Adsorption of acid dyes by bamboo derived activated carbon

Bamboo, indigenous to Hong Kong and China, is widely used as scaffolding in construction and building projects. However, over 50,000 tonnes of bamboo scaffolding waste is disposed as landfill waste each year. Nevertheless, these wastes can be used as raw materials for the production of a range of high value added activated carbons. The bamboo cane can be heated (charred) at a high temperature in the presence of selected activation chemicals to produce activated carbons for various applications e.g. adsorbents, catalysts or catalyst supports. In the present study, activated carbons produced by thermal activation of bamboo with phosphoric acid were used for adsorption of acid dyes. Two acid dyes with different molecular sizes were used, namely Acid Yellow 117 (AY117) and Acid Blue 25 (AB25). It was found that dye with smaller molecular size, AB 25, was readily adsorbed onto the carbon while the larger size dye, AY117, showed little adsorption. It is possible to tailor-make the carbon for the adsorption of dye mixtures in industrial applications, especially textile dyeing. Furthermore, experimental results were fitted to equilibrium isotherm models, Langmuir, Freundlich and Redlich-Peterson.

The preparation and investigation of high BET surface area activated carbons from scrap construction bamboo by low temperature chemical activation has been demonstrated. The high surface area carbon shows nearly three times higher adsorption capacity for small dye molecule, AB25, than the commercial carbon, F400. For AY117, it has similar capacity as F400. However, the low surface area carbon shows poor adsorption for both dyes. Both surface area and porosity of the carbon have played an important role in the adsorption of the dyes. The Redlich–Peterson isotherm model can be used to describe the adsorption of the acid dye onto both bamboo carbon and F400 reasonably well.