Adsorption of a textile dye in aqueous phase using mesoporous activated carbon prepared from Iranian milk vetch

• Iranian milk vetch was used as precursor for activated carbon.
• The adsorption of a textile dye onto as-prepared activated carbon was evaluated.
• The isotherm data were well described by the Langmuir isotherm model.
• The process followed pseudo-second order kinetic model.
• As-prepared activated carbon had more adsorption capacity than that of commercial activated carbon.

The aim of the present study was to prepare activated carbon from milk vetch and utilize as-prepared activated carbon for sequestering Acid orange 7 (AO7) as an azo dye from batch flow mode experimental reactors. The result of SEM analysis confirmed porous structure for the activated carbon in which the major portion of the pore diameter size distribution was lower than 100 nm with frequency of 67%. As results, the adsorption of AO7 was decreased from 45.90 to 33.35 mg/g with increasing initial pH from 3 to 11, respectively. Increasing adsorbent dosage from 0.5 to 1.5 g/L resulted in increasing the decolorization efficiency (%) from 59.96 to 89.40%, respectively. The experimental data were best represented by the pseudo-second order kinetic model (R2 = 0.9865) regarding intraparticle diffusion rate. Among studied isotherm models, the adsorption of AO7 onto activated carbon obeyed Langmuir model (R2 = 0.9907) with a maximum adsorption capacity of about 99 mg/g. The obtained value for mean free energy (0.25 kJ/mol) indicated that the adsorption of AO7 is physical in nature. Comparatively, as-prepared activated carbon derived from milk vetch had more adsorption capacity than that of commercial activated carbon for the adsorption of AO7 at the same operational conditions.