Influence of Dual Surface Functionalized Nanoparticles on Flocculation and Dewatering of Kaolinite Suspensions
Creators: name: Karaki, Taha
Publisher: name: Schulich School of Engineering
Year: 2022
Subjects: subject: Kaolinite suspension
subject: mature fine tailings
subject: settling
subject: flocculation dewatering
subject: nanoparticles
subject: nanoflocculants
subject: polyacrylamide
subject: sodium lauryl sulfate.
subject: Physical Sciences

description: Mature fine tailings (MFT) generated from oil sands extraction processes in Alberta are the most challenging mine tailings to settle and dewater. MFT typically contains almost 35 wt% of fine clays covered by a layer of residual bitumen. These clays are essentially composed of kaolinite mineral (&lt;2 microns in size), which represents over a third of the solid composition of MFT. This thesis investigates the effect of nanoparticle grafted with dual polymer (i.e., hydrophobic and hydrophilic species), termed as nano-flocculants, on enhancing the flocculation and consolidation of kaolinite suspensions. Four different types of eco-friendly nanoparticles were initially synthesised, using the hydrothermal method, and subsequently functionalized with polyacrylamide (PAM) and sodium lauryl sulfate (SLS) at room conditions. The flocculation and dewatering performance for each nano-flocculent was evaluated by measuring the initial settling rate (ISR), supernatant turbidity, capillary suction time (CST) and specific resistance to filtration (SRF).Results showed that the initial settling rate of kaolinite increased from 0.45 m/h to 20.4 m/h after introducing the dual surface functionalized nanoparticles. It appears that ISR is nanoparticle specific, where iron-based nanoparticles showed the highest ISR owing to their higher density and the capability of grafting significant amounts of PAM and SLS compared with other types of nanoparticles. It appears that surface activity of these nanoparticles allowed grafting more segments of PAM/SLS, which provided additional bridging and capturing sites of the suspended kaolinite particles. The effect of coexisting pollutants, e.g., bitumen and cations, on kaolinite settling and interactions with nano-flocculants were comprehensively addressed. As for the dewatering study, results showed that adding 3000 mg/L of nano-flocculants reduced the CST value to as low as 17 s and SRF to as low as 0.16×10^10 m/kg, compared with 90 s and 1.4×10^11 m/kg for conventional flocculants, respectively. It appears that the presence of hydrophobic agent (SLS) bonded to the PAM backbones greatly enhanced the dewatering performance of nano-flocculants. Settling and consolidation model (S-model) was modified and successfully used to describe the flocculation and dewatering behavior of the applied nano-flocculants using phenomenological model parameters. The proposed model presented a straightforward approach to predict and capture all characteristics of the settling and consolidation performance for each nano-flocculants.Experimental and modeling results obtained from this study provide clear insights into the phenomenon that governs the synergistic effects of nanoparticle grafted with dual polymer on flocculation and subsequent dewatering of kaolinite-based suspensions.