Yogesh Chandra Sharma

Nano‐adsorbents for the removal of metallic pollutants from water and wastewater

Of the variety of adsorbents available for the removal of heavy and toxic metals, activated carbon has been the most popular. A number of minerals, clays and waste materials have been regularly used for the removal of metallic pollutants from water and industrial effluents. Recently there has been emphasis on the application of nanoparticles and nanostructured materials as efficient and viable alternatives to activated carbon. Carbon nanotubes also have been proved effective alternatives for the removal of metallic pollutants from aqueous solutions. Because of their importance from an environmental viewpoint, special emphasis has been given to the removal of the metals Cr, Cd, Hg, Zn, As, and Cu. Separation of the used nanoparticles from aqueous solutions and the health aspects of the separated nanoparticles have also been discussed. A significant number of the latest articles have been critically scanned for the present review to give a vivid picture of these exotic materials for water remediation.

Kinetics studies of synthesis of biodiesel from waste frying oil using a heterogeneous catalyst derived from snail shell

Waste frying oil was used to produce biodiesel using calcined snail shell as a heterogeneous base catalyst. Trans esterification reactions were carried out and the yield and conversion of the product were optimized by varying the methanol to oil molar ratio, catalyst amount, reaction temperature, and time. A biodiesel conversion of 99.58% was obtained with a yield of 87.28%. The reaction followed first order kinetics. The activation energy (E(A)) was 79kJ/mol and the frequency factor (A) was 2.98×10(10)min(-1). The fuel properties of the biodiesel were measured according to ASTM D 6751 and found to be within the specifications. Snail shell is a novel source for the production of heterogeneous base catalyst that can be successfully utilized for synthesis of biodiesel of high purity.

Removal of ni(II) from aqueous solutions by sorption

Adsorption of Ni(II) from its aqueous solutions on China clay, a cheap clay mineral, has been found quite favourable; a maximum removal of 75.3% was obtained at 50 mg L‐1 metal concentration and a pH of 6.5 at 30°C. Dynamic modelling of the nickel uptake has been worked out and found to be of the first order. The rate constant was found to be 9.21 x 10‐1 min‐1 under the above optimum conditions of the experiment. Coefficients of the mass transfer and intraparticle diffusion were also evaluated and found to be 2.8 x 10‐2 cm s‐1 and 4.50 x 10‐2 cm2 s‐1 respectively. Langmuirs model was used for the equilibrium modelling and the constants were calculated at 30, 40 and 50°C. Thermodynamic study at different temperatures was undertaken and the values of change in the standard free energy (?G°), enthalpy (?H°) and entropy (?S°) are reported. Low temperature and high pH favour the removal of nickel (II) by adsorption on China clay.

High Yield and Conversion of Biodiesel from a Nonedible Feedstock (Pongamia pinnata)

An efficient approach has been adopted for the synthesis of biodiesel developed from karanja, a nonedible oil feedstock. A two-step reaction was followed for synthesis of biodiesel. Karanja oil possessing a high free fatty acid content was esterified with sulfuric acid, and the product obtained was further converted to fatty acid alkyl esters (biodiesel) by transesterification reactions. A moderate molar ratio of 6:1 (methanol/oil) was efficient for acid esterification with 1.5% v/v H2SO4 and 1 h of reaction time at 60+/-0.5 degrees C, which resulted in reduction of FFA from 19.88 to 1.86 mg of KOH/g. During alkaline transesterification, 8:1 molar ratio (methanol/oil), 0.8 wt % sodium hydroxide (NaOH), 1.0 wt % sodium methoxide (CH3ONa), or 1.0 wt % potassium hydroxide (KOH) as catalyst at 60+/-0.5 degrees C gave optimized yield (90-95%) and high conversion (96-100%). Optimum times for alkaline transesterification were 45 min for CH3ONa and 1 h for NaOH and KOH. Conversion of karanja oil feedstock to its respective fatty acid methyl esters was identified on a gas chromatograph-mass spectrometer and determined by 1H nuclear magnetic resonance and gas chromatography. The fuel properties, such as cetane number of the methyl ester synthesized, were studied and found to be within the limits and specification of ASTM D 6751 and EN 14112 except for oxidation stability.

Application of a new adsorbent for fluoride removal from aqueous solutions

Hydrous bismuth oxides (HBOs) have been investigated as a possible adsorbent for fluoride removal from water. Apart from bismuth trioxide (Bi2O3) compound, three additional HBOs, named as HBO1, HBO2, and HBO3 were synthesized in the laboratory and examined for their relative potentials for fluoride removal from aqueous solutions. HBO1 was observed to have highest fluoride removal at 10mg/L initial concentration in aqueous environment. Among competitive anions, sulfate and chloride affect the fluoride removal by HBO1 more adversely than bicarbonate. Characterization of HBOs using X-ray diffraction (XRD) pattern analyses indicated crystalline structures, and the broad chemical composition of materials showed successive increase of Bi(OH)3 from HBO1 to HBO3, with decrease of BiOCl in the same order. Fourier Transform Infrared (FTIR) spectroscopy analyses indicated presence of Bi-O bond and successively increasing number of peaks corresponding to OH ion from HBO1 to HBO3. Scanning Electron Microscopic (SEM) images of HBOs show rough and porous structure of the materials. Presence of higher proportion of chloride compound in HBO1 with respect to others appears to be the factor responsible for its better performance in fluoride removal from aqueous solutions.

Rapid scavenging of methylene blue dye from a liquid phase by adsorption on alumina nanoparticles

The adsorption behavior of methylene blue on as-synthesized alumina nanoparticles has been investigated. The adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), TG/DTA/DTG, X-ray diffractrometry and scanning electron microscopy. N2 adsorption–desorption measurements were carried out to analyze the porous structure and surface area of the adsorbent and results revealed that the adsorbent is mesoporous with a specific surface area of 76 m2 g−1. Batch experiments indicated that solution pH, initial dye concentration, contact time, temperature and the presence of ions had prominent impact on the dye removal process. The sorption kinetic data were found to be in accordance with pseudo-second order kinetics. The mechanistic interaction of the adsorbate–adsorbent system was also interpreted with the help of Weber–Morris model and the Boyd model and it was found that the adsorption process is controlled by a film diffusion mechanism. The investigation of adsorption isotherms suggested that the data fitted Langmuir isotherm model. The values the thermodynamic parameters for the process of removal were determined and the negative values change in free energy, ΔG0, indicated the spontaneous nature of the sorption process. A high desorption efficiency of 90.11% indicated a possible regeneration of the adsorbent. The adsorbent displayed almost the same adsorption capacity even after three cycles of regeneration bringing down the cost of treatment.

Magnetic Fe3O4 nanoparticles for adsorptive removal of acid dye (new coccine) from aqueous solutions

The ability of magnetic Fe₃O₄ nanoparticles (MFN) to remove new coccine (NC), an acidic dye, from aqueous solutions was studied. Parameters including ionic strength, pH, and temperature were evaluated. MFN, prepared by precipitation method, exhibits an average particle size of 12.5 nm, specific surface area of 85.5 m²/g, and pH(zpc) of 5.9. Results of kinetic adsorption experiments indicated that the pseudo-second-order rate of adsorption increased with increasing initial NC concentration. Findings also revealed that the equilibrium data could be fitted into Langmuir adsorption isotherm. The adsorption is favored at low pH, high temperature, and low ionic strength, whereupon a maximum adsorption capacity of 1.11 x 10⁻⁴ mol/g was determined for NC. Thermodynamic functions indicated that the adsorption process is spontaneous and exothermic in nature. Tests of regeneration showed that after 5 regeneration cycles the adsorption capacity of NC decreased to 35% to its original capacity.

Heavy metal pollution of river Ganga in Mirzapur, India

A study on the heavy metal pollution of River Ganga in the Mirzapur region, India has revealed that the river is polluted. The samples were collected from both the confluence of sewers and the river and from midstream points. The river is the dumping ground for domestic, municipal and industrial effluents. All the samples were analysed for certain physiochemical parameters i.e. temperature, pH, chloride content, alkalinity, dissolved oxygen and chemical oxygen demand. On analysis, the concentrations of most of the heavy metal ions were found to be above the prescribed limits for potable waters in the samples collected from confluence points. Cadmium and cobalt were in the range 13.37–32.73 μg/L and 10.50–26.77 μg/L respectively. Copper, iron and manganese were found in the range of 38.0–157.80 μg/L, 19.75–72.77 /ug/L and 34.25–105.55 yug/L respectively. Nickel was recorded to be in the range 67.25–176.13 mg/L while lead and zinc were in the range of 34.25–185.75 μg/L and 94.25–423.75 μg/L. Concentrations ...

Synthesis and application of polypyrrole coated tenorite nanoparticles (PPy@TN) for the removal of the anionic food dye ‘tartrazine’ and divalent metallic ions viz. Pb( ii ), Cd( ii ), Zn( ii ), Co( ii ), Mn( ii ) from synthetic wastewater

The present study deals with the synthesis of polypyrrole coated tenorite nanoparticles. The synthesized nanoparticles were characterized by XRD, TEM, SEM and EDS. TEM images showed the formation of nanoparticles with 26–30 nm diameter. The BET surface area of the nanoparticles was determined to be 425 m2 g−1 while the pore diameter of the nanoparticles was found to be 3.57 nm which showed the formation of mesoporous nanoparticles. The pHzpc of the nanoparticles was determined to be 4.4. The removal efficiency of the synthesized nanoparticles for an anionic food dye ‘tartrazine’ was investigated. Decreased removal was observed, when the dye concentration was increased from 100 to 200 mg L−1. It was observed that an acidic medium was favorable for tartrazine removal. A thermodynamic study suggested the endothermic nature of tartrazine adsorption. The value of Ea for the present system was found to be 26.97 kJ mol−1. The best suitable kinetic model was well explained by the pseudo second order model. Langmuir adsorption capacity was measured to be 42.50 mg g−1. Exhausted (dye loaded) nanoparticles were used as an efficient adsorbent for the removal of divalent metallic ions viz. Pb(II), Cd(II), Co(II), Mn(II), Zn(II) and were found to be efficient for the removal of metallic species from a single solute system as well as a multi-solute system. This study reveals that polypyrrole coated tenorite nanoparticles are very efficient for dye removal and the dye loaded exhausted adsorbent is equally good for metal removal because tartrazine loading on nanoparticles makes the surface suitable for metal interaction. Thus, the synthesized nanoparticles prove to be a good candidate for the treatment of dye and metal bearing wastewater.

Kinetic and equilibrium modeling for removal of nitrate from aqueous solutions and drinking water by a potential adsorbent, hydrous bismuth oxide

The kinetic, equilibrium modeling and adsorption characteristics of hydrous bismuth oxides (HBOs) have been investigated for the removal of nitrate from aqueous solutions. The three HBO samples, designated as HBO1, HBO2 and HBO3 were synthesized by a controlled precipitation method. Among three HBO samples, HBO3 accounts for a maximum nitrate uptake of 0.22 mg N g−1 with an initial nitrate concentration of 14 mg N L−1, therefore this was selected for detailed studies. HBO3 was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive spectrometry. The adsorption characteristics and process variables were investigated by examining different parameters such as pH, contact time, initial nitrate concentration and temperature. Solution pH remarkably influences the nitrate sorption process as the sorption capacity was found to increase from 0.056 to 0.22 mg N g−1 with the increase of pH from 2.0 to 7.0. The sorption capacity was also found to increase with increasing concentration and temperature, while the presence of competing anions such as Cl−, HCO3− and SO42− impeded the nitrate sorption capacity. The sorption kinetic data were found to be consistent with a pseudo-first-order kinetic model. The equilibrium data agree well with Freundlich model and the highest monolayer adsorption capacity of HBO3 for removal of nitrate ions was found to be 0.97 mg N g−1 at 313 K. An investigation of the thermodynamic parameters indicated the spontaneous and endothermic nature of the sorption process. In a nutshell, HBO3 shows significant potential for removal of nitrate ions from aqueous solution as well as drinking water.