Green liquor dregs and slaker grits residues characterization of a pulp and paper mill for future application on ceramic products

Green liquor dregs and slaker grits are pulp and paper mill residues usually landfilled. Whit high calcium carbonate content, its use as alternative raw materials in traditional ceramic products becomes an interesting study field. In order to evaluate its incorporation potential, the residues characterization with diverse approaches was performed and for the first time reunited exploring this eco-friendly intent. Green liquor dregs and slaker grits were characterized by its chemical and mineralogical composition (XRF, XRD, FT-IR); physical and morphological characteristics (particle size, BET surface area, density, SEM) and thermal properties (TGA). Chemical and mineralogical analysis reveals the high calcium carbonate content in calcite form especially on slaker grits, that has less inorganic and organic contaminants than green liquor dregs. Smaller irregular-shaped particles and bigger surface area was found on this last residue, comparing with slaker grits. The thermal analysis indicated a lower calcite decomposition for green liquor dregs (720 °C), while this event on slaker grits occurred 40 °C above (760 °C). Thus, it was observed the residues behavior and characteristics are much alike calcium carbonate itself, especially slaker grits, considering its composition, morphology and thermal events. As conclusion, the potentiality uses of green liquor dregs and slaker grits as alternative raw materials on ceramic products was revealed. Being able to incorporate clay, concrete, glasses and great majority of other ceramic products, these residues use will generate excellent benefit-cost ratio to industries and environment.