Aggregation Process and Mechanism of Pitch Deposits with Ca2+ in Papermaking White Water

Abstract

The lipophilic colloidal substances (CS) in papermaking white water mainly originate from sizing agents applied during paper manufacturing operations and wood extractives, such as resin acids and fatty acids. In this study, the aqueous dispersions of sodium resinate and sodium stearate were used to simulate the colloidal substances concentrated in white water. The aggregation process and mechanism of pitch deposits developed from soluble colloidal particles were investigated by the determination of turbidity and zeta potential of colloidal substances simulacra dispersions as a function of Ca 2+ concentration, as well as through morphological observation, structural characterization, and contact angle measurement of calcium-induced pitch deposits. The results showed that the micelles with hydrophilic groups extending in the water could be formed when the colloidal substances accumulated to a certain concentration. The Ca 2+ can exchange Na + of colloidal substance micelles, and hydrophobic pitch deposits can then be produced by either particleparticle collision or "layer by layer" adsorption with addition of Ca 2+ , or by both of the mechanisms mentioned above. The complete destabilization of the colloidal substance simulacra occurred when the Ca 2+ concentration reached 5 mmol/L. The initial contact angles of water on the surfaces of calcium resinate and calcium stearate discs were 90.2° and 96.0°, respectively.

Analysis of dissolved and colloidal substances in old corrugated containers’ whitewater and dissolved substances’ impact on colloidal substances’ stability

“…The solids of the whitewater were separated to obtain the supernatant as the DCS water. The DCS water was dialyzed with deionized water by a dialysis tube for 48 h (deionized water replaced every 4 h), then obtained the CS (Johnsen et al 2004;Chen 2016).…”

“…However, when the Ca 2+ concentration reached 10 mmol/L and continued to rise, the turbidity, average particle size, and zeta potential of CS tended to be gentle and close to the effect of Ca 2+ alone. This may have been due to the constant concentration of Na + in the solution, which was equivalent to acting as a "buffer" in the system (Chen 2016). In addition, there is competition between Na + and Ca 2+ for adsorption sites.…”

Polyethyleneimine Addition for Control of Dissolved and Colloidal Substances: Effects on Wet-End Chemistry

“…In an earlier study the mechanism of the aggregation process was studied for a DCS simulacra system, which included rosin acid sodium, sodium stearate, and sodium polyacrylate (Chen et al 2015). When the concentration of Ca 2+ in system reached 5 mmol/L, the DCS and Ca 2+ interacted with each other to form complexes having substantially neutralized surface charge.…”