Investigation of flocculation properties and floc structure of coal processing plant tailings in the presence of monovalent and divalent ions

Abstract

Low-rank coals are generally processed with wet methods including washing, flotation, etc. Fine-sized tailings of these processes are discharged to tailing ponds with a significant amount of associated water which contains a high amount of dissolved ions. These tailings should be dewatered employing coagulation/flocculation in terms of technological and environmental aspects. In this study, the coagulation/flocculation behavior of coal processing plant tailings obtained from Manisa, Turkey was investigated in the presence of monovalent (Na + , K +) and divalent (Mg 2+ , Ca 2+) ions and an anionic flocculant (SPP-600). First, the coagulation properties of coal tailings were determined. Then, the flocculation experiments were carried out, and the turbidity values of the suspensions were measured. Moreover, the sizes of the flocs were determined using a laser diffraction particle size analyzer to analyze the strength of the flocs. The results of the coagulation experiments showed that while divalent ions were more effective at 10-1 mol/dm 3 , higher settling rate and lower turbidity values were obtained in the presence of monovalent ions at 1 mol/dm 3 concentration. The optimum flocculant dosage was obtained as 150 g/Mg from the flocculation experiments. The floc size and strength measurements indicated that the larger flocs were obtained with Na + than Ca 2+ in the presence of the flocculant. The strongest flocs were obtained at 10-1 mol/dm 3 Ca 2+ + 150 g/Mg flocculant. It can be concluded from this study that the coagulation followed by the flocculation method can be employed to obtain fast flocculation behavior and low turbidity for the dewatering of coal tailings.

Leveraging the Dielectric Barrier Discharge Plasma Process to Create Regenerative Biocidal ePTFE Membranes

“…At pH = 3, ξ = 2.4 mV denotes that the isoelectric point of commercial ePTFE is in the pH range between 3 and 3.5, which is consistent with the literature. 66,67 Meanwhile, ePTFE_D_240 in a neutral environment has ξ = −25.07 mV which suggests that the DMAEMA monomer rendered the ePTFE surface with a "weak positive charge" owing to the presence of few quaternary amines, as demonstrated by the N 1s core level in Figure S5. As the aqueous solution became more basic, the surface charge of ePTFE_D_240 became more negative, reaching −26.45 mV at pH = 11 due to the deprotonation of amine.…”

Application of low-field NMR in the study of flocculant-aided filtration process of coal tailings

“…The properties of floc and filter cake are usually analysed to explore the mechanism of flocculantaided filtration. The floc property mainly includes floc size and compactness, which can be investigated by combining the light scattering or image technique with fractal theory (Gungoren et al, 2020). The filter cake property can be characterized by observation techniques such as scanning electron microscope (SEM) and X-ray microtomographic techniques (Thapa et al, 2009;Lin and Miller, 2000;Raspati et al, 2013).…”