The current examination studied the chemical treatment of raw timber sawdust (TS–OH)n by chemical agents (acid and base) used for removing two anionic dyes namely, Thiazole Yellow (TY) and Bright Yellow (BY) from aqueous solutions. To assess the effects of the different conditions including pH, contact time, and temperature on the removal of dyes, Batch experiments were conducted. This results obtained from the adsorption of the two dyes, were found to be endothermic with the second-order rate kinetics, which followed the Langmuir isotherm. The monolayer saturation capacities were 1408.4507 and 140.845 mg g-1for Thiazole Yellow and Bright Yellow; respectively. By increasing the temperature of the operation, the adsorption was positively affected. The positive changes in the entropy (ΔS0) and heat of adsorption (ΔH0); and the negative changes in Gibbs free energy (ΔG0) indicated the feasible and spontaneous adsorption of (TY and BY) on the adsorbent. The results revealed that 1 M aqueous NaCl completely desorbed the anionic dyes from the matrices, and when the chemically modified (TS–OH)n was reused for three repeated cycles, there was just a slight decrease in its applicability. These findings indicated that by chemical treatments, a low value by-product of the timber industry can be modified into a useful adsorbent.
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