Synthesis of Calcium-Deficient Tobermorite under Atmospheric Pressure and Its CO<sub>2</sub> Adsorption Ability

DOI Web Site Web Site 5 Citations Open Access
  • YASUE Tamotsu
    Department of Industrial Chemistry, Faculty of Science and Engineering, Nihon University
  • ASANO Gota
    Department of Industrial Chemistry, Faculty of Science and Engineering, Nihon University
  • KOJIMA Yoshiyuki
    Department of Industrial Chemistry, Faculty of Science and Engineering, Nihon University
  • ARAI Yasuo
    Department of Industrial Chemistry, Faculty of Science and Engineering, Nihon University

Bibliographic Information

Other Title
  • カルシウム欠損型トバモライトの常圧合成と二酸化炭素の吸着能
  • カルシウム ケッソンガタ トバモライト ノ ジョウアツ ゴウセイ ト 2サンカ

Search this article

Description

Synthesis and CO2 adsorption ability of calcium-deficient tobermorite were investigated. The calcium-deficient tobermorites with Ca/(Al+Si) atomic ratios lower than that of the theoretical composition, 0.83, were prepared by the reaction in the system CaCl2-Na2SiO3-AlCl3-H2O under atmospheric pressure. The calcium-deficient tobermorites were characterized by means of X-ray diffraction, thermal analysis (TG-DTA), infrared spectroscopy and chemical analysis. The calcium-deficient tobermorite was formed from starting solutions with Ca/(Al+Si) atomic ratios lower than 0.95. Most Ca2+ ions existing in interlayers of the tobermorite, 20% of total Ca2+, were removed successively by decreasing the initial Ca/(Al+Si) atomic ratio from 0.95 to 0.70, and then the basal spacing of the calcium-deficient tobermorite expanded by replacing one Ca2+ ion site with two Na+ ions until the atomic ratio of 0.7. However, the layer structure of the tobermorite was destroyed at the atomic ratios below 0.7. The amount of Na+ ions to compensate for charge deficiency in calcium-deficient tobermorites obtained at an initial Ca/(Al+Si) atomic ratio of 0.7 and initial Al/(Al+Si) atomic ratio of 0.10 was changeable by number of washings with pure water. The composition after washing was expressed by the formulas of Ca4Na0.4[(Al+Si)6O11H2]⋅4H2O including ion defects after ten times washings (5g/dm3 H2O) and Ca4Na2.1[(Al+Si)6O22H2]⋅4H2O after one time washing (5g/100cm3 H2O). The maximum exchange capacity for Na+→K+ of Na+ present in the calcium-deficient tobermorite was 95meq/100g irrespective of the amount of Na+. The adsorption capacity of CO2 at 60°C in the tobermorite increased with increasing Na/(Al+Si) atomic ratio and reached a maximum value of 3.0mmol/g at the atomic ratio of 0.36. The desorption of CO2 and adsorption of Na+ progressed simultaneously on washing the tobermorite which adsorbed CO2 with 1N NaCl solution. Accordingly the tobermorite washed with NaCl solution was available as CO2 adsorbent. when the adsorption and desorption were repeated many times, the formation of CaCO3 originated from partial carbonation in the tobermorite was unavoidable, and consequently, the adsorption capacity of CO2 decreased successively with increasing recycle number. On the other hand, when the calcium-deficient tobermorite after desorption of CO2 was heated at 200°C, its adsorption capacity was kept at 2.0mmol/g even after using five times.

Journal

Citations (5)*help

See more

Keywords

Details 詳細情報について

Report a problem

Back to top