Adsorption of dyes from aqueous solutions on nanoporous carbon materials obtained from polymeric precursors

Adsorption of orange II, methyl orange and methylene blue from aqueous solutions on three carbon materials was studied. The first material for studies was the microporous activated carbon obtained from sulfonated styrene-divinylbenzene resin (AC-SDVB), the second - ordered mesoporous carbon obtained from phenol-formaldehyde resin (OMC-PF) and the third - commercial micro-mesoporous activated carbon from Chemviron Carbon (AC-F400). Adsorption isotherms of the above-mentioned dyes on the carbon materials were studied under laboratory conditions at 25 degrees C. The experimental data was described using the well-known Langmuir, Freundlich and Langmuir-Freundlich adsorption isotherm equations. On the basis of the correlation coefficient (R-2) value, it was demonstrated that the Langmuir equation best described this data. The maximum adsorbed amounts for the three dyes were determined. The highest value was obtained for AC-SDVB: 625 mg/g for orange II and about 500 mg/g for methyl orange and methylene blue. These values were approximately five times higher than the maximum adsorption values for individual dyes on OMC-PF and AC-F400 (maximum adsorption values were about 100 mg/g). The difference in the effectiveness of dye adsorption on the carbon materials tested was the result of a much more developed porous structure of carbon AC-SDVB, compared to other two carbons. The specific surface area of AC-SDVB was 2480 m(2)/g, 660 m(2)/g for OMC-PF and 1260 m(2)/g for AC-F400. In addition, the values of standard characteristic numbers for activated carbons, methylene number and iodine number, were also evaluated. The highest value of both the methylene number, equal to 30 cm(3), and the iodine number of 1900mg/g were obtained for AC-SDVB. In conclusion, some of the porous carbon materials obtained from polymers, characterized by excellent structural parameters, are particularly efficient in adsorption of dyes from aqueous solutions.