Flocculation Of Fine Particles Research Articles

Chemical and physical identification and classification of an artificial soil (circular economy)

The perception and explanation of changes in the mechanical behaviour of contaminated soils are associated with physical classification and chemical composition. Elements are evolutionary in this type of soil and in the context of a contaminated environment. Let’s start by evaluating a group of artificial soils. The matrix is a granitic residual soil with a mixture (M) of hydraulic lime with used lubricating oil. The samples used have proportions of 5, 10, 15 and 20% of M in the residual granitic soil. A soil sample with 5% oil (OS5) was also made, which constitutes the optimal oil content in the soil. Afterwards, the alteration of the physical-chemical identification and the evolutionary classifications of these artificial soils were studied. The structure of the soil is altered, and this is associated with the flocculation of fine particles by the effect of lime and oil and will probably influence the mechanical behaviour of the soils. In chemical terms, it is assumed an increase in the leaching index, a decrease in the chemical mobility index and an increase in losses when it comes to artificial samples. These indices show some potential in the assessment of pollution, but eventually need adjustments, mainly in the scales.

Morphological characteristics of starch sol-gel and its influences on flocculation of fine particles

Pasting starch into sol-gels by alkali is one of the most common methods for its use as flocculants in flotation. Any variation in its gelatinization process, however, could lead to different starch solutions with certain charges, sizes, and configurations of the segments, influencing their flocculating properties onto mineral surfaces. The purpose of this study is to identify the morphological characteristics of the starch sol–gel digested with different concentrations of alkali and their flocculation mechanisms on hematite through a series of tests, such as viscosity, turbidity, adsorption, pasting titration, settling, zeta potential All results pointed out that the gel-sol transition of starch was possibly governed by alkali concentrations or starch to alkali weight ratios. As the sodium hydroxide concentration increases, an increase in viscosity but a decrease in turbidity of the starch solution was obtained, inducing an upwards trend in the settling rates of the particle flocs. A suitable sol–gel by 1.25% sodium hydroxide (a 1.6 wt ratio of starch to NaOH) at turbidity of near 2 NTU and a viscosity of 258 mL/g harvested a maximum adsorption density of 11.5 mg/g hematite at a settling rate of 7.1 × 10−5 m/s. A certain amount of acidic contents on the segment chains resulting from alkali gelatinization play an important role in determining the morphological characteristics of the starch sol–gel at different pH values affecting adsorption density on iron oxides. It is worthy to be noted that the starch remnants at very small sizes produced by high concentrations of NaOH by over 1.50% or at a starch to alkali weight ratio of less than 1.3 were hard to achieve high efficiency on flocculating the particles but occasionally dispersing them instead. It could attribute to the less possibility of “bridging interactions” between the particles and these small segments with negative charges, which may limit the size and compactness of the particle flocs, and, consequently, reduce their settling rates.

The effect of CO2 sparging on the flocculation and filtration rate of concentrated hematite slurries

Filtration of hematite ore slurries can be a bottleneck in some hematite processing plants due to inadequate filtration rates caused by the dispersion of fine particles. Flocculation of fine particles in the slurry decreases the specific cake resistance of the filter cake allowing for increased filtration rates. CO2 sparging of hematite slurry was shown to increase the filtration rate by altering the pH and the surface chemistry of the particles. It was shown that an increase in filtration rate of 278% can be accomplished by lowering the pH from 11 to 6.5 using CO2 at a lab scale. This was attributed to increased flocculation of hematite and silica particles in the ore.

Flocculation of fine particles in ceramic wastewater using new types of polymeric flocculants

AbstractIt appears to be quite a few national and international studies were reported regarding flocculation and settling properties of ceramic industry wastewater containing various mineral matters. Cleaning of ceramic industry wastewaters with ever increasing environmental standards needs effective and economical solid–liquid separation processes. In this study, quantity and type of optimum flocculant concentration were investigated for solid–liquid separation of Umpac ceramic plant (located at Usak, Turkey) wastewaters. A new generation of flocculants namely unique molecular architecture (UMA) are used to obtain high settling velocity along with high solid content waste and circulation water with low turbidity values. Zeta potential of the tailings including quartz, feldspar, clorite, and mica was also measured at different pH values. The flocculation tests were performed in the presence of different types of polymers at different polymer dosages. It seems that Magnafloc 5250 shows higher performance than the anionic flocculant SPK 508 and other anionic UMA flocculants Magnafloc 6260 and Magnafloc 3230. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Quantifying the response of optical backscatter devices and transmissometers to variations in suspended particulate matter

Optical instruments have been used effectively in studies of sediment dynamics for several decades. Without accurate instrument calibrations, calculated concentrations of suspended particulate matter (SPM) may be unreliable, with implications for interpretations of sedimentary processes and sediment fluxes. This review aims to quantify the effect of variations in SPM characteristics on the response of optical instruments (optical backscatter sensors OBS and transmissometers) and to note the implications for users of these instruments. A number of factors have a significant impact on instrument response, for example; a change in grain size from medium sands to fine silts may lead to a×100 increase in instrument response; flocculation of fine particles may decrease instrument response by×2; and the presence of plankton in suspension may lead to poor instrument calibrations of SPM concentration. Calibrations carried out in environments either with multi-modal bottom sediments, where flocculation of fine-grained sediments is likely, or where the hydrodynamics or grain type are highly variable must also include a determination of the changing nature of the suspended load in space and time. A more complete understanding of instrument response to SPM and of calibration requirements may enable optical devices to be used to a greater potential as long-term measures of SPM concentration, and also enable improvements in calculations of net sediment fluxes.

Changes in suspended-matter floc size during the tidal cycle in the dollard estuary

Measurements of in situ particle size of suspended matter in a tidal channel in the Dollard (Dutch Wadden Sea) indicated systematic variations in floc size during the tidal cycle that can be explained by assuming settling during slack tide, resuspension during the early ebb and early flood, flocculation of fine particles into large ones during most of the tide, and deflocculation of large flocs into smaller particles during or after settling to the bottom. There was a characteristic difference in floc-size variation during ebb and during flood. During the ebb maximum floc size coincided with maximum suspended-matter concentration (maximum collision frequency); during the flood maximum floc size continued to increase towards high-water slack tide. The adjacent tidal flats had a marked influence on floc size: where the flats were small, the highest percentages of large flocs (> F128 μm) occurred around slack tide when current velocities are low. Where the adjacent flats were broad and extensive, high percentages also occured during intermediate periods. Flocs of maximum size are probably not in equilibrium with the bulk of the suspended matter: they are mainly formed during periods of high suspended-matter concentrations of short duration.

A model of flocculation by very-high-molecular-weight polymers

A simple model is proposed to describe flocculation of fine particles by high polymers. The model is based on the assumption that the number of colloid particles attached to a single polymer molecule is a random quantity, and that a minimum number of particles must be attached to a polymer molecule to trigger its removal from the system. The predictions of the model are confronted with experimental data concerning the stability of the system polyacrylamide-sol AgJ.