Microstructural And EDX Analysis

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3. Results and discussion
3.1. Microstructural and EDX analysis Fig. 1 and 2 show the surface morphology and EDX spectrum of FC and alum, respectively after coagulation/flocculation. The EDX analysis shows the adsorption of CB on FC and alum. As determined by EDX, detailed chemical composition of the dried flocs of FC and alum are presented in Table 1 and show that major elements of FC flocs are N, Fe, O, Cl, and of alum are N, Al, O, K, O, S. The weight % of element N defined the adsorption of CB on FC and alum. The floc of FC contains higher weight % of N as compared to alum, as can see in Table 1.

3.2. Effect of pH In this study, the reduction efficiencies were observed to be optimum at pH 5 for FC coagulant whereas the
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The final pH of the solution was estimated, after the completion of process and it was observed that the final pH of the solution decreased with FC and increased with alum. At optimum pH, the CB removal was 73.13 and 67.19 % with FC and alum, respectively. The corresponding COD removal was 64.13 and 55.68 % with FC and alum, respectively. With FC and alum dosing, the maxima CB and COD removals resulted in the pH range 5–6. Results also showed that percentage reductions decreased with increasing pH (>6) with minimum reduction occurring at pH 8 for both coagulants tested, as can be seen in Fig. 3. When solution pH (7) increases the positive charge of hydrolyzed substances of metal salts decreases, and this reduces the coagulants capability to neutralize the negative charge of dissolved organic matter, and consequently leads to a less removal (Hussain et al., 2014). Hydrolyzed …show more content…
In order to estimate this factor, the settling time for the flocs generated to reach half of the sample height in jar-tests was noted. The outcomes are shown in Fig. 5. This might be due to the charge neutralization, sweep flocculation and patch aggregation (Wei et al., 2016). The coagulant addition significantly affect the settling time. At the initial stage, a fast and steady reduction in height of the flocs-supernatant interface with time was seen for both FC and alum coagulants; this phenomena is called the regime of zone settling. Thereafter, the height of the flocs-supernatant interface reduce slowly with time approaching steady state (transition settling), finally a position called compression settling of slurry is achieved. The increase in flocs size prefers the flocs settling speed and hence diminishes the settling time of the flocs generated. The flocs formed by alum settle faster than the flocs formed by

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