The Study On The Sorption Properties Of Kaolin、Bentonite And Its Composite Materials For Strontium

Kaolin and bentonite is used widely in wastewater treatment due to low prices and rich production. This paper focuses on the sorption mechanism of the clay to the waste water and makes better use of the environmental conditions to have a higher sorption rate of clay. Besides, the sorption effect of natural clay is not ideal, so the clay is modified to get clay composite adsorbent for a high sorption rate and provide more broad prospects for the practical application.In this paper, the purified kaolin and Gaomiaozi bentonite and the carboxymethyl chitosan/Bentonite composite that modified by Gaomiaozi bentonite are as adsorbent. The paper is studied about the effect of time, adsorbent concentration, pH value and ion strength, humic acid, foreign ions and temperature on Sr(II) sorption. The main results are as follows:1. The XRD, FT-IR and SEM images show that carboxymethyl chitosan has been inserted into Gaomiaozi bentonite interlayer. The synthesis of carboxymethyl chitosan/Bentonite composite is successful.2. There is a significant effect on Sr(Ⅱ) sorption onto the kaolin, bentonite and its composite for the sorption time. With the increasing time, the sorption rate increases significantly. The sorption equilibrium is reached in a short time.3. The effect of adsorbent concentration on the sorption of Sr(Ⅱ) onto kaolin, bentonite and its composites is mainly expressed in the following conclusions. With the increase of the concentration, the sorption sites on adsorbent surface also increases, the complexes with Sr(Ⅱ) have been formed more and the sorption rate also increases.4. The effect of pH on Sr(Ⅱ) sorption onto kaolin, bentonite and its composite is also strongly. The sorption mechanism is mainly due to the ion exchange function for a large number of functional groups on the surface with Sr(Ⅱ); when the pH value is low, the concentration of H~+ is high, functional groups are protonated, the protonated groups and positively charged Sr(Ⅱ) have electrostatic repulsion, there are competition between H~+ and Sr(Ⅱ) for sorption position; when the pH increases, due to the deprotonation, the adsorbent surface charged more negatively, the adsorbent and the complex is strengthened, therefore Sr (Ⅱ) sorption rate is greatly improved; the ionic strength is also confirmed that the sorption mechanism is mainly ion exchange and complexation.5. Humic acid and foreign ions have a certain influence on Sr(Ⅱ) sorption onto kaolin, bentonite and its composite, the influence mechanism is that humic acid can form the complex with Sr(II), the coordination and complexation between the foreign ions and Sr(II).6. By fitting the experimental data and the kinetic equation, the sorption behavior of Sr(II) on clay and its composites are fitted well with the second-order kinetic equation, the sorption rate is controlled by the chemical sorption mechanism.7. The sorption isotherms of Sr(II) on clay and its composite are fitted well with the Langmuir model. The thermodynamic study also shows the sorption process is a spontaneous and endothermic; the sorption behavior is promoted by higher temperature.