Adsorptive removal of direct textile dyes by low cost agricultural waste: Application of factorial design analysis

This research work involved the use of factorial experimental design technique to investigate the biosorption of Everdirect Orange-3GL and Direct Blue-67 dyes from aqueous solution on rice husk. A 53 full factorial experimental design was employed to study the effect of three factors: initial dye concentration, biosorbent dose and pH at five levels. The efficiency of rice husk for dyes removal has been determined after 3 h of treatment at 30 °C using suitable size of biosorbent (0.255 mm). Main and interaction effects were analyzed by analysis of variance (ANOVA), F-test and P-values to define most important process variables affecting the dyes biosorption. The statistical model was best fitted with high coefficient of determination (R2 = 0.999) for Everdirect Orange-3GL and Direct Blue-67 dyes. The most significant variable was thus found to be pH for both the dyes. FT-IR studies showed that hydroxyl functional groups participated in the biosorption of dyes.