Flocculation kinetics of precipitated calcium carbonate (PCC) with sterically stabilized nanocrystalline cellulose (SNCC)

The interactions between precipitated calcium carbonate (PCC) and sterically stabilized nanocrystalline cellulose (SNCC) have been studied. SNCC is produced by periodate oxidation of cellulose fibres and consists of a crystalline cellulose region from which dialdehyde modified cellulose chains are protruding from both ends. The morphology of SNCC can be controlled by the degree of oxidation, which depends on the amount of periodate and the reaction time. In this study, three SNCCs with different reaction times were prepared and their interactions with PCC particles were examined. These SNCC particles have similar diameters (5-10 nm) and their length is reduced with increasing reaction time, whereas the length of the protruding chains is increased. Adsorption isotherms of three SNCCs and dialdehyde modified cellulose (DAMC) on PCC particles were determined. It was found that DAMC had a higher affinity than SNCCs, and the affinity of SNCC increased with reaction time. This indicates that DAMC chains adsorb stronger than the crystalline region of SNCC on PCC. The PCC flocculation induced by three SNCCs was monitored by photometric dispersion analysis, which showed that SNCC particles could bridge PCC to induce flocculation at low dosages (above 1 mg/g). SNCC induced the maximum flocculation when its fractional coverage is above 50%, implying that PCC particles coated by SNCC continue to flocculate, as observed experimentally. Further addition of SNCC to PCC suspensions results in slower flocculation rates and smaller floc sizes. (C) 2016 Published by Elsevier B.V.