Cementitious Additives for Chloride Ion Immobilization of Flue Gas Desulfurization Brine

Waste management in coal‐fired power plants presents a significant industrial challenge. Co‐disposal of flue gas desulfurization sludge and reject fly ash (RFA) requires solidification/stabilization before landfilling, due to high concentrations of toxic heavy metals and salts. Cementitious additives enhance the encapsulation capacity of brine‐RFA mixes by activating reactions and precipitation of toxic‐element binding phases. This study assesses chloride ion (Cl − ) immobilization capacity of binary, ternary, and alkali‐activated blends of Portland cement (PC), calcium aluminate cement (CAC), calcium sulfoaluminate cement (CSA), blast furnace slag (BFS), and metakaolin (MK) under NaCl exposure using thermodynamic modeling. Ternary blends of 45% CAC, 10% PC, and 45% MK, and 50% CSA, 10% PC, and 40% MK achieved the highest Cl − sequestration, while 58% CSA and 42% BFS, and 86% BFS with 14% NaAlO 2 achieved the highest Cl − binding capacity in their respective categories.