Effect of Dosages of CACs on RR158 Dye Removal

The effect of CAC's (varying from 7.500 to 20.000 g/L) on the RR158 dye removal efficiency of six different initial dye concentrations of 20, 40, 60, 80, 100 and 120 mg/L is presented in Fig. 11 which shows that the removal of RR158 increased with an increase in the adsorbent dosage. However, once almost all RR158 was adsorbed, the contribution of additional CAC's was found to be insignificant. The dye removal increased from 11.75 ± 10.60 to 57.18 ± 10.60% when there was an increase in the adsorbent dosage from 7.5 ± 0.001 to 20 ± 0.001 g/L for dye solution of 20 mg/L, and from 12.18 to 47.11% at constant dye concentration of 40 mg/L. The rapid increase in adsorption with increasing adsorbent dose can be attributed to greater surface area and availability of more adsorption sites. Thus, the increase in colour removal at higher doses of

Dosage And Removal Rate

Adsorbent dosage |g/LJ

Fig. 11 Graph of percentage dye removal with respect to adsorbent dosage. Experimental conditions: room temperature, agitation: 200 rpm o

Adsorbent dosage |g/LJ

Fig. 11 Graph of percentage dye removal with respect to adsorbent dosage. Experimental conditions: room temperature, agitation: 200 rpm adsorbent could be due to the very fast superficial adsorption onto the CAC's surface that produced a lower solute concentration in the solution than when the adsorbent dose was lower (Garg 2008). The adsorption rate increased slowly after the critical dose of 7.500 g/L for dye solution of 60, 100 and 120 mg/L. However, the adsorption efficiency dropped from 20.00 ± 10.60% to 12.48 ± 10.60% when the adsorbent dosage rose from 7.500 ± 0.001 to 12.500 ± 0.001 g/L for the dye solution of 80 mg/L. The drop in the dye removal could basically be due to the sites remaining unsaturated during the adsorption process. The decrease in dye uptake value was due to the splitting effect of flux (concentration gradient) between the adsorbate and the adsorbent.

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