Characterization of the Supernatant

A representative sample of the supernatant (ST) was obtained after each step of the TSA by hydrothermal technique and centrifugation (at 2000 rpm). The sample was filtered by using Whatman filter paper No. 42 and diluted sufiftciently, in the subsequent step, for analysis [14]. 

The pH and EC of the sample were measured by using a water quality analyzer (Model PE 136, Elico Ltd., India). The results of the pH and EC tests are presented in Tables 5.4, 5.5, 5.6 and 5.7, respectively [14]. 

A clean and filtered sample of the supernatant, ST, was used for determination of concentration of soluble Si and Al, present in the fly ash. 

For this purpose, the inductively coupled plasma-atomic emission spectrometry (ICP-AES) set up (Model 8440, Plasma lab, GBC Scientific Equipment Pvt. Ltd., Australia) was employed. The results of the analyses are presented in Tables 5.8, 5.9, 5.10 and 5.11, respectively. 

Based on reanalysis of ICP-AES data, percentage variation of these elements has been quantified by assigning a parameter, a, defined as per the relationship presented in Eq. 5.1. 

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