Flocculation Agents Research Articles

Production, characterization, and flocculation mechanism of cation independent, pH tolerant, and thermally stable bioflocculant from Enterobacter sp. ETH-2.

Synthetic high polymer flocculants, frequently utilized for flocculating efficiency and low cost, recently have been discovered as producing increased risk to human health and the environment. Development of a more efficient and environmentally sound alternative flocculant agent is investigated in this paper. Bioflocculants are produced by microorganisms and may exhibit a high rate of flocculation activity. The bioflocculant ETH-2, with high flocculating activity (2849 mg Kaolin particle/mg ETH-2), produced by strain Enterobacter sp. isolated from activated sludge, was systematically investigated with regard to its production, characterization, and flocculation mechanism. Analyses of microscopic observation, zeta potential and ETH-2 structure demonstrates the bridging mechanism, as opposed to charge neutralization, was responsible for flocculation of the ETH-2. ETH-2 retains high molecular weight (603 to 1820 kDa) and multi-functional groups (hydroxyl, amide and carboxyl) that contributed to flocculation. Polysaccharides mainly composed of mannose, glucose, and galactose, with a molar ratio of 1∶2.9∶9.8 were identified as the active constituents in bioflocculant. The structure of the long backbone with active sites of polysaccharides was determined as a primary basis for the high flocculation activity. Bioflocculant ETH-2 is cation independent, pH tolerant, and thermally stable, suggesting a potential fit for industrial application.

Harvesting freshwater Chlorella vulgaris with flocculant derived from spent brewer’s yeast

One of the key bottlenecks of the economically viable production of low added value microalgal products (food supplements, feed, biofuels) is the harvesting of cells from diluted culture medium. The main goals of this work were to prepare a novel flocculation agent based on spent brewer’s yeast, a brewery by-product, and to test its harvesting efficiency on freshwater Chlorella vulgaris in different environments. The yeast was first autolyzed/hydrolyzed and subsequently chemically modified with 2-chloro-N,N-diethylethylamine hydrochloride (DEAE). Second, optimal dosage of modified spent yeast (MSY) flocculant for harvesting C. vulgaris was determined in culture media of various compositions. It was found that the absence of phosphorus ions decreased (0.4mgMSY/gbiomass), while the presence of algogenic organic matter (AOM) increased (51mgMSY/gbiomass) the required dosage of flocculant as compared to complete mineral medium with phosphorus and without AOM (12mgMSY/gbiomass).

Experimental study on application of a new charging flocculation agent for catfish farming water treatment in Vinh Long province

The charging flocculation agent “Kiyomaru” is a natural inorganic substance produced from volcanic ash (“Shirasu”) by calcining it in the special firing furnace to generate high porosity, then applying a strong electric charge to some substances included in the ingredient of “Shirasu” by special processing. “Kiyomaru” consists of 24.7 % Na, 11.5 % Al, 19.6 % Si, 22.5 % S, 1.8 % K, 19.0% Ca, 09% Fe, which can consider as an ecological water depurative, having rapid rate of flocculation and sedimentation, cheaper facility cost, simplification of post-processing sludge, low cost and high performance, overwhelming flocculation capacity. Apart from effective treatment of the waters contaminated with high content of suspending solid (up to 10,000 ppm), the agent can remove some heavy metals such as Fe, Mn, As, etc., odour and some organic substances (COD). From 2013 to the present, Environmental Technology Center (ENTEC) in cooperation with HALVO Company Ltd. and Japan Port Consultants Ltd. funded by the Department of Science and Technology of Vinh Long prpvince have implemented the study on experiemental study on application of “Kiyomaru” for catfish farming water treatment in Vinh Long province. The obtained results shown that when using the “kiyomaru”, the efficency of color, turbidity, suspended solid and iron removal as well as the rate of coagulation and sedimentation are generally higher than those comparing with the traditional coagulants.

Coagulation–flocculation mechanisms in wastewater treatment plants through zeta potential measurements

Based on the polyelectrolyte-contaminant physical and chemical interactions at the molecular level, this article analyzed and discussed the coagulation–flocculation and chemical precipitation processes in order to improve their efficiency. Bench experiments indicate that water pH, polyelectrolyte (PE) dosing strategy and cationic polyelectrolyte addition are key parameters for the stability of metal–PE complexes. The coagulation–flocculation mechanism is proposed based on zeta potential (ζ) measurement as the criteria to define the electrostatic interaction between pollutants and coagulant–flocculant agents. Polyelectrolyte and wastewater dispersions are exposed to an electrophoretic effect to determine ζ. Finally, zeta potential values are compared at pH 9, suggesting the optimum coagulant dose at 162mg/L polydadmac and 67mg/L of flocculant, since a complete removal of TSS and turbidity is achieved. Based on the concentration of heavy metals (0.931mg/L Sn, 0.7mg/L Fe and 0.63mg/L Pb), treated water met the Mexican maximum permissible limits. In addition, the treated water has 45mg O2/L chemical oxygen demand (COD) and 45mg C/L total organic carbon (TOC). The coagulation–flocculation mechanism is proposed taking into account both: zeta potential (ζ)–pH measurement and chemical affinity, as the criteria to define the electrostatic and chemical interaction between pollutants and polyelectrolytes.

Elimination of Dyes Present in Textile Industry Wastewater Using Adsorbent Materials Prepared from Broccoli Stem

This paper presents the results of the adsorption of textile dyes in static systems, using adsorbent materials prepared from broccoli waste collected after harvest. The adsorption capacities of the non-activated lignocellulosic residue (BrocNat), the chemically activated waste using sodium hydroxide (BrocNaOH), the thermally activated at 823 K ash (AshBroc), and the chemically activated carbon using phosphoric acid at 673 K (CarBrocQ) were tested. Aqueous solutions containing cationic and anionic dyes as well as textile effluents generated after the dyeing process of a cotton-processing factory containing vat and reactive dyes were treated. Lignocellulosic materials were only effective in removing dyes when they were found in aqueous solution. The carbonaceous adsorbent CarBrocQ presented removal percentages close to 100% and between 13 and 75% for reactive and vat dyes contained in the effluents respectively. To accomplish the complete elimination of color from effluents containing vat dyes, these were treated before adsorption, using aluminum chlorohydrate and poly(acrylamide-co-sodium acrylate) as coagulant and flocculant agents, respectively. The COD of the effluent containing vat dyes was reduced up to 93% after both treatments were combined, and the removal of color was absolute. The high adsorption capacity of CarBrocQ occurs because of its high specific surface area, which was determined by N2 adsorption to be 1177 m2g-1. In the case of the lignocellulosic material, the specific surface area was determined by means of adsorption of methylene blue, and it was 485 m2g-1 for both. The adsorption capacity of CarBrocQ was compared with that of commercial carbons, and proved to be similar. The adsorption results obtained indicate that broccoli waste can be used to prepare activated carbon with applications in the removal of dyes present in textile effluents.

Comparison of the influence of polyaspartic acid and polylysine functional groups on the adsorption at the Cr2O3—Aqueous polymer solution interface

Polyamino acids are a group of synthesized polymers obtained by polymerization of a given kind of amino acid monomer. Because of high biodegradability of this class of polymers, they can be used as flocculation or stabilization agents in the environmental aspects. Therefore determination of their influence on the stability of the aqueous suspension of metal oxides is important. An influence of different functional groups of polyamino acids, their molecular weight and concentration on the adsorption at the chromium (III) oxide (Cr2O3)—aqueous solution interface was determined. Experiments were carried out for four values of solution pH varying from 3 to 10 (3, 4, 7.6 and 10, respectively). Two polymers were used: anionic polyaspartic acid (ASP) of 6800 and 27,000 as well as polylysine (LYS) of 4900 and 33,000 molecular weights. Changes of surface charge density of colloidal Cr2O3 in the presence and in the absence of macromolecular substances were determined using potentiometric titration. In these studies the influence of the concentration and molecular weight of the ionic polymers on the pHpzc value was determined. Additionally, due to the lack of appropriate literature data, potentiometric titration of the selected polymers was performed to determine pKa values.

Correlation between Asphaltene Stability in n-Heptane and Crude Oil Composition Revealed with In Situ Chemical Imaging

Five crude oil samples with different physical properties have been studied with respect to asphaltene stability. The attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic imaging approach of n-heptane-induced precipitation has been used to monitor crude oil behaviour under dilution with a flocculation agent. For each sample, the dynamics of asphaltene precipitation has been observed by applying this chemical imaging method. Based on these data, the stability of crude oil samples has been compared and the correlation between asphaltene stability and crude oil properties has been proposed.

Harvesting of microalgae using flocculation combined with dissolved air flotation

This study explored efficient methods of harvesting the Tetraselmis sp. KCTC12236BP using flocculation and dissolved air flotation. Concentration ranges of flocculation agents were optimized using jar tests (batch flocculation experiments) using inorganic (aluminum sulfate, ferric sulfate) and organic (chitosan) flocculants in a pH range of 4 ∼ 10. The optimal dosage and pH level were 1.2 g/L and pH 5 ∼ 6 for aluminum sulfate, 0.7 g/L and pH 4 ∼ 8 for ferric sulfate, and 5.0 mg/mL and pH 7 ∼ 8 for chitosan. The highest harvesting efficiency achieved with each of the four compounds was 85.6, 92.6, 93, and 91.3%, respectively.

The Stability and Breakage of Oil-in-water From Polymer Flooding Produced Water

Produced water from polymer flooding was much more difficult to be treated than that from water flooding. The mechanisms of polymer stabilizing the oil-in-water emulsion were the decreases of interfacial tension and electric conductivity, and the increases of zeta potential and bulk phase viscosity. Inorganic flocculant, the combination of inorganic flocculant and polymer degradation agent, and the combination organic flocculant and coagulant were used to break the oil-in-water emulsion stabilized with polymer. It was the most effective way to use the combination of organic flocculant and coagulant for treating polymer stabilizing oil-in-water emulsion.

Submicron capsules extracted from rapeseed as novel flocculant agents for the treatment of turbid water

Flocculation is an important step in water treatment as it is responsible for the separation of suspended solids and colloids. The currently used flocculants have certain limitations with respect to environmental impact and disposal as well as potentially being harmful to human health, which has encouraged the study of natural flocculants originating from oleaginous plants. Oil-bodies are individual small organelles in which oleaginous seeds store triacylglycerols reserves. In this article, the flocculant properties of oil-bodies have been investigated. Oil-bodies flocculate at pH 5, 7 and 9 and high ionic strength (100 mM NaCl) and it was demonstrated that their intact structure is necessary for the flocculation activity as treatment with protease K and diethyl ether, that remove the protein coat and the oil-core, respectively, dramatically decreased the flocculation activity. This study shows that oil-bodies have the potential to be novel, natural, sustainable, environmentally friendly and biodegradable flocculant candidates for water treatment.

Effect of algogenic organic matter (AOM) and sodium chloride on Nannochloropsis salina flocculation efficiency

This study evaluates the effect of polymer molecular weight and charge density, algogenic organic matter (AOM), and salt concentration on harvesting efficiency of marine microalgae. Aluminum chloride (AlCl3), chitosan, and five synthetic cationic polymers of different molecular weights and charge density levels were used as flocculation agents. Polymer flocculation of marine microalgae was most efficient when using the highest charge density polymer (FO4990). The flocculant dosage irrespectively of the agent chemistry and charge density was affected by the amount of AOM secreted into the culture media. The presence of AOM increased the amount of required flocculant 7-fold when using synthetic cationic polymers; 10-fold with chitosan; and ~3-fold with AlCl3. Salt concentration of 5 or 35 g/L NaCl alone did not significantly affect removal efficiency, indicating that AOM were the main cause for the increased flocculant dosage requirement. The synthetic cationic polymer (FO4990) was the least expensive flocculation agent.

Chemical modification of cobalt ferrite nanoparticles with possible application as asphaltene flocculant agent

Asphaltenes can cause enormous losses in the oil industry, because they are soluble only in aromatic solvents. Therefore, they must be removed from the petroleum before it is refined, using flocculant agents. Aiming to find new materials that can work as flocculant agents to asphaltenes, cobalt ferrite nanoparticles were chemically modified through acid-base reactions using dodecylbenzene sulfonic acid (DBSA) to increase their lipophilicity. Nanoparticle synthesis was performed using the co-precipitation method followed by annealing of these nanoparticles, aiming to change the structural phase. Modified and unmodified nanoparticles were tested by FTIR-ATR, XRD and TGA/DTA. In addition, precipitation onset of the asphaltenes was performed using modified and unmodified nanoparticles. These tests showed that modified nanoparticles have a potential application as flocculant agents used to remove asphaltenes before oil refining, since the presence of nanoparticles promotes the asphaltene precipitation onset with the addition of a small amount of non-solvent.

New range of natural products for pre-treatment of water desalination plants

Water desalination plants performance and time evolution of its main operational parameters may be influenced by the presence of certain substances both in solution and in suspension in natural waters. Within these substances, humic acids, which percentage may rise up to 50% of total organic matter, could lead to film formation on membranes surface if removal treatments are not properly implemented. Moreover, contact with disinfectant agents such as chlorine can cause the formation of trihalomethanes (THMs) as undesirable reaction side products. Synthetic coagulant and flocculant dosing programs are included as pre-treatments in water desalination plants as a first stage on water processing in order to remove colloidal matter, from both organic and inorganic sources. However, coagulant and flocculant overdosing not only may be null from the treatment effectiveness point of view but also might lead to recalcitrant fouling phenomena. ADIC GR102, a natural polymer, was used as a flocculant agent in natural organic matter removal processes leading to similar organic matter removal yields and Flocculation Index values to those obtained with currently marketed products. Several assays performed at 80% of coagulant requirement to destabilize the suspension and relatively low dosage of ADIC GR102 opened the doors to a promising future water treatment strategies.

Using nano-chitosan for harvesting microalga Nannochloropsis sp.

In this study, chitosan and nano-chitosan were used as flocculants agents for harvesting microalga Nannochloropsis sp. chitosan was modified to nano-chitosan by crosslinking with sodium tripolyphosphate. The effects of type and dosage of flocculants and the pH of the culture were investigated on biomass recovery. Optimum dosages for both bio-flocculants were found. The results showed that the dosage of flocculant consumption decreases by 40% and biomass recovery increases by 9% when nano-chitosan instead of chitosan is used as flocculant agent. Also, the recycled water from the harvesting process was reused which increases the growth of microalgae by about 7%. Finally, the cost analysis of harvesting process showed the feasibility of using nano-chitosan as flocculation agent.

Chitosan as flocculant agent for clarification of stevia extract

Stevia is used as a sweetener due to its low calorific value and its taste, which is very similar to that of sucrose. After extraction from dried leaves, stevia extract is dark in colour, and therefore needs to be whitened to increase acceptance by consumers. In this study we tested chitosan, a cationic polyelectrolyte, as flocculant agent for the whitening of the Stevia extract. Positive charges of chitosan can interact electrostatically with a counter-ion, sodium tripolyphosphate (TPP), and then chitosan precipitates. A factorial design was used to study the whitening process, in which Glycosides Removal, Colour Removal, Turbidity Removal and Soluble Solids Removal were evaluated. The studied factors were Chitosan Mass and pH of the TPP solution. The results showed that chitosan is a good flocculant agent, being able to flocculate both the glycosides and the pigments that make the extract coloured.

Branched Dextran‐graft‐Polyacrylamide Copolymers as Perspective Materials for Nanotechnology

AbstractBranched dextran‐graft‐polyacrylamide copolymers (D‐g‐PAAn) with different number of PAA‐grafts have been synthesized for further conversion them to polyelectrolytes dextran‐graft‐(polyacrylamide‐co‐polyacrylic acid). It is shown that D‐g‐PAAn internal structure in water solution is more compact in comparison with linear polyacrylamide and depends upon the distance between PAA grafts. The branched polyelectrolytes are obtained by alkaline hydrolysis of synthesized D‐g‐PAAn samples. The conversion of nonionic polymers to partial anionic form depends upon the macromolecular internal structure of D‐g‐PAAn. The degree of transformation of amide groups to carboxylate ones is higher for branched copolymers than for linear PAA at the same condition. The synthesized branched copolymers are shown to be perspective as flocculation agents and the matrices for synthesis of the stable Ag nanosystems.

Carbohydrates Production and Bio-flocculation Characteristics in Cultures of Arthrospira (Spirulina) platensis: Improvements Through Phosphorus Limitation Process

Carbohydrates are a desirable biomass compound for the generation of several biofuels. Phosphorus nutrient limitation causes a significant increase in the carbohydrate content of the cyanobacterium Arthrospira (Spirulina) platensis. Carbohydrates accumulated up to a content of 63.09 ± 3.43 % (±SD) in both batch and semi-continuous cultures. In order the production of carbohydrate-rich biomass through nutrient limitation to be maximized, it is suggested that the limited nutrients have to be supplied in amounts that they on one hand can support the biomass production while on the other hand they alter the composition of the biomass. In this study, phosphorus of 1.82 ± 0.16 mg g−1 of dry biomass was the optimized amount for the maximization of carbohydrates production by A. platensis. Regarding the need to decrease the application amounts of nutrients for biomass production, this study demonstrates that the phosphorus supply could be decreased an order of magnitude with no significant decrease in biomass production. In addition, it was observed that biomass rich in carbohydrates bio-flocculates, during settling without the addition of any flocculation agent or any other intervention. The bio-flocculation efficiency appears to be related with the carbohydrate content of the biomass. In maximum carbohydrate content (60 %), the biomass bio-flocculated at 68.49 ± 7.73 % the first 15 min and reached 80.25 ± 5.58 % 60 min after settling. The produced carbohydrates might be used as feedstock for biofuel generation, while the bio-flocculation and the overall settling characteristics of the carbohydrate-rich biomass could make its harvesting process much easier.

Decolorization Effect of Mycelium Pellet on Saline Azo Dye Wastewater

A fungus with efficient dye decolorization and that generates a microbial flocculation agent was isolated from a wastewater environment and screened. This bacterial strain imposed a significant decolorization effect on azo dyes. On the basis of morphological and microscopic features, the fungus was identified and named A-6. The results show that the decolorization process of the fungus exhibited two types of actions: adsorption decolorization of mycelium and flocculated decolorization of extracellular products in the dyes. The decolorization ratio reached 99.20%

Clay nanopaper composites of nacre-like structure based on montmorrilonite and cellulose nanofibers—Improvements due to chitosan addition

Clay nanopaper are nanocomposites with nacre-like structure and multifunctional characteristics including high modulus, significant strength and toughness as well as fire retardancy and low oxygen transmission rate (OTR). Montmorrilonite (MTM) and nanofibrillated cellulose (NFC) hydrocolloids are combined with a chitosan (CS) solution to form high MTM content nanopaper structures by the use of a previously developed papermaking approach. Chitosan functions as flocculation agent and decreases dewatering time to less than 10% compared with MTM–NFC clay nanopaper. The effect of chitosan on the clay nanopaper structure was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Properties were measured by uniaxial tensile testing, thermogravimetric analysis (TGA), OTR and moisture adsorption experiments. A nacre-like multilayered structure was confirmed and the chitosan–clay nanopaper showed favorable mechanical properties at clay contents as high as 44–48wt%.

Characterization of microdevices for ferrous chloride separation for biosensing applications

Ferrous chloride has a variety of applications such as a reducing flocculation agent in waste-water treatment, especially for wastes containing chromate, in the laboratory synthesis of iron complexes and it is employed as a reducing agent in many organic syntheses. The device used for experiment was fabricated on the silicon wafer as support for two electrodes in a SU8 polymer microchannel with an inlet, for the injection of aqueous solution of ferrous chloride, and two outlets, for the two by-products of separated solutions. The various parameters of the device were measured by White Light Interferometer (WLI) and Scanning Electron Microscopy (SEM). The magnetic field created by applying different types of potential between two electrodes determined ferrous chloride to separate in ferrous oxide and chlorine (in gaseous form). If a protein is added in this solution we have the possibility to immobilize the protein on the iron particles and on the channel area. The electrical results were collected using a semiconductor system analyzer Keithley and were examined subsequently. The Fe complexes deposited on the electrodes were characterized by XRD analyses.