Settling of Bentonite Particles in Gelatin Solutions for Stickwater Treatment

The settling of calcium and sodium bentonite coated with adsorbed protein from gelatin solutions was investigated across pH 3 to 9. The particle settling or sedimentation was achieved at acidic environment regardless of the amount of protein adsorbed by the particles. The settling is attributed to the formation of “house of cards” structure by bentonite platelets and it is strongly influenced by solution pH. The collapse of this formation resulted in floc formation or particle suspension where no settling can be observed. Few possible settling mechanisms were proposed based on the charge balance and interactions between bentonite platelets and protein molecules in the system. The findings are intended for treatment of gelatin-rich stickwater (meat rendering waste water) using bentonite as low-cost adsorbent. Integrating adsorption and settling into one unit operation has multiple benefits; reducing BOD by removing the proteins and bentonite is directly modified with organics and can be recovered via gravity settling for composite additive application.