Enhanced adsorption performance of La(III) and Y(III) on kaolinite by oxalic acid intercalation expansion method

This paper reported a new method to enhance adsorption performance of La(III) and Y(III) on kaolinite by enlarging the interlayer space of kaolinite. The intercalation method could enlarge the interlayer space of kaolinite effectively in previous research literatures, whereas there were few studies on utilizing further reaction of intercalators to expand and exfoliate kaolinite by generating gas. The expanded kaolinite (EKH) involved in this study could enhance adsorption performance of La(III) and Y(III) significantly. The EKH in a state between extended and exfoliated was obtained undergoing two steps. Firstly, H2C2O4 was inserted into the kaolinite layers through the secondary substitution liquid phase intercalation method. Secondly, the Kaol-H2C2O4 (KH) intercalation complex was rapidly calcined with H2C2O4 and Na2CO3, the power provided by the neutralization reaction promoted the thermal decomposition of H2C2O4 between the kaolinite layers to produce a large amount of gas. XRD showed that the interlayer space of the KH intercalation complex expanded from 0.717 nm to 1.112 nm. The specific surface area and total pore volume of the EKH were 1.5 and 2.2 times higher than unmodified kaolinite respectively. The surface of EKH possessed higher zeta potential with more negative charges. The results of batch adsorption experiments showed that the adsorption capacity (101.5 mg/g and 78.9 mg/g) of EKH to La(III) and Y(III) was much higher than that of kaolinite (17.1 mg/g and 9.8 mg/g). Pseudo-second-order model and Langmuir model manifest the adsorption kinetics and isotherm. Therefore, the EKH prepared by the intercalation expansion method could be prospectively applied to the treatment of La(III) and Y(III) in in-dustrial wastewater.