Chemical Physics Laboratory

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.

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.

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.