High Efficiency Chromium Reducing Agent for Cement Based on Nitrite Intercalated LDHs

Abstract

Abstract: Based on the structural reconstruction ability of layered double hydroxides (LDHs), the nitrite intercalated LDHs were prepared. In this paper, nitrite intercalated LDHs was added into cement as a new type of chromium reducing admixture. Reduction efficiency, resistance to storage and stability under ball milling temperature conditions of nitrite intercalated LDHs were investigated. The mechanism of reduction and solidification of soluble Cr⁶⁺ in cement using nitrite intercalated LDHs was revealed. The results show that nitrite ions released from LDHs-NO₂ interlayer mixing with water rapidly reduce soluble Cr⁶⁺ and effectively decrease soluble Cr⁶⁺ content in cement. The addition of 0.2%(mass fraction) LDHs-NO₂ reduces the soluble Cr⁶⁺content in cement from 40.26 mg/kg to 9.36 mg/kg, and improves the compressive strength of cement by about 2 MPa. The reduced Cr³⁺ exchanges with Al³⁺ into LDHs laminate to achieve stable chemical solidification. The reduction efficiency of synthetic nitrite intercalated LDHs is better than FeSO₄·7H₂O. Furthermore, synthetic nitrite intercalated LDHs remains reductive stability when the cement is stored for a period and treated at ball mill temperature.

Key words: layered double hydroxide, hexavalent chromium, cement, steel slag, reduction efficiency, solid waste recycling, raw material substitution

CLC Number:

TQ172.1

YUAN Bo, ZHAO Liang, LI Bo, CHEN Wei, TANG Pei, CAO Hailin, GUO Yue. High Efficiency Chromium Reducing Agent for Cement Based on Nitrite Intercalated LDHs[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2023, 42(5): 1542-1550.

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