Adsorption of indigo carmine and methylene blue dye: Taguchi's design of experiment to optimize removal efficiency

In the present study, Taguchi's experimental methodology has been applied to find optimum level (value) of adsorption parameters (factors) for the removal of indigo carmine dye (ICD) and methylene blue dye (MBD) using activated carbon derived from Acacia Nilotica sawdust (ACSA). The effect of significant adsorption parameters, viz. adsorbent dose (m), initial concentration (C-0), temperature (T) and contact time (t), on the adsorption capacity (q(t)) of ACSA for each dye has been discussed. Average values and S/N ratio for each parameter at three different levels have been estimated using L-9 orthogonal array (OA). Analysis of variance (ANOVA) has been used to identify the significant parameters and the most favourable optimal conditions for both raw data and S/N data. The study revealed that, for ICD, initial dye concentration is found to be the most significant parameter with 55.8% contribution followed by ACSA dose, temperature and contact time with 35.7%, 5% and 3.4% contribution, respectively. For MBD, the ACSA dose (m) is found to be the most significant parameter with 46.4% contribution followed by initial dye concentration, temperature and contact time with 44%, 5.3% and 4.4% contribution, respectively. The contact time (t) is found to be the least significant parameter in the overall sorption process for both ICD and MBD. The optimized levels of parameters for both dyes are found to be A(1), B-3, C-3 and D-3. The predicted and average confirmatory values of total dye adsorbed (q(t)) on ACSA at optimized levels were found to be 31.02 and 31.01mg/g, respectively, for ICD and 57.35 and 57.36mg/g, respectively, for MBD. The percentage removal of ICD and MBD at optimized levels was found to be 77.5% and 95.4%, respectively.