Study on the adsorbing characteristics of expanded graphite for organic dyes

Author(s): Xiu-Yan Pang, Pu Lv, Yong-Qiang Feng, Xin-Wei Liu

The adsorbing characteristics of expanded graphite for dyes in single component solution have been investigated. Five reference sorbates were basic fuchsine with tritane structure, auramine lake yellow O with biphenyl structure and acid brilliant red 3B, oxamine blue GN(B) ,methyl orange all with azobenzene structure. Expanded graphites were characterized by expanded volume, specific surface area and pore cubage. Sorption isotherm, Langmuir constants and free energy change (G°) were detected and calculated, respectively. Influence of pH on absorbency and adsorbance, and impact of NaCl, NaSO4, NaNO3 on adsorbance were investigated. It was demonstrated that adsorption of dye on expanded graphite was a spontaneous process. Both dyes’ molecular weight and molecular structure affected sorption type and saturation adsorbance. Linear relationship was obtained between sorption capacity and specific surface area. Expanded graphite kept a stronger sorption for dyes with weak polarity than that with strong polarity. The presence of salts and the proper adjustment of pH would improve the sorption capacity. Contrastive adsorption experiment to sewage from woolen mill testified expanded graphite possessed a higher decolor rate to dyes than active carbon.

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