Adsorption of anionic wood dyes on KOH-activated carbons from Pinus radiata sawdust

Chemically activated carbons synthesized from pine sawdust were applied efficiently for the elimination of wood dyes from aqueous solutions. Different proportions (1:2 and 1:4) of activating agent (KOH) and activation temperatures (600 and 850 degrees C) were used. Carbon surface morphology was characterized. The effect of pH (2-12), initial adsorbate concentration (5-500 mg L-1), and carbon dosage (0.1-0.5 g L-1) on dye adsorption were studied in batch mode. Langmuir model described well the adsorption equilibrium. The maximum found adsorption capacities were 1221.58, 1673.03, and 240.38 mg g(-1) for blue and red at 500 mg L-1 and black at 100 mg L-1, respectively, using activated carbon at 850 degrees C and 1:4 (ACPS-4-850); at 25 degrees C, adsorbent dose 0.4 g L-1 for blue and black and 0.3 g L-1 for red dye and without change the pH for blue and red and at pH = 2 for black dye. The pseudo-second-order model explained the kinetics of adsorption except for the black dye at 100 mg L-1 using ACPS-4-850 for which it was the pseudo-first-order model. Desorption studies performed with ACPS-4-850 revealed that the adsorption was irreversible by chemical regeneration, whereas for the black dye, regeneration was efficient using H2O2 as desorbing agent.