Carbon dioxide capture with aqueous calcium carbide residual solution for calcium carbonate synthesis and its use as an epoxy resin filler

Calcium carbide residue (CCR) is a waste obtained from the production of acetylene gas by the hydration reaction of calcium carbide. This residue is generated in large quantities annually and requires appropriate disposal. The main composition of the residue is calcium hydroxide (Ca(OH)₂). Ca(OH)₂ can react with CO₂ gas and form CaCO₃ particles. This process is well known but not very attractive since Ca(OH)₂ is obtained from limestone using an energy-intensive thermal conversion process. This paper examined the synthesis of CaCO₃ from CCR solutions by capturing CO₂ with the aid of triethanolamine (TEA) solutions at doses of 0, 5, 10 and 20% w/w. The precipitated CaCO₃ was characterized, and the application of CaCO₃ as a filler in epoxy resin was tested. The results showed that the precipitated CaCO₃ was mainly calcite, with a 76.6% yield. Cubic calcite was primarily obtained in TEA solutions, whereas small and agglomerated spherical vaterite and cubic calcite particles were formed in non-TEA solutions. The CaCO₃-filled epoxy composites showed higher compressive strength than the neat resin. However, the transparency of specimen plates was reduced. These results can serve as guidelines for the application of CCR slurry filtrate obtained from the sedimentation ponds of acetylene plants and help to reduce the amount of wastewater that needs to be treated. CO₂ gas from industrial flue gas combined with TEA solution could be applied to precipitate CaCO₃ for carbon-neutral manufacturing.