Analysis of coal ash samples from thermal power plants of India for their gallium content using NAA and EDXRF techniques.

Coal fly ash (CFA) is an important secondary source for the recovery of gallium (Ga) which has a high potential for its wide applications in many strategic fields such as cellular communications and direct broadcast satellite. Various coal fly and bottom ash samples obtained from thermal power plants located in different parts of India were investigated for their gallium content using NAA and EDXRF techniques. The concentration of gallium in NIST SRM 1633b CFA is not available in NIST certificate and hence was established using k based IM-NAA method along with the other certified elements like As, Ce, Co, Eu, Fe, K etc.

Performance of various mathematical functions for the in-situ relative detector efficiency towards its applicability for k IM-NAA.

The in-situ relative detection efficiency strongly influences the characteristics of the k-based internal monostandard neutron activation analysis (IM-NAA). In the present work, various mathematical functions were explored for the establishment of in-situ relative detector efficiency calibration and compared their performance based on the reduced chi-square (χ) values. Among the various mathematical functions, the polynomial logarithm with 6th order was found to be associated with the minimum mean standard deviation for the experimental data and the lowest value of reduced χ after carrying out multiple iterations using Nelder-Mead algorithm.