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1

Role of dissolved mineral species in quartz flotation and siderite solubility simulation

Luo X., Wang Y., Ma M., Song S., Zhang Y., Deng J., Liu J.

Physicochemical Problems of Mineral Processing

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2017

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Vol. 53, iss. 2

1241--1254

EN

Quartz is, in most cases, the major gangue mineral found in the iron ores. Although it can be activated by calcium at strong alkaline pH, quartz nevertheless, reports to the concentrate with Fe when the iron ores contain siderite. It causes a poor concentrate grade and separation between quartz and iron minerals. The effect of siderite on reverse anionic flotation of quartz from hematite was studied in our previous investigations. In this work, the effect of siderite dissolution on the quartz recovery in the froth product and the effect of pH, ions and temperature on siderite dissolution were investigated. Microflotation, PHREEQC simulation, solution chemistry calculation and Fourier transform infrared spectroscopy (FTIR) measurements were conducted. It was observed that the dissolved species of siderite exhibited negative impact on quartz flotation. This influence became weak to some extent by either stripping the dissolved species or shortening dissolution time. Siderite was easily dissolved in the presence of calcium ion under strong alkaline conditions and its solubility increased with increasing the calcium ion concentrate and temperature. When the calcium ion was added as an activator of quartz under strong alkaline conditions (pH>9.96), calcium existed mainly in the CaCO3 precipitation form according to the solubility rule in the presence of siderite. This form could adsorb onto quartz surfaces and further the chemical reaction between starch and quartz was monitored by FTIR measurements. This study provides a further supplement for previous study. A potential strategy is suggested that finding a collector used at low temperature or flotation under neutral (or weak alkaline) medium is helpful to the reverse flotation of iron ores containing siderite.

2

Investigation of quartz flotation from decarburized vanadium bearing coal

Ren L., Zhang Y., Bian Y., Liu X., Liu C.

Physicochemical Problems of Mineral Processing

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2015

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Vol. 51, iss. 2

755--767

EN

Ether diamine (Fm 2835-2L) was used as a collector for flotation of quartz. It allows flotation of quartz from mica and calcite. The adsorption mechanism of Fm 2835-2L on quartz was investigated by flotation tests, zeta-potential measurements and infra-red (FTIR) spectra measurements. Results show that Fm 2835-2L adsorbs on the quartz surface in physical adsorption with no new products, changing its zeta potentials, and increasing its hydrophobicity. The effect of calcium ions on flotation of quartz was investigated by flotation tests and zeta-potential measurements. Results show that under neutral or weakly acidic conditions calcium cation can adsorb onto the surfaces of quartz, increase the zeta potential of quartz particles, which in turn causes weaker aggregation of quartz particles and lower flotation recovery of quartz. Under the alkaline conditions the hydrolytic components of calcium are also adsorbed on the quartz surface and increase the zeta potential of quartz particles, which causes stronger aggregation of quartz particles and higher flotation recovery of quartz. However, the hydrolytic components such as CaOH+, Ca(OH)2(aq) and Ca(OH)2(s) were not formed in significant amounts in the best flotation tests.

3

Endothelial cell responses to fluid shear stress

Kamiya A.

Biocybernetics and Biomedical Engineering

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2000

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Vol. 20, no. 3

21-33

EN

Implications of vascular endothelial cell (EC) responses to flow-oriented wall shear stress are outlined from the bioengineering viewpoint. These responses regulate the adaptive remodeling of the vascular system including capilIary networks, in a negative feedback mechanism maintaining the shear stress level constant. The preserved set point of the stress is selected so as to optimize the mass transport function of the system. To initiate such shear-dependent responses, EC has a mechano-sensor conjugated with second messengers, one of which is cytoplasmic Ca(2+) transient. The evidence that wall shear stress is the real factor inducing the transient, is visualized from an in vitro flow loading experiment to cultured ECs using mediums differing in viscosity.

PL

W artykule przedstawiono implikacje występowania reakcji komórki śródbłonka na naprężenia ścinające w ścianie naczynia, związane z przepływem płynu. Reakcje te kontrolują adaptację systemu naczyń krwionośnych, łącznie z siecią kapilar, utrzymując naprężenia ścinające na stałym poziomie za pomocą mechanizmu ujemnego sprzężenia zwrotnego. Zadany poziom naprężeń jest tak dobrany, aby optymalizować funkcję transportu masowego układu naczyniowego. W celu inicjacji reakcji, zależnej od poziomu naprężeń ścinających, komórki nabłonka wykorzystują mechano-sensor połączony z innymi "przekaźnikami", z których jednym jest transport wapnia. Dowód, że naprężenia ścinające w ściance naczyń są czynnikiem uruchamiającym ten "transport" jest widoczny podczas badań in vitro mechanizmu przepływu medium o różnej lepkości w hodowli komórek śródbłonka.