体系pH的影响有关。

Distribution of Cu(II) desorption rate in variable charge soils relative to concentrations of NaNO3 and its affecting factors

To investigate the distribution of Cu(II) desorption rate, a test was conducted on using electrolyte solutions, including de-ionized water, varied in NaNO3 concentration from low to high, to desorb successively copper ions, which adsorbed in de-ionized water or 0.1 mol L-1 NaNO3, by two variable charge soils, Ali-Haplic Acrisol and Hyper-Rhodic Ferralsol, which collected from jinxian and kunming respectively. Results showed that there were obviously difference of Cu(II) desorption rate under different condition of stripping liquid with increasing pH. In de-ionized water, the pH-dependent Cu(II) desorption rate always displayed a linear declining curve; in NaNO3 solutions, Cu(II) desorption rate peaked with the tendency of rising for the first and down latter, but the total of Cu(II) desorption rate was all declined with increasing pH. Which desorbed in 0.1 mol L-1 NaNO3 has the greatest desorption rate of Copper ions. In general, the Cu(II) desorption rate in de-ionized and in NaNO3 solutions dominated at low pH and at high pH, respectively. The Cu(II) desorption rate in NaNO3 was closely relative to the content of ferric oxide in soils and the NaNO3 concentrations in adsorption, the more content of ferric oxide, or the higher concentrations of NaNO3 in adsorption, the lower ratio that can be desorbed by NaNO3 above pH 3.7~4.0. The reasons which lead to the above-mentioned phenomena should be the effect of ion-strength, the proportion of changeable state of Cu(II) and the effect of desorption on pH of system. In this paper, the difference between desorption that occurred in single concentration of NaNO3 and that in multiple concentrations of NaNO3.