Kaolin Content Research Articles

In Situ Synthesis and Characterization of Graphitic Carbon Nitride/Metakaolin Composite Photocatalysts Using a Commercial Kaolin

Kaolin-based graphitic carbon nitride (g-CNx) composite photocatalysts were synthesized from a urea precursor using a commercial kaolin. Structural characterization by X-ray diffraction and infrared spectroscopy (FTIR) verified the successful thermal polycondensation of g-CNx along the thermal dehydroxylation of kaolinite to metakaolin at 550 °C. The g-CNx content of the composites were estimated by thermogravimetry and CHN analysis, ranging from ca. 87 m/m% to ca. 2 m/m% of dry mass. The addition of kaolin during the composite synthesis was found to have a significant effect: the yield of in situ formed g-CNx drastically decreased (from ca. 4.9 m/m% to 3.8–0.1 m/m%) with increasing kaolin content. CHN and FTIR indicated the presence of nitrogen-rich g-CNx, having a specific surface area of 50 m2/g, which synergistically increased after composite synthesis to 67–82 m2/g. Estimated optical band gaps indicated the affinity to absorb in the visible light spectrum (λ < 413 nm). Photocatalytic activity upon both UV and artificial sunlight irradiation was observed by hydroxyl radical evolution, however, without the synergistic effect expected from the favorable porosity.

Self-Assembly of Three-Dimensional Hyperbranched Magnetic Composites and Application in High-Turbidity Water Treatment.

In order to improve dispersibility, polymerization characteristics, chemical stability, and magnetic flocculation performance, magnetic Fe3O4 is often assembled with multifarious polymers to realize a functionalization process. Herein, a typical three-dimensional configuration of hyperbranched amino acid polymer (HAAP) was employed to assemble it with Fe3O4, in which we obtained three-dimensional hyperbranched magnetic amino acid composites (Fe3O4@HAAP). The characterization of the Fe3O4@HAAP composites was analyzed, for instance, their size, morphology, structure, configuration, chemical composition, charged characteristics, and magnetic properties. The magnetic flocculation of kaolin suspensions was conducted under different Fe3O4@HAAP dosages, pHs, and kaolin concentrations. The embedded assembly of HAAP with Fe3O4 was constructed by the N-O bond according to an X-ray photoelectron energy spectrum (XPS) analysis. The characteristic peaks of -OH (3420 cm-1), C=O (1728 cm-1), Fe-O (563 cm-1), and N-H (1622 cm-1) were observed in the Fourier transform infrared spectrometer (FTIR) spectra of Fe3O4@HAAP successfully. In a field emission scanning electron microscope (FE-SEM) observation, Fe3O4@HAAP exhibited a lotus-leaf-like morphological structure. A vibrating sample magnetometer (VSM) showed that Fe3O4@HAAP had a relatively low magnetization (Ms) and magnetic induction (Mr); nevertheless, the ferromagnetic Fe3O4@HAAP could also quickly respond to an external magnetic field. The isoelectric point of Fe3O4@HAAP was at 8.5. Fe3O4@HAAP could not only achieve a 98.5% removal efficiency of kaolin suspensions, but could also overcome the obstacles induced by high-concentration suspensions (4500 NTU), high pHs, and low fields. The results showed that the magnetic flocculation of kaolin with Fe3O4@HAAP was a rapid process with a 91.96% removal efficiency at 0.25 h. In an interaction energy analysis, both the UDLVO and UEDLVO showed electrostatic repulsion between the kaolin particles in the condition of a flocculation distance of <30 nm, and this changed to electrostatic attraction when the separation distance was >30 nm. As Fe3O4@ HAAP was employed, kaolin particles could cross the energy barrier more easily; thus, the fine flocs and particles were destabilized and aggregated further. Rapid magnetic separation was realized under the action of an external magnetic field.

Effects of low clay content on the anisotropic behavior of sand-clay mixtures: laboratory investigation using TSHCA

Undrained behavior of sandy soil with fines content is a challenge in geotechnical research. In this article, the effect of low clay content (plastic Kaolin) on the anisotropic behavior of sand is studied. In the technical literature, there are different data about the effect of fine particles (generally high percentage), but there are not enough studies on low fines content (especially plastic fines) and anisotropic conditions. For this purpose, 30 undrained tests are performed using a torsional shear hollow cylindrical apparatus (TSHCA) with constant (αo) and (b) values on Firoozkuh sand. The specimens had Kaolin contents of 0, 3, 5, 7 and 10%, and the inclination angle (αo) is varied from 15o to 60o. The specimens are prepared by dry deposition method and are consolidated under P'c= 100 and 200 kPa. The results of the experiments show that increasing the (αo) leads to more contractive behavior in sand. By adding clay particles to the host sand up to 3%, the peak strength of the specimen is increased (7% and 6% for α=15°and 30°, respectively), and then with the increase of clay content up to 10%, the strength of the specimen is decreased (33% and 22% for α=15°and 30°, respectively). But at α = 60o, with the addition of 5% clay, decrease in the peak strength is observed (about 15%) and with a further increase in the clay content, unlike the angles of 15o and 30o, increase in the peak strength of the specimen is observed, so that at 10% clay, the strength of the specimen is higher than the host sand (about 7%), which can be attributed to the cohesion nature of the clay particles. With the increase of clay content, anisotropy degree is decreased. In other words, with the increase of fines content, the anisotropic behavior is decreased.

Clay Tailings Flocculated in Seawater and Industrial Water: Analysis of Aggregates, Sedimentation, and Supernatant Quality.

High-molecular-weight anionic polyacrylamide was used to analyze the effect of kaolin on the structure of particle aggregates formed in freshwater and seawater. Batch flocculation experiments were performed to determine the size of the flocculated aggregates over time by using focused beam reflectance measurements. Sedimentation tests were performed to analyze the settling rate of the solid-liquid interface and the turbidity of the supernatant. Subsequently, a model that relates the hindered settling rate to the aggregate size was used to determine the mass fractal dimension (Df). Flocculation kinetics revealed that greater amounts of kaolin generated larger aggregates because of its lamellar morphology. The maximum size was between 10 and 20 s of flocculation under all conditions. However, the presence of kaolin reduced the settling rate. The fractal dimension decreased with the increase in the kaolin content, resulting in the formation of irregular and porous aggregates. By contrast, factors such as the flocculation time, water quality, and quartz size had limited influences on the fractal dimension. Seawater produced a clearer supernatant because of its higher ionic strength and precoagulation of particles. Notably, the harmful effect of clays in seawater was reduced.

Efficient Recovery of Feldspar, Quartz, and Kaolin from Weathered Granite

Weathered granite contains a high concentration of feldspar, quartz, and kaolin. However, while it becomes rich in clay due to strong physical weathering, the granite minerals that are not fully weathered are still very hard, which makes the grinding process more difficult and limits its use. This study proposes a multi-step process involving grinding, desliming, and flotation to address this issue. The study determines the appropriate grinding time and power index for the original ore, as well as the optimal desliming method using a hydrocyclone. To remove iron-containing impurities like mica, a combination of NaOL/BHA/A CO collectors is used for the reverse rough flotation of quartz. Additionally, a combination of DDA/SDS collectors is employed to separate quartz and feldspar through flotation, resulting in a quartz product with a silicon dioxide content of 99.51%. The objective of efficiently recycling feldspar, quartz, and kaolin from weathered granite is accomplished. Additionally, the inclusion of intermediate mineral components as by-products of feldspar and raw materials for aerated bricks is introduced, resulting in the complete utilization of all components. This innovative approach ensures a clean and environmentally friendly process, eliminating the need for solid waste disposal.

Preliminary study on the water film at the soil–structure interface under cyclic loading

Offshore foundations usually experience long-term cyclic loading, where the weakly bound water at the soil-structure interface can be transformed into free water. The free water enriched at the soil–structure interface would influence the mechanical characteristics of the soil near the interface, weakening the interface strength and posing a significant threat to the safety and stability of offshore foundations. This study proposed a novel concept, i.e. the characteristic water film thickness, to quantify the enrichment degree of water film at the soil–structure interface under cyclic loading. A series of cyclic shearing tests were carried out by using self-developed cyclic loading equipment combined with a small constant temperature centrifuge. The influence of different clay and salt contents on the characteristic water film thickness was investigated and analyzed. It was found that both the kaolin and salt contents significantly impacted the characteristic water film thickness, where it was positively correlated with the kaolin content while negatively correlated with the salt content. The research outcome enriched the understanding of the weakening mechanism underlying the load and deformation transfer between soil–structure interface.

Kaolin loaded gelatin sponges for rapid and effective hemostasis and accelerated wound healing

Severe trauma with massive active blood loss, including liver and spleen rupture, arterial bleeding and pelvic fracture, will lead disability, malformation and even death. Therefore, it is very important to develop new, fast and efficient hemostatic materials. In this study, a novel Gelatin/Kaolin (GE/KA) composite sponge was developed. Meanwhile, to further investigate the effect of kaolin content on sponge properties, we prepared four types of sponges: GE/5% KA, GE/10% KA, GE/15% KA and GE/20% KA. The results of coagulation test in vitro showed that compared to the other groups, there were more activated adhered platelets and red blood cells on the surface of GE/15% KA. The results of hemostasis test in vivo showed that compared to other experimental groups, the GE/15% KA group had significantly less hemostasis time (liver hemostasis model: 69.50 ± 2.81 s; femoral artery hemostasis model: 75.17 ± 3.06 s) and bleeding volume (liver hemostasis model: 219.02 ± 10.39 mg; femoral artery hemostasis model: 948.00 ± 50.69 mg), and was similar to the commercial hemostasis material group. Additionally, the material properties of the sponge were characterized and its biocompatibility was verified as well through cell experiments and in vivo embedding experiments. All these results indicate that the optimal content of kaolin is 15%, which provides a theoretical basis for subsequent research. All in all, the novel GE/KA composite sponge prepared in this study can be used as a multifunctional hemostatic wound dressing for the treatment of complex wounds under various trauma scenes.

Kaolin–Polyvinyl Alcohol–Potato Starch Composite Films for Environmentally Friendly Packaging: Optimization and Characterization

This research paper introduces an innovative methodology to produce biodegradable composite films by combining kaolin, polyvinyl alcohol (PVA), and potato starch (PS) using a solvent casting technique. The novelty of this study resides in the identification and implementation of optimal synthesis conditions, which were achieved by utilizing the Response Surface Methodology—Central Composite Design. The study defines starch, polyvinyl alcohol (PVA), and kaolin as independent variables and examines their influence on important mechanical qualities, water absorption capacity, moisture content, and degradability as primary outcomes. The study establishes the ideal parameters as 5.5 weight percent Kaolin, 2.5 g of starch, and 3.5 g of PVA. These settings yield notable outcomes, including a tensile strength of 26.5 MPa, an elongation at break of 96%, a water absorption capacity of 21%, a moisture content of 3%, and a remarkable degradability of 48%. The study emphasizes that the augmentation of kaolin content has a substantial impact on many properties, including degradability, tensile strength, and elongation at break. Simultaneously, it leads to a reduction in the water absorption capacity and moisture content. The study’s novelty is reinforced by conducting an additional examination on the ideal composite film, which includes investigations using FTIR, TGA, and SEM-EDX techniques. The consistency between the predicted and experimental results is noteworthy, as it provides further validation for the prediction accuracy of Design Expert software’s quadratic equations. These equations effectively capture the complex interactions that exist between process parameters and selected responses. This study presents novel opportunities for the extensive utilization of PVA/PS composite films, including kaolin in various packaging scenarios, thereby significantly advancing sustainable packaging alternatives. The statistical analysis provides strong evidence supporting the relevance of the models, hence increasing our level of trust in the software’s prediction skills. This conclusion is based on a 95% confidence level and p-values that are below a threshold of 0.05.

Rheological, mechanical, and morphological behaviour of polypropylene composites reinforced with ultrafine kaolinite particles

To develop charge/matrix interactions and improve the rheological, mechanical, and morphological performances of the matrix polypropylene, PP/kaolinite composites were prepared using the melt intercalation method at 190 °C. The rheological and mechanical properties of polypropylene/kaolin composites have been evaluated at various concentrations of untreated and/or treated kaolin. It was shown that the melt flow index (MFI) varies visibly but slightly compared to that of the matrix with increasing kaolin content. Furthermore, when the kaolin loading is enhanced, the apparent shear viscosity (ηapp) of the composites increases compared to the matrix and decreases with the increase in the shear rate (γapp). Also, while the shear stress (τapp) is reduced, the flow curve shifts upwards with increasing the kaolin concentration. The systems obeyed the power-law model in shear stress-shear rate variations and were shear thinning as power-law index (n) values increased with kaolin content. Moreover, the mechanical properties of the obtained composites were significantly affected by the dispersion of the filler into the matrix and by the weak interactions at the interface PP/kaolinite. SEM micrographs show a poor dispersion of the nanoclay within the polypropylene matrix and the formation of agglomerates with different sizes.

Research on the Tribological Properties of Layered Kaolin Lubricant Additives

Lubricant additives are the main means to improve the performance of lubricants. In this article, green and inexpensive layered kaolin were selected as lubricant additives, and the effects of the type of modifier, concentration, particle size of kaolin additives, and working temperatures on the tribological performance of lubricants were investigated. The results showed that the Span80 modifier can effectively improve the dispersibility and friction reduction effects of kaolin oil samples. Compared with kaolin oil samples without the modifier, the modified kaolin oil can reduce the friction coefficient by 40.9% and the wear spot diameter of the steel balls by 43.8%. The layered kaolin additive can significantly reduce the friction coefficient and wear of steel balls in lubrication, and the friction coefficient showed a trend of decreasing and then increasing with increasing kaolin additive concentration and particle size. The optimal added concentration and particle size of kaolin are 5 wt% and 2 μm, respectively, which can reduce the friction coefficient by 41.9% and 65.63% and the wear spot diameter by 12.31% and 50.72%, respectively, compared with the base oil. At five temperatures, compared with the base oil, the kaolin oil samples all showed better friction reduction and anti-wear properties. The micro and nano size of the kaolin additive, the layered structure, and the chemically reactive film generated on the surface are the main reasons for its good lubrication performance.

EFFECT OF FILLING A POLYURETHANE MATRIX WITH KAOLIN ON DAMPING EFFICIENCY, MECHANICAL AND THERMAL PROPERTIES.

One of the ways to reduce the cost of a polymermaterial is to replace the weight part of its composition with a cheaper natural filler. In this work, the objects of study are polyurethane composites synthesized by the insitumethod, containing the mineralfiller kaolin from 10 to 40 mass parts. Filling with kaolin significantly lowers the price of polyurethane material, and its cost is reduced by almost 30 percent when the content of the filler is 40 mass parts. Morphological studies have shown that kaolin particles are uniformly dispersed in the poly­urethane matrix, but thereis a tendency for the iragglomerationas the filler concentration increases. Viscoelastic, mechanical, and thermal properties of polyurethane composites wer studied. The damping efficiency of polyurethane materials was estimated from the results of dynamic mechanical analysis. Itis found that the filler additions lightly decreases the effective damping temperature range of polyurethane composites, but their heat resistance and mechanical properties improve. The method of thermogravimetricanalysis was shown the presence of kaolin significantly changes the character of thermo-oxidative destruction of composites. The temperature interval of the intensive decomposition stage increases for filled systems and the temperature of the maximum rate of weight loss at the decomposition stage (Tmax) increases with increasing kaolin content. According to the results of mechanical studies, an increase in the kaolin content in polyurethanes leads to an increase in the storage modulus (E') and a significant decrease in the relative elongation (ε). Thus, filling with kaolin significantly reduces the cost of polyurethane composites and contributes to their expansion of functional properties due to increased heat resistance and improved mechanical characteristics.

On the relationship between superplasticizer demand and specific surface area of calcined clays in LC3 systems

Calcined clays have received significant attention as a primary supplementary cementitious material (SCM) for reducing the CO2 footprint of cement, especially when combined with limestone in limestone calcined clay cement (LC3). However, it is widely recognized that the use of calcined clays leads to increased water and admixture demand, posing challenges in terms of slump-retention and rheology when using conventional admixtures developed for OPC. Superplasticizer demand is commonly correlated with the kaolin content of the raw clays. In this paper, we investigate and demonstrate the strong influence of the specific surface area of calcined clays on superplasticizers dosage by studying four different LC3 compositions ranging from 65% to 35% clinker content, using five calcined clays and two superplasticizers.

KAOLIN FORMATION IN YATAĞAN (MUĞLA) LIGNITE DEPOSIT

The 30-km-long and 10-km-wide, coal-bearing Yatağan Basin is located in SW Anatolia, close to the eastern coast of the Aegean Sea, Türkiye. The basement consists of Menderes Massif metamorphics in the NW part of this intermontane basin, c. 80-km2-large area (Turgut lignite deposit). The Neogene and Quaternary sedimentary filling comprises fluvioterrestrial, limnic and telmatic sediments which contain a mineable coal seam up to 15 m thick, unconformably overlain the basement. Two fresh and six weathered samples were picked up from the Menderes Massif gneiss outcrops of the catchment area. Eight sedimentary rocks, inorganics over and underlying the coal seam, were obtained from four borehole cores. All samples were examined under the optical microscope; XRD, SEM-EDX and ICP-MS analyses were later performed. This study aims to examine the mineralogical content and geochemical processes of the sedimentary rocks from different formations, namely Sekköy and Turgut Formations, which are over- and underlying the lignite horizon, to assess the clay mineral formations and transformations. Gneiss samples contain mainly quartz, plagioclase, K-feldspar, muscovite and biotite with a lesser amount of tourmaline, chlorite, garnet, apatite, zoisite, zircon and Fe-oxides. The -2 µm fraction consists mainly of illite, with fewer smectite and kaolinite. Sericitizitation of feldspar is the main product in gneisses. Coal over-and underlying sedimentary rock samples contain mainly quartz, plagioclase, K-feldspar, muscovite, and biotite with less pyrite and iron oxides. The -2 µm fraction of the sedimentary rock samples consists of variable clay mineral contents. Kaolin content is higher in acidic conditions with an opposite correlation to smectite occurrences. The geochemistry of Menderes Massif gneisses shows that it gave felsic material to the catchment area, whereas the geochemistry of sedimentary rocks is not coherent in all cases. Geochemical parameters like CIA and PIA proved that weathering processes of the source materials prevailed during the generation of these sedimentary units.

Collaborative improvement of electrical‐thermal‐mechanical properties of kaolin‐filled ethylene propylene diene monomer and mechanism analysis

AbstractWith the rapid development of offshore wind power, large‐capacity wind turbine generators have put forward higher electrical and mechanical performance requirements for the cable. In this paper, kaolin/ethylene propylene diene monomer (EPDM) composites are prepared to investigate the effect of kaolin content on the electrical properties, mechanical properties and thermal conductivity of EPDM composites. The results show that appropriate amount of kaolin could synergistically improve the electrical‐thermal‐mechanical properties of EPDM. The composite with 30 wt% kaolin content achieves the best performance. The breakdown strength of kaolin/EPDM composites increases by 13.47%–72.19 kV/mm compared with that before modification, and the volume resistivity increases from 1013 to 1015 Ω·cm after modification. In addition, with the doping of kaolin, the tensile strength of composites significantly improves by over 500%–6.97 MPa, and the thermal conductivity of the composite is slightly improved. This work has important guiding significance for the development of insulation materials for cables.Highlights Kaolin in EPDM scattered more uniform after modification. The addition of kaolin improves the electrical‐thermal‐mechanical properties of the composite. Kaolin/EPDM composites have promising applications.

Wettability Characteristics of Low-Rank Coals Under the Coupling Effect of High Mineralization and Surfactants.

This paper investigates the unclear influence mechanism of the surfactant effect on improving coal seam wettability and CO2-enhanced coalbed methane technology to enhance the gas extraction efficiency in some coal mines under highly mineralized environments in China. Specifically, the microinfluence mechanism of the coupling effect of nonionic surfactant OP-10 and highly mineralized coal samples under special treatment on the wettability of coal seam is examined. By measuring the contact angle and surface tension of the samples, it is confirmed that high mineralization can limit the effect of surfactants on improving the wettability of coal seams to a certain point. Infrared spectroscopy and X-ray diffraction measurements were conducted on the samples under coupling conditions. It is found that high mineralization impedes the effectiveness of surfactants in enhancing the wettability of coal seams. The surfactants interact with coal samples at the functional group level, producing new hydrophilic functional groups and increasing the content of kaolin with strong hydrophilic properties, thereby increasing the wettability of coal seams. However, these hydrophilic functional groups disappear under coupling conditions and hydrophobic functional groups are produced. Additionally, high mineralization inhibits the effect of surfactants on the phase composition of coal samples. The findings of this research provide a theoretical basis for water injection of highly mineralized coal seams and methane replacement recovery by carbon dioxide technology, promoting the practical application of water injection and gas injection displacement of coal seams.

Synthesis of FeNi@kaolin soft magnetic composites with adjustable magnetic properties under different DC bias fields

Constructing the high-quality insulating layer and verifying the effects of DC bias field on magnetic properties is crucial in optimizing magnetic components based on soft magnetic composites. In this paper, a novel APTES-involved insulation technique has been developed to successfully coat kaolin on FeNi particles. Additionally, magnetic properties can be effectively regulated by changing the dosage of kaolin. The results show that anti-magnetization capacity and resistivity are improved by increasing kaolin content. Loss separation model and magnetic field simulation were used to investigate how the coating layer and DC bias field influence core loss for FeNi@kaolin SMCs. It can be found that structural demagnetizing field and eddy current were believed to be the main determinants of core loss variation in ideal sinusoidal waves, while the degree of magnetization state away from saturation plays a leading role in core loss under larger DC bias fields. Therefore, FeNi SMCs insulated with 1 wt% and 7 wt% kaolin exhibit the lowest core loss at DC bias field of 0 Oe and above 100 Oe, respectively. This work not only provides an effective insulating technique, but also supplies deeper insights into optimizing SMC-based magnetic components under larger DC bias fields.

Clay mineralogical evidence of near-equatorial Palaeocene–Eocene Thermal Maximum in Barmer Basin, India

Abstract The Palaeocene–Eocene Thermal Maximum (PETM) was a global extreme climatic event, but it is relatively unknown from lower latitudes or equatorial regions in comparison to mid- and high latitudes. The present study provides the first clay mineralogical evidence of the PETM and subsequent hyperthermal events in a near-equatorial region represented by the Akli Formation in the Barmer Basin, India. The 32 m-thick succession of the Akli Formation shows abrupt changes in smectite and kaolin abundances preceding, during and succeeding the PETM event. Within the studied section, the kaolin content increases from 5–8% pre-PETM to 30–35% during the PETM, and then again decreases to 5–6% during the post-PETM period. The smectite, however, is marked by a corresponding decrease and its transformation into kaolin in acid weathering conditions. The transformation of the smectite is first marked by hydroxy interlayering and then transformation into kaolin during the PETM. The transformation of smectite into kaolin also resulted in extensive precipitation of iron oxide in sediments. The clay mineralogical changes in the Palaeocene–Eocene transition sediments of the Akli Formation were caused by 3–5°C warming and a 25–50% increase in rainfall during the hyperthermal events. Unusually high charcoal (~20%) fragments during the Palaeocene–Eocene transition also suggest warming and widespread biomass burning during the PETM in the lower latitudes.

Effects of Microencapsulated Phase Change Material on the Behavior of Silty Soil Subjected to Freeze–Thaw Cycles

Freeze–thaw (F-T) cycles are one of the most important factors affecting the performance of silty soils with high kaolin content in seasonally freezing regions. This study investigates the improvement of a high-plasticity clayey silt soil (MH) with microencapsulated phase change material (mPCM) to prevent changes in mechanical properties when subjected to freeze–thaw cycles. Unconfined compression, one-dimensional compression, and freeze and thaw tests were performed to evaluate the behavior of treated soil under different freeze/thaw cycles and with different mPCM ratios. It has been observed that the mPCM additive decreased the unconfined compression strength (UCS); however, the strength of the soil held constant during the increasing F-T cycles, and the increase in the mPCM additive content increased the strength of the soil. The inclusion of mPCM affected the compression of the soil and increased settlement (∆H), although the settlement remained constant with increasing freeze–thaw cycles. It has been noted that the compression behavior, which is least affected by the unconfined compressive strength and freeze/thaw cycles, is achieved with the addition of 10% mPCM. As a result of the tests, it was determined that the most suitable additive mPCM ratio is 10% for the compression and strength behaviors.

Optimum conditions for high-speed solid-liquid separation by ballasted flocculation.

In the ballasted flocculation, high-speed sedimentation of suspensions is achieved using a microsand as a ballast material and a polymer flocculant combined with microflocs made of polyaluminum chloride (PAC) as an inorganic coagulant. In this study, three turbid water samples containing kaolin clay (kaolin concentration: 20, 200, and 500 mg/L) were treated by coagulation-sedimentation and ballasted flocculation. The effects of pH and PAC dosage, which are the controlling parameters for coagulation, and the microsand (silica sand) and polymer dosages, which are the controlling parameters for ballasted treatment, on the treatment efficiency and floc settling velocity were examined. The floc settling velocity under the optimum conditions was 17 times higher than that of the conventional coagulation-sedimentation process using PAC. The turbidity was 0.54 turbidity unit (TU) (TU as the kaolin standard), and its removal efficiency was 99.7%. Furthermore, turbid water samples with different kaolin concentrations (20 and 500 mg/L) were treated via the ballasted flocculation. In this study, fundamental information on the optimization of each dosage condition of coagulant, ballast, and polymer and pH condition in ballasted flocculation was obtained, and the removal mechanisms under optimal, underoptimistic and overoptimistic conditions were proposed.

Bioflocculation characteristics of bound extracellular polymers substances from Pseudomonas sp. XD-3 and behavior of polysaccharides

This study aimed to investigate the bioflocculation characteristics of bound extracellular polymers substances (B-EPS), which were extracted from Pseudomonas sp. XD-3. The flocculation efficiency of B-EPS achieved about 80%− 95% with an initial pH of 4–7, kaolin concentrations of 3–7 g L−1, temperature of 25–100 ℃ and B-EPS dosage of 9–105 mg L−1. The bioflocculation process of B-EPS conformed to pseudo-second-order kinetic mode, suggesting that the bioflocculation belonged to chemical adsorption process. Enzymatic hydrolysis experiments demonstrated that both polysaccharides and proteins were active components for bioflocculation. The polysaccharides were irregular aggregates with rough and porous surfaces and contained hydroxyl and carboxyl groups, which helped to promote bridging effect. Ribose, glucose and galactose were the main monosaccharides of polysaccharides. The molecular weight of the polysaccharides was relatively small, but the relatively loose configuration exposed more ion bridging sites, thus promoting the bioflocculation. Optimizing the ingredients of culture medium and culture time for B-EPS were effective strategies to increase the yield of flocculation active components. When the conditions were 10% of 2 g L−1 KH2PO4 + 5 g L−1 K2HPO4, 0.05% of Tween-80, citrate as carbon source and 32–48 h of culture time, both proteins and polysaccharides in B-EPS were significantly improved. This study gives an in-deep understanding on the flocculation characteristics of a novel bioflocculant from Pseudomonas sp. XD-3, which is conducive to the widespread application of bioflocculation.