Dewatering of Mine Tailings Slurries Using Superabsorbent Polymers (SAPs) Reclaimed from Industrial Reject of Baby Diapers: A Preliminary Study

Abstract

Traditional deposition of tailings slurry in a tailings storage facility (TSF) can create risks of dike failure. In order to minimize these risks and slurry spillage, the surface deposition technique of densified tailings (DT) through dewatering of the slurry has emerged. The DT technique has the potential to maximize water reuse, improve the shear strength of surface tailings, and reduce the ecological footprint of TSF. The consistency of DT covers a continuum ranging from thickened state, to paste state, to dry state. Despite its efficiency and economic feasibility, DT densification using thickeners sometimes proves unable to achieve the design target solids mass concentration (C w% ). Hence, the use of superabsorbent polymers (SAPs) seems to represent a promising alternative, owing to their higher water absorbent capacity. In this paper, superabsorbent polymers (SAPs) reclaimed from industrial reject of baby diapers (Na-polyacrylates) are explored as a promising alternative to mine tailings slurries dewatering. To this end, laboratory-scale dewatering tests have been performed using two grades of Na-polyacrylate SAPs (grade 1 SAP = SAG-A06P coarse-grained, and grade 2 = SAG-M01P-100 medium-grained) for the tailings slurries densification. A higher water absorbency (or swelling capacity) was observed using the coarser SAPs (SAG-A06P) compared to the finer SAPs (SAG-M01P-100). The preliminary results showed that a SAP volume dosage in the range 10-13 kg of SAP/m 3 of slurry allowed achieving a final solids mass concentration (C w%_final ) ≥ 70%, despite the occurrence of gel-blocking phenomenon.Minerals 2019, 9, 785 2 of 18 the slurry. The thickened tailings technology has the potential to maximize water reuse, improve the shear strength of surface tailings, and reduce the ecological footprint of TSF by taking up a smaller area and volume [9,10]. The consistency of dewatered-or densified-tailings covers a continuum ranging from slurry state to thickened state (like molasses), to paste state (like toothpaste), and finally to dry state (like soil) [11]. In the mining industry, this consistency is usually defined according to the pulp mass density or the solids mass concentration (C w% = 100 × M dry-tailings /M slurry ). Thus, the thickened tailings would have a final C w% of between 45% and 70%, the paste tailings with a final C w% of between 70% and 85%, and the dehydrated tailings with a final C w% of greater than 85% [11,12].When the operation is underground, an alternative or supplement to the surface storage would be returning to the voids created up to 50% of the tailings in the form of cemented paste backfill [1,10,[13][14][15]. When sulphide minerals in mine waste stored in surface are exposed to air and in the presence of water and their acid neutralization potential is not sufficient, or has been exhausted [1], these waste can produce acid mine drainage (AMD). Due to the stringent environmental regulations, these large amounts of wastes must be managed adequately. More often than not, the mining industry...

Dewatered and Stacked Mine Tailings: A Review

“…Large-scale application of SAPs is limited because of high costs and difficulties in scaling up the technology. Preliminary work by Sahi et al (2019) demonstrated that SAPs can be reclaimed and reused, 80 but desorbing the water incurs additional operating and equipment costs.…”

Lessons from Tailings Dam Failures—Where to Go from Here?

“…However, this cost comparison ignores cost reductions due to increased process water recovery, the reduced storage volume required with increasing tailings dewatering, the consequently reduced containment required, and With increasing the mechanical dewatering of tailings, costs increase dramatically. Thickening is about 1.5 times more costly than conventional slurry tailings, high-density thickening about 3 times more costly, paste about 8 times more costly, and filtration about 27 times more costly than slurry tailings [31]. However, this cost comparison ignores cost reductions due to increased process water recovery, the reduced storage volume required with increasing tailings dewatering, the consequently reduced containment required, and the reduced cost of rehabilitation and enhanced potential post-closure land use.…”

Understanding the Behavior of Sodium Polyacrylate in Suspensions of Silica and Monovalent Salts

“…An alternative involves the application of a polyacrylic acid such as sodium polyacrylate (NaPA), which is a low molecular weight polymer with properties and a chain length that can be modified through varying reaction conditions [2]. This polymer has an interesting behavior that can be used in many applications [3][4][5][6][7], including in the lithium industry [8] and tailing treatment in mining operations [9,10]. In the context of mineral processing, it finds common usage in the mining industry as a dispersant additive for enhancing the flotation stage's efficiency and improving tailings fluidity.…”