Radheshyam R. Pawar

Al-intercalated acid activated bentonite beads for the removal of aqueous phosphate.

The separation of fine spent sorbents from treated water after remediation is a major difficulty associated with phosphate wastewater treatment technology. In this study, a novel aluminium-pillared acid activated bentonite powder (Al-ABn) and alginate immobilized aluminium-pillared acid activated bentonite beads (Al-ABn-AB) were synthesized and used for the removal of aqueous phosphate. The phosphate removal behaviour of adsorbents were evaluated by batch experiments as a function of various parameters such as pH, initial concentration, contact time, temperature, adsorbent dose and presence of coexisting ions. The sorption isotherm studies by Langmuir model showed 12.87 and 11.11 mgP/g maximum phosphate uptake capacity for Al-ABn and Al-ABn-AB, respectively. The kinetic studies confirm that the adsorption of phosphate by Al-ABn and Al-ABn-AB follows a pseudo-second-order model. The feasibility of Al-ABn-AB was also assessed in continuous mode in fixed bed column and the loading capacity obtained was 4.55mg/g. The adsorption capacity of Al-ABn-AB beads remained at relatively high even after four regeneration cycles. Furthermore, the applicability of the synthesized adsorbents towards real municipal wastewater confirmed that novel synthesized Al-ABn and Al-ABn-AB are the promising adsorbents for the removal of phosphate from contaminated water.

Thin film nanocomposite (TFN) hollow fiber membranes incorporated with functionalized acid-activated bentonite (ABn-NH) clay: towards enhancement of water vapor permeance and selectivity

As the use of membrane technology for gas separation has grown, various membrane materials have been developed by numerous researchers to demonstrate separation processes. The present study was intended to make a novel thin film nanocomposite (TFN) membrane hybridized with amino functionalized acid-activated bentonite (ABn-NH) clay. It was projected that the ABn-NH-TFN membranes could improve water vapor permeation performance. The present work was done paying attention to how the incorporation of ABn-NH could affect the TFN membrane physicochemical properties and permeation performance. Thin films of ABn-NH-TFN membranes were prepared using interfacial polymerization on the inner surface of a polysulfone (PSf) hollow-fiber membrane support for the separation of a water vapor/N2 gas mixture. The prepared material and thin film composite membranes were fully characterized using physicochemical techniques including X-ray diffraction, BET surface analysis, thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle analysis. The concentration effect of ABn-NH clay (0–1.0 wt%) on the permeation of water vapor and N2 was investigated. According to SEM images of the composite membranes, 0.5 wt% of ABn-NH clay particles shows good dispersion on a thin selective layer. Water vapor permeation results showed that with the incorporation of ABn-NH particles into the polyamide membrane, the permeance increases enormously. The most advantageous performance, that of ABn-NH-TFN-3 (0.5 wt%) membrane, was achieved with a water vapor permeance of 2809 GPU and a water vapor/N2 selectivity of 913, with a membrane prepared with 2.0 wt% MPD and 0.2 wt% TMC monomer concentrations of coating solution.

Clay catalysed rapid valorization of glycerol towards cyclic acetals and ketals

Biodiesel production usually results in a huge amount of glycerol, raising a critical need to transform it into high value products. The present study highlights that solvent-free, conventional thermal activation, and non-conventional microwave/ultrasonic activation in the liquid phase are able to selectively transform glycerol into cyclic acetals and ketals using an optimised acid activated clay catalyst. Several parameters for the acid activation of bentonite clay were optimized under mild reaction conditions with a high concentration of clay (6%) and varying the acid concentration in the range of 6 to 15 N. The acid-activated clay samples were characterized by XRD, FT-IR, BET, and XRF analysis. The active sites of the catalyst were examined by volumetric titration and confirmed by pyridine adsorbed FT-IR and advanced NH3-TPD analyses. The activation performed at relatively mild conditions, i.e.; 6 N H2SO4 and 6% w/v clay, reproducibly resulted in an improved surface area (180 m2 g−1) and surface acidity (23 mg KOH g−1), with superior quantitative Bronsted and Lewis acidic sites. Moreover, the eco-friendly process involving a catalyst, microwave, or ultra-sonication were successfully utilized to achieve a commercially valuable hyacinth fragrance, in addition to furan-based fuel additive precursors exhibiting a high conversion of glycerol and excellent selectivity within much less activation time (2 min).

Porous synthetic hectorite clay-alginate composite beads for effective adsorption of methylene blue dye from aqueous solution

The present study deals with the preparation and characterization of mesoporous synthetic hectorite (MSH) clay which further encapsulated with Na-alginate for the preparation of mesoporous synthetic hectorite-alginate beads (MSH-AB) where Ca2+ act as a cross-linking agent. The detail characterization of MSH and MSH-AB were carried out by various physicochemical techniques. The thermogravimetric analysis study showed better thermal stability results for MSH-AB. The textural properties results of MSH and MSH-AB showed the high surface area 468, 205m2/g, and the pore volume of 0.34, 0.29cm3/g respectively. The applicability of powder MSH and MSH-AB in wet (W) and dry (D) forms were assessed for the removal of cationic dye, methylene blue (MB) by optimizing various batch adsorption parameters. The Langmuir monolayer adsorption capacity obtained for MSH-AB-W showed significant high adsorption efficacy (i.e., 785.45mgMB/g) compared to the MSH-AB-D (357.14mgMB/g) and powder MSH materials (196.00mgMB/g). The adsorption isotherm studies showed that the Langmuir isotherm model was best suitable for MSH, whereas the Freundlich model was utilised to describe the adsorption behavior of organized hydrogel composite beads. The pseudo-second-order kinetics model was observed best for MB sorption onto MSH, whereas pseudo-first order useful to describe the kinetic behavior of MSH-AB. The regeneration experimental results revealed that MSH-AB-W could be recycled more than six cycles with high MB removal efficiency. Furthermore, the adsorption property of the MSH-AB-W was examined for the binary mixture of MB with other dye solutions such as Methyl Red (MR), Methyl Orange (MO), Alizarine Yellow (AY), and Remazol Brilliant Blue (RBB) to evaluate the selective adsorption efficiency. The MSH composite beads were found potentially suitable as an efficient, selective and recyclable adsorbent for the removal of MB from the aqueous solutions.