Presence Of Flocculant Research Articles

Role of Organic Matter Present in the Water Column on Turbidity Flows

Turbidity flows are known to be affected by the density difference between sediment plumes and the surrounding water. However, besides density, other factors could lead to changes in flow propagation. Such a factor is the presence of suspended organic matter. Recently, it was found that flocculation does occur within plumes upon release of a sediment/organic matter mixture in a lock exchange flume. In the present study, mineral sediment (illite clay) was released into the outflow compartment containing water and synthetic organic matter (polyacrylamide flocculant). Even though the density of water was barely affected by the presence of flocculant, flow head velocity was observed to be larger in the presence of flocculant than without. Samples taken at different positions in the flume indicated that flocs were created during the small current propagation time (about 30–60 s) and that their sizes were larger with higher flocculant dosage. The size of flocs depended on their positions in the flow: flocs sampled in the body part of the flow were larger than the ones sampled at the bottom. All these properties are discussed as a function of sediment–flocculant interactions.

Modeling of Particle Size Distribution in the Presence of Flocculant

This study presents a mathematical description of the solid fraction aggregation process in the presence of a flocculant and its result. The basis is a population balance equation. The model is realized in Python language. Verification was carried out using red mud from the investigated enterprise; Flomin AL P 99 VHM was used as a flocculant. The mean square deviation for the parameter “mean aggregate diameter” is equal to 19.88 μm. The time required for the model calculation is about 3 min. The time spent on modeling depends on the number of calculation channels. In this study, 40 channels (20 with PSD source data, and 20 with empty values required for the calculation) were used for the calculation. The time spent on the model calculation is much shorter than the inertia via each of the communication channels for the studied symmetric radial type thickener. A user interface is developed, where the input parameters are the initial pulp particle size distribution, viscosity and density of pulp in the thickener, particle surface area, concentration and flow rate of flocculant, concentration of solid particles, inner diameter and height of the feed well, and simulation time. The result of the simulation is particle size distribution in the feed well of the washer and the mean flocculus diameter.

An Investigation on the Turbidity Removal from Natural Stone Processing Plant Wastewater by Flocculation

This study aimed to determine the effects of three different high molecular weight (HMW) flocculants (anionic, cationic and non-ionicflocculants) on the fine particles removal from natural stone (foid-bearing rock) processing plant wastewater at alkaline pH conditions.The test results were investigated in terms of turbidity values depending on pH of the medium, flocculant concentration and time (0–60min). According to the results obtained, the turbidity values of the wastewater in the absence of the flocculants were pH dependent anddecreased as the pH increased, resulted in the minimum turbidity values at pH 12. In the presence of the flocculants, the pH dependedturbidity removal efficiencies varied with flocculant type, flocculant concentration and time. The best results were obtained at highlyalkaline pH values (pH 12) with the turbidity removal efficiency of ≤99% in the presence of non-ionic flocculant. In the case of anionicand cationic flocculants, the minimum turbidity values were also obtained at pH 12 with turbidity removal efficiencies over 90%.

Resistance exercise recovers the structure of cartilage and synovial membrane of the ankle joint of rats after sciatic compression

Abstract Aim to determine the effects of sciatic compression and treatment with resistance exercise on the morphology of the ankle joint of Wistar rats. Methods 32 male rats, aged 10 ± 1 week, weighing 376±22 grams were divided into the following four groups (n=8/group): CG (control), LG (lesion), EG (exercise) and LEG (lesion and exercise). Three days after sciatic compression, the animals in the EG and LEG were submitted to resistance exercise by climbing stairs (five days/week) for three weeks and a load of 100 grams was added. The exercise was carried out in two sets of ten consecutive ascents of the steps. The ankle joint tissues were analyzed for their morphometry and morphology using light microscopy. Results Regarding the number of chondrocytes, the LG and EG had more cells in the anterior articular cartilage in the tibia (62 and 43%) and in the talus (57 and 45%) when compared to the CG. In the LEG there was a 25% and 26% reduction of chondrocytes in the anterior cartilage in the tibia and talus when compared to the LG. Changes were observed in the tibia and talus in the LG, with the presence of flocculation, invagination of the subchondral bone, discontinuity of tidemark and pannus covering the subchondral bone in the talus, as well as changes in the synovial membrane. These alterations were minimized in the articular cartilage and synovial membrane in the LEG. Conclusions exercise restores the tissue morphology of ankle joint in Wistar rats after sciatic compression.

Viscoelasticity and yielding properties of flocculated kaolinite sediments in saline water

The effect of salinity on the yielding properties and viscoelastic behaviour of flocculated kaolinite sediments was studied through stress growth and creep-recovery tests. Turbulent flocculation was performed on a detachable cylinder using the plunger method to promote efficient and controlled mixing. The suspensions were prepared at natural pH (between 5.8–6.0) with salinities in the range 0–0.5M NaCl. Once a suspension was prepared, it was allowed to settle for 2.5h, during which time the variation in sediment height was small. The sediment was removed with minimal disturbance and subjected to stress growth or creep-recovery tests on a rheometer operated in control rate and control stress modes, respectively. Kaolinite suspensions in the presence of flocculant and salt in concentrations larger than a small although critical concentration (NaCl 0.001M) exhibit an inverse relationship between yield stress and settling rate with salt concentration, and direct relationship between shear strain and salt concentration. It is concluded that the particle network becomes denser and the crosslinking weaker with increasing salt. At the critical concentration of 0.001M NaCl, flocculation is best, the initial settling rate and yield stress are the highest, and shear strain the lowest. The response of the floc network to salinity changes is the result of two mechanisms competition: (i) charge screening of both anionic particles and flocculant by salt counterions, and (ii) shielding of the active sites on the flocculant by salt cations that causes the polymer to fold into compact structures adopting balled-up conformations. The first mechanism promotes flocculation while the second supresses flocculation.

Determination of the volumetric solids fraction of saturated polydisperse ore tailing sediments

The objective of this work is to determine the concentration profile of a saturated polydisperse ore tailing sediment without the presence of flocculant and in steady state. To this end, a method to resolve the balance of effective solid stress σ(z) and concentration profile ϕ(z) is developed. This method considers a stress distribution in a saturated and static granular medium in equilibrium with the hydrostatic pressure of the surrounding fluid. To resolve the coupled problem (σ(z),ϕ(z)), a new constitutive equation for the volumetric solids fraction is proposed based on the concept of the compressibility of porous material. As a result, a method to estimate the axial concentration and effective stress distribution profile as a function of quantifiable physical parameters is obtained. The solution is validated using a series of laboratory experiments consisting of batch sedimentation tests of suspensions at different concentrations and carried out in graduated cylinders. In this work, the experimental results and simulations for three different types of material are presented: a) tailings with high coarse particle content, b) typical tailings and c) copper ore concentrate. It is concluded that the developed model allows the determination of concentration profiles, with the obtained results very close to experimental observations. In addition, the model can characterize a specific tailing type through physical parameter kc. Finally, it is concluded that the effective stress profile obtained by the model is of a non-linear nature, which explains the conventional use of potential or exponential correlations for effective solid stress.

Effect of the composition of the medium and electroflotation processing parameters on extraction efficiency of chromium(III) dispersed phase from aqueous solutions

Influence exerted by the composition of the medium (solution pH, ionic composition, presence of flocculants and surfactants), physicochemical properties of the dispersed phase (particle size, electrokinetic potential), and technological parameters of the electroflotation process (volume current density, magnetic treatment, solution temperature) on the efficiency of the electroflotation extraction of poorly soluble chromium(III) compounds from aqueous solutions was studied. It was shown that the extraction efficiency directly depends on the composition of the medium, which determines the physicochemical properties of poorly soluble chromium(III) compounds, and on the size of particles and their minimum surface charge. The optimal technological parameters of the electroflotation process are suggested.

Effect of xanthan and guar gums on the formation and stability of soy soluble polysaccharide oil-in-water emulsions

The incorporation of relevant amounts of non-adsorbing hydrocolloids to oil-in-water (O/W) emulsions is a suitable alternative to reduce creaming. The effect of incorporating xanthan gum (XG) or guar gum (GG) in soy soluble polysaccharide (SSPS) stabilized oil-in-water (O/W) emulsions was studied. The emulsions contained 6wt.% of SSPS, 20wt.% Perilla seed oil (PSO), an omega-3 vegetable oil, and variable amounts of XG or GG ranging from 0.03 to 0.3wt.%. The presence of minute amounts of XG or GG in fresh emulsions significantly decreased the emulsion droplet size (EDS) although such low concentrations did not provide enough continuous phase viscosity to arrest creaming. Emulsion microstructure indicated the presence of flocculation even at high concentrations of XG or GG caused by a depletion mechanism. All emulsions with XG or GG exhibited pseudoplastic behavior while the control emulsions showed an almost Newtonian behavior. Emulsion droplet polydispersion generally decreased with increase in the continuous phase viscosity indicating the importance of continuous phase viscosity in the dissipation of shear energy throughout the emulsion during homogenization. The characteristics of the emulsions were closely related to the rheological changes of the continuous phase.

THE ROLE OF TEP IN ESTUARINE HYDROSEDIMENTARY FUNCTIONING: IMPACT ON SETTLING VELOCITY OF AGGREGATES

Transparent exopolymer particles (TEP) are widely recognized to promote sediment aggregation in eutrophic environments. Flocculation in presence of TEP of various suspended sediment concentrations of material sampled on the bank of the Cam River was quantified at the laboratory for turbulence level consistent with slack water and mid ebb conditions measured in the Cam River estuary during dry season of 2009. Stickiness and concentrations of TEP were let to naturally fluctuate by incubation (aging in the dark) for up to nine days. We found that the impact of turbulence on overall buoyancy of TEP-governed aggregation was always opposite between slack water and mid ebb conditions for any duration of incubation; always negative for slack water conditions but for 126 hours of incubation and significantly negative for mid ebb conditions but for 126 hours of incubation. Suspended sediment concentration (SSC) consistently limited aggregates buoyancy, negative or positive. We propose a conceptual model that relates measured and inferred parameters to observed hydrosedimentary processes.

Impact of seawater salts on the viscoelastic behavior of flocculated mineral suspensions

The impact of several electrolytes present in seawater on the rheological properties of flocculated alumina suspensions was assessed by using creep testing at pH conditions both above and below the isoelectric point. Flocculated suspensions were obtained by adding a high molecular weight anionic polymer flocculant to a cylinder of alumina suspension and aggregating the suspension using the plunger method. The suspension was allowed to sediment and the supernatant liquid decanted prior to tests of the viscoelastic properties of the resulting sediment. Salts analyzed were MgCl2, CaCl2 and NaCl, known as water structure makers, and KI and KCl, known as water structure breakers. A high salt concentration of 0.5M was used to approach the ionic strength of seawater. For both pH's studied, the sediments demonstrated viscoelastic non-linear behavior observed as a non-linear relationship between yield strain and applied stress. In the absence of flocculant, it has been observed that the viscosity and yield stress of a suspension increase in the presence of structure maker salts for the case of both silica and alumina suspensions. In the presence of flocculant, new results are found: when the solid and flocculant were of opposite charge, the shear yield stress of the alumina suspensions increased with the breaker character of the salts, however when the solid and flocculant were of similar charge, then the yield stress is independent of the character of the salts. Similar water structures on the interacting surfaces lead to strong particle networks. The work demonstrates the importance of salt-surface interaction to the rheology of suspensions in the presence of polymer flocculants, as is typical of many mineral processing operations world-wide.

Effective harvesting of the microalgae Chlorella protothecoides via bioflocculation with cationic starch

In the present work, the flocculation efficiency of cationic starch (Greenfloc 120) was tested on the fresh water microalga Chlorella protothecoides under different conditions (pH and flocculant concentrations). Different concentrations of Greenfloc 120 (0, 2.5, 5, 10, 20, 40mgL−1) were screened against different algal densities (0.44, 0.56 and 0.77gL−1). Once the optimal flocculation concentration had been established (40mgL−1 for all different biomasses densities) a more detailed analysis was performed in order to investigate if different pH (4.0, 7.7, and 10.0) could increase the flocculation efficiency of cationic starch. Highest flocculation efficiency without addition of Greenfloc 120 was obtained at pH 10, while in the presence of flocculant, the efficiency increased for all the tested pH values, with a maximum of 98% for pH 7.7 and 10. Cationic starch confirmed to be as an easy to use, efficient and cost-effective flocculant for harvesting of microalgae.

Performance of membrane bioreactor in presence of flocculants

This study focused on evaluating the effects of flocculant addition on the performance of membrane bioreactor (MBR). Two different flocculants, aluminum sulfate (alum) and polyaluminum chloride (PACl), were tested and the performance of MBR system in terms of COD removal, membrane fouling, and sludge properties was investigated. Addition of both flocculants resulted in significant reduction of membrane fouling rate and polyaluminum chloride was found more effective than alum. The sustainable filtration time at optimum dosage of alum and PACl was, respectively, 2.5 and 4.2 times more than that in control MBR which had no flocculant. Additionally, sludge oxygen uptake rate (OUR) improved in the presence of both flocculants and average OUR values obtained from flocculant-added membrane bioreactors was about 1.5 times more than that in control MBR. The results also revealed that there were no significant difference in COD removal of flocculant-added MBRs and control MBR and the treatment in all the three MBRs led to high COD removal efficiencies.

Microbially induced flotation of alumina, silica/calcite from haematite

Selective separation of haematite from alumina and silica/calcite was achieved through microbiologically induced flotation and flocculation in presence of Bacillus subtilis. Bacterial metabolites containing extracellular proteins were characterized from mineral-grown bacterial cell free extract. Bacteria can adhere to mineral surfaces and influence subsequent flotation of the minerals. Cells and metabolic products of bacteria were used in flotation, flocculation and adsorption studies on oxide minerals. Bacteria functions as a stronger depressant for haematite. Selective affinity of the bacterial cells towards the mineral surface was observed through adsorption studies. Bacterial byproduct like extracellular protein (EP) was isolated from bacteria. The protein profile of the EP of bacterial cells grown in presence and absence of minerals (haematite, corundum, quartz and calcite) was also studied. The role of such proteins in selective mineral separation was demonstrated through microbially induced selective flotation. This study has demonstrated the utility and amenability of microbially induced mineral beneficiation through the use of bacterially generated metabolic products and mineral-grown bacterial cells.

Retention of PCC and GCC fillers on chemical pulp fines surfaces

We studied the retention of precipitated and ground calcium carbonate fillers (PCC and GCC, respectively) on chemical pulp fines surfaces by measuring the amounts of adsorbed fillers on the surfaces of the primary and secondary fines and long fiber fractions of eucalyptus pulp in the presence of a polymeric flocculant (CPAM). The mechanism of filler particle retention and adsorption on fines surfaces was clarified in more detail by measuring the kinetics of PCC adsorption in the absence of flocculant. The results showed that the primary and secondary fines fractions adsorb more PCC and GCC fillers on their surfaces (per gram of pulp) than the long fiber frac-tion in both the absence and presence of flocculants. In the absence of flocculants the adsorption of PCC both on fines and on the fiber fractions follows Langmuir kinetics, implying that the adsorption is in dynamic equilibrium with filler detachment and the maximum possible amount of filler that can be adsorbed corresponds to the monolayer coverage of particles. At low flocculant doses, i.e., doses that are relevant to papermaking, the fines fractions adsorb significantly more filler than the fiber fractions. In this case, their high surface charge density promotes CPAM adsorption onto fines, which in turn increases the adsorption of fillers to the fines surfaces through polymer bridges.

As(V) Recovering‐Separation from Aqueous Systems by DAF Technique

As(V) oxyanions removal from aqueous systems by dissolved air flotation (DAF) using Fe2O3 · xH2O as solid support and sodium laurate as anionic surfactant was investigated. The influencing factors of the process: pH, support, surfactant, and As(V) concentrations, the presence of flocculant and foreign ions, conditioning time and dissolved air pressure were discussed, as they may affect in a great extent the separation efficiency. The systematic study aims to establish the optimum operating parameters of the process, to investigate the equilibrium and mechanism of separation.

The effect of coagulation on the toxicity and mutagenicity of reclaimed municipal effluents

The objectives of this work were the assessment of the effectiveness of coagulation on the reclamation of secondary effluents and the evaluation of the quality of reclaimed waters by the examination of their ecotoxic and mutagenic properties. Aluminum coagulants resulted in higher removal of organic content, than iron coagulant, reaching up to 40%; the removal of heavy metals, such as zinc and copper was enhanced by the addition of a low strength anionic flocculant. The toxicity of pre-concentrated samples to the bacteria Vibrio fischerii was related to the heavy metal content, especially zinc and copper, indicating the significance of the metals bioavailability and their potential interactive effects. The secondary effluents exhibited mutagenic effects on strain TA 98; these effects were increased during coagulation with ferric chloride (both in absence and presence of flocculant). However, the addition of aluminum coagulants resulted in a decrease of mutagenic potential of secondary effluents, due to the extended removal of organic matter.

Microbially-induced flocculation and flotation for pyrite separation from oxide gangue minerals

Selective separation of pyrite from quartz and calcite was achieved through microbiologically induced flotation and flocculation in presence of Bacillus polymyxa. Adsorption behavior of bacterial cells onto pyrite, calcite and quartz was established. Surface chemical changes on various minerals brought about by bacterial interaction were established through zeta-potential measurements as a function of pH. It has been shown that pyrite can be separated from quartz and calcite through either selective flocculation or flotation after interaction with cells of B. polymyxa or bioproteins separated from the bacterial metabolite. The results of this study are significant from the viewpoint of desulphurisation of flotation tailings with respect to environmental control.

Influence of surfactants on filter cake parameters during vacuum filtration of flocculated iron ore sludge

The influence of certain surfactants on the dewatering of fine iron ore sludge flocculated with anionic flocculants has been investigated in a laboratory-scale vacuum filtration unit. The filtration data have been used in calculating the cake parameters from an integrated form of Darcy's law. A narrow concentration range of surfactant enables reduction of the specific cake resistance and an enhanced rate of filtration. The non ionic surfactant polyethylene oxide (PEO) was most effective in reducing the moisture content of the cake. Filter cake with 12.6% moisture content has been obtained using this surfactant. The surface tension reduction mechanism is responsible to some extent for the enhanced dewatering, but does not account for all the effects. A complex surfactant adsorption mechanism in the presence of flocculants seems to play a greater role in enhancing dewatering.

Flocculation in presence of organic macromolecules of natural water and secondary effluents

Flocculation processes were studied in three types of water representing turbid natural surface water, controlled synthetic systems of reference clay minerals suspensions in the presence of humates and fulvates at various degrees of interactions, and municipal wastewater treatment plant effluents. These systems contain suspended and colloidal dispersed solids accompanied by organic substances in dissolved or colloidal form. The presence of organic anionic macromolecules and soluble organics in water affects flocculation processes by raising the flocculant demand appreciably and hence affects the final water quality. Extraction and elimination of the organics from natural suspended solids, and removal of soluble organics from effluents reduced the organic content, thus decreasing considerably the flocculant demand. The addition of the extracted and separated organics to pure clay dispersions increased accordingly the cationic polyelectrolyte flocculant demand.

Flocculation in presence of organic macromolecules of natural water and secondary effluents

Flocculation processes were studied in three types of water representing turbid natural surface water, controlled synthetic systems of reference clay minerals suspensions in the presence of humates and fulvates at various degrees of interactions, and municipal wastewater treatment plant effluents. These systems contain suspended and colloidal dispersed solids accompanied by organic substances in dissolved or colloidal form. The presence of organic anionic macromolecules and soluble organics in water affects flocculation processes by raising the flocculant demand appreciably and hence affects the final water quality. Extraction and elimination of the organics from natural suspended solids, and removal of soluble organics from effluents reduced the organic content, thus decreasing considerably the flocculant demand. The addition of the extracted and separated organics to pure clay dispersions increased accordingly the cationic polyelectrolyte flocculant demand.