Synergistic mechanism of CTAB and nonionic polyacrylamide on pore structure of kaolinite filter cake

Abstract

Filtration rate and water content of filter cake are decisive indicators in tailings solid–liquid separation processes, with the pore structure of the filter cake playing crucial roles in determining these outcomes. This work aims to investigate the effect of different filter aids on filter cake characteristic and to elucidate the mechanism of surface wettability regulation and flocculation on the pore structure of the filter cake using X-ray microtomography (XMT) to capture the porous structure of the filter cake. The results indicated that the filtration rate of the kaolinite suspension reached 12.25 × 10 -3 mL/(s·cm2) when the dose of cetyl trimethyl ammonium bromide (CTAB) was 0.3 mmol/L and nonionic polyacrylamide (NPAM) was 40 g/t. In comparison to the case without CTAB, the water content of the kaolinite filter cake decreased from 40.21% to 34.91%. Analysis of the filter cake structure demonstrated that the percentage of isolated pores in the filter cake, obtained via CTAB pretreatment followed by NPAM flocculation, was reduced to 10.12%, with uniform pore space development, good homogeneity, and an increased pore throat coordination number. These enhancements effectively improved the connectivity of the filter cake pores and created more pathways for water migration during the filtration process. Concurrently, the pore throat radius ratio in the filter cake decreased from 1.15 to 1.10, minimizing capillary resistance during water migration, resulting in a significant increase in filtration speed and efficacy.