First-ever study on the removal of Direct Red 13 (DR13), a bis azo dye, extensively used in textile industry from aqueous media using inexpensive nutraceutical industrial turmeric root spent (NITRS) as a biosorbent is reported. The effects of various factors like initial dye concentration, adsorbent dosage and as also particle size, pH and temperature of media were studied. The experimental data collected under equilibrium conditions were analysed by two-parameter isotherm models of Langmuir, Freundlich and Tempkin. The pseudo-first order and pseudo-second order models were applied in adsorption kinetic studies. Kinetic data fitted well to pseudo-first order model. SEM images of NITRS depict high fibrous matrix with hierarchical porous structure. By FTIR analysis of the spent indicated the presence of cellulosic and ligno-cellulosic materials which impart hydrophilic and hydrophobic properties. Thecentral composite experimental design (CCD) and the analysis of variance (ANOVA) indicated maximum DR13 adsorption of23 mg/l by NITRS. The ANOVA also indicated the influence of each parameter and their combinations on the final adsorption capacity of the system. The investigation indicated that NITRS can be a cost-effective and a natural biosorbent for the remediation of toxic DR13 dye
