New polyacrylonitrile (PAN)-based porous carbons for the removal of industrial wood dyes from aqueous solutions

Synthetic dyes degradation is a difficult task due to their complex aromatic structure, although its elimination by adsorption is effective. The aim of this research is to produce porous carbons derived from polyacrylonitrile (PAN) as wood dyes adsorbents. PAN is a nitrogen-rich precursor transformed at high temperature into highly porous carbonaceous structure with uniform and size-tunable pores useful for the adsorption of bulky molecules such as dyes. Three types of porous carbons were synthesized: N-doped carbon (P-C), N-doped activated carbon with 4-fold excess of KOH (P-ACT) and N, S-co-doped carbon with sulfur in a 1:1 weight ratio (P-S). Synthesis was performed in two stages: oxidation (280ºC) and carbonization (800ºC). Carbon characterization was performed by different techniques (BET, SEM, EDX, XPS, RAMAN, and pHPZC). Adsorption experiments were conducted on batch mode to study the effect of pH (2, natural and 12), solid/liquid ratio (0.5 and 2 g L-1) and initial concentration (23-27 and 230-285 mg L-1) on the adsorption of a red dye used industrially for preparing dyed wood veneers. Adsorption data were analyzed and well fitted by the pseudo-second-order kinetic model. P-ACT showed the best results of dye removal capacity at all concentrations and pH´s.