Highly Efficient Cd2+ Removal Using Tobermorite with pH Self-Adjustment Ability from Aqueous Solution

Juan Qin; Sujuan Yuan; Mauricio Córdova-Udaeta; Keishi Oyama; Chiharu Tokoro

doi:10.3390/ma16031314

Highly Efficient Cd²⁺ Removal Using Tobermorite with pH Self-Adjustment Ability from Aqueous Solution

Materials (Basel). 2023 Feb 3;16(3):1314. doi: 10.3390/ma16031314.

Authors

Juan Qin¹, Sujuan Yuan¹, Mauricio Córdova-Udaeta², Keishi Oyama², Chiharu Tokoro^{2

3}

Affiliations

¹ School of Chemistry and Chemical Engineering, Nantong University, Nantong 226019, China.
² Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan.
³ Faculty of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.

Abstract

Cadmium (Cd), as a type of heavy metal, can increase the incidence of many diseases, even in low concentrations. In this study, tobermorite was hydrothermally synthesized and then applied to adsorb Cd²⁺ from an aqueous solution. The physicochemical characteristics of the synthesized tobermorite were detected, and the results indicated that the well-crystallized tobermorite had a lot of mesopores and a large specific surface area of 140.92 m²/g. It acquired a pH self-adjustment ability via spontaneously releasing Ca²⁺ and OH^- into the aqueous solution. The effects of different factors on Cd²⁺ removal were investigated. For Cd²⁺, the removal efficiency could reach 99.71% and the maximum adsorption capacity was 39.18 mg/g using tobermorite. The adsorption data was best fitted with the pseudo-second-order kinetic and Langmuir isotherm models. In addition, there was no strict limit on the solution pH in Cd²⁺ adsorption because the tobermorite could adjust the solution pH to an alkaline atmosphere spontaneously. The efficient removal of Cd²⁺ using tobermorite was a result of surface complexation and ion exchange.

Keywords: adsorption; cadmium; calcium; pH self-adjustment; tobermorite.

Abstract

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