A. Sivashanmugam

Performance evaluation of low cost adsorbents in reduction of COD in sugar industrial effluent

Studies on reduction of chemical oxygen demand (COD) in effluent from sugar industry have been carried out by employing different absorbents optimizing various parameters, such as initial concentration of adsorbate, pH, adsorbent dosage and contact time. Experimental studies were carried out in batches using metakaolin, tamarind nut carbon and dates nut carbon as adsorbents by keeping initial adsorbent dosage at 1 g l(-1), agitation time over a range of 30-240 min, adsorbent dosage at 100-800 mg l(-1) by varying the pH range from 4 to 10. Characterization of there adsorbents were done using techniques such as Fourier transforms infra red spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM). The experimental adsorption data fitted well to Langmuir and Freundlich adsorption isotherms. The isotherms of the adsorbents indicate appreciable adsorption capacity. Higher COD removal was observed at neutral pH conditions. Studies reveal that maximum reduction efficiency of COD takes place using metakaolin as an absorbent at a dosage of 500 mg l(-1) in a contact time of 180 min at pH 7 and it could be used as an efficient absorbent for treating sugar industrial effluent.

Glycine-Assisted Sol-Gel Combustion Synthesis and Characterization of Aluminum-Doped LiNiVO4 for Use in Lithium-Ion Batteries

Phase-pure inverse spinel LiNiVO 4 and LiAl x Ni 1-x VO 4 have been synthesized with good surface morphology by a sol-gel method using glycine as a chelating agent. The product was characterized by thermogravimetric and differential thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and galvanostatic cycling studies. Surface morphology examinations of the undoped LiNiVO 4 particles showed micrometer-sized, cube-shaped grains, while that of aluminum-doped particles showed uniform spherical particles. As compared to the solid-state synthesis route, the sol-gel combustion process greatly reduces the temperature (250°C) for preparing LiNiVO 4 and LiAl x Ni 1-x VO 4 . Subsequent calcination between 650 and 850°C significantly enhances the crystallinity of the synthesized LiNiVO 4 and LiAl x Ni 1-x VO 4 powder. The discharge capacity and cycling performance of the LiAl 0.1 Ni 0.99 VO 4 was found to be superior at a calcination temperature of 250°C.

Electrochemical Behavior of LiM0.25Ni0.25Mn1.5O4 as 5 V Cathode Materials for Lithium Rechargeable Batteries

Glycine-assisted sol-gel-synthesized multiple-doped spinels, LiM 0.25 Ni 0.25 Mn 1.5 O 4 (M = Cr, Fe, and Co) have been studied as 5 V cathode materials. The sol-gel technique provides homogeneity, high purity, lower processing temperature, controlled particle size, and morphology. The synthesized samples were subjected to physical characterization studies, viz., thermogravimetric and differential thermal analysis, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical charge-discharge studies. Galvanostatic charge-discharge studies of the samples reveal that LiFe 0.25 Ni 0.25 Mn 1.5 0 4 using glycine as a chelating agent delivers a stable capacity of 120 mAh g -1 even after 20 cycles when cycled between 3 and 5 V.

Sol-Gel Synthesis of 5 V LiCu x Mn2 − x O4 as a Cathode Material for Lithium Rechargeable Batteries

Spinel LiCu x Mn 2-x O 4 (0.025 < x ≤ 0.1) has been synthesized using oxalic acid as the chelating agent using a sol-gel method to obtain submicrometer-sized particles, good surface morphology, homogeneity, agglomeration, and high crystallinity involving short heating time. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and thermogravimetric and differential thermal analysis were carried out for the physical characterization of the synthesized powder. The XRD patterns of LiCu x Mn 2-x O 4 show the single-phase spinel product, which is in good agreement with the JCPDS card (35-782). SEM images show that the particles, on the average, are of 50 nm in size and are present as agglomerated clusters at all dopant levels. Electrochemical cycling studies of the compound were carried out between 3 and 5 V to understand the redox behavior of Cu 2+ ions. The charge-discharge cycling studies of spinel material with Cu stoichiometry of x=0.1 calcined at 850°C exhibit an initial discharge capacity of 130 mAh g -1 and stabilized at 120 mAh g -1 .

Synthesis, Characterization, and Electrochemical Properties of LiCr x Ni y Mn2 − x − y O4 Spinels as Cathode Material for 5 V Lithium Battery

Sol-gel assisted spinel LiCrxNiyMn2�xyO4 0 x 0.4 and 0 y 0.4 has been synthesized. The thermal study of the precursor was carried out by thermogravimetric and differential thermal analyses. Furthermore, the material has been subjected to X-ray diffraction, scanning electron microscopy, Fourier transform IR spectroscopy analysis, X-ray photoelectron spectroscopy, cyclic voltammetry studies, and electrochemical charge-discharge studies. The X-ray diffraction of LiCrxNiyMn2�xyO4 matches well with the Joint Committee on Powder Diffraction Standard card no. 35-782, confirming the formation of a single-phase spinel. Charge-discharge studies were carried out between 3 and 5 V to understand the electrochemical behavior of the undoped and doped spinels. LiCr0.25Ni0.25Mn1.5O4 calcined at 850°C possesses a particle size of around 70 nm and exhibits an initial discharge capacity of 105 mAh g�1 stabilizing at 98 mAh g�1 over the investigated 20 cycles. However, maleic acid derived LiCr0.25Ni0.25Mn1.5O4 delivers a stable higher discharge capacity of 115 mAh g�1 over the investigated 20 cycles and is a promising 5 V cathode material. In this present study, LiCrxNiyMn2�xyO4 0 x 0.4 and 0 y 0.4 using glycine or maleic acid as chelating agents has been synthesized by a sol-gel technique. The physical and electro- chemical studies of the synthesized material have been done, and the experimental results are discussed. Experimental Figure 1 shows the flow chart for the synthesis of LiCrxNiyMn2�xyO4 by a sol-gel method using glycine or maleic acid as chelating agents. Stoichiometric amounts of nitrates of lithium, manganese, chromium, and nickel were uniformly mixed and dissolved in triple-distilled water. This solution was continu- ously stirred for some time with mild heating to obtain a homoge- neous solution. The solution was added drop by drop into an aque- ous solution of 3 M glycine o r1Mm aleic acid solution, which is used as chelating agent. The pH of the solution was adjusted be- tween 5 and 7.5 using ammonia solution. The process of stirring and heating was continued until a solid gel was obtained. Furthermore, the gel was initially heated overnight at 110°C. The thermal behav- ior of the gel precursors was characterized by thermogravimetry TG and differential thermal analysis DTA in a PL Thermal Sci- ences Instrument model STA 1500. All experiments were carried out in air at a heating ramp of 20°C/min with typically 50 mg samples. Furthermore, this gel mass was calcined at different temperatures, viz., 250, 400, 600, and 850°C fo r8hi nalumina crucibles. The resulting calcined samples are physically characterized using an X-ray diffractometer XRD, JEOL 8030 with nickel filtered Cu K radiation, a scanning electron microscope SEM, Hitachi S-3000 H, a Fourier transform infrared FTIR spectroscope Perkin-Elmer, model paragon-500 spectrophotometer, and an X-ray photoelectron spectroscope XPS, VG electron spectroscope X-ray source Al K radiation with a scan range of 0-1200 eV binding energy. The col-

Electrochemical Performance of Al ∕ MnO2 Dry Cells: An Alternative to Lechlanche Dry Cells

Aluminum-MnO 2 (Al/MnO 2 ) dry cells of D size configuration are investigated as an alternative to the Lechlanche dry cell, where aluminum is replaced for zinc as the anode, MnO 2 as the cathode, and a mixture of aluminum chloride/ammonium chloride/chromium chloride as the electrolyte. Investigations regarding the optimization of conducting material, electrolyte composition, and electrochemical performance of the cell at different temperature and current drains (100, 200, and 400 mA) are carried out. Internal resistance and storage life of the fabricated aluminum dry cells are also evaluated. The results suggest that Al/MnO 2 dry cells exhibit a superior performance than their Zn counterpart.