Niyoti Shenoy

Direct determination of uranium in seawater by laser fluorimetry

A method for estimation of uranium in seawater by using steady state laser flourimetry is described. Uranium present in seawater, in concentration of approximately 3 ng ml(-1) was estimated without prior separation of matrix. Quenching effect of major ions (Cl(-), Na(+), SO(4)(-), Mg(+), Ca(+), K(+), HCO(3)(-), Br(-)) present in seawater on fluorescence intensity of uranium was studied. The concentration of phosphoric acid required for maximum enhancement of fluorescence intensity was optimized and was found to be 5%. Similarly the volume of concentrated nitric acid required to eliminate the quenching effect of chloride and bromide completely from 5 ml of seawater were optimized and was found to be 3 ml. A simple equation was derived using steady state fluorescence correction method and was used for calculation of uranium concentration in seawater samples. The method has a precesion of 1% (1s, n=3). The values obtained from laser fluorimetry were validated by analyzing the same samples by linear sweep adsorptive stripping voltametry (LSASV) of the uranium-chloranilic acid (2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone) complex. Both the values are well in agreement.

Removal and recovery of cobalt from aqueous solutions by adsorption using low cost lignocellulosic biomass—coir pith

The applicability of low-cost lignocellulosic biosorbent-coir pith, for removal of cobalt (II) from aqueous solutions using batch adsorption studies has been explored herein. Adsorption characteristics of coir pith were investigated systematically by varying the experimental parameters such as, solution pH, initial metal ion concentration, contact time, adsorbent dose and temperature. The studies revealed that optimum adsorption of cobalt onto coir pith occurred in the pH range of 4.0 – 7.0. Sorption kinetics of cobalt was found to be quite rapid under ambient conditions and the process followed second-order kinetics. The experimental data have been analyzed using non-linearized forms of Langmuir, Freundlich and Redlich–Peterson adsorption isotherms for mathematical description of the process. Desorption studies showed that the quantitative recovery of Co (II) from the spent coir pith was achieved by using 0.5 N HCl. The suitability of this adsorbent for real situation has been observed, when complete removal of cobalt from nuclear power plant coolant water was obtained. The present studies successfully demonstrated the use of coir pith as an efficient adsorbent material for removal of cobalt from aqueous solutions.

Application of Ion Chromatography for the Determination of Nitrate in Process Streams of Thermal Denitration Plant

A simple, accurate, and rapid analytical methodology for the determination of nitrate content in process streams of thermal denitration plant has been developed. The nitrate content in these process streams varies over a wide range of concentration (0.1–150 g L−1). Quantitative determination of nitrate was accomplished by anion exchange chromatography with conductometric detection in suppressed mode. The method requires a simple sample dilution step. A Metrosep A supp 3 analytical column connected in series with a Metrosep RP guard column was used for nitrate separation. A solution containing a mixture of 1.8 mM Na2CO3 and 1.7 mM NaHCO3 was used as eluent. The limit of detection for the determination of nitrate is 0.02 µg mL−1 and the relative standard deviation was 5% for the overall method. No interference was observed from either the chloride or closely eluting “system peak” in the determination of nitrate. The method was validated using an ion selective electrode based determination. The method has a high throughput and 6 samples were analyzed per hour to provide the data on the process parameters. No interference was observed from the other anionic impurities, namely chloride and sulphate. In the case of process streams from thermal denitration of Zr raffinate the method requires a sample pretreatment for the removal of large excess of zirconium from the sample matrix. Onguard-H cartridges were found most suitable for this purpose. The concentration of different anions could be measured simultaneously.