Kaolin Particles Research Articles

Efficient removal of fluoroquinolones antibiotics by using kaolin-tannic acid-Fe(III) composite adsorbents from water

In this work, a series of novel composite adsorbents (k-TAFe) was designed and fabricated through a one-step method, that is, the chelation crosslinking of tannic acid, kaolin particles and different contents of Fe(III). k-TAFe had a high efficiency in adsorption of various fluoroquinolones antibiotics (FQs) from water. The detailed performance of k-TAFe in FQs adsorption, including the influences of Fe(III) content, solution pH, inorganic and organic additives, adsorption time and FQs' concentration, has been investigated systematically using ofloxacin (OFL), one of popular FQs, as an example. The maximal OFL uptake of k-TAFe was 0.405mmol/g at an initial pH of 6.0. On the basis of the analysis of the x-ray photoelectron and fourier transform-infrared spectra before and after adsorption, the comparison in the apparent performance of k-TAFe in adsorption of seven FQs with similar structures and their two sub-structural analogs, and theoretical calculation, multiple adsorption mechanisms, including chelating effect, hydrogen bonding, electrostatic attraction, and π-π electron–donor–acceptor interactions, were involved and discussed in detail. Among them, chelating effect due to Fe(III) played a key role in OFL adsorption, and the addition of kaolin particles synergistically enhanced Fe(III) fixed on the composite adsorbents, increased the Fe(III) contents, and caused an improved OFL uptake of k-TAFe. Because of the evident advantages of environmental-friendliness, high adsorption performance and low cost, k-TAFe as an efficient adsorbent has notable application potentials in removal of FQs from water.

Influences of charge properties and hydrophobicity on the coagulation of inorganic and organic matters from water associated with starch-based coagulants

In this work, two series of binary graft cationic starch-based coagulants (CS-DMCs and CS-DMLs) with different hydrophobicities and charge densities (CDs) were prepared by graft copolymerization of acrylamide with 2-(methacryloyloxy)-N,N,N- trimethylethanaminium chloride and acryloyloxyethyl dimethyl benzyl ammonium chloride, respectively, on the starch (St) backbone. Kaolin particles, sodium humate (NaHA), and bovine serum albumin (BSA) were used as the simulated sources of inorganic colloidal particles and different organic pollutants in the micropolluted turbid surface water. The influences of the CD and hydrophobicity associated with the St-based coagulants on the removal of kaolin particles, NaHA, and BSA from single, binary, and ternary pollutant aqueous systems were investigated systematically. On the basis of the apparent coagulation performance, the floc characteristics, and the zeta potentials of the supernatants after coagulation, the coagulation mechanisms associated with the structural features of the St-based coagulants and the pollutants treated were explored and discussed in detail. The St-based coagulants with a higher CD and a stronger hydrophobicity showed better coagulation performance due to the synergistic effects of charge neutralization and hydrophobic association. The maximum efficiencies of the optimized St-based coagulant in removal of Kaolin, NaHA and BSA were 93.85%, 100% and 97.52% in their respective single pollutant systems. In addition to these simulated water samples, a real micropolluted turbid surface water tested and compared, further confirming the superiority of the hydrophobically modified cationic St-based coagulants, especially in the purification of organic pollutants in water.

Laser sintering of coated polyamide 12: a new way to improve flammability

In this study coatings of kaolin and talc particles were successfully applied on the surface of polyamide 12 powder intended for laser sintering (LS). Microscopic observations revealed that using carboxymethyl cellulose (CMC) as surface modifier for fillers led to a better coverage of polymer grains with a surface coverage between 6 and 16% as a function of filler type and content. Differential scanning calorimetry measurements showed that the addition of talc and kaolin led to an increase in the crystallization temperature of PA12, but at the expense of processability. Process parameters were optimized in order to manufacture LS samples with the different coated powders. Fire behavior assessed by cone calorimetry showed that the use of CMC resulted in a significant decrease in the peak of heat release rate depending on the filler type and content. This behavior can be partially explained by an interaction between CMC, fillers and polymer, with the formation of amide linkage between carboxyl part of CMC and amine end groups of polyamide, resulting in an increase in the complex viscosity of materials.

Particle shape trends across experimental cohesive and non‐cohesive sediment gravity flow deposits: Implications for particle fractionation and discrimination of depositional settings

AbstractFractionation of particles in deep‐water sediment gravity flows is an important factor in the resulting deposit and for discriminating sedimentary environments, but remains poorly understood. Quantitative characterization of particle shape was performed for more than ten‐thousand particles of experimental gravity flow experiments (both of cohesive and non‐cohesive nature) made using coal and kaolin particles. Eleven particle shape parameters were calculated and their distribution and trends within the experimental basin were evaluated. Results indicate the existence of non‐normal distributions and observable correlations between particle shape parameters. Shape parameters such as circularity and roundness are dominant controls on shape variation. Strong correlations exist between mean shape parameters and along‐flow distance from the source for particles in non‐cohesive flow experiments. Important differences were observed between shape parameter distributions of particles sampled at different areas within the experimental basin, which can be grouped based on their depositional setting (proximal or distal) using multivariate statistical analysis, especially for the non‐cohesive flow experiments. A tendency for more elongated and irregularly‐shaped particles at the more distal and marginal areas of the studied experimental basin was observed and validated by previous field studies in real‐world deep‐marine deposits. Besides, fractionation of particles is less‐pronounced in cohesive flows compared with non‐cohesive ones suggesting the soundness of discrimination of depositional settings based solely on particle shape characteristics is strongly dependent on parent flow characteristics. Yet, results highlight the potential of particle shape analysis in revealing spatial particle shape trends due to hydrodynamic fractionation and discriminating different depositional settings within submarine fans. This methodology may be applied to seafloor and subsurface samples to help identify the flow process and depositional environment.

Synthesis and Evaluation of Asymmetric Mesoporous PTFE/Clay Composite Membranes for Textile Wastewater Treatment

Asymmetric mesoporous composite PTFE membranes wit 40, 50, and 85 wt.% of a clay (kaolin) were fabricated and characterized using a scanning electron microscope equipped with EDX for morphology and elemental analysis. The surface chemistry of the membranes was checked using Fourier transform infrared spectroscopy. The effect of incorporating the clay on the hydrophilicity, permeability, morphology, and antifouling properties of the fabricated membranes was investigated. It was observed that incorporating kaolin particles improved the mechanical properties but decreased the contact angle of the membranes, thereby resulting in an improvement in the membrane permeability. The performance of the three composite UF membranes was evaluated through the treatment of a real textile effluent sample containing indigo dye. The results confirmed that these membranes are effective in the removal of COD, color, and turbidity. Indeed, at a transmembrane pressure of 2.5 bar, almost total removal of the turbidity, COD removal > 85%, and color removal > 97% were attained. Furthermore, membrane A85 (with 85% clay) showed the best performance, with a water flux of 659.1 L·h−1·m−2·bar−1. This study highlights the potential of incorporating low-cost clay material for the enhancement of the performance of mixed organic/inorganic matrix membranes, which can be applied to textile wastewater treatment.

Detrimental effect of calcium on grinding performance of a kaolin-containing ore

The presence of kaolin in ores may cause many problems in mineral processing industries. However, no study was conducted investigating the influence of kaolin on grinding efficiencies in any clay-containing ores. The primary objective of this research is to investigate the influence of kaolin on the grinding efficiency in the absence and the presence of Ca2+; the reason is that the presence of Ca2+ had already a positive effect on flotation and filtration of various clay containing ores. The experiments were performed using a rod mill to determine the grinding performance of the kaolin-containing ores by determining P80. The zeta potential measurements and the settling tests of pure kaolin were used to study the surface properties and the settling behaviour of pure kaolin particles. The rheology tests were used to analyse the changes in the slurry rheology of the products obtained after grinding the kaolin-containing ores. The results showed that the additions of Ca2+ ions reduced the repulsion forces between kaolin particles as confirmed by the zeta potential measurements as well as reduced settling rates. As a result, the agglomeration between kaolin particles increased, leading to the increase in the slurry shear stress (i.e., viscosity) and thus reducing the grinding performance significantly. The grinding performance was reduced by the addition of Ca2+ ions when there was a high clay percentage (40%) and a high solid percentage (70%). This paper demonstrated the importance of controlling Ca2+ concentrations in plant water to maximize the grinding performance of kaolin-containing ores.

Characterization and morphology of spray dried kaolin particles

Characterization and morphology of spray dried kaolin particles

Modeling Potassium Capture by Aluminosilicate, Part 1: Kaolin

Additives rich in Si and Al such as kaolin may be applied in PF biomass boilers to fix alkali metals in species that are more benign than the alkali salts released in biomass combustion. In this study, models for the reaction of gas-phase potassium salts with kaolin particles are developed for the conditions appearing in PF boilers such as short residence times, high temperatures, and small size of the additive particles. The reaction between gaseous potassium components and kaolin particles has been modeled with a shrinking core model (SCM) and a uniform conversion model (UCM). The SCM takes into account the effects of chemical kinetics, diffusion in a gas film surrounding the particle, diffusion in a product layer, and thermochemical equilibrium on the reaction progress. The UCM covers diffusion in a gas film surrounding the particles, chemical kinetics, and thermochemical equilibrium. Both models are able to accommodate the effects of change in temperature, particle size, reaction time, and potassium component concentration. Literature data from experiments in an entrained flow-reactor (EFR) at 800–900 °C were used to derive the chemical kinetic rate coefficients of the reaction between kaolin and KOH. The models were then evaluated against experimental data for alkali salts of KCl, KOH, K2CO3, and K2SO4 covering temperatures of 800–1450 °C, kaolin particle sizes of 4–14 μm, residence times of 0.8–1.9 s, and salt/additive molar ratios of 0.05–0.96. The evaluation indicated that both SCM and UCM were suitable for a wide range of conditions, but the UCM captured the effect of particle size better. The modeling outcomes suggested that if the reaction time was long enough, the thermochemical equilibrium would be the major limitation in capturing potassium by kaolin at high temperatures and high potassium concentrations. At lower temperatures, however, the conversion was mainly limited by chemical kinetics. The mass-transfer limitation was less critical under the investigated conditions. The developed models can account for the reaction of gas-phase potassium salts with kaolin at local conditions relevant to PF boilers using biomass.

Reduction in Insect Attachment Caused by Different Nanomaterials Used as Particle Films (Kaolin, Zeolite, Calcium Carbonate)

In the present investigation, we compared the reduction in attachment ability of the southern green stinkbug Nezara viridula (Hemiptera: Pentatomidae) to glass induced by three different nanoparticle (kaolin, zeolite, and calcium carbonate) films. Using traction force experiments, behavioral experiments, and scanning electron microscopy observations, we analyzed the insect attachment ability and linear speed on untreated and treated glass with the three particle films. The three nanomaterials strongly reduced insect attachment ability mainly owing to contamination of attachment pads. The ability to reduce insect attachment was different for the three tested particle films: kaolin and zeolite induced a significantly higher reduction in N. viridula safety factor than calcium carbonate. The coating of the surface was more uniform and compact in kaolin and zeolite compared to calcium carbonate particle film. Moreover, kaolin and zeolite particles can more readily adhere to N. viridula attachment devices, whereas calcium carbonate particles appeared less adherent to the cuticular surface compared to the two aluminosilicate (kaolin and zeolite) particles. Only the application of kaolin reduced insect linear speed during locomotion. Nanoparticle films have a great potential to reduce insect attachment ability and represent a good alternative to the use of insecticides for the control of pentatomid bugs and other pest insects.

Physicochemical factors affecting flocculating properties of the proteoglycan isolated from Rhodococcus opacus

The water-soluble fraction of proteoglycan RS-89 isolated from the Rhodococcus opacus FCL89 and composed of 64.6% polysaccharide and 9.44% protein has been studied as regards its flocculating activity. The RS-89 polysaccharide component includes mannose, galactose and glucose at the molar ratio of 2.7: 1.3: 1. The basic factors affecting flocculating activity of the RS-89 have been established. Additionally, the kinetics of kaolin sedimentation without and with the bioflocculant was investigated. The presence of divalent metal ions had a positive effect on the flocculating activity of the RS-89. The addition of Ca2+ increased the RS-89 flocculating activity in comparison to the other studied metals. It was proved that the proteoglycan RS-89 achieved the highest flocculating activity at the concentration equal to 2 mg/L and in the presence of 10 mmol/L of Ca2+. The zeta potential values are less negative when there is an interaction between the kaolin particles and metal ions without the RS-89 in the tested systems. Therefore, the proposed mechanism to describe the proteoglycan interaction with kaolin particles in the presence of divalent ions includes charge neutralization and a bridging mechanism.

Enhanced membrane fouling control and trace organic compounds removal during microfiltration by coupling coagulation and adsorption in an electric field

Coupling electric field, coagulation, and powdered activated carbon (PAC) adsorption in the microfiltration (MF) process was an effective strategy for membrane fouling alleviation and trace organic compounds (TrOCs) elimination. In the electric field, the surface charges of bovine serum albumin (BSA) molecules and kaolin particles distributed along the direction of the electric field and formed electric dipoles, which lowered electrostatic repulsion between BSA-BSA, BSA-kaolin, and kaolin-kaolin, resulting in enhanced particle aggregation and turbidity reduction. Electrophoretic migration also strengthened the interaction between particles and polyaluminum chloride (PACl). Protein removal showed a significant linear correlation with the transmembrane pressure (TMP), and the slope variation of the fitting curves reflected the role of the electric field in the BSA removal and membrane fouling control. Under the synergistic function of electric field, coagulation, and PAC adsorption, the MF system achieved an 80.7% reduction on membrane fouling, an average BSA removal of 76.4%, and TrOCs elimination of 65.3%–81.7%. Electrochemical oxidation was the main contributor to the TrOCs removal when 2.5 V voltage was applied, and could also prolong the service life of PAC.

Magnetic coagulation and flocculation of a kaolin suspension using Fe3O4 coated with SiO2

In order to improve dispersibility, chemical stability and magnetic flocculation performance, Fe3O4 was functionalized through SiO2 coating. The characterization of Fe3O4/SiO2 particles was analyzed, such as morphology, size, structure, chemical composition, zeta potential, magnetic and thermal properties. Magnetic flocculation of kaolin particles was investigated under different pH conditions, Fe3O4/SiO2 dosages and Ca2+ concentrations. Flocculation factors were further analyzed using response surface methodology. A modified Derjaguin-Landau-Verwey-Overbeek (MDLVO) model was applied, and the size and fractal dimension of magnetic flocs were analyzed to establish the mechanism of flocculation. Results showed that Fe3O4/SiO2 is a core-shell nanocomposite with a specific surface area of 65.14 m2/g and saturation magnetization of 46.54 emu/g. Coating with SiO2 greatly reduced the median equivalent-volume diameter (D50) of Fe3O4 from 10.48 to 2.88 µm. A kaolin removal efficiency of 93.8% was achieved under conditions of an initial turbidity of 200 NTU, pH 7.0, 1.0 g/L Fe3O4/SiO2, and 4.5 mmol/L Ca2+. Response surface analysis indicated that interactions occur between Fe3O4/SiO2 and Ca2+, as well as Ca2+ and pH. Fe3O4/SiO2 can be effectively detached from the aggregates and reused, maintaining a removal efficiency of more than 87.7% after ten cycles of use. The energy barrier between kaolin and Fe3O4/SiO2 was significantly reduced due to the electrostatic interaction of Ca2+. Furthermore, the MDLVO theory predicted that magnetic forces induce collision and movement between Fe3O4/SiO2 and kaolin-Ca2+. The floc structures formed in the magnetophoresis process significantly affect the flocculation of kaolin particles.

A Criterion for Estimating the Strength of Flocculated Aggregates in Salt Solutions

A simple criterion is proposed to quantitatively estimate the resistance of aggregates based on incremental mechanical shear disturbances. Aggregate strength can be affected by the hydrodynamic conditions under which flocculation occurs; therefore, an experimental method is standardized to determine the resistance of aggregate structures that are formed under defined conditions of salinity (NaCl 0–0.1 M), mixing time (3 min), and mean shear rate (G = 273 s−1). Kaolin particles were flocculated in saline solutions with an anionic flocculant of high molecular weight. The method involves increasing the mean shear rate (G = 0–1516 s−1). Each increment represents a new experiment that starts from the base of 273 s−1. Target aggregates are increasingly fragmented as mechanical disturbance increases. The monotonic relationship between the mean shear rate increments (ΔG) and the final size of the aggregates is used for a quantitative estimate of the resistance of the target aggregates since this resistance underlies this relationship. The evolution of aggregate size is analyzed by the Focused Beam Reflectance Measurement (FBRM) method, which may capture the chord length distribution on concentrated slurries. To estimate and compare the resistance of the target aggregates in solutions with different salinities, a pseudo-first-order model that describes the rupture degree as a function of shear rate increments obtains the characteristic shear rate. The rupture percentage is reached with considerably lower agitation increments at higher salinity than at low salinity. This criterion is expected to help improve the efficiency of solid–liquid separation processes, especially in plants operating with seawater, be it raw or partially desalinated.

Optimizing Performance of Porcelain Insulators: How does Particle Size Influence Dielectric and Mechanical Strengths?

Porcelain insulators are mostly created from the combination of the particles of Clay, Silica, Kaolin, and Feldspar. This implies that different particle sizes contribute to the insulating properties of the materials. In this paper, we attempt to create a set of model porcelain materials by critically analysing the particle sizes that are most likely to yield the best insulator results. Materials sourced from Edo State, Nigeria were processed to produce Porcelain insulator samples. For each of the component minerals, a 65g mass was compacted and pressed at 500 Psi (3.4 KN) into a steel cylindrical mould via hydraulic press, this was closely followed by firing at 1200°C. Porosity, bulk density, insulation volume resistivity, as well as dielectric strength, and their relationship with particle sizes were evaluated. Results obtained showed that porosity of the Porcelain materials shared a direct relation with particle sizes, while the bulk density showed an inverse relationship. It was also observed that the 150 µm particles yielded the most effective insulators, given higher insulation volume resistivity and dielectric strength. Altering particle size from 150 µm tends to lower the insulation volume resistivity and dielectric strength.

Microstructural evolution and mechanical behaviour of alkali activated fly ash binder treated clay

This work focuses on the use of alkali activated fly ash-based binder to enhance engineering characteristics of soft clay-rich soils and as a substitute to standard stabilisers (e.g., lime or cement). Especially, it examines the microstructural evolution of a calcium-rich fly ash from coal combustion-based binder activated by a sodium-based alkaline solution. To this end, the processes generating the microstructure and the evolution of the pore network over time are investigated. A second point addressed by this study is how the presence of kaolin particles affects the microstructural features of the binder. The microstructure has therefore been investigated by considering the binder alone and the binder mixed with kaolin. The effects of microstructural evolution have been observed at macroscopic level by means of one-dimensional compression tests.The combination of completing techniques has been used including Optical microscopy, Scanning Electron Microscopy and Mercury Intrusion Porosimetry in order to gain an overview of the complex pore structure.Microstructural changes occur around calcium-containing phases derived from fly ash which are the reactive phases of the system. Namely, the dissolution of calcium-rich grains leads to the formation of new compounds that first cover the grain surfaces and then further grow into the available space. Furthermore, the evolution of the pore network over time is characterized by a progressive filling of capillary pores by new compounds while small nanometric pores are being formed and associated with the newly formed silicate-calcium chains. Similar tendencies are observed when the binder is mixed with the soil although the general porosity is lesser due to the filling of pores by small-sized kaolinite platelets. Experimental evidences at microscale level have been linked to the macroscopic behaviour of treated soil.

Immobilization of endoglucanase on kaolin by adsorption and covalent bonding

In the current research, endoglucanase, one of the enzymes of the cellulolytic complex, was immobilized on kaolin by two different techniques, adsorption, and covalent bonding. A comparative study was conducted between free, adsorbed, and covalently immobilized endoglucanase. For the covalent bonding, the kaolin particles were functionalized with 3-aminopropyltriethoxysilane (APTES) and activated with glutaraldehyde. Immobilization by adsorption was performed using the kaolin without any treatment. Recovered activities after the endoglucanase immobilization by adsorption and covalent bonding were found to be 60 ± 2.5 and 65 ± 3.5%, respectively. The studies of optima pH and temperature, as well as thermal stability, showed that the catalytic characteristic of the enzyme was maintained after the immobilization by both adsorption and covalent bonding. Even after 8 cycles of use, the endoglucanase immobilized by the two techniques retained about 86% of its initial activity. The results showed that the adsorption was as effective as covalent bonding for the immobilization of endoglucanase on kaolin. However, the adsorption technique seems to have a greater potential for use in future studies, as it is simpler, cheaper, and faster than covalent immobilization. Therefore, in this work it was demonstrated that endoglucanases can be immobilized efficiently on kaolin through a very simple immobilization protocol, offering a promising strategy for performing repeated enzymatic hydrolysis reactions.

Feasibility Evaluation on Single-Collector Collision Model to Separate Microplastics in Micro Bubble Flotation Process

Objectives:The single collector collision (SCC) model is a model that predicts the separation efficiency of particles based on the collision efficiency between microbubbles and particles in the particle separation process. In order to remove micro-plastics (MPs) particles, which have recently been known to be harmful, we tried to analyze the impact and separation efficiency of MPs based on the SCC model and evaluate its application feasibility.Methods:Based on the SCC model, the collision efficiency prediction for MPs particle removal was simulated and the separation efficiency was evaluated. In addition, a series of flotation experiments were conducted using a flotation device that injects microbubbles to remove MPs particles suspended in water, and the experimental results and predicted values were compared.Results and Discussion:Using the SCC model, the collision efficiency according to the size distribution of MPs particles was not significantly different from that of typical particles (clay, kaolin) in water. Based on this collision efficiency, the maximum removal efficiency of MPs particles separated from the water body is predicted to reach about 90%. On the other hand, the initial collision-adhesion coefficient () of the MPs particles based on the SCC model was 0.03 to 0.1, showing a slight difference from the clay particles having the range of 0.3 to 0.4. The flotation separation efficiency of the MPs particles evaluated and predicted by applying this initial collision-adhesion coefficient showed a range similar to the measured value. In addition, the particle separation efficiency according to the increase of the measured bubble volume concentration to improve the particle separation efficiency also showed a pattern similar to the predicted value.Conclusions:In the flotation process, the initial collision-adhesion efficiency of the MPs particles predicted by the SCC model was lower than that of the kaolin particles. Based on the simple and simple model SCC theory, it was confirmed that it can be applied to the flotation separation analysis of MPs particles.

Scavenging Effects of Kaolin on Fine Ash Formation during Zhundong Coal Combustion

The previous work found that the additive kaolin could scavenge not only sodium (Na) but also calcium (Ca) and magnesium (Mg), which is the important ash fluxing agents in low rank coal combustion. Such scavenging effects of kaolin on fine ash formation were studied in the present work. A typical Zhundong coal and its blends with kaolin at dosages of 1, 2 and 4 wt% were combusted in an electrically heated drop tube furnace (DTF) at 1300°C. The fine ashes generated were collected and size segregated by a low pressure impactor (LPI). The morphology and chemical composition of fine ash were analyzed by scanning electron microscopy equipped with an energy-dispersive spectrometer (SEM-EDS). In addition, char/ash particles were sampled at various positions of DTF to elucidate how kaolin additive affected the fine ash formation process. The results further showed that apart from the scavenging of volatile Na, kaolin additive could also strongly scavenge the refractory Ca, Mg and Fe in the fine ash during Zhundong coal combustion, which transformed the sintered particles with irregular shape into melted spherical particles, and finally resulted in the considerable decrease of these elements in both PM_0.4 and PM_0.4-10 by melting and agglomeration. The close contacts between kaolin particles and coal resulted from physically mixing were a key factor responsible for the reaction of kaolin with the refractory Ca, Mg and Fe.

Comparative investigation of the influence of kaolin and dolomite on the properties of polyurethane foam

This work investigates the influence of kaolin and dolomite on the properties of polyurethane foam. The selected fillers were pulverized and sieved to obtained < 90 μm that were used as reinforcements in the polyurethane matrix in a randomly dispersed mode. The matrix constituents were mixed in the same ratio while fillers were introduced via a one-shot system approach in predetermined proportions of 3–7 wt.%. The work was carried out to identify optimum fillers to be utilized in the production of polyurethane rigid foams given the effect of the fillers on the physical, mechanical, and chemical properties of the foam. FTIR, XRF, and SEM and mechanical property tests were carried out on the filled polyurethane foam. The presence of the fillers in the foam showed a rupture in the structure of the foams with the cells having similar arrangements. The addition of dolomite and Kaolin degrades the sulfonic acid groups and promoted the appearance of Si–O stretching vibration band. The density, hardness, flexural and compressive strengths of the polyurethane foam were enhanced with the the addition of dolomite and kaolin particles.

Characterization and Molecular Docking of Kaolin Based Cellulosic Film for Extending Ophthalmic Drug Delivery

Ophthalmic delivery of dexamethasone can control inflammation and also some forms of uveitis. But it is effective therapeutically over a short period of time and frequent instillation is required. hydroxypropyl methylcellulose matrix films containing dexamethasone were prepared by casting method in presence and absence of particulate kaolin for extending ophthalmic drug delivery. Fourier-transform infrared spectroscopy confirmed the complexation of dexamethasone and kaolin in the film via formation of hydrogen bond and the observed shouldering at 1032 cm-1 increased with corresponding higher amount of kaolin binding. Differential scanning calorimetry thermogram resulted in almost complete amorphization of dexamethasone in the film. X-ray diffractogram demonstrated almost disappearance of kaolinite diffraction and the reduced order of dexamethasone crystal lattice in all the film formulations. Submicrons, tubular and nano-fibrous morphology of the kaolin and drug particles were seen in the scanning electron microscope images of the film. Relatively extended diffusion controlled drug release and ophthalmic permeation behavior were observed with the increase of kaolin loading in the film. Stable complex facilitated the sustained ophthalmic delivery of dexamethasone and prolonged anti-inflammatory activity. Molecular docking study also revealed the complex formation of dexamethasone with kaolin and hydroxypropyl methyl cellulose to understand the fitting and stable configuration of drug-carrier interaction. Kaolin-based hydroxypropyl methyl cellulose hydrogel film containing dexamethasone as a model drug can enhance the corneal residence time for anti-inflammation for an extended period of time.