Bio-sorptive Removal of Methyl Orange by Micro-Grooved Chitosan (GCS) Beads: Optimization of Process Variables Using Taguchi L9 Orthogonal Array

Batch biosorption studies of methyl orange (MO) dye removal using newly formed micro-grooved chitosan (GCS) gel beads were synthesized by using NaOH-based gelling solution supplemented with Na2CO3 at different volume ratios (v/v) of NaOH-to-Na2CO3. The newly formed GCS gel beads with the best adsorption capacity corresponding to the volume ratio of NaOH-Na2CO3 were selected as potential biosorbent in subsequent adsorption studies. Taguchi orthogonal array of L9 (3(3)) was adopted to investigate the simultaneous variations of three controlling factors, namely: pH of MO (pH 3, 7, 11), initial concentration of MO (30 ppm, 50 ppm, 90 ppm) and new GCS adsorbent dosage (0.35 g, 0.5 g, 1 g). The dye removal percentage (removal%) was found to be between (30.09 +/- 4.66)% and (98.15 +/- 0.23)%. The average uptake capacity (q(e)) of MO by GCS adsorbent was varied from (1.22 +/- 0.03)mg/g to (9.14 +/- 0.00)mg/g. The highest mean of S/N ratio was selected to obtain maximum adsorption performance. The optimum operating condition for the highest removal% was achieved at pH 3 with 1 g of adsorbent dosage and 30 ppm of MO concentration, whereas the maximum q(e) was identified at pH 3 with adsorbent dose of 0.35 g and 90 ppm of MO concentration. The morphology of GCS gel beads before and after adsorption was analysed using field emission scanning electron microscopy (FESEM). The adsorption results were best fit to two parameter Harkins-Jura isotherm (R-2 = 0.9979). This affirmed that the adsorption of MO dye solution by GCS gel beads was a multilayer adsorption.