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Discrimination of Six Flotation Kinetic Models Used in the Conventional Flotation and Carrier Flotation of -74 ?m Coal Fines.

ABSTRACT: In this study, experimental results of conventional flotation and carrier flotation were characterized by six commonly used flotation kinetic models. Two statistical criteria (coefficient of determination, R 2, and root mean square error, RMSE) were used for comparison of fitting performance of different models. All kinetic models tested gave good levels of goodness of fit, but the second-order model with rectangular distribution (model 6) provided the best fitting performance for the experimental data of conventional flotation and carrier flotation. On this basis, two parameters, that is, modified flotation rate constant (K m) and selectivity index (SI), were used to evaluate the difference in flotation separation selectivity between conventional flotation and carrier flotation. Comparisons of K m and SI values indicated that carrier flotation significantly improved the flotation rate constant of combustible materials and flotation separation selectivity of ultrafine coal (-74 ?m). In addition, measurements of average bubble size and water recovery indicated that both the coalescence of bubbles and the drainage of liquid in the froth were promoted when coarse coal particles (contact angle >90°) were employed as the carrier to assist the flotation recovery of ultrafine particles, which in turn favored the inhibition effect of the entrainment of gangue materials in carrier flotation compared to conventional flotation.

SUBMITTER: Bu X

PROVIDER: S-EPMC7301532 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Discrimination of Six Flotation Kinetic Models Used in the Conventional Flotation and Carrier Flotation of -74 μm Coal Fines.

Bu Xiangning X Wang Xuexia X Zhou Shaoqi S Li Biao B Zhan Hanhui H Xie Guangyuan G

ACS omega 20200602 23

In this study, experimental results of conventional flotation and carrier flotation were characterized by six commonly used flotation kinetic models. Two statistical criteria (coefficient of determination, <i>R</i> <sup>2</sup>, and root mean square error, RMSE) were used for comparison of fitting performance of different models. All kinetic models tested gave good levels of goodness of fit, but the second-order model with rectangular distribution (model 6) provided the best fitting performance ...[more]

PMID: 32566847

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Project description:This paper reports on the efficiency of five aluminum coagulants for the treatment of a paper mill wastewater by dissolved air flotation (DAF). The coagulants studied were: alum, a polyaluminum chloride coagulant of high aluminum content and intermediate basicity (PAC-MB), another with intermediate aluminum content and high basicity (PAC-HB), a polyaluminum nitrate sulfate of intermediate aluminum content and basicity (PANS) and one hybrid coagulant formed by the combination of PANS and a mixture of polyamines (PANS-PA). The influence of Al speciation on contaminants removal and the main flocculation mechanisms involved have been analyzed. High removal of suspended solids together with significant removal of dissolved and colloidal material (COD and silica) were obtained, which is required for extended reuse of this process water. PAC-HB was the best product for removing suspended solids (85%) and soluble silica (50%) with a rather limited COD removal (5%), while PANS-PA obtained high turbidity (90%) and silica removal (45%) together with a significant soluble COD removal (15%). Monomeric Al (Ala, Alm) was more efficient in removing suspended solids and soluble COD than polymeric or colloidal Al (Alc, Alu), but the latter was more efficient in removing soluble silica. Results demonstrated that the main flocculation mechanism varies with the aluminum dosage, being predominantly charge neutralization at low dosages and sweep flocculation at high dosages. The floc strength factor however, was very high and similar for all the coagulants and dosages tested (85-90%), as it was mainly determined by the behavior of the pre-flocculated suspended solids present in wastewater. The reflocculation factor varied from 45 to 75% at the lowest dosages to almost zero at the highest dosages, confirming the transition from charge neutralization to sweep flocculation. The flocs formed by PANS-PA had lower strength than the others and it decreased with the dosage while its reflocculation factor was almost zero, even at low dosages. Due to the polyamines present in this coagulant, its flocculation mechanism is through both charge neutralization and patch formation, especially at low dosages, and sweep flocculation and interparticle bridge formation at high dosages.

Project description:Microbial-Induced Calcite Precipitation (MICP) stimulates soil microbiota to induce a cementation of the soil matrix. Urea, calcium and simple carbon nutrients are supplied to produce carbonates via urea hydrolysis and induce the precipitation of the mineral calcite. Calcium chloride (CaCl2) is typically used as a source for calcium, but basic silicate rocks and other materials have been investigated as alternatives. Weathering of calcium-rich silicate rocks (e.g., basalt and dolerite) releases calcium, magnesium and iron; this process is associated with sequestration of atmospheric CO2 and formation of pedogenic carbonates. We investigated atmospheric carbon fluxes of a MICP treated sandy soil using CaCl2 and dolerite fines applied on the soil surface as sources for calcium. Soil-atmosphere carbon fluxes were monitored over 2 months and determined with an infrared gas analyser connected to a soil chamber. Soil inorganic carbon content and isotopic composition were determined with isotope-ratio mass spectrometry. In addition, soil-atmosphere CO2 fluxes during chemical weathering of dolerite fines were investigated in incubation experiments with gas chromatography. Larger CO2 emissions resulted from the application of dolerite fines (116 g CO2-C m-2) compared to CaCl2 (79 g CO2-C m-2) but larger inorganic carbon precipitation also occurred (172.8 and 76.9 g C m-2, respectively). Normalising to the emitted carbon to precipitated carbon, the environmental carbon cost was reduced with dolerite fines (0.67) compared to the traditional MICP treatment (1.01). The carbon isotopic signature indicated pedogenic carbonates (δ13Cav = -8.2 ± 5.0‰) formed when dolerite was applied and carbon originating from urea (δ13Cav = -46.4 ± 1.0‰) precipitated when CaCl2 was used. Dolerite fines had a large but short-lived (<2 d) carbon sequestration potential, and results indicated peak CO2 emissions during MICP could be balanced optimising the application of dolerite fines.

Dataset Information

Discrimination of Six Flotation Kinetic Models Used in the Conventional Flotation and Carrier Flotation of -74 ?m Coal Fines.

Publications

Discrimination of Six Flotation Kinetic Models Used in the Conventional Flotation and Carrier Flotation of -74 μm Coal Fines.

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