Sridevi Janardhanam | Central leather research Institute (original) (raw)

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Papers by Sridevi Janardhanam

Lime fleshing waste is one of the major hazardous solid wastes from leather industry. Utilization... more Lime fleshing waste is one of the major hazardous solid wastes from leather industry. Utilization of the waste is one of the appropriate strategies to address the environmental issues and to realize economical returns. A process of preparation of beef extract from limed fleshing waste has been developed. The beef extract prepared is intended for microbial application. According to the process developed, the alkalis present in the fleshing waste were neutralized and removed by washing. Then the fleshing waste was hydrolyzed thermally and the hydrolysate obtained was lyophilized. The prepared product was characterized. The characteristics of the prepared product were compared with those of a widely accepted market product (Hi-Media).

Degradation of recalcitrant phenolic syntan by electro-oxidation was investigated. The kinetics o... more Degradation of recalcitrant phenolic syntan by electro-oxidation was investigated. The kinetics of degradation of phenolic syntan was followed both in terms of TOC and COD measurements. The generation of oxidants such as Cl 2 , HOCl and free radicals of oxychloride in the presence of NaCl electrolyte was also monitored and their role in the oxidation of organics was discussed. The generation of cClO free radicals was ascertained by electron spin resonance (ESR) spectroscopy coupled with the spin trapping technique. The effect of pH, electrolyte concentration and current density on the degradation of phenolic syntan was discussed. Also, the current efficiency (CE) and energy consumption (EC) were estimated. It was observed that the oxidation of phenolic syntan was proportional to the current density and electrolyte concentration. The kinetics of the degradation of phenolic syntan was found to follow first order rate equation with an R 2 value of 0.9966. The intermediate compounds formed during electrooxidation were characterised using AOX, FT-IR and NMR techniques and the degradation pathway proposed. These results clearly suggest the effectiveness of the electrochemical technique for the treatment of wastewater containing a high concentration of phenolic syntan.

Magnesium tetra borate (MTB) doped with rare earths (REs) was prepared by the solid state sinteri... more Magnesium tetra borate (MTB) doped with rare earths (REs) was prepared by the solid state sintering
technique. Among the different RE dopants studied in this phosphor, gadolinium-doped phosphors
resulted in a dosimetric peak at a relatively higher temperature. The thermoluminescence (TL) emission
spectra of RE-doped MTB showed characteristic RE3+ emissions. Electron paramagnetic resonance
measurements were carried out in these phosphors to identify the defect centers formed during gamma
irradiation and to establish a mechanism for the TL process. Signals corresponding to (BO3)2−, O−
v
were seen upon irradiation which vanished on annealing at 250 ◦C, showing the role of these centers in
the TL process. The thermal activation energies calculated based on the decay of these signals matched
well with those calculated on the basis of the usual conventional method showing the validity of the
mechanism of TL.

Lithium tetraborate doped with manganese synthesised by solid-state sintering technique exhibits ... more Lithium tetraborate doped with manganese synthesised by solid-state sintering technique exhibits a dosimetric peak at 2808C.
The high-temperature glow curve results in no fading for three months. The sensitivity of Li2B4O7:Mn is determined to be 0.9
times that of TLD-100. The infrared spectrum of this phosphor indicates the presence of bond vibrations corresponding to BO4
tetrahedral and BO3 triangles. The mechanism for thermoluminescence in this phosphor was proposed based on the thermoluminescence
(TL) emission spectra, kinetic analysis of TL glow curves and electron paramagnetic resonance (EPR) measurements
on non-irradiated and gamma-irradiated phosphors. It was identified that oxygen vacancies and Boron oxygen hole centre
(BOHC) are the electron and hole trap centres for TL in this phosphor. When the phosphor is heated, the electrons are released
from the electron trap and recombine with the trapped holes. The excitation energy during the recombination is transferred to the
nearby Mn21 ions, which emit light at 580 nm.

In the present investigation, an attempt was made to treat the pharmaceutical wastewater (PWW) by... more In the present investigation, an attempt was made to treat the pharmaceutical wastewater (PWW) by
Iron impregnated poly acrylamide (IPA) compound in a fluidized bed reactor as heterogeneous catalyst.
The IPA was characterized by XRD, SEM, EDX, TGA, DSC, fluorescence spectroscopy and diffuse
reflectance spectroscopy (DRS). The experiments were carried out under batch and continuous mode
operations. The quantitative removal of COD, BOD5, NH4
+-N and TKN from the PWW was evaluated. The
oxidation of organics in PWW was confirmed through UV–visible, fluorescence and FT-IR spectroscopy.
In this study, the mechanism of oxidation of the persistent organic pollutants in pharmaceutical
wastewater in terms of the generation of OH radical using IPA was evaluated. The OH radical was
identified by electron paramagnetic resonance (EPR) spectroscopy and with 5,5-dimethyl-1-pyrroline-
N-oxide (DMPO) spin trapping method.

Polycrystalline powder samples of cadmium tetra borate were synthesized by a simple solid state s... more Polycrystalline powder samples of cadmium tetra borate were synthesized by a simple solid state sintering technique and gamma irradiated sample showed a simple Thermoluminescence (TL) glow peak around 460 K. The TL kinetic parameters of gamma irradiated phosphor were determined by initial rise (IR), isothermal decay (ID), peak shape (PS), variable heating rate (VHR) and glow curve de-convolution method. The kinetic parameters such as activation energy (E), frequency factor (s) and order of kinetics (b) were calculated by IR, ID, PS and VHR methods are in the order of $ 1.05 eV, 10 9 -10 12 s À 1 and 1.58, respectively. From the results of TL and PL emission studies carried out on the phosphor revealed that the defect centers related to TL is different from that for PL. EPR measurements were carried out to identify the defect centers formed in cadmium tetra borate phosphor on gamma irradiation. Based on EPR studies the mechanism for TL process in cadmium tetra borate is proposed in this paper