• Dewatering by volute screw press requires large and shear-resistant polymer flocs. • High MW anionic PAM is able to form such flocs with oil sands fluid fine tailings. • Tannic acid helps flocculation-dewatering by forming associative polymer complexes. • It greatly reduces the critical dosages of the high MW anionic PAM flocculant. Efficient dewatering of fluid fine tailings (FFT) is essential for advancing sustainable tailings management in the mining sector. Addressing this challenge relies on both the development of dewatering technologies and the optimization of flocculation chemistry. This study investigated the use of two biopolymers, tannic acid (TA) and alginate, as co-additives with an anionic high molecular weight polyacrylamide (K-PAM) for the treatment of oil sands FFT using a volute screw press (VSP). For FFT samples with sand-to-fines ratios (SFR) of 0.01 and 1.0, pre-addition of TA or alginate was found to significantly lower the critical dosage of K-PAM. At sub-critical K-PAM dosages, both biopolymers enhanced the solids content and undrained shear stress of the dewatered VSP cake, meanwhile reducing the solids loss in the filtrate and runoff streams. This improvement was particularly pronounced for high-SFR FFT. At above-critical K-PAM dosages, however, the two biopolymers adversely affected FFT dewatering regardless of SFRs, producing VSP cakes with lower solids content than using K-PAM alone. Studies revealed that K-PAM dominated the flocculation and viscoelastic properties of the floc network, while the two biopolymers modified FFT flocculation and VSP dewatering in different ways. Tannic acid partially neutralized particle surface charge and chemically complexed with K-PAM, and the complexation was promoted by dissolved metal ions to develop a stronger floc matrix. Alginate could associate with K-PAM mainly through physical entanglement to reinforce the floc network strength. These findings help understand biopolymer-assisted flocculation, reduce synthetic flocculants consumption, and improve operational sustainability in mine tailings dewatering.
Wang et al. (Fri,) studied this question.