Showing papers by "Ajaya Kumar Singh published in 2020"

Adsorption of heavy metal ions by various low-cost adsorbents: a review

Abstract: Environmental pollution, particularly from heavy metal ions in the wastewater, is one of the most serious concerns of the world. In the pursuit of remedial action, various conventional methods such...

Cationic Dye Removal Using Novel Magnetic/Activated Charcoal/β-Cyclodextrin/Alginate Polymer Nanocomposite.

Abstract: New magnetic iron oxide (Fe3O4)/activated charcoal (AC)/β-cyclodextrin (CD)/sodium alginate (Alg) polymer nanocomposite materials were prepared by direct mixing of the polymer matrix with the nanofillers. The obtained materials were utilized as nano-adsorbents for the elimination of methylene blue (MB), a hazardous water-soluble cationic dye, from aqueous solutions, and showed excellent regeneration capacity. The formation of the nanocomposites was followed by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometry (EDX), Fourier-transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), X-ray diffraction (XRD) and adsorption of N2 at -196 °C. The rate of adsorption was investigated varying several factors, namely contact time, pH, amount of adsorbent and MB concentration on the adsorption process. Studies dealing with equilibrium and kinetics were carried out in batch conditions. The obtained results indicated that the removal rate of MB was 99.53% in 90 min. Langmuir's isotherm fitted better to the equilibrium data of MB. Fe3O4/AC/CD/Alg polymer beads shows amazing adsorption capacities in the elimination of cationic dyes (2.079 mg/g for polymer gel beads and 10.63 mg g-1 for dry powder beads), in comparison to other adsorbent materials. The obtained adsorbent is spherical with hydrophobic cross-linked surface properties that enable an easy recovery without any significant weight loss of in the adsorbent used.

Surfactant-assisted cerium oxide and its catalytic activity towards Fenton process for non-degradable dye

Abstract: Water pollution kills nearly 2 million people and costs trillions of dollars every year, which continuously threatens the survival of both human and animal species in the world. The textile industry is considered as pollutant-releasing industries in water. In this research work, we firstly report the synthesis of cerium oxide (CeO2) nanoparticles in the range of quantum dots (QDs). Syntheses of cerium oxide nanomaterials were assisted by using three different surfactants, i.e., sodium dodecyl sulfate (SDS; anionic), cetyltrimethylammonium bromide (CTAB; cationic), and cetylpyridinium chloride (CPC; cationic); the surfactants control the growth and particle size of the prepared material. The nanomaterials were characterized by UV-visible spectroscopy, X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, high-resolution transmission electron microscopy (HRTEM), and thermogravimetric/differential thermal analyses (TG/DTA), together with Fourier transform infrared (FTIR) spectroscopy and photoluminescence (PL). The particle size of such CeO2 nanoparticles ranges between 1.66 and 4.36 nm. Their catalytic role was successfully investigated in Fenton reaction for the oxidative removal of methylene blue (MB) dye. The efficiency of Fenton reaction using such CeO2 QDs has been used to highlight the importance of such nanosized catalysts for wastewater treatment.

Assessing the Photocatalytic Degradation of Fluoroquinolone Norfloxacin by Mn:ZnS Quantum Dots: Kinetic Study, Degradation Pathway and Influencing Factors.

Abstract: Norfloxacin (NOFX), a broadly used fluoroquinolone antibiotic, has been a subject of great concern in the past few years due to its undesirable effect on human beings and aquatic ecosystems. In this study, novel Mn doped ZnS (Mn:ZnS) quantum dots (QDs) were prepared through a facile chemical precipitation method and used as photocatalysts for NOFX degradation. Prior to photodegradation experiments, morphological and optical parameters of the QDs were examined through transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray analysis, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, fluorescence spectroscopy, Brunauer-Emmett-Teller analysis, and differential thermal and thermogravimetric analyses. Mn:ZnS QDs exhibited excellent properties of photodegradation, not only under UV irradiation but also in sunlight, which induced NOFX to photodegrade. The utmost photodegradation efficiency was obtained under optimal conditions (25 mL of NOFX, 15 mg/L, pH 10, 60 min UV irradiation, 60 mgs QDs), adopting first order kinetics. In addition, hydroxyl radicals produced by the conduction band electrons were found to be the primary reason dominating the transformation of NOFX in basic conditions, while holes, oxygen atoms, as well as the doped metal (Mn) enhanced the degradation. The QDs showed excellent reusability and stability in four repeated cycles. Finally, four different pathways were predicted, derived from the identified intermediates, with piperazinyl ring transformation being the primary one. It is expected that the synthesized Mn:ZnS QDs could be utilized as efficient photocatalytic materials for energy conversion and ecological remediation.

Muffle atmosphere promoted fabrication of graphene oxide nanoparticle by agricultural waste

Abstract: Graphene is a radiant star in the field of nanomaterials. It has gained prominent interest since of its very good mechanical, thermal, optical and electronic possessions. The basic chemical reactio...

Chloramine-T/N-Bromosuccinimide/FeCl3/KIO3 Decorated Graphene Oxide Nanosheets and Their Antibacterial Activity.

Abstract: In this work, we report the synthesis of graphene oxide nanosheets (GO NS) using four different oxidants, namely, chloramine-T (CAT), FeCl3, N-bromosuccinimide (NBS), and KIO3. Fourier transform infrared spectroscopy (FTIR) was used to characterize the functional groups present in the synthesized GO. The microstructure analysis was performed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) to investigate the morphology of GO. High-resolution transmission electron microscopy (HRTEM) studies demonstrated the nanostructure and crystalline phases of GO. The antibacterial activity of the prepared GO NS was investigated against pure cultures of Pseudomonas pneumonia and Staphylococcus aureus. The synthesized GO NS with CAT-GO (C-GO) exhibited very good antibacterial activity towards pathogens.

Catalytic Properties of Graphene Oxide Synthesized by a “Green” Process for Efficient Abatement of Auramine-O Cationic Dye

Abstract: The management of water pollution in the world is an important need and easy to implement methods are urgently needed for water purification. In this study, efforts were made to assess the efficien...

Chicken feathers derived materials for the removal of chromium from aqueous solutions: kinetics, isotherms, thermodynamics and regeneration studies

Abstract: In the present study, chicken feathers (CFs), obtained from animal waste, were used as bio-adsorbent for the removal of hazardous Cr(VI) ions from aqueous solutions. Fourier transform infrared spec...

Synthesis of Ag Nanoparticle-Decorated ZnO Nanorods Adopting the Low-Temperature Hydrothermal Method

Abstract: Vertically aligned and highly dense Zinc oxide (ZnO) nanorods (NRs) have been successfully synthesized by a two-step hydrothermal method and decorated by silver (Ag) nanoparticles (NPs) via a dip coating technique. Absorption spectra indicate the presence of metal Ag NPs. The photoluminescence (PL) spectrum of as-grown ZnO nanorods shows ultra violet (UV) emission centered around 390 nm and a sharp defect-related emission peak around 580 nm. The presence of Ag NPs on the ZnO NRs shows a significant red shift in PL peak position in the visible region and a complete quenching of UV emission. The changes in UV–Vis and PL spectra of ZnO NRs decorated with Ag metal NPs are studied and discussed.

Degradation of methylene blue and methyl violet using graphene oxide/NiO/β-cyclodextrin nanocomposites as photocatalyst

Abstract: We report the synthesis of graphene oxide/nickel oxide/β-cyclodextrin (GO/NiO/β-CD) nanocomposite and the efficiency of the nanocomposite in decolourising two different dyes, methylene blue (MB) an...

Treatment of pharmaceutical wastewater by heterogeneous Fenton process: an innovative approach

Abstract: With indiscriminate use and disposal, antibiotics enter the water bodies and thus are categorized as emerging pollutants. We report the studies on the degradation of norfloxacin, a well-known antibiotic, using hydrogen peroxide (H2O2) and zinc oxide nanoparticles (ZnO) by heterogeneous Fenton process in the presence of sunlight. We fabricated ZnO nanoparticles by hydrothermal method. The geometry of norfloxacin was optimized using Hartree–Fock density functional theory. We used UV–Vis spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy techniques to determine various crystal properties, i.e., structure, morphology, size and shape of the ZnO nanoparticles. However, we evaluated the crystal size, particle size and their distribution employing Debye–Scherrer equation and ImageJ processing. The catalytic efficacy of ZnO nanoparticles was assessed by the abatement of norfloxacin at pH 10. The activity and stability of used ZnO catalyst for norfloxacin degradation were established. The recovered catalyst is reusable up to six times without activity loss. Liquid chromatography–mass spectrometry analysis confirmed the presence of various intermediates. A probable reaction mechanism for degradation of norfloxacin is proposed. The ZnO-catalyzed heterogeneous Fenton process proves to be the ideal approach for the degradation of antibiotics in wastewater. Herein, we report that generation of hydroxyl radical by the action of sunlight along with ZnO nanoparticles from hydrogen peroxide effectively degrades norfloxacin. Its structure has been optimized by density functional theory using Gauss view computational software. ZnO nanoparticles have been characterized by various techniques, e.g., XRD, SEM, TEM, etc. Various intermediate products have been recognized by LCMS analysis.

Sensing Ability of Ferroelectric Oxide Nanowires Grown in Templates of Nanopores

Abstract: Nanowires of ferroelectric potassium niobate were grown by filling nanoporous templates of both side opened anodic aluminum oxide (AAO) through radiofrequency vacuum sputtering for multisensor fabrication. The precise geometrical ordering of the AAO matrix led to well defined single axis oriented wire-shaped material inside the pores. The sensing abilities of the samples were studied and analyzed in terms of piezoelectric and pyroelectric response and the results were compared for different length of the nanopores (nanotubes)—1.3 µm, 6.3 µm and 10 µm. Based on scanning electronic microscopy, elemental and microstructural analyses, as well as electrical measurements at bending and heating, the overall sensing performance of the devices was estimated. It was found that the produced membrane type elements, consisting potassium niobate grown in AAO template exhibited excellent piezoelectric response due to the increased specific area as compared to non-structured films, and could be further enhanced with the nanowires length. The piezoelectric voltage increased linearly with 16 mV per micrometer of nanowire’s length. At the same time the pyroelectric voltage was found to be less sensitive to the nanowires length, changing its value at 400 nV/µm. This paper provides a simple and low-cost approach for nanostructuring ferroelectric oxides with multisensing application, and serves as a base for further optimization of template based nanostructured devices.

Synthesis, characterization and antibacterial activity of a graphene oxide based NiO and starch composite material

Abstract: This work reports a novel, facile and hydrothermal approach to prepare graphene oxide/NiO/Starch composite materials (GO/NiO/Starch). The composite materials were fully characterized by Scanning El...

A micellar mediated novel method for the determination of selenium in environmental samples using a chromogenic reagent.

Abstract: A novel, simple, sensitive and rapid spectrophotometric method for the determination of selenium(IV) in an acidic medium using rhodamine B hydrazide (RBH) has been developed. The method is based on the micellar mediated oxidation of RBH by Se(IV) in an acidic medium to produce a pinkish violet color of rhodamine B, which was monitored spectrophotometrically at λmax 585 nm. The sensitivity of the method was found to increase when the reaction was performed in a micellar medium. Beer's law was obeyed in the concentration range of 0.002–0.032 μg mL−1. The reaction variables such as time, temperature, reagent concentration, and acidity have been optimized for the reaction. Sandell's sensitivity and molar absorptivity for the reaction system were found to be 0.00004 μg cm−2 and 42.52 × 106 L mol−1 cm−1, respectively. The developed method was successfully applied for the determination of Se(IV) in several real samples with quantitative results.

Fabrication of Transparent ITO/Ga-Doped ZnO Coating as a Front Panel Electrode toward Efficient Thin Film Solar Cells

Abstract: Bi-layer coatings from sputtered indium tin oxide (ITO) and gallium doped zinc oxide (Ga:ZnO) were investigated for transparency in the visible range of the electromagnetic spectrum, optical rejection ability in the near infrared spectrum and conductivity for the novel quantum dot based solar cells. The multilayer stack with optimized films thickness and surface roughness exhibit improved optical properties without to worsen the electrical ones, especially after additional oxidation during reactive sputtering of the metal-oxides. With an average optical transmittance of 90.7% over the visible region, average optical rejection greater than 65 % in the infrared range and resistivity lower than 100 Ω.cm, this coating is good candidate for front panel in CdS/ZnS core-shell quantum dots based solar cells. The efficiency of the cell increased with approximately 3 % as compared to the case with ITO only electrode. The results might be ascribed to the relatively low surface roughness and to the narrowed transmittance spectrum after ITO/Ga:ZnO interface has been established, targeting absorption of visible light only.

Selective Spectrophotometric Method for the Determination of Mercury(II) in Water Samples

Abstract: A simple spectrophotometric method is proposed for the rapid determination of mercury(II). The procedure is based on the hydrolysis of iodine in the presence of Hg(II), resulting in the formation o...

Kinetics of Micellar Effect of Non-Ionic Surfactant on Oxidative Degradation of Ciprofloxacin

Abstract: Oxidative degradation kinetics of leading fluoroquinolone family drug ciprofloxacin (CIP) by chloramine-T (CAT) in TX-100 micelle media was studied spectrophotometrically at 275 nm and 298 K. In pseudo-first-order conditions the rate constant (kobs) decreased regularly with increasing [TX-100]. To understand the self-organizing activities of TX-100, CMC values in varying reaction conditions had been evaluated. The role of non-ionic surfactant in the oxidative degradation process of ciprofloxacin by chlorinating agent chloramine-T is explained in terms of mathematical model explained by Menger-Portnoy. The reaction showed first to zero order dependence on [CAT] and fractional order on [CIP]. Increasing [H+] decreased the rate of reaction. The effect of ionic strength and solvent polarity of the medium in reaction conditions were studied. The effects of added salts [HSO4Na], [KCl], [KNO3] and [K2SO4] had also been studied. The stoichiometry of the reaction determined was 1:2 and the oxidation products were identified by LC-EI-MS. The analysis of degradation product of ciprofloxacin evidently reveals that the piperazine moiety is active site for oxidation in the reaction. Activation parameters were studied to propose appropriate mechanism for the reaction.