Valorization of baghouse dust from lime industry through carbonation processes.

Baghouse dust from the lime industry typically contains substantial amounts of CaO and NaCl. Owing to its high chloride content, this dust is unsuitable for direct incorporation into finished products and is therefore commonly diluted and discharged as waste. Meanwhile, CO2 emissions represent another major environmental concern associated with lime production. To address both issues, this study employed the Modified Solvay Process and a direct carbonation method to synthesize NaHCO3, aragonite, and vaterite. In the Modified Solvay Process, baghouse dust was dissolved in deionized water to obtain a saturated NaCl solution, which subsequently reacted with CaO, NH4HCO3, and CO2 to form NaHCO3. The effects of CaO concentration, NH4HCO3 dosage, and reaction temperature on NaHCO3 production were systematically investigated to determine the optimal operating conditions. The residual CaO after the Modified Solvay Process was further converted into aragonite and vaterite. Aragonite was produced by adjusting reaction time, temperature, and stirring speed without the addition of extra chemicals, whereas vaterite formation was controlled through reaction time and temperature, with ethylene glycol added as a modifier. Under optimal conditions, 100 g of baghouse dust yielded 16.0 g of NaHCO3. Aragonite with a phase fraction of 84.70% and an aspect ratio of 17.22, as well as vaterite with a phase fraction of 87.20% and an average particle size of 730.51 nm, were also successfully obtained. The total CO2 capture was 35.7 g. In short, this study demonstrates a feasible approach to valorizing lime-industry baghouse dust while simultaneously mitigating CO2 emissions.