Dhanesh Tiwary

Lanthanum dithiocarbamates as potential extreme pressure lubrication additives

BackgroundThe extreme pressure lubrication (EPL) properties of bipyridyl adducts of different lanthanum dithiocarbamates of the type LaL3·bipy (where LH = dimethyl dithiocarbamate (Me2DTCH), piperidine dithiocarbamate (PipDTCH), morpholine dithiocarbamate (MorphDTCH), and diphenyl dithiocarbamate (Ph2DTCH); bipy = 2,2′-bipyridyl) have been evaluated with a four-ball lubricant tester using steel balls of 12.7-mm diameter and molybdenum disulfide as a reference additive. Various tribological parameters, viz. mean wear scar diameter, friction coefficient, mean specific pressure, initial seizure load, 2.5-s seizure delay load, weld load, flash temperature parameter, mean Hertz load, pressure wear index, etc., have been determined. The surface topography of wear scar has been studied by atomic force microscopy and scanning electron microscopy. Energy-dispersive X-ray analysis has been performed to give the composition of the wear scar surface.ResultsExperimental results indicate that admixtures containing bipyridyl adducts of lanthanum dithiocarbamates in paraffin oil exhibit better EPL properties than paraffin oil alone or with a reference additive (MoS2).ConclusionsIn view of very high efficiency, the synthesized compounds can be recommended for their application as EPL additives.

Emerging trends in photodegradation of petrochemical wastes: a review

Various human activities like mining and extraction of mineral oils have been used for the modernization of society and well-beings. However, the by-products such as petrochemical wastes generated from such industries are carcinogenic and toxic, which had increased environmental pollution and risks to human health several folds. Various methods such as physical, chemical and biological methods have been used to degrade these pollutants from wastewater. Advance oxidation processes (AOPs) are evolving techniques for efficient sequestration of chemically stable and less biodegradable organic pollutants. In the present review, photocatalytic degradation of petrochemical wastes containing monoaromatic and poly-aromatic hydrocarbons has been studied using various heterogeneous photocatalysts (such as TiO2, ZnO and CdS. The present article seeks to offer a scientific and technical overview of the current trend in the use of the photocatalyst for remediation and degradation of petrochemical waste depending upon the recent advances in photodegradation of petrochemical research using bibliometric analysis. We further outlined the effect of various heterogeneous catalysts and their ecotoxicity, various degradation pathways of petrochemical wastes, the key regulatory parameters and the reactors used. A critical analysis of the available literature revealed that TiO2 is widely reported in the degradation processes along with other semiconductors/nanomaterials in visible and UV light irradiation. Further, various degradation studies have been carried out at laboratory scale in the presence of UV light. However, further elaborative research is needed for successful application of the laboratory scale techniques to pilot-scale operation and to develop environmental friendly catalysts which support the sustainable treatment technology with the “zero concept” of industrial wastewater. Nevertheless, there is a need to develop more effective methods which consume less energy and are more efficient in pilot scale for the demineralization of pollutant.

Studies on Lanthanum Complexes of 1-Aryl-2,5-Dithiohydrazodicarbonamides in Paraffin Oil as Extreme Pressure Lubrication Additives

Testing of lanthanum complexes of 1-aryl-2,5-dithiohydrazodicarbonamides of the formula LaL3 [LH=1-phenyl-2,5-dithiohydrazodicarbonamide(PhTHC), 1-methylphenyl-2,5-dithiohydrazodicarbon-amide(p-MePhTHC), 1-methoxyphenyl-2,5-dithiohydrazodicarbonamide(p-MeOPhTHC), 1-phenyl-2,5-dithiohydrazodicarbonamide(p-ClPhTHC)] for their application as extreme pressure lubrication (EPL) additives was performed on four ball tester using steel balls of 12.7 mm diameter and MoS2 as reference additive. The efficiency of the complexes has been evaluated using the tribological parameters, wear scar diameter, friction coefficient, initial seizure load, 2.5 s seizure delay load, weld load, mean Hertz load, flash temperature parameter and pressure wear index. The tested complexes behave as good extreme pressure additives; however, the best performance is shown by the p-methoxyphenyl derivative. The surface morphology of the wear scar on steel ball has been studied by atomic force microscopy and scanning electron microscopy. In presence of this complex, roughness of the worn surface is significantly reduced. The composition of wear scar has been analyzed by energy dispersive X-ray spectroscopy. The presence of lanthanum and sulfur in energy dispersive X-ray spectrum emphasizes role of additive in the tribofilm formed on the surface.

Comparative study of dye degradation using TiO2-activated carbon nanocomposites as catalysts in photocatalytic, sonocatalytic, and photosonocatalytic reactor

AbstractIn the present study, activated carbon-based TiO2 nanocomposites with carbon loading were synthesized by sol–gel method for photocatalytic, sonocatalytic, and sonophotocatalytic degradation of colored compound in wastewater. The prepared catalysts were characterized by Brunauer–Emmet–Teller surface area analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared analysis (FT-IR). The degradation efficiencies of the synthesized composites were determined by the degradation of Direct Blue-199 dye under three different reactors viz., photocatalytic, sonocatalytic, and sonophotocatalytic. Reaction kinetic modeling was done for these processes and the degradation rate was found maximum for sonophotocatalytic process as compared to individual ones. However, on considering the energy efficiency and degradation efficiency, photochemical reactor was found to be most economical. Therefore, for the treatment of wastewater-containing dye from industries, a photocataly...

Current and emerging trends in bioremediation of petrochemical waste: A review

ABSTRACT Various industries release harmful petrochemical contaminants into the environment. To treat these petrochemical contaminants at source, different physical, chemical, and biological methods have been proposed and applied worldwide. However, physical and chemical methods have their own advantages and limitations; in this review, we majorly focused on the biodegradation of petrochemical wastes. First, a background study on the literature available in this field is presented. Second is a review of the toxic effects of petrochemical waste and various physical and chemical processes, followed by elaborate biological processes available for petrochemical waste degradation. Further, different aspects of bioremediation, such as modes, factors, limitations, and future perspectives are critically reviewed and presented. It was found that most of the studies performed on bioremediation of petrochemical waste employed bacteria for the degradation purpose. Some studies also made use of algae, fungi, yeast, genetically modified organisms, biosurfactants, or a consortium of these microbes. Moreover, use of bioremediation is still limited at field scale due to certain limitations, which have been elaborated in this article. Overall, we strongly believe that with bioremediation capturing the attention of environmentalists worldwide, there is still a prevailing need to scale up from lab to land level applications and adaptations.

Chromium removal from aqueous media by superparamagnetic starch functionalized maghemite nanoparticles

AbstractSuperparamagnetic starch functionalized maghemite nanoparticles (SMhNPs) were synthesised by a co-precipitation method viain situ functionalization and used as nano-adsorbents for the removal of Cr(VI) from aqueous waste. The characterization of the prepared nanoparticles was done by XRD, FTIR, TEM and VSM techniques. Adsorption of Cr(VI) on the surface of superparamagnetic starch functionalized maghemite nano-adsorbents was investigated and the removal was higher in acidic pH as compared to that exhibited in basic medium. The adsorption of Cr(VI) by the SMhNPs followed pseudo-second order kinetics and the adsorption isotherm data fits well the Freundlich adsorption isotherm. The KF value for Cr(VI) removal by SMhNPs is found to be 24.76 mg.g−1, which is significantly better than the adsorption capacities reported in literature for maghemite nanoparticles. Thermodynamic studies revealed that the adsorption of Cr(VI) onto the superparamagnetic starch functionalized maghemite nano-adsorbents is spontaneous and endothermic in nature. Graphical AbstractThe low activation energy for the adsorption of Cr (VI) (31.54 kJ.mol−1) suggests that it was physically adsorbed on starch functionalized maghemite nanoparticles. Given the reversible nature of such adsorption, the adsorbent was found to demonstrate very good recovery and recyclability, making it a relatively cheap eco-friendly alternative.

The radical cation of trimethylamine–boron hydride: An EPR study

Exposure of dilute solutions of trimethylamine–boron hydride (Me3N–BH3) in freon (CFCl3) at 77 K to ionizing radiation gave a radical cation whose EPR spectrum was that expected for the parent radical cation. This resembled those obtained for the BH4 radical previously studied, having a nearly isotropic hyperfine coupling to boron, and a large coupling to two equivalent protons. The possibility that this might be a σ1-radical the SOMO being the N–B σ-bond is dismissed: the favoured structure places the hole on two hydrogens and on boron only.

Assessment of groundwater quality using WQI and GIS near the Karsara municipal landfill site, Varanasi, India

The present paper reports the evaluation of the groundwater quality around the municipal landfill site in Varanasi City, Uttar Pradesh, India. Leachate pollution index (LPI) and water quality index (WQI) have been used to determine the quality of leachate of landfill and groundwater in the study area. LPI value (16.81) of landfill leachate revealed the presence of significant amount of the pollutants. WQI of groundwater samples near the landfill site has been calculated and water quality map has been prepared by using WQI in GIS environment for both pre- and post-monsoon periods of the year 2016. Results of WQI revealed that 35% groundwater samples are good, 35% marginal, 20% excellent, and 10% are in fair category in pre-monsoon period while in post-monsoon 70% samples are marginal, 15% excellent, 10% fair, and 5% are in good category. WQI map shows that most of the study area near the landfill site is in fair category during pre-monsoon season but in threatened category during post-monsoon season. The results of the physicochemical analysis of groundwater have shown that the water is not safe for drinking purpose as some parameters like TDS, hardness, total alkalinity, and nitrate and iron content were observed to be above the acceptable limit (WHO and BIS) of drinking water quality. This study revealed that WQI and LPI can also be an important monitoring tool for landfill policy makers and the public to safeguard groundwater pollution risk from the landfill.