ORIGINAL PAPER Uptake of Indosol Dark-blue GL dye from aqueous solution by water hyacinth roots powder: adsorption and desorption study Md. M. R. Khan • M. Z. B. Mukhlish • M. S. I. Mazumder • K. Ferdous • D. M. R. Prasad • Z. Hassan Received: 9 July 2011 / Revised: 23 December 2012 / Accepted: 10 April 2013 / Published online: 14 November 2013 Ó Islamic Azad University (IAU) 2013 Abstract Adsorption characteristics of water hyacinth roots powder for the removal of Indosol Dark-blue GL dye were investigated in batch mode. Operating variables, such as initial solution pH, presence of detergent, adsorbent dosage, initial concentration and contact time, were stud- ied. The results showed that the adsorption of dye increased with increasing the initial concentration and contact time. The adsorption is highly pH dependent and adsorption capacity increased with decrease in pH. Kinetic study revealed that the uptake of Indosol Dark-blue GL was very rapid within the first 15 min and equilibrium time was independent of initial concentration. Batch equilibrium experiments were carried out at different pH and found that equilibrium data fitted well to Langmuir isotherm model. The maximum sorption capacity of the adsorbent was found as 86 mg g -1 at pH 3 which reduced to 64 mg g -1 at pH 5. The presence of detergent reduced the sorption capacity of the adsorbent significantly. Using equilibrium and kinetic data, the forward and backward rate constants were determined from the unified approach model. Desorption study revealed that the dye can be recovered by swing the pH from low to high. Keywords Water hyacinth roots powder  Langmuir model  Unified approach model  Detergent  Indosol Dark-blue GL Introduction Various industries such as textiles, leather, printing, paper and plastics extensively use dyes in order to color their products. Most of the dyes used for industrial purposes are synthetic compounds with complex aromatic molecular structures, which make them resistant to light, heat and oxidizing agents, non-biodegradable and toxic to life, with carcinogenic and mutagenic effects (Noroozi et al. 2007). The presence of very low concentrations of dyes ( \ 1 mg L -1 ) in the effluent is highly visible and is considered undesirable. Bangladesh having around thousands of textile factories mostly situated near big cities produces huge amount of dye containing wastewater which is being drained into the rivers. A recent survey showed that the aquatic environment of the rivers (e.g., Buriganga, Kar- nafully, etc.) is in the worst situation (Mozumder et al. 2008). The best way to keep our surface water healthy is to treat the effluents and make them less hazardous before discharging into water stream. In Bangladesh, only few factories have effective effluent treatment plant. The gov- ernment of this country has therefore decided not to allow any textile factory without proper effluent treatment plant (ETP), which is under implementation stage. Reactive dyes are the most problematic compared to other form of dyes (Vandevivere et al. 1998; Geethakarthi and Phanikumar Md. M. R. Khan (&)  M. Z. B. Mukhlish  M. S. I. Mazumder Department of Chemical Engineering and Polymer Science, Shahjalal University of Science and Technology, Sylhet 3114, Bangladesh e-mail: mrkhancep@yahoo.com K. Ferdous Centre for Environmental Process Engineering, Shahjalal University of Science and Technology, Sylhet 3114, Bangladesh D. M. R. Prasad Faculty of Chemical and Natural Resources Engineering, Universiti Malaysia Pahang, Gambang, 26300 Kuantan, Pahang, Malaysia Z. Hassan Faculty of Chemical Engineering, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia 123 Int. J. Environ. Sci. Technol. (2014) 11:1027–1034 DOI 10.1007/s13762-013-0363-4