Chinese Journal of Chemistry, 2007, 25, 596—604 Full Paper * E-mail: fazlullah52@yahoo.com Received June 5, 2006; revised September 6, 2006; accepted January 1, 2007. Project supported by the University of Peshawar, Pakistan. © 2007 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Kinetics of Acid Blue 1 Adsorption from Aqueous Solution by Carbonaceous Substrate Produced from Biotic Precursor FAZLULLAH, Khan Bangash* ,a SULTAN, Alam a IRSHAD, Ahmad b a Institute of Chemical Sciences, University of Peshawar, Peshawar 25120, Pakistan b National Center of Excellence in Geology, University of Peshawar, Peshawar 25120, Pakistan Adsorption of acid blue 1 from aqueous solution onto carbonaceous substrate produced from the wood of Paulownia tomentosa was investigated. The samples characterized by FTIR, SEM, EDS and XRD techniques, indi- cated that the surface functional groups like carboxyl, lactones or phenols and ethers have disappeared at high acti- vation temperature (800 ℃) and as a result porous structure was developed that has a positive effect on the adsorp- tion capacity. Bangham and parabolic diffusion models were applied to the kinetic adsorption data, which show that the adsorption of acid blue 1 was a diffusion controlled process. The reaction rate increased with the increase in temperatures of both the adsorption and activation. Thermodynamic parameters like ΔE ≠ , ΔH ≠ , ΔS ≠ and ΔG ≠ were calculated from the kinetic data. The negative values of ΔS ≠ reflected the decrease in the disorder of the system at the solid-solution interface during adsorption. Gibbs free energy (ΔG ≠ ), representing the driving force for the affin- ity of dye for the carbon surface, increased with the increase in sample activation and the adsorption temperatures. Keywords activated carbon, chemical treatment, thermal activation, adsorption, functional group, XRD, SEM, EDS, FTIR Introduction Textile industry is the backbone of Pakistan econ- omy. The treatment of textile wastewater at present is a major problem that contains a number of contaminants, including acids, dissolved solids, toxic compounds and dyes. 1 The sources of such pollution lie in the rapid in- crease in the use of synthetic dyes. More than 10000 chemically different dyes are being manufactured. The world dyestuff and the dye intermediate production is estimated to be around 7×10 8 kg/annum, 2 and about 5% to 10% is discharged to wastewaters. A small amount of dye in water, about 10—50 mg/L, is highly visible and affects the aesthetic merit, transparency and gas solubility of the water bodies. The dyes are difficult to remove under aerobic conditions from the textile ef- fluents and are probably decomposed into carcinogenic aromatic compounds. 3 A number of technologies have been developed over the years for this purpose. These include chemical precipitation, electroflotation, ion ex- change, reverse osmosis and adsorption onto activated carbon, etc. Cost effectiveness of the method is the main issue. Low cost and non-conventional adsorbents in- cluding agriculture wastes such as wood, natural com- post, planer shell, walnut shell and biomass, chitosan, peat etc., have also been tried for the removal of dyes from water and wastewaters. 4-13 Activated carbons have antiquity adsorptive use for the removal of tastes and odors from domestic and industrial water supplies, clean-up of cane, beet and corn-sugar solutions, vegeta- ble and animal fats and oils, alcoholic beverages, chemicals, pharmaceuticals and dyes. 14-19 In order to explore low cost adsorption material, we used the wood of a fast growing wild plant Paulownia tomentosa for the removal of acid blue 1 from aqueous solution. In this work we report the effect of activation temperature on the adsorptive properties of the prepared carbon samples. Experimental Acid blue 1 The dye used was supplied by Sigma-Aldrich (Cata- logue No. 19821, dye contents＝50%, formula weight＝ 566.68, λ max ＝635 nm) and its structure is shown in Scheme 1. Preparation of carbon The wood of Paulownia tomentosa collected from the Pakistan Forest Institute, Peshawar was air dried, and then heated continuously on a flame burner for 8 h in an iron container having an outlet for the emission of volatile matter. Carbon obtained was cooled in the con- tainer and ground with the help of pestle and mortar and screened with U.S. standards mesh (150—180 μm). It was then treated with 0.5 mol/L aqueous solution of