In situ kinetics and flocs conformation studies of kaolinite flocculated by Chi-g-CPAM

This study presents a comparative study of the flocculation behavior of kaolinite induced by chitosan-graft-poly(acrylamide-dimethyl diallyl ammonium chloride) (Chi-g-CPAM) and a commercial cationic polyacrylamide (CPAM). The flocculation behaviour was characterised in terms of both flocculation kinetics and the corresponding morphology changes during flocculation. Both Chi-g-CPAM and CPAM were grafted from silica wafers by means of atom transfer radical polymerization (ATRP). The quartz crystal microbalance with dissipation (QCM-D) tests were conducted. The equilibrium time flocculated by Chi-g-CPAM was found to be 0.46 times as that of CPAM, together with a larger total mass of kaolinite layer. The flocculation behaviour by Chi-g-CPAM can be well captured by a pseudo-first-order model. In contrast, the presence of CPAM leads to a more complex kinetics. A relatively larger fitting slope (0.4663) was obtained at the initial stage but the fitting slope droped to 0.2026 after 800 min, indicating a densification process caused by CPAM. The flocculation kinetics of CPAM can be captured by the Elovich model for the inital stage but the combination of pseudo-first-order and pseudo-second-order models for the latter stages, which can be attributed to the long chain of CPAM. With a dosage of 75 g/t, the settling test with Chi-g-CPAM exhibits the same turbidity in the supernatant but a smaller layer thickness of the settlement compared to CPAM. The study enables a better understanding of the flocculation behavior and contributes to the development of efficient flocculants in mineral processing and tailings treatment.

Automated summary

This study compared the flocculation behavior of kaolinite induced by Chi-g-CPAM and CPAM. The flocculation kinetics and morphology changes were characterized. Chi-g-CPAM showed a shorter equilibrium time and a larger total mass of kaolinite layer compared to CPAM. Chi-g-CPAM followed a pseudo-first-order model while CPAM had a more complex kinetics. The study provides insights into flocculation behavior and contributes to the development of efficient flocculants in mineral processing and tailings treatment.