Pardeep Singh

Adsorptional removal of methylene blue by guar gum-cerium (IV) tungstate hybrid cationic exchanger.

Guar gum-cerium (IV) tungstate nanocomposite (GG/CTNC) cationic exchanger was synthesized using simple sol gel method. The GG/CTNC was characterized using X-ray diffraction (XRD), Fourier transmission infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray spectrophotometer (EDX). The XRD studies confirmed amorphous and fibrous in nature of GG/CTNC. The high percentage of oxygen in the nanocomposite material confirmed the functionality tungstate (WO4(-)). The ion exchange capacity of GG/CTNC for Na(+) ion was observed to be 1.30 mequivg(-1). The hybrid exchanger was used as potential adsorbent for the removal of methylene blue (MB) from aqueous system. The correlation coefficients value indicated a good fit of monolayer Langmuir model to the adsorption of methylene blue onto GG/CTNC. The adsorption kinetic study revealed that the adsorption process followed the pseudo second order kinetic. The Gibbs free energy (ΔG) values confirmed the spontaneous nature of adsorption process.

Adsorptional photocatalytic mineralization of oxytetracycline and ampicillin antibiotics using Bi2O3/BiOCl supported on graphene sand composite and chitosan

In present study, heterojunctioned Bi2O3/BiOCl (BO/BOC) was synthesized via in situ chemical reduction and oxidation of BiOCl nanoplates. BiOCl was reduced to metallic Bi in KHB4 solution followed by oxidation in H2O2 solution to produce BO/BOC. The BO/BOC was supported over graphene sand composite and also on chitosan using wet impregnation method to report BO/BOC/GSC and BO/BOC/CT nanocomposite. The morphology and compositional characteristics of BO/BOC/GSC and BO/BOC/CT were investigated by FESEM, TEM, HRTEM, FTIR, XRD, EDX, RAMAN, BET and UV-visible diffuse reflectance spectral analysis. The photocatalytic activity of BO/BOC/GSC and BO/BOC/CT was performed for mineralization of ampicillin (AMP) and oxytetracycline (OTC) antibiotics under solar light. The adsorption process had significant effect on photodegradation of AMP and OTC. The adsorption of both OTC and AMP onto BO/BOC/GSC and BO/BOC/CT followed pseudo second order kinetics. Simultaneous adsorption and degradation process (A+P) resulted in higher degradation rate of investigated antibiotics. The applicability of power law model indicates the intricacies of mineralization process. During A+P process, OTC and AMP were mineralized to CO2·H2O, NO3(-) and SO4(2-) ions. Both BO/BOC/GSC and BO/BOC/CT exhibited significant recycle efficiency.

A super beta bipolar transistor using SiGe-base surface accumulation layer transistor(SALTran) concept: a simulation study

Current gain is an important design parameter of bipolar transistors. While a SiGe base is commonly used to increase the current gain, the recently reported surface accumulation layer transistor (SALTran) concept has been shown to give a similar current gain enhancement. Using two-dimensional numerical simulation studies, we show for the first time that a combination of the SiGe base and the SALTran concept can be used to realize super beta bipolar transistors with peak current gains more than 12000.

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.

Solar light-facilitated oxytetracycline removal from the aqueous phase utilizing a H2O2/ZnWO4/CaO catalytic system

Abstract A CaO-supported ZnWO4 nanocomposite (ZnWO4/CaO) was successfully synthesized using a novel hydrothermal method and was characterized by scanning electron microscopy (SEM), tunnelling electron microscopy (TEM), X-ray diffraction (XRD), electron diffraction X-ray (EDX), Fourier transform infrared spectroscopy (FTIR) and UV–visible (UV–vis) spectral analysis. The ZnWO4/CaO composites exhibited rod-like morphologies with variable lengths from 45 nm to 147 nm and diameters from 26 nm to 36 nm. The catalytic efficiency of the synthesized ZnWO4/CaO composites was displayed for the photodegradation of oxytetracycline (OTC) antibiotic from the aqueous phase. The synergistic degradation of OTC was investigated in the presence of H2O2 and ZnWO4/CaO. The rate of photodegradation followed pseudo-first-order kinetics. The antibiotic removal was strongly influenced by the catalyst loading, H2O2 concentration, pH and OTC concentration. Using a solar/H2O2/ZnWO4/CaO catalytic system, 85% COD removal was attained for OTC degradation in 210 min. The oxidative degradation occurred through hydroxyl radicals. The prepared nanocomposites possessed high recyclability and were easily separated from the aqueous solution by a simple sedimentation process.

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.

Soil Carbon Dynamics Under Changing Climate—A Research Transition from Absolute to Relative Roles of Inorganic Nitrogen Pools and Associated Microbial Processes: A Review

Abstract It is globally accepted that soil carbon (C) dynamics are at the core of interlinked environmental problems, deteriorating soil quality and changing climate. Its management remains a complex enigma for the scientific community due to its intricate relationship with soil nitrogen (N) availability and moisture-temperature interactions. This article reviews the management aspects of soil C dynamics in light of recent advances, particularly in relation to the availability of inorganic N pools and associated microbial processes under changing climate. Globally, drastic alterations in soil C dynamics under changing land use and management practices have been primarily attributed to the variation in soil N availability, resulting in a higher decomposition rate and a considerable decline in soil organic C (SOC) levels due to increased soil CO2 emissions, degraded soil quality, and increased atmospheric CO2 concentrations, leading to climate warming. Predicted climate warming is proposed to enhance SOC decomposition, which may further increase soil N availability, leading to higher soil CO2 efflux. However, a literature survey revealed that soil may also act as a potential C sink, if we could manage soil inorganic N pools and link microbial processes properly. Studies also indicated that the relative, rather than the absolute, availability of inorganic N pools might be of key importance under changing climate, as these N pools are variably affected by moisture-temperature interactions, and they have variable impacts on SOC turnover. Therefore, multi-factorial studies are required to understand how the relative availability of inorganic N pools and associated microbial processes may determine SOC dynamics for improved soil C management.

Nanoparticles for Biofuels Production from Lignocellulosic Waste

Lignocellulosic biomass is a sustainable alternative to current biofuels. The conversion of biomass-based sugars into biofuels, which emerged in 1970, is gaining more attention due to fossil fuel issues. Biohydrogen and bioethanol from cellulosic wastes is a sustainable and solves economic issues. This chapter reviews the use of nanoparticles for the bioconversion of biomass into biofuels.

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.