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Influences of magnesium ions in water on gelatinization characteristics of starch and its flocculation behaviors on particles

Tang Min, Niu Xiaoying, Wen Shuming

Physicochemical Problems of Mineral Processing

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2024

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Vol. 60, iss. 1

art. no. 178149

EN

It is inevitable for the occurrence or built-ups of disturbing cations, especially Ca2+ or Mg2+ ions, in process water during the flotation of iron oxides by using starch as flocculants. In addition to alkali concentrations and temperature, water quality could have an essential role in changing the physicochemical properties of the starch solution and consequently disturbing its flocculation performance on particles. This study aims to identify the effects of magnesium ions on the gelatinization characteristics of starch and its flocculation properties on particles through a series of tests, such as flotation tests, settling tests, size analyses, zeta potentials, powder contact angle, Fourier Transform Infra-Red (FTIR) and X-ray Photoelectron Spectroscopy (XPS) measurement. All results show that magnesium ions at ≤ 4 mmol/L have a positive role due to enlarging the sizes of the particle flocs and accelerating their settling rates. The occurrence of Mg2+ ions at higher concentrations during starch gelatinization only obtains a starch sol-gel with entangled configurations and preoccupied active sites, resulting in the slower settling rate of the particle flocs and less hydrophilicity on mineral surfaces. It could be attributed to the cross-link interactions of magnesium-based precipitates with the acidic groups, especially carboxyl groups on the starch remnants. The suitable acid/base interactions between Mg(OH)2/MgCO3 compounds with these groups in the starch suspension could be beneficial for enhancing the flocculation of hematite as they could build bridges among the pieces and enlarge their sizes as a “load carrier” for aggregation with minerals. However, too much cross-linking could reentangle the remnants, block their adsorption sites on mineral surfaces, and eventually, weaken the flocculation capacity of starch.

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Study on the floc-bubble adhesion behavior of hematite in static flow field

Zhang Jinxia, Feng Hongjun, Niu Fusheng, Sun Weiguang, Zhao Yawei

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 1

124--133

EN

To investigate the adhesion of hematite flocs to gas bubbles in floc floatation, this paper develops an observation system for floc-bubble collision and adhesion with two charge-coupled device (CCD) cameras. The sizes of flocs and bubble were 45.36μm and 0.90mm, respectively, and the distance between a floc and the bubble center (sedimentation distance) was set to 0.25cm. Three surfactants, namely, sodium oleate, lauryl amine and sodium dodecyl sulfate (SDS), were selected for our research. Several experiments were conducted to disclose how surfactant concentration and pH affect the surface adhesion between hematite flocs and bubbles. Then, the adhesion mechanism was discussed in details based on the experimental results. The results show that the highest adhesion probability was achieved for the said floc and bubble at the lauryl amine concentration of 8mg/L, the sedimentation distance of 0.25cm and the pH of 9. After touching the bubble, the hermamite floc slid on the bubble surface, forming a stable three-phase interface after 67ms. Then, the radial position of the floc no longer changed, despite the floc motion on the bubble surface. According to the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and the potential energy of the van der Waals force, there was a repulsive force between the floc and the bubble in the absence of surfactant and an attractive force in the presence of the surfactant of lauryl amine. In addition, a thin solvation shell is conducive to the adhesion between the floc and the bubble.

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Floc size measurement by the laser knife and digital camera in an agitated vessel

Kysela B., Muller Z., Ditl P.

Inżynieria Chemiczna i Procesowa

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2005

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T. 26, z. 3

461-468

EN

The flocculation and coagulation are frequently used in drinking water and wastewater treatment where flocculent systems for water purification are designed as large agitated tanks. The flocculent price represents about a half of operating water treatment costs. For this reason, the knowledge of flocculation mechanics is desirable. The optical methods are used to determine the crystal growth. There are basically two approaches to optical measurements of particle growth. The first one was initially developed for investigation of the crystal growth. In the paper, the results of the development of the non-invasive method based on the laser knife visualisation, digital camera recording and an image analysis have been presented.

PL

Flokulacja i koagulacja są stosowane często w procesie wytwarzania wody pitnej i przetwarzania ścieków. Układy flokulacyjne w oczyszczaniu wody występują w mieszalnikach dużej skali. Koszty flokulacji wynoszą około połowy kosztów całkowitej obróbki, a więc znajomość mechanizmu flokulacji jest pożądana. Rozmiary cząstek mierzy się metodami optycznymi. Przedstawiono wyniki badań nieinwazyjnej metody pomiaru opartej na wizualizacji zjawiska z zastosowaniem noża laserowego, cyfrowej rejestracji i analizy obrazu.