Synthesis of Mesoporous Calcium Silicate by Ultrasonic-Assisted Template Method and Evaluation of Its Adsorption Characteristics for Cd(II)
Mesoporous calcium silicate (MCS) was prepared from calcium nitrate and sodium silicate by ultrasonic-assisted template method. The effects of different templates (sodium dodecyl sulfate, cetyl trimethyl ammonium bromide, P123, and cetyl trimethyl ammonium bromide–tetramethyl ammonium hydroxide) on the pore size and surface topography of MCS were investigated. Calcium silicate synthesized was characterized by X-ray diffraction, scanning electron microscopy, the Brunauer–Emmett–Teller method, and Fourier transform infrared spectroscopy. The adsorption performances of the MCS synthesized for Cd2+ were also investigated. Results showed that the MCS synthesized using cetyl trimethyl ammonium bromide as template under ultrasonic treatment acquired a mesoporous slit-pore structure with a specific surface area of 244.32 m2 g−1 and pore size (DBJH) of 11.2 nm. MCS showed extremely high adsorption capacity for Cd2+ at pH 5.0–7.5, and the adsorption capacity for Cd2+ was 509.91 mg g−1 at 293 K, which was much higher than those of the adsorbents in literature. The equilibrium adsorption data of MCS for Cd2+ all fitted the Langmuir and Redlich–Peterson models, and more closely with the Redlich–Peterson model. The adsorption of MCS toward Cd2+ was a spontaneous endothermic reaction driven by increased entropy involving both physical and chemical modes. The adsorption of MCS for Cd2+ was better described by the pseudo-second-order model than by the pseudo-first-order model, with an activation energy of 13.4327 kJ mol−1. Thus, it is evident that MCS can be a promising excellent adsorbent for the treatment of Cd2+-containing wastewater.
KeywordsMesoporous calcium silicate Ultrasonic-assisted template synthesis method Cd2+ Adsorption charateristics
This research was supported by the National Nature Science Foundation of China (Grant No. 51378201) and the Key Scientific Research Program of Hunan Education Department (Grant No. 16A069).
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