G. Pugazhenthi

Effect of graphene content on the properties of poly(lactic acid) nanocomposites

In the current work, the influence of temperature on the exfoliation of expandable graphite (EG) and its structural properties were investigated in detail. The EG exfoliated at 750 °C was subjected to sonication and further used as reinforcement material in the poly(lactic acid) (PLA) matrix to investigate the influence of “graphene” (GR) on the structural, morphological, thermal, optical, mechanical and oxygen barrier properties of PLA composites. X-ray diffraction results disclose the effect of sonication time on the dispersion ability of GR in the PLA matrix. A high resolution transmission electron microscopy image of GR demonstrates a monolayer structure of GR. Thermo-gravimetric analysis reveals that the Tonset value for the PLA composite with 0.5 wt% GR content increases by 6 °C over neat PLA, when 10% weight loss is taken as a point of comparison. The increase in the thermal stability of PLA composites is also verified by an increase of activation energy (Ea) value evaluated by the Coats–Redfern method. Differential scanning calorimetry analysis confirms that GR acts as a nucleating agent that enhances the melting point of PLA composites over neat PLA. The enhancement of tensile strength (17%) and elongation at break (51%) is obtained for PLA composites over neat PLA.

Effect of Organomodified Ni-Al Layered Double Hydroxide (OLDH) on the Properties of Polypropylene (PP)/LDH Nanocomposites

This work addresses the effect of organomodified layer double hydroxide (OLDH) on the properties of PP/LDH nanocomposites prepared by melt intercalation method using a single screw extruder with maleic anhydride grafted polypropylene (PP-g-MA) as a compatibilizer. For this, Ni-Al LDH was first prepared by the co-precipitation method at constant pH using their nitrate salts. The above synthesized pristine LDH was organically modified using sodium dodecyl sulphate (SDS) by the regeneration method. The structural and thermal properties of LDH and PP nanocomposites were performed by X-ray diffraction (XRD), FTIR spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The influence of LDH loading on the mechanical and thermal properties of the nanocomposite was also investigated. The XRD results confirmed the formation of exfoliated PP/LDH nanocomposites. PP/LDH nanocomposites exhibited enhanced thermal stability relative to the pure PP. When 10% weight loss was selected as a point of comparison, the decomposition temperature of PP/LDH (5 wt%) nanocomposite was 15.3°C higher than that of pure PP. The DSC result indicated an increase in crystallization and melting temperature of the PP/LDH nanocomposites compared to pure PP. Overall, the mechanical properties of the PP/LDH nanocomposites increased with an increase in the LDH content. The maximum improvement of tensile strength, Youngs modulus, flexural strength, and flexural modulus for the PP/LDH nanocomposite was found to be 11, 22.5, 28, and 22%, respectively, over neat PP. For comparison purposes, a nanocomposite with 5 wt% modified bentonite (PP/B5) was also prepared under the same operating condition and there was no significant improvement in mechanical properties (tensile strength and modulus).

Performance assessment of an analcime-C zeolite–ceramic composite membrane by removal of Cr(VI) from aqueous solution

This article describes the synthesis of an analcime-C zeolite membrane on a ceramic support by in situ hydrothermal crystallization. A circular shaped ceramic support was firstly fabricated using low cost raw materials by a uni-axial pressing method and sintering process. Subsequently, the zeolite composite membrane was prepared with the repeated coating of analcime-C on the ceramic support through an in situ crystallization technique. The synthesized zeolite composite membrane was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), porosity, average pore size and pure water permeability. The influence of the number of coatings on the characteristics of the zeolite membrane was also explored. The obtained results clearly demonstrate that the porosity, pore size and water permeability of the membrane decrease significantly with the multiple coating of zeolite over the ceramic support. The porosity, average pore size and pure water permeability of the zeolite membranes are estimated to be 38–24%, 285–155 nm and 2.18 × 10−7 to 4.53 × 10−8 m3 m−2 s−1, respectively for various coatings (1–3). Finally, the separation performance of three times coated zeolite membrane was evaluated by removal of chromium(VI) from aqueous solution by ultrafiltration (UF) at various operating conditions (applied pressure, concentration and pH). The maximum rejection of 84% is achieved at an applied pressure of 207 kPa. Moreover, the separation performance of membrane is better as compared to other membranes reported in the literature.

Influence of Processing Conditions on the Properties of Polystyrene (PS)/organomontmorillonite (OMMT) Nanocomposites Prepared via Solvent Blending Method

A series of polystyrene (PS)/organomontmorillonite (OMMT) clay nanocomposites was prepared by effectively dispersing the inorganic nanolayers of OMMT clay in the organic PS matrix via the solvent blending method using xylene as a solvent. The resulting samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The XRD and TEM results show that the intercalation/exfoliation of OMMT can be divided into solvent swelling and layer breaking processes and is affected by several reaction parameters such as nanofiller loading, refluxing temperature, and refluxing time. TGA data show that the PS/OMMT nanocomposites have significant enhanced thermal stability. When 50% weight loss is selected as a point of comparison, the thermal decomposition temperature of PS/OMMT nanocomposite with 7 wt% of OMMT is 15°C higher than that of pure PS. The glass transition temperature (Tg) of PS/OMMT nanocomposites is about 5.0–6.2°C higher than that of pure PS. The water uptake capacity of PS/OMMT nanocomposites is negligible when compared with pure PS.

Influence of Sintering Temperature on the Properties of Porous Ceramic Support Prepared by Uniaxial Dry Compaction Method Using Low-Cost Raw Materials for Membrane Applications

In this article, we have reported the fabrication of stable macroporous ceramic support using low-cost inorganic raw materials by uniaxial dry compaction technique. The supports were prepared by mixing of inexpensive raw materials such as kaolin, quartz, calcium carbonate, sodium carbonate, boric acid, sodium metasilicate, and polyvinyl alcohol as a binder. The prepared green supports were sintered at different temperatures ranging between 900 and 1000°C. The raw materials and the sintered supports were characterized by thermogravimetric analysis, particle size distribution (PSD), X-ray diffraction, and scanning electron microscopy analysis. The influence of sintering temperature on the membrane structure, porosity, flexural strength, chemical stability, and the pure water permeability was also examined. It was observed that the average pore size and the flexural strength of the sintered supports increase with an increase in the sintering temperature. The porosity of the sintered supports was obtained in the ranges between 22 and 40%. The chemical stability of the sintered supports was found to be good. Based on the results obtained, the support sintered at 950°C (porosity of 30%, mechanical strength of 28 MPa, and average pore size of 3.45 µm) was considered as the optimum support for membrane applications. The ceramic support cost was estimated to be

Performance of Low Cost Ceramic Microfiltration Membranes for the Treatment of Oil-in-water Emulsions

67/m2 according to the raw material price. Henceforth, these low-cost membrane supports with better properties could be suggested for cheaper application in chemical and biochemical processes.

Removal of Crystal Violet Dye from Aqueous Solution Using Calcined and Uncalcined Mixed Clay Adsorbents

Using the uniaxial compaction method, ceramic disk type microfiltration membranes were fabricated using mixtures of clays to yield membranes M1, M2, and M3. These were obtained with distinct compositions of raw materials at a sintering temperature of 900°C. Membrane characterization was conducted using thermogravimetric analysis (TGA), particle size distribution (PSD), X-ray diffraction (XRD), and scanning electron microscope analysis (SEM). Morphological characterization of these membranes includes the evaluation of average porosity, pore size, mechanical stability, chemical stability, and hydraulic permeance. With varying composition of the raw materials, it is observed that the average porosity and pore size of the membrane varied between 23–30% and 0.45 to 1.30 µm. For all membranes, the flexural strength varied within the range of 10-34 MPa. Chemical stability tests indicate that the membranes are stable in both acidic and basic media. The hydraulic permeance of M1, M2, and M3 membranes is about 3.97 × 10−6, 2.34 × 10−6, and 0.37 × 10−6 m3/m2 s kPa, respectively. Further, the performance of these membranes was studied for the microfiltration of synthetic oily wastewater emulsions. Amongst all membranes, membrane, M2 performance is satisfactory as it provides oil rejection of 96%, with high permeate flux of 0.65 × 10−4 m3/m2 s at a lower transmembrane pressure differential of 69 kPa for the oil concentration of 200 mg/L.

Cross flow ultrafiltration of Cr (VI) using MCM-41, MCM-48 and Faujasite (FAU) zeolite-ceramic composite membranes

In this work, calcined and uncalcined mixed clays containing kaolin, ball clay, feldspar, pyrophyllite, and quartz are examined as a potential adsorbent for the removal of crystal violet dye from aqueous solution. These clays are characterized by nitrogen adsorption/desorption isotherms, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and thermo gravimetric analysis (TGA). The kinetics and thermodynamic parameters as well as the effects of the pH, the temperature, and the adsorbent dosage have also been investigated. The experimental results indicate that the Langmuir model expresses the adsorption isotherm better than the Freundlich model. The obtained result showed a tremendous increase in the crystal violet adsorption capacity (1.9 × 10−3 mol g−1) after calcination, which is one order greater than that of the uncalcined mixed clay. The mechanism of the adsorption process is elucidated on the basis of experimental data. The percentage removal of crystal violet dye increases with increasing the pH, the temperature, and the adsorbent dosage. The investigation of kinetic studies indicates that the adsorption of crystal violet on calcined and uncalcined mixed clays could be described by the pseudo-second-order model. The negative Δ G 0 values obtained from the thermodynamic investigation confirm that the adsorption is spontaneous in nature. The adsorption results suggest that the calcined and uncalcined mixed clays can also be used as low cost alternatives to the expensive activated carbon for the removal of dyes from aqueous solution.

Modelling and optimization of critical parameters by hybrid RSM-GA for the separation of BSA using a tubular configured MFI-type zeolite microfiltration membrane

This work describes the removal of Cr (VI) from aqueous solution in cross flow mode using MCM-41, MCM-48 and FAU zeolite membranes prepared on circular shaped porous ceramic support. Ceramic support was manufactured using locally available clay materials via a facile uni-axial compaction method followed by sintering process. A hydrothermal technique was employed for the deposition of zeolites on the ceramic support. The porosity of ceramic support (47%) is reduced by the formation of MCM-41 (23%), MCM-48 (22%) and FAU (33%) zeolite layers. The pore size of the MCM-41, MCM-48 and FAU membrane is found to be 0.173, 0.142, and 0.153 μm, respectively, which is lower than that of the support (1.0 μm). Cross flow ultrafiltration experiments of Cr (VI) were conducted at five different applied pressures (69-345 kPa) and three cross flow rates (1.11 × 10(-7) - 2.22 × 10(-7) m(3)/s). The filtration studies inferred that the performance of the fabricated zeolite composite membranes is optimum at the maximum applied pressure (345 kPa) and the highest rejection is obtained with the lowest cross flow rate (1.11 × 10(-7) m(3)/s) for all three zeolite membrane. The permeate flux of MCM-41, MCM-48 and FAU zeolite composite membranes are almost remained constant in the entire duration of the separation process. The highest removal of 82% is shown by FAU membrane, while MCM-41 and MCM-48 display 75% and 77% of Cr (VI) removal, respectively for the initial feed concentration of 1000 ppm with natural pH of the solution at an applied pressure of 345 kPa.

Synthesis and characterization of exfoliated PMMA/Co–Al LDH nanocomposites via solvent blending technique

This paper deals with the fabrication of a MFI-type zeolite membrane via an in situ hydrothermal synthesis technique on a low cost porous tubular ceramic substrate. To formulate the zeolite layer on the porous substrate, the hydrothermal solution was prepared using silicate solutions. The MFI zeolite (as synthesized and calcined) was characterized by X-ray diffraction (XRD), thermogravimetry (TG) and Fourier transform infrared spectroscopy (FTIR) analysis. The fabricated ceramic substrate as well as the zeolite membrane was characterized by field emission scanning electron microscopy (FESEM), porosity and water permeability measurements. The porosity, mean pore size and water permeability of the zeolite membrane were evaluated to be 51%, 0.272 μm and 4.43 × 10−7 m3 m−2 s−1 kPa−1, respectively. The separation efficiency of the membrane in terms of permeate flux and rejection was studied with BSA as a model protein. Three operating parameters, BSA concentration (100–500 ppm), pH (2–4) and applied pressure (68.94–275.79 kPa), were optimized for the better separation efficiency of the membrane using response surface methodology (RSM) followed by a bi-objective genetic algorithm (GA). The non-linear models predicted by RSM were further optimized by a GA. The appropriate optimum conditions were obtained as a BSA concentration of 100 ppm, solution pH of 2 and applied pressure of 275.79 kPa. These predicted conditions were experimentally validated and a higher permeate flux and rejection of BSA were obtained as 4.63 × 10−5 m s−1 and 81.98%, respectively. Further, the separation efficiency of prepared membrane was compared with other membranes used for BSA separation stated in the literature.