Puspalata Rajesh - Academia.edu (original) (raw)

Papers by Puspalata Rajesh

Journal of the Indian Chemical Society

Advances in environmental research, 2012

Trihalomethanes, produced as a result of chlorination of drinking water, are considered a potenti... more Trihalomethanes, produced as a result of chlorination of drinking water, are considered a potential health hazard. The trihalomethane formation potential (THMFP) of a raw water source may indicate the maximum trihalomethanes (THMs) that are likely to be produced when chlorine reacts with natural organic matter (NOM) present in the water. A study was conducted to evaluate the THMFP in seven different drinking water sources in the vicinity of Kalpakkam, a rural township, on the east coast of India. Water from seven stations were analysed for THMFP. THMFP was compared with surrogate parameters such as dissolved organic carbon (DOC), ultraviolet absorbance (UV 254) and bromide. The data showed that THMFP was high in water from open wells as compared to closed bore wells, possibly due to more photosynthetic activity. Proximity to sea, and consequently the levels of bromide, was an important factor that influenced THM formation. THM surrogate parameters showed good correlation with THMFP.

Radiochimica Acta, 2009

Density measurements of plutonium metal and its alloys are performed at Los Alamos National Labor... more Density measurements of plutonium metal and its alloys are performed at Los Alamos National Laboratory (LANL) using a technique based on the Archimedes principle. The goal is to find and characterize a fluid for density determination of large objects made of plutonium to replace the currently used monobromobenzene. Physical and chemical properties must be considered while selecting the fluid. Chemical properties of the fluid must ensure low corrosion rates and good resistance to radiological decomposition. The study was carried on to evaluate the corrosion rates of Pu metal cause by FC-43 and the FC-43 decomposition products of radiolysis. The results of these studies proved favourable for this application. The evaluation of the surface reactions between FC-43 and Pu metal will be conducted in the near future.

IOP Conference Series: Materials Science and Engineering, 2010

• Density measurements of large plutonium objects are performed at LANL based on the Archimedes p... more • Density measurements of large plutonium objects are performed at LANL based on the Archimedes principle • We searched for a replacement of monobromobenzene (CSH5Br) fluid which is currently used in the technique After an evaluation of properties of various fluids Perfluorotributylamine (3M FC-43) was chosen as the best candidate

Radiation Physics and Chemistry, 2008

Experimental measurements of molecular hydrogen including the use of isotopic techniques are comb... more Experimental measurements of molecular hydrogen including the use of isotopic techniques are combined with track model calculations to determine H atom yields in the radiolysis of water. The production of H atoms in the radiolysis of water is relatively small, but is ...

International Journal of Biological Macromolecules, 2022

Supramolecular Chemistry in Corrosion and Biofouling Protection, 2021

Materials Chemistry and Physics, 2016

Environmental Science and Pollution Research, 2015

Chlorine addition as a biocide in seawater results in the formation of chlorination by-products s... more Chlorine addition as a biocide in seawater results in the formation of chlorination by-products such as trihalomethanes (THMs). Removal of THMs is of importance as they are potential mutagenic and carcinogenic agents. In this context, a study was conducted that used ionizing radiation to remove THMs from chlorinated (1, 3, and 5 mg/L) seawater by applying various dosages (0.4-5.0 kGy) of gamma radiation. Bromoform (BF) showed a faster rate of degradation as compared to other halocarbons such as bromodichloromethane (BDCM) and dibromochloromethane (DBCM). In chlorine-dosed seawater, total irradiation dose of 0.4 to 5 kGy caused percentage reduction in the range of 6.9 to 76.7 %, 2.3 to 99.6 %, and 45.7 to 98.3 % for BDCM, DBCM, and BF, respectively. During the irradiation process, pH of the chlorinated seawater decreased with increase in the absorbed dose; however, no change in total organic carbon (TOC) was observed. The results show that gamma dose of 2.5 kGy was adequate for maximum degradation of THM; but for complete mineralization, higher dose would be required.

Corrosion Engineering Science and Technology

Type 304 stainless steel and carbon steel are extensively used as structural materials in the rea... more Type 304 stainless steel and carbon steel are extensively used as structural materials in the reactor coolant systems of nuclear power plants. The corrosion of these structural materials during normal operation and the subsequent neutron activation of their corrosion products leads to the build-up of radiation on the out-of-core surfaces of the coolant systems. The Dilute Chemical Decontamination (DCD) process is one of the methods used to remove the activity that becomes embedded in the oxide layers formed over these structural materials. Permanganate based oxidising reagents are generally used to dissolve chromium from oxide films containing iron, chromium and nickel on the surfaces of Type 304 stainless steel and other chromium-containing alloys. This study has investigated the behaviour of carbon steel in oxidising permanganate based acidic media. The corrosion/decomposition rate varied with temperature. With permanganate concentrations above 1 center dot 5 mM for permanganic ac...

Radiation Physics and Chemistry, 2002

The reactions of e À aq ; H-atoms and some one-electron reducing radicals with 2-aminopyridine (2... more The reactions of e À aq ; H-atoms and some one-electron reducing radicals with 2-aminopyridine (2-AmPy) and 3aminopyridine (3-AmPy) were studied using pulse radiolysis technique. The initial electron adduct of 2-AmPy, was found to react with the parent molecule to give a dimer radical at pH 4.8 and 9 which has entirely different spectrum from the initial adduct. The yield of the dimer radical increased with increasing concentration of the parent compound. The equilibrium constant for dimer formation was found to be 198 and 142 dm 3 mol À1 , respectively, at pH 4.8 and 9. In the case of 3-AmPy however, dimer formation was not observed. H-atoms add to both the compounds giving H-adducts as in the case of pyridine. The radicals derived from alcohols were able to reduce 2-AmPy to give pyridinyl type radical. However, in the case of pyridine and 3-AmPy these radicals were unable to give pyridinyl radical but react at acidic pHs by addition to the pyridine ring giving non-reducing species.

The Journal of Physical Chemistry A, 1998

Pulse radiolysis technique was used to study the reactions of e aq - , H atoms, and other reducin... more Pulse radiolysis technique was used to study the reactions of e aq - , H atoms, and other reducing radicals such as COO - /COOH, (CH 3 ) 2 COH, CH 3 CHOH, and CH 2 OH radicals with 8-hydroxyquinoline (8HQ) at various pH's. e aq - reacts with 8HQ with high rate constants (k 2 = 3 × 10 10 at ...

Research on Chemical Intermediates, 1995

The reactions of primary species of water radiolysis such as e-aq , H ~ and "OH, and some specifi... more The reactions of primary species of water radiolysis such as e-aq , H ~ and "OH, and some specific one electron reductants and oxidants with 2-mercaptobenzimidazole have been studied at various pHs. "OH radical reaction with MBZ at pH 7 gave a transient species having absorption maxima ()~m~x) at 330 and 590 nrn. The transient species (pK a = 3.6) was found to be neutral at this pH and was a mild oxidant. The initial transient species formed by the reaction of MBZ with e~q at pH 7 and with H atom at pH 0 were found to react with the parent molecule to form another transient species which has an absorption spectrum similar to that obtained by "OH radical reaction with kma x at 590 rim. However the reaction is not quantitative. The kinetic, spectral, acidbase and redox properties of the transient species are reported.

Research on Chemical Intermediates, 1997

Rate constants for the reactions of e~q, H and OH radicals with 2-pyridine carboxaldehyde and 2-p... more Rate constants for the reactions of e~q, H and OH radicals with 2-pyridine carboxaldehyde and 2-pyridine methanol have been determined by pulse radiolysis technique. Reactions of reducing radicals such as acetone ketyl radicals and COl" with these compounds were also evaluated at various pHs. The species produced by the reaction of reducing radicals with these solutes was a strong reductant itself. While pyridinyl were produced in the case of 2-pyridine methanol, one-electron reduction of 2-pyridine carboxaldehyde led to the formation of PyCHOH radical. The one-electron reduction potential of PyCHOH radicals was estimated by establishing an equilibrium with MV + radical cations to be-0.6V vs NHE. OH radical reaction with 2-pyridine carboxaldehyde gave an OH adduct, while in the case of 2-pyridine methanol, OH radicals reacted partly by H-abstraction from the-CH2OH group. SO4" radical reaction with 2-pyridine carboxaldehyde produced a species which was reducing in nature. The rate constants for the reaction of C-,q and OH radicals are compared with similar values obtained in the case of other 2-pyridine derivatives to see if there is any electron-inductive effect.

Research on Chemical Intermediates, 2000

The reactions of e-aq, H-atoms, OH radicals and some one electron oxidants and reductants were st... more The reactions of e-aq, H-atoms, OH radicals and some one electron oxidants and reductants were studied with dithio-oxamide (DTO) in aqueous solutions using pulse radiolysis technique. The transient species formed by the reaction of e-aq with DTO at pH 6.8 has an absorption band with λmax at 380 nm and is reducing in nature. H-atom reaction with DTO at pH 6.8 also produced the same transient species. The semi-reduced species was found to be neutral indicating that the electron adduct gets protonated quickly. However at pH 1, the species produced by H-atom reaction had a different spectrum with λmax at 360 and 520 nm. Reaction of acetone ketyl radicals and CO2 radicals with DTO at pH 6.8 gave transient spectra which were identical to that obtained by eaq reaction. However at pH 1, the spectrum obtained by the reaction of acetone ketyl radicals with DTO was similar to that obtained by H-atom reaction at that pH. The transient species formed by OH radical reaction with DTO in the pH range 1-9.2 also has two absorption maxima at 360 and 520 nm. This spectrum was identical with the spectrum obtained by H-atom reaction at pH 1. This means that all these radicals viz. OH, H-atom and (CH3)2COH radicals react with DTO at pH 1 by H-abstraction mechanism. The transient species produced was found to be sensitive to the presence of oxygen. One-electron oxidizing radicals such as Br2-and SO4 radicals reacted with DTO at neutral pH to give the same species as produced by OH radical reaction having absorption maxima at 360 to 520 nm. At acidic pHs, only Br2 and Cl2 radicals were able to oxidize DTO to give the same species as produced by OH radical reaction. The semioxidized species is a resonance stabilized species with the electron delocalized over theN -C-S bond. This species was found to be neutral and non-oxidizing in nature.

Research on Chemical Intermediates, 2001

Reactions of 1-naphthylamine-1-sulphonic acid (NASA) with hydroxyl radicals and oneelectron oxida... more Reactions of 1-naphthylamine-1-sulphonic acid (NASA) with hydroxyl radicals and oneelectron oxidants such as N 3 , Br ¡ 2 and Cl ¡ 2 radicals have been studied at various pHs using pulse radiolysis technique. Rate constants for the reaction of N 3 and Br ¡. 2 radicals with NASA at neutral pH were found to be 5 £ 10 9 and 4 £ 10 8 dm 3 mol ¡1 s ¡1 respectively. These reactions led to the formation of a cation radical (semi-oxidized species). OH radical reaction with NASA (k D 7:2 £ 10 9 dm 3 mol ¡1 s ¡1) at neutral pH gave a mixture of species, namely, a semi-oxidized species as well as an adduct species. Cl ¡. 2 radicals reacted with NASA rather slowly (k D 7 £ 10 7 dm 3 mol ¡1 s ¡1) at pH 1 to give the semioxidised species. However, even at pH 1, OH radical reaction with NASA gave a mixture containing semi-oxidized as well as an adduct species. The OH-adduct species having¸m ax at 340 nm decays at acidic pHs to give semi-oxidized species having¸m ax at 370 nm. Electron adduct of NASA was found to be a strong reducing radical.

Research on Chemical Intermediates, 2008

Reactions of 2-and 3-nitroanilines (2-and 3-NA) with e − aq , H-atoms and one-electron reductants... more Reactions of 2-and 3-nitroanilines (2-and 3-NA) with e − aq , H-atoms and one-electron reductants have been studied using pulse radiolysis in aqueous solutions. Reactions of e − aq were found to be quite fast with both 2-NA and 3-NA resulting in their corresponding semi-reduced species which are reducing in nature. Reduction potentials for 2-NA/2-NA •− have been estimated to be approx. −0.56 V vs. NHE and that for 3-NA/3-NA •− was found to be between −0.185 V and −0.45 V vs. NHE. Semi-reduced 2-NA has main absorption peak at 300 nm with a shoulder in the 350 nm region and a broad weak band in the 470-500 nm region, whereas semi-reduced 3-NA possesses an absorption peak at 520 nm. Reducing radicals such as (CH 3) 2 C • OH and CO •− 2 reacted with 2-NA, producing semi-reduced species, whereas reactions of these radicals with 3-NA produced their corresponding radical-adduct species.