| A huge volumes of wastewater was generated by many industries such as textile, paper, leather. Printing etc, contain several kinds of dyestuffs and other products. Many dyes and their by-products can cause serious health problems to human beings, and are also toxic for living organisms. Adsorption is a very effective separation technique and now it is considered to be superior to other techniques for water treatment in terms of ease of operation, low cost, and insensitive to toxic substances. The present study is aimed at studying the raw fir sawdust (RFS) and modified fir sawdust (MFS) for methylene blue and congo red adsorption:to investigate the adsorption influencing factors such as pH, adsorbent dosage, and the addition of salt and surfactant; to investigate the adsorption model, such as adsorption isotherms, adsorption kinetics and intraparticle diffusion model; to characterize the adsorbent by Fourier Transform Infrared Spectroscopy. The main results are as follows:1. The effect of adsorbent dosage on adsorption indicated that MB and CR adsorbed by RFS and MFS increased with the increase amount of adsorbent. The effect of initial pH suggested that there was little change under the condition of pH ranged from4to12for MB adsorption; with the pH of CR increased, the amount of adsorption decreased. The effect of contact time on adsorption revealed that compared with the MFS, the process of the adsorption of RFS was more faster to attain equilibrium, with the increase of the initial dye concentration, the amount of the adsorption on RFS and MFS increased. The addition of NaCl inhibited the adsorption of MB on both two adsorbents, while promoted the adsorption capacity of CR. The effect of SDBS (sodium dodecyl benzene sulfonate) on the MB adsorption turned out to be small, and the exist of CTAB (cetyltrimethyl ammonium bromide) suppressed the MB removal. For CR, the addition of SDBS and CTAB promoted the adsorption on RFS, while inhibited the adsorption on MFS.2. Adsorption of MB and CR on RFS and MFS fited the Langmuir isotherm best among the Langmuir and Freundlich isotherm. The Langmuir capacities of MB on RFS and MFS were51.8mg/g and108mg/g, and the Langmuir capacities of CR on RFS and MFS were19.8mg/g and42.6mg/g,respectively. The Freundlich parameter indicated that the adsorption was a favorable process; the study of D-R isotherm model showed that the adsorption of MB, CR on RFS and MFS were chemical adsorption processes. Kinetic data showed that the adsorptions were best fitted with the pseudo-second-order model. The intraparticle diffusion model analysis indicated that intraparticle diffusion was not the rate control process and can be neglected.3. The FTIR analyses revealed that there are differences of the surface characteristic between RFS and MFS, C=O and C-H vibration took part in the modification process, moreover, the functional group such as hydroxyl group and carboxy group played the important role in the adsorption of MB and CR. The mechanisms of the adsorption can be concluded as the surface functional groups reaction, electrostatic force, ion exchange, etc.The results of the study showed that there is a great potential for fir sawdust to dye removal from wastewater, which modification process improve the adsorption capacity. |
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