Nitin Labhsetwar

Magnesium incorporated bentonite clay for defluoridation of drinking water.

Low cost bentonite clay was chemically modified using magnesium chloride in order to enhance its fluoride removal capacity. The magnesium incorporated bentonite (MB) was characterized by using XRD and SEM techniques. Batch adsorption experiments were conducted to study and optimize various operational parameters such as adsorbent dose, contact time, pH, effect of co-ions and initial fluoride concentration. It was observed that the MB works effectively over wide range of pH and showed a maximum fluoride removal capacity of 2.26 mgg(-1) at an initial fluoride concentration of 5 mg L(-1), which is much better than the unmodified bentonite. The experimental data fitted well into Langmuir adsorption isotherm and follows pseudo-first-order kinetics. Thermodynamic study suggests that fluoride adsorption on MB is reasonably spontaneous and an endothermic process. MB showed significantly high fluoride removal in synthetic water as compared to field water. Desorption study of MB suggest that almost all the loaded fluoride was desorbed ( approximately 97%) using 1M NaOH solution however maximum fluoride removal decreases from 95.47 to 73 (%) after regeneration. From the experimental results, it may be inferred that chemical modification enhances the fluoride removal efficiency of bentonite and it works as an effective adsorbent for defluoridation of water.

New modified chitosan-based adsorbent for defluoridation of water

In the present study, the metal-binding property of chitosan is used to incorporate titanium metal and applied as an adsorbent for fluoride adsorption. Titanium macrospheres (TM) were synthesized by a precipitation method and characterized by FTIR, SEM, and XRD. The Langmuir and Freundlich adsorption models were applied to describe the adsorption equilibrium and the adsorption capacities were calculated. Thermodynamic parameters of standard free energy change (DeltaG(o)), standard enthalpy change (DeltaH(o)), and standard entropy change (DeltaS(o)) were also calculated. The effects of various physico-chemical parameters such as pH, initial concentration, adsorbent dose, and the presence of coexisting anions were studied. The fluoride uptake was maximum at neutral pH 7 and decreased in acidic and alkaline pH. The presence of coexisting anions has a negative effect on fluoride adsorption. TM was found to have very fast kinetics in the first 30 min and then the rate slowed down as equilibrium was approached. A comparison of fluoride removal in simulated and field water shows a high adsorption capacity in simulated water.

Visible light assisted photocatalytic reduction of CO2 using a graphene oxide supported heteroleptic ruthenium complex

A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation

Study of nano-structured ceria for catalyticCO oxidation

Mesoporous, nano-structured ceria has been synthesized using a low-cost biopolymer chitosan as a template, and the same material has been studied for its CO oxidation activity. The ceria thus prepared shows low crystallite size (6.5 nm), high surface area (BET-SA 144.2 m2 g−1) and mesopores (32.4 A) without ordered structure. Different ceria samples have been synthesized by manipulating the chitosan : cerium ratio and synthesis temperature. These ceria samples have been characterized using XRD, BET-SA, SEM, FTIR, UV-DRS, PL and TEM techniques. The ceria samples show fluorite structure with cubic symmetry and increased lattice volume. The nano-structured ceria thus synthesized lowers the CO oxidation temperature by 30–60 °C as compared to the commercial ceria. The improved catalytic activity primarily appears to be the effect of improved surface area and pore characteristics of nano-structured ceria. Also the expansion in lattice cell volume leads to the improvement in redox properties of ceria, thereby facilitating the formation of surface oxygen vacancies. Such mesoporous ceria without ordered structure could be useful as an oxidation catalyst as well as a support for various catalysts. The platinum incorporated mesoporous ceria also shows excellent CO oxidation.

Alumina supported, perovskite oxide based catalytic materials and their auto-exhaust application

Abstract Substituted lanthanum manganate type perovskites have been synthesized following co-precipitation and a modified in situ method. These perovskites have been supported on cordierite honeycomb with and without alumina washcoat. Alumina washcoated supports with lanthana pre-coat, have been found suitable for the in situ synthesis of perovskites to avoid reactivity of perovskite precursors with alumina (in absence of lanthana pre-coat). This modified synthesis has resulted in remarkable improvement in surface area while, excellent catalyst adhesion has also been observed. The catalyst composition has also been promoted by a small amount of platinum, which has resulted in improved catalytic activity. These catalysts have been first evaluated using a pure gas laboratory evaluation assembly. Catalysts prepared on alumina washcoated honeycomb having lanthana pre-coat, shows better activity than the samples prepared by co-precipitation method. Catalytic converter prototypes have been prepared using the selected catalyst and evaluated on engine and chassis dynamometers. The converter shows good conversion activity for all the three pollutants, viz. CO, HC and NO x . These results substantiate the possibility of using supported perovskites for automobile applications. The detailed characterization of supported perovskites, however, could not be done conclusively and demand for further investigations, to properly understand the interaction of pre-coat, alumina washcoat and catalyst.

Synthesis and visible light photocatalytic activity of nanocrystalline PrFeO 3 perovskite for hydrogen generation in ethanol–water system

AbstractNanocrystalline PrFeO3 perovskite type orthoferrite was synthesized at 700°C by using three different synthesis methods, namely sol–gel, template and combustion method. The synthesized materials were characterized by XRD, BET-SA, SEM, HRTEM, XPS, FTIR and UV-DRS techniques to understand their physico-chemical properties. Characterization data reveal the formation of nanocrystalline PrFeO3 perovskite composition with improved physical properties, possibly due to lower synthesis temperature used. PrFeO3 synthesized by sol–gel method consists of crystallite size of about 20 nm with absorption maxima at 595 nm wavelength in visible light range. This photocatalyst shows hydrogen generation of about 2847 μmol.g−1.h−1, under visible light irradiation in ethanol–water system. The photocatalyst was further investigated for various operational parameters such as photocatalyst dose variation, illumination intensity, time, etc. in a view to optimize the hydrogen generation as well as to understand mechanistic aspects. This material appears to follow a semiconductor type mechanism for ethanol-assisted visible light photocatalyic water-splitting and can also be an interesting candidate to develop hetero-junction type photocatalysts. ᅟPrFeO3–type perovskite was synthesized by sol–gel, template and combustion methods. PrFeO3 synthesized by sol–gel method consists of crystallite size of about 20 nm with absorption maxima at 595 nm wavelength in visible light range. This photocatalyst shows hydrogen generation of about 2847 µmol.g-1.h-1, under visible light irradiation in ethanol-water system, and follows semiconductor type mechanism with alcohol acting as sacrificial donor.

N-doped mesoporous alumina for adsorption of carbon dioxide.

N-doped mesoporous alumina has been synthesized using chitosan as the biopolymer template. The adsorbent has been thoroughly investigated for the adsorption of CO2 from a simulated flue gas stream (15% CO2 balanced with N2) and compared with commercially available mesoporous alumina procured from SASOL, Germany. CO2 adsorption was studied under different conditions of pretreatment and adsorption temperature, inlet CO2 concentration and in the presence of oxygen and moisture. The adsorption capacity was determined to be 29.4 mg CO2/g of adsorbent at 55 degrees C. This value was observed to be 4 times higher in comparison to that of commercial mesoporous alumina at a temperature of 55 degrees C. Basicity of alumina surface coupled with the presence of nitrogen in template in synthesized sample is responsible for this enhanced CO2 adsorption. Adsorption capacity for CO2 was retained in the presence of oxygen; however moisture had a deteriorating effect on the adsorption capacity reducing it to nearly half the value.

Low-cost catalysts for the control of indoor CO and PM emissions from solid fuel combustion.

Cu-Mn based mixed oxide type low-cost catalysts have been prepared in supported form using mesoporous Al(2)O(3), TiO(2) and ZrO(2) supports. These supports have been prepared by templating method using a natural biopolymer, chitosan. The synthesized catalysts have been characterized by XRD, BET-SA, SEM, O(2)-TPD and TG investigations. The catalytic activity for CO as well as PM oxidation was studied, in a view of their possible applications in the control of emissions from solid fuel combustion of rural cook-stoves. The trend observed for the catalytic activity of the synthesized catalysts for CO oxidation was ZrO(2)>TiO(2)>Al(2)O(3) while for PM oxidation it was observed to be TiO(2)>ZrO(2)>Al(2)O(3). The effect of CO(2), SO(2) and H(2)O on CO oxidation activity was also investigated, and despite partial deactivation, the catalysts show good CO oxidation activity. An effective regeneration treatment was attempted by heating the partially deactivated catalysts in presence of oxygen. Redox properties of TiO(2) and ZrO(2) and their structure appeared to be responsible for their promotional activity for CO and PM oxidation reactions. These unordered mesoporous materials could be useful for such reactions where mass transfer is more important than shape and size selectivity.

Photocatalytic Degradation of Phenolics by N-Doped Mesoporous Titania under Solar Radiation

In this study, nitrogen-doped mesoporous titania was synthesized by templating method using chitosan. This biopolymer chitosan plays the dual role of acting as a template (which imparts mesoporosity) and precursor for nitrogen. BET-SA, XRD, UV-DRS, SEM, and FTIR were used to characterize the photocatalyst. The doping of nitrogen into TiO2 lattice and its state was substantiated and measured by XPS. The photocatalytic activity of the prepared N-doped mesoporous titania for phenol and o-chlorophenol degradation was investigated under solar and artificial radiation. The rate of photocatalytic degradation was observed to be higher for o-chlorophenol than that of phenol. The photodegradation of o-chlorophenol was 98.62% and 72.2%, while in case of phenol, degradation to the tune of 69.25% and 30.58% was achieved in solar and artificial radiation. The effect of various operating parameters, namely, catalyst loading, pH, initial concentration and the effect of coexisting ions on the rate of photocatalytic degradation were studied in detail.

Photo-assisted oxidation of thiols to disulfides using cobalt “Nanorust” under visible light

Heterogeneous “Nanorust” containing cobalt oxide has been developed for the visible light assisted oxidation of thiols to disulfides using molecular oxygen as an oxidant under alkaline free conditions and therefore more environmentally friendly. Pyrolysis of heterogenized tetrasulfonated cobalt(II) phthalocyanine (CoPcS) supported on mesoporous ceria (CeO2) transforms it into a novel heterogeneous “Nanorust” containing CoOx-C,N@CeO2 which exhibited higher catalytic activity than the homogeneous CoPcS as well as the ceria immobilized CoPcS catalyst. Importantly, these catalysts could easily be recovered and recycled for several runs, which makes the process greener and cost-effective.