Comparative Dewatering Performance of Slurries Conditioned with Synthetic Polymers vs. Eco-Friendly Polymers

Khachan, M; Bader, Rebecca A.; Bhatia, Shobha K; Maurer, Brett W.

doi:10.1061/41165(397)312

Cited by 12 publications

(5 citation statements)

References 13 publications

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“…Geotextile tubes filled with slurries can be laid out and stacked on an impermeable pad where the filtrate can be collected. Like other dewatering processes, reagent addition has been investigated to improve the quality of the filtrate and facilitate consolidation of the solids. − Geotextile tubes offer the rare advantage of completely enclosing residues, protecting them from fugitive dusting in windy conditions …”

Section: Design and Construction Of Stacked Tailings Facilitiesmentioning

confidence: 99%

Dewatered and Stacked Mine Tailings: A Review

et al. 2022

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Tailings storage is a prescient issue in mining, representing a visible and destructive liability. Dewatering tailings to a paste-like consistency is a popular option to reduce tailings volumes and increase dam safety, but dewatering further to a bulk cake consistency has mostly been reserved for small operations in locations where seismicity or terrain prohibited the construction of dams. The recent high-profile failures of tailings dams such at Fundão and Brumadinho facilities along with the push toward socially conscious investing have generated renewed and urgent interest in tailings dewatering, including stacked (“filtered” or “dry-stack”) tailings. While geochemistry and civil engineering topics relating to tailings in general are both extensively studied, very little academic literature is available specifically on stacked tailings, with discussion mostly confined to conference articles or extrapolation about the behavior of dewatered tailings. Furthermore, the nomenclature around and definition of this method of tailings storage is inconsistent, which can make researching the topic unnecessarily tedious and confusing and, in the worst case, can open the door to intentional misrepresentation of a tailings storage facility’s safety as this is a technology still being scaled up. In this article, the term stacked tailings (ST) is introduced to describe what has been otherwise called filtered tailings or dry-stack(ed) tailings to remedy the inaccuracies with the two existing names and gather the existing literature in one place. Topics covered include the existing definitions of dewatered and stacked tailings; opportunities and barriers to adoption; and construction and general operation for such tailings storage facilities. These are supplemented by an overview of literature in geotechnical and geochemical topics relevant to tailings dewatering (ex. clays) and tailings storage facilities. Emerging dewatering technologies and innovations which might be useful in the scaling up of the technology are also discussed. The aim is to provide a thorough background on the topic for a general audience, outline gaps in the literature, and encourage further exploration of stacked tailings and tailings cake by furnishing a comprehensive list of sources. Stacked tailings are discussed in a rigorous way to make the topic a more approachable way to encourage standardization and adoption, scale up, and the development of associated technologies.

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Section: Design and Construction Of Stacked Tailings Facilitiesmentioning

confidence: 99%

Dewatered and Stacked Mine Tailings: A Review

et al. 2022

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“…Synthetic polymers, especially acrylamide-based, are used extensively in geotextile tube dewatering. Several studies (Kang & McLaughlin, 2016; Khachan et al, 2011; Koerner & Koerner, 2006; Lee et al, 2011) have shown that polyacrylamide is highly effective in reducing dewatering time and increasing sediment retention in geotextile tubes.…”

Section: Introductionmentioning

confidence: 99%

“…Khachan et al (2011) studied dewatering performance of cationic polyacrylamide versus a starch-based polymer (starch phosphate). Varying doses of each flocculant were mixed into silt slurries of 33% solid concentration for 180 seconds.…”

Section: Introductionmentioning

confidence: 99%

“…Based on the measured turbidity of the supernatant in jar tests and the dewatering time obtained from pressure filtration tests, it was determined that the wheat starch-based flocculant is the most effective natural flocculant among the nine prepared flocculants. Khachan et al (2014, 2011) have shown that both flocculants are effective in geotextile tube dewatering. Here, the optimum dose necessary for effective flocculation, and thus dewatering rates and capabilities, were measured for each polymer.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Cationic Polyacrylamide and Cationic Starch on Aquatic Life

Duggan

Morris

Bhatia

et al. 2019

J. Hazard. Toxic Radioact. Waste

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Geotextile tubes with polyacrylamide flocculants are widely used in dewatering applications. Due to variations in solid concentrations during dredging, excess flocculant is sometimes released into the environment, where it might have toxic effects. This study determined optimum doses for a cationic polyacrylamide (CPAM) and a natural-based polymer alternative, cationic starch (C. Starch). Slurry samples were treated with optimum and 50% overdoses of each compound, and residual polymer concentrations were measured. Overdosed C. Starch resulted in low residuals (<2 ppm), but overdosed CPAM resulted in 17.4 ppm residual polymer. The relative toxicity of CPAM and C. Starch was also tested using zebrafish embryos. 100% of embryos that had their chorion removed and 71.8% of embryos that retained their chorions, were dead or dying after 7 days of exposure to CPAM. In contrast, there was no statistically significant difference in the numbers of embryos that were dead or dying, when exposed to C. Starch, compared to controls. These data strongly suggest that C. Starch should be considered as a replacement to CPAM in dewatering applications.

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“…Therefore, cationic synthetic polymers have been used extensively as ''conditioners'' for slurry (soil-water mixture) flocculation in the geotextile tube dewatering industry. Multiple studies have been conducted which show the benefits of using cationic polyacrylamide (CPAMs) flocculants in geotextile tube dewatering [1][2][3]. The CPAMs, which have relatively long molecular chains due to their high molecular weight, cause soil particles to attach to their surface through charge neutralization and bridging mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Influence of Synthetic and Natural Fibers on Dewatering Rate and Shear Strength of Slurries in Geotextile Tube Applications

Spritzer

Khachan

Bhatia

2015

Int. J. of Geosynth. and Ground Eng.

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This study investigates the effect of fibers on the dewatering time, filter cake properties, and shear strength of filter cakes with fine-grained silty clay. Synthetic nylon fibers with lengths of 6, 12, and 18 mm and one natural jute fiber with an average length of 8 mm were added to slurries with 33 % fines in concentrations of 0.5 % by soil mass. Optimum dose tests for particle flocculation showed that slurries reached a turbidity of 20 NTU with up to 19 % less flocculatant material compared to slurries with no fibers. Pressure filtration tests showed that the dewatering time decreased significantly with both synthetic and jute fibers, but were not dependent on fiber length. However, fall cone tests and unconsolidated undrained tests showed that the increase in shear strength was dependent on fiber length. Increases in shear strength were over 100 % with 12 mm nylon fibers, while filter cakes with 6 and 18 mm nylon fibers increased the shear strength by 43 %. Jute fibers did not show as high of a strength gain as the nylon fibers, but did increase dewatering times by an average of 14-22 % compared to filter cakes with nylon fibers.

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Comparative Dewatering Performance of Slurries Conditioned with Synthetic Polymers vs. Eco-Friendly Polymers

Cited by 12 publications

References 13 publications

Dewatered and Stacked Mine Tailings: A Review

Dewatered and Stacked Mine Tailings: A Review

Effects of Cationic Polyacrylamide and Cationic Starch on Aquatic Life

Influence of Synthetic and Natural Fibers on Dewatering Rate and Shear Strength of Slurries in Geotextile Tube Applications

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