Effects of monovalent and divalent ions in coal gasification brine on the froth entrainment and flotation kinetics of anthracite coal

Abstract

Water plays a critical role in various stages of flotation, which brings a lot of pressure to the flotation processing plants resided in dry areas. In this regard, it will be of significance to explore the feasibility of using wastewater resources in mineral flotation. Coal gasification brine (CGB) that contains a high concentration of salts becomes the subject of interest of this study. In this study, a synthetic CGB solution, which was prepared by adding NaCl, MgCl2, and CaCl2 to ultrapure water based on the composition of salts in a real CGB, was used in the flotation of anthracite coal. The comparison results based on the first-order model showed that flotation in the presence of the synthetic CGB solution gave a higher flotation selectivity (SI =7.086) than that of flotation in ultrapure water (SI=3.545). Water recoveries and average bubble sizes in the froth showed that the addition of the three salt ions (Na + , Mg 2+ , and Ca2 +) was conducive to diminishing the entrainment of gangue materials as a result of the reduction of water reporting to the froth. Additionally, the zeta potentials and induction time measurements indicated that only divalent ions of Ca 2+ and Mg 2+ significantly compressed the double electrical layer and enhanced the attachment between bubbles and coal particles according to DLVO theory, which was further confirmed by the calculation of interaction energy between coal and bubbles. The findings of the present work may promote the use of CGB as a potential water resource in coal flotation.

Recovery of carbon and cryolite from spent carbon anode slag of electrolytic aluminum by flotation based on the evaluation of selectivity index

“…3 . Since K and R ∞ were comprehensively considered in the calculation of SI , some researchers have applied SI to compare the effects of different factors on flotation performance ( Sripriya et al, 2003 ; Vapur et al, 2010 ; Marion et al, 2017 ; Zheng et al, 2020 ). Where, R is the combustible/ash matter recovery in %; R ∞ is the ultimate percentage (%) recovery; K is the first-order rate constant (min −1 ), and t refers to the cumulative flotation time (min).…”

“…3. Since K and R ∞ were comprehensively considered in the calculation of SI, some researchers have applied SI to compare the effects of different factors on flotation performance (Sripriya et al, 2003;Vapur et al, 2010;Marion et al, 2017;Zheng et al, 2020).…”

“…Flotation kinetics results are often described using cumulative recovery versus time in batch flotation. Typically, the widely used and classical first-order kinetic model is applied to analyze the effects of different factors (i.e., emulsified reagent, salt ions, and operation parameters) on the flotation performance of the minerals ( Bu et al, 2017a ; Chen et al, 2019 ; Zheng et al, 2020 ; Zhou et al, 2020 ). In terms of the correlation of flotation kinetics for carbon anode slag, currently, fewer studies have examined the influence of different operating factors on flotation performance.…”

Effects of Flotation Reagents on Flotation Kinetics of Aphanitic (Microcrystalline) Graphite

“…Flotation kinetics are often used to compare flotation effects under different conditions [6,18,19]. The classical first-order kinetic model is most commonly used to describe the flotation yield-time curve.…”