Haresh M. Mody

Adsorption of an anionic dye from aqueous medium by organoclays: equilibrium modeling, kinetic and thermodynamic exploration

Adsorption of an anionic dye, remazole brilliant blue R (RBBR) from aqueous solution, on organically modified attapulgite (ATP) and bentonite (BNT) clays was investigated. Beneficiated attapulgite and bentonite clay samples were modified by the cationic surfactant cetyltrimethylammoniumbromide (CTAB) by the ion exchange method. The efficiency of these adsorbents for the uptake of RBBR was examined by a series of adsorption isotherms using a batch technique at three different temperatures. A modified Freundlich equation has been proposed to describe the isotherms and compared with Langmuir, Freundlich and Redlich–Peterson (RP) models. Predicated values of RBBR adsorbed on modified clay using Freundlich, modified Freundlich, and RP models were identical along with the normalized standard deviation for all three models. These values were lower than those of Langmuir model. Values of r2 for RP and modified Freundlich were found to be identical and better than that of Langmuir for all the isotherms. Adsorption of RBBR followed a pseudo second order kinetic model. Negative values of free energy change, ΔG indicated spontaneity of the adsorption of RBBR on both of organoclays. An increase in adsorption of RBBR with an increase in temperature may be attributed to activated adsorption and hence an endothermic process. This was further supported by positive values of heat of adsorption, ΔH. The adsorption capacity of modified attapulgite is lower than that of modified bentonite. However, considering the requirement of CTAB for modification of the clay, attapulgite is the more economical adsorbent than modified bentonite.

Montmorillonite-Alginate Nanocomposites as a Drug Delivery System: Intercalation and In Vitro Release of Vitamin B1 and Vitamin B6

Sustained intestinal delivery of thiamine hydrochloride (Vitamin B 1; VB1) and pyridoxine hydrochloride (Vitamin B6; VB6) seems to be a feasible alternative to existing therapy. The vitamins (VB1/VB6) intercalated in montmorillonite (MMT) and intercalated VB1/VB6-MMT hybrid is further used for synthesis of VB1/VB6-MMT-alginate nanocomposite beads by gelation method and in vitro release in the intestinal environment. The structure and surface morphology of the synthesized VB1/VB 6-MMT hybrid, VB1/VB6-alginate and VB1/VB 6-MMT-alginate nanocomposite beads were characterized by XRD, FT-IR, TGA and SEM. In vitro release experiments revealed that the VB1/VB 6 releases suddenly from VB1/VB6-MMT hybrid and is pH dependent. The controlled release of VB1/VB6 from VB1/VB6-MMT-alginate nanocomposite beads was observed to be controlled as compared to their release from VB1/VB 6-MMT hybrid and VB1/VB6-alginate beads.

Organic free low temperature direct synthesis of hierarchical protonated layered titanates/anatase TiO2 hollow spheres and their task-specific applications

Layered protonated titanates and corresponding anatase TiO2 shapes, specifically the hollow spheres, are the most important functional materials and have attracted much attention because of their superior performance. Here, a facile organic substrate (both as solvent or surfactant) free, low temperature aqueous solution based chemical protocol for the direct synthesis of 3D arranged hierarchical hollow spheres of protonated layered dititanate (H2Ti2O5·H2O), is proposed. The spheres had a high surface area (as high as 334 m2 g−1), and were prepared through hydrothermal treatment of freshly prepared peroxo titanium carbonate complex in the presence of ammonium hydroxide. Ammonium hydroxide is crucial in the formation of spherical arrangement of titanate sheets and the size of the spheres is tunable by changing the amount of ammonium hydroxide. The titanate spheres can easily be converted to pure anatase TiO2 with identical morphology on subsequent calcination. The synthesized titanate spheres showed very high removal capacity for toxic heavy metals like Pb2+ and methylene blue from aqueous solution. Corresponding anatase TiO2 spheres manifested as a brilliant anode material for lithium ion batteries with excellent cyclability. TiO2 spheres also showed good photocatalytic activity.

Montmorillonite/poly-(ε-caprolactone) composites as versatile layered material: Reservoirs for anticancer drug and controlled release property

This work evaluates intercalation of tamoxifen (Tmx) in interlayer gallery of Na(+)-MMT (Montmorillonite, MMT) (Tmx-MMT), which is further compounded with poly-(ε-caprolactone) (PCL) (Tmx-MMT/PCL, MPs), for oral chemotherapy of breast cancer. The X-ray diffraction patterns, thermal and spectroscopic analyses indicated the intercalation of Tmx into the MMT interlayer that stabilized in the longitudinal monolayer mode by electrostatic interaction. No significant change in structural and functional properties of Tmx was found in the MMT layers. In vitro study of drug release profiles showed controlled release pattern. The genotoxic effect of drug was in vitro evaluated in human lymphocyte cell culture by comet assay, and results indicated moderate reduction in DNA damage when pristine Tmx was intercalated with MMT and formulated in composites. The Tmx-MMT hybrid efficacy was also confirmed on HeLa and A549 cancer cells by in vitro cell viability assay. In vivo pharmacokinetics (PK) of formulated Tmx in rats was examined and the results showed that plasma Tmx levels were within therapeutic window as compared to pristine Tmx. Therefore, Tmx-MMT hybrid and microcomposite particles (MPs) can be of considerable value in chemotherapy of malignant neoplastic disease with reduced side effects. This study clearly indicated that MMT not only plays a role as a delivery matrix for drug, but also facilitates significant increase in the delivery proficiency.

Alumina-pillared clay of improved thermal stability

Abstract The ion-exchange reaction of smectite clay with a cationic oligomer of hydroxy aluminum (COHA) in the presence of a preswelling agent resulted in better thermal stability of the resultant aluminapillared clay (APC). This is attributed to a more homogeneous distribution of pillars between the interlayer spacing of the clay particles in the presence of the preswelling agent. The effect of the period of aging of the COHA solution on the thermal stability of the product was also studied. A longer aging period of the COHA solution also improved the thermal stability of the product.

Investigations on the development of MCM-41 as a potential mesoporous silica based reference material for the analysis of multi-textural properties

Investigations on the time dependent analysis of the structural and textural properties of the mesoporous silica material MCM-41 were performed by analyzing the samples at regular intervals for one year by powder X-ray diffraction (PXRD) and nitrogen sorption techniques for samples stored (i) under a dry nitrogen atmosphere in a glove box and (ii) under dry ambient atmospheric conditions. The stability and durability of this high surface area material gave promising results under both storage conditions in terms of its structural and textural properties. Under the typical storage conditions employed, the values of various textural properties, including the surface area (SA, m2 g−1), pore volume (PV, cm3 g−1), pore diameter (PD, A) and wall thickness (WT, A) determined by nitrogen adsorption were found to be 1030 ± 49, 1.015 ± 0.066, 27.55 ± 0.60 and 17.04 ± 0.61 respectively for the glove box samples. Almost identical values (SA = 1022 ± 45 m2 g−1), (PV = 0.933 ± 0.065 cm3 g−1), (PD = 27.54 ± 0.14 A), (WT = 16.58 ± 0.81 A) were obtained for the samples under ambient atmospheric conditions. The experimental analysis indicated that this material has potential as a standard reference material for the analysis of the multi-textural characteristics of high surface area mesoporous materials.