In this work, batch adsorption experiments are carried out for crystal violet dye using mesoporous MCM-41 synthesized at room temperature and sulfate modified MCM-41 prepared by impregnation method using H 2 SO 4 as sulfatising agent. The surface characteristics, pore structure, bonding behavior and thermal degradation of both the MCM-41 samples are characterized by nitrogen adsorption/desorption isotherms, X-ray diffraction (XRD) patterns, Fourier transform infrared (FT-IR) spectroscopy and thermo gravimetric analysis (TGA). The adsorption isotherm, kinetics and thermodynamic parameters are investigated for crystal violet (CV) dye using the calcined and sulfated MCM-41. Results are analysed using Langmuir, Freundlich and Redlich-Peterson isotherm models. It is found that the Freundlich model is an appropriate model to explain the adsorption isotherm. The highest adsorption capacity achieved is found to be 3.4 × 10 −4 mol g −1 for the sulfated MCM-41. The percentage removal of crystal violet dye increases with increase in the pH for both the MCM-41 adsorbents. Kinetics of adsorption is found to follow the second-order rate equation. From the thermodynamic investigation, it is evident that the adsorption is exothermic in nature. CVCrystal Violet CTAB Cetyltrimethylammonium Bromide TEOS Tetraethylorthosilicate a 0 Unit cell Parameter (nm)Pseudo-first-order rate constant (min −1 ) k 2 Pseudo-second-order rate constant (gmol −1 min −1 ) k d Diffusion coefficient (dimensionless) K F Freundlich isotherm constant (mol/g(dm 3 /mol) 1/n ) K L Langmuir constant (dm 3 mol −1 ) K RP Redlich-Peterson constants (mol g −1 ) m Mass of the adsorbent (g) n Adsorption intensity (dimensionless) q e Amount of dye adsorbed at equilibrium (mol g −1 ) Q max Maximum adsorption capacity (mol g −1 ) S 0 Entropy (KJ mol −1 K −1 ) S BET BET surface area (m 2 g −1 ) V Volume (dm 3 ) V mes Mesoporous volume (cm 3 g −1 )Greek letters βFull width at half maximum (degrees) θAngle of diffraction (degrees) λ Wavelength (nm) λ max Maximum absorbance wavelength (nm) Adsorption (2009) 15: 390-405 391

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Mesoporous MCM-41 was synthesized at room temperature using tetraethoxysilane (TEOS) with cetyltrimethylammonium bromide (CTAB) and employed as an effective adsorbent for the adsorption of methylene blue dye from aqueous solution. The as-synthesized MCM-41 was calcined at 250 and 550 o C to study the relation between the surface area and pore volume with surfactant removal. The synthesized MCM-41 was characterized using thermo gravimetric analysis (TGA), X-ray diffraction (XRD) patterns, nitrogen adsorption/desorption isotherms and Fourier transform infrared (FT-IR) spectroscopy. The MCM-41 calcined at 550 o C showed higher surface area (1,059 m 2 g −1 ) with pore volume of 0.89 ml g −1 and was used for the investigation of adsorption isotherms and kinetics. The experimental results indicated that the Freundlich and Redlich-Peterson models expressed the adsorption isotherm better than the Langmuir model. In addition, the influence of temperature and pH on adsorption was also investigated. The decrease in temperature or the increase in pH enhanced the adsorption of dye onto MCM-41. A maximum adsorption capacity of 1.5×10 −4 mol g −1 was obtained at 30 o C. The kinetic studies showed that the adsorption of dye on MCM-41 follows the pseudo-second-order kinetics.

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In this work, a macroporous ceramic support was fabricated using inexpensive clays available in India by uniaxial compaction technique. Green ceramic supports were developed by mixing of kaolin, pyrophyllite, feldspar, ballclay, quartz, and calcium carbonate of desired composition with polyvinyl alcohol as a binder and were sintered at different temperatures (850°C, 900°C, 950°C, and 1000°C). The raw materials and sintered supports were characterized using thermogravimetric analysis, particle size distribution (PSD), X‐ray diffraction, and scanning electron micrograph analysis. The effect of sintering temperature on porosity, mean pore size, pore size distribution, shrinkage, flexural strength, and pure water permeability was investigated. Chemical stability tests for the sintered supports were conducted with 20 wt% of H2SO4, HCl, and NaOH solutions and the supports showed good chemical resistance. The porosity of the sintered supports was in the range of 41–46%. It was observed that the average pore diameter and flexural strength of the supports increases with increase in sintering temperature. Based on these results, the support sintered at 950°C (porosity=44%, mechanical strength=28 MPa, and average pore diameter=1.01 μm) was considered as the optimum support for membrane applications. Solvent permeation studies were conducted for 950°C sintered support and the results confirmed that the support was hydrophobic in nature.

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