@misc{oai:repo.qst.go.jp:00068413,
 author = {Ishikawa, Nao and Uchida, Shigeo and Tagami, Keiko and Nakamaru, Yasuo and 石川 奈緒 and 内田 滋夫 and 田上 恵子 and 中丸 康夫},
 month = {Mar},
 note = {Selenium (Se) is one of the elements that have some radioactive isotopes. One of them is a fission product with long half-life, about 1.1 million years. Therefore, Se is an important pollutant for radioactive waste management.
Soil organic substances influence pollutant sorption on soil. Recently, some researchers have studied Se sorption onto many types of soils. However, no study has been carried out for Se adsorbability onto soil organic substances.
 In this study, Se sorption onto humic acid, a soil organic substance, was discussed using a simple kinetic approach, that is, the pseudo-second order chemical sorption equation. This equation was described by t/qt=1/h+t/qe, where qt: amount of sorbate on the surface of the sorbent at any time, t; h: initial sorption rate; and qe: the amount of sorbate at equilibrium. 
 Humic acid (HA) was purchased from Wako Pure Chemicals Industries Ltd. Batch sorption tests using Se-75 were carried out to obtain data sets. Elevated amounts of HAs were selected, 100, 200, 500, and 1000 mg. Each was placed in a plastic bottle (30 mL), and then 9 mL of deionized water (milli-Q quality) were added. Prior to adding Se-75, the suspension was shaken at 120 reciprocations per min for 24 h at 23 deg C using an end-over-end shaker. One mL of Se solution, which included 8 kBq of Se-75 with 0.1 - 3 micro-g of stable Se as a carrier, was added to each sample bottle: The initial concentrations of Se in the bottles were adjusted from 10 to 300 micro-g/L. In order to determine the time required to reach the sorption equilibrium, the sample suspensions were destructively taken at times from three hours to twenty days after the addition of Se in HA suspensions. Each sample suspension was filtered through a 0.45-micro-m membrane filter. Gamma rays of Se-75 in the filtrate were measured with a NaI scintillation counter (Aloka ARC-380) to determine its activity concentration.
 The results of Se sorption onto humic acid showed that t was proportional to t/qt. In addition, qe calculated from the pseudo-second order chemical sorption equation corresponded to qe obtained from a batch experiment. Therefore, Se sorption onto humic acid fit the pseudo-second order chemical sorption equation. On the other hand, the amount of Se sorbed was proportional to the initial Se concentration, and also proportional to the logarithm of the solid-liquid ratio. As a result, an empirical model was derived with two parameters, the initial Se concentration and solid-liquid ratio, to predict the sorption capacity of Se sorbed on HA., the 32th Waste Management Symposium (WM'06)},
 title = {The kinetic sorption of Se onto humic acid},
 year = {2006}
}