Efficient Cd(II) Removal from Aqueous Solution Using Mechanically Activated CaCO3: Removal Pathway and Mechanism
2022
Wang, Zhenlei | Zhao, Yunliang | Wen, Tong | Zhang, Tingting | Bai, Haoyu | Song, Shaoxian | Zhang, Qiwu
Cd(II) pollution in water will cause serious threats to the environment and human health. The general remediation protocol for Cd(II) pollution by hydroxide (Ca(OH)₂ or NaOH) is still faced with filtering difficulties and high effluent pH. To develop an applicable method for the Cd(II) removal in water, we prepared an activated calcium carbonate (CaCO₃) material by changing the crystallinity, particle size, and surface activity of CaCO₃, and investigated the corresponding Cd(II) removal capacity from aqueous solutions. The results showed that more than 99.9% of Cd(II) was removed within 10 min in an initial concentration of 50 mg L⁻¹. Moreover, the effluent pH is close to neutral after removal of Cd(II), and the sediment is filtered well. Comparative experiments and characterizations have demonstrated that the excellent Cd(II) removal performance of activated CaCO₃ is due to the mechanical activation changes the surface activity of the original stable CaCO₃, promotes the slow-release dissolution equilibrium of the active carbonate groups, and thus the coprecipitation of cadmium hydroxide and cadmium carbonate on CaCO₃ particles. This research demonstrates that mechanical activation of CaCO₃ could be used as a repair material for efficient removal of heavy metal pollution in water, which can solve the problems of filtration and high effluent pH of alkaline precipitation.
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