Application of wood sawdust modified with cationic surfactants for efficient removal of acidic dyes from aqueous solutions: Kinetic and thermodynamic studies

Reza Ansari, Babak Seyghali


In this paper, application of sawdust prepared from Narra wood (SD) modified with cationic surfactant of cetyltrimethylammonium bromide (SD/CTAB) was used for removal of two typical acid dyes commercially named as Acid Green 25 (AG25) and Acid Red 14 (AR14) from aqueous solutions. The effects of experimental variables, such as pH, initial dye concentration, adsorbent dose, contact time and temperature were investigated in order to find out the optimized conditions for removal of selected test dyes. Langmuir and Freundlich Isotherms were used to analyse the experimental adsorption data. Pseudo- first and second order models suggested by Lagergren, Ho & McKay were used for kinetic study. The van 't Hoff equation employed for obtaining of thermodynamic parameters. It was found that upon simple treatment of sawdust with a cationic surfactant, the adsorption capacity of sawdust for uptake of anionic dyes is improved considerably. The monolayer maximum adsorption capacity of SD/CTAB toward AG25 and AR14 dyes calculated using Langmuir isotherm model was 17.5 and 18.9 mg g−1 at 298 K, respectively. Based on kinetics and thermodynamic studies, it was found that adsorption process using SD/CTAB follows pseudo second-order rate equation and the adsorption investigated system is spontaneous and endothermic in nature. Exhausted adsorbent can also be regenerated for reuse with high performance. It was found that via simple treatment of agricultural wastes such as wood sawdust with cationic surfactants it is possible to improve the sorption capacity of sawdust for removal of anionic dyes from aqueous wastes considerably.

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