A research on the cadmium ions adsorption of Sulfhydryl- and sulfo-functionalized UIO-66 with silica layer from water

Abstract

In this study, adsorption behavior on UIO-66, UIO-66@mSi-SH and UIO-66@mSi-SO3H were investigated with a great emphasis on cadmium. The UIO-66@mSi-SH was synthesized by postsynthetic modification with silica layer, and sulfo-functionalized UIO-66 with silica layer (UIO-66@mSi-SO3H) was obtained from oxidizing UIO-66@mSi-SH with H2O2. All prepared adsorbents were characterized by FT-IR, SEM, XRD and BET. The BET value of UIO-66 can reach 1304.59 m2 g−1. To fit the adsorption behavior curve of Cd2+, the isothermal adsorption curve (Langmuir, Freundlich and D-R models) and kinetic model (Quasi first-order kinetic, Quasi second-order kinetic and Elovich model) were utilized. It shows that the basic mechanism of adsorption process was determined by R2, AIC and other constants and the adsorption performance is shown as UIO-66@mSi-SO3H > UIO-66@mSi-SH > UIO-66. Langmuir and Elovich models showed better fitting results of UIO-66@mSi-SO3H adsorption process for Cd2+, and the R2 values were 0.97471 and 0.97817 respectively. The theoretical maximum adsorption capacity of UIO-66@mSi-SO3H for Cd2+ is 409.96 mg g-1 by Langmuir isothermal adsorption. The UIO-66@mSi-SO3H shows great adsorption capacity for Cd2+ with a surface area of 126.728 m2 g−1 and a pore volume of 0.102 cm3 g−1, which is approximately 93.73 % higher than UIO-66. Besides, more than 90 % adsorbents was able to be regenerated in shorter time after 5 cycles.