The Study Of Removal Of Ionic Dyes From Aqueous Solution By Magnetic Multi-wall Carbon Nanotubes

Dyes are the organicc ompounds which can bring bright and firm color to other substances.Today there are more than 10,000 dyes available commercially.Dyes can be classified into three categories: 1. anionic: direct, acid, and reactive dyes, etc; 2. cationic: basic dyes; and 3. non-ionic: disperse dyes.Dyes usually have a synthetic origin and complex aromatic molecular structures which possibly come from coal-tar based hydrocarbons such as benzene, naphthalene, anthracene, toluene, xylene, etc.The complex aromatic molecular structures of dyes make them more stable and more difficult to biodegrade.Synthetic dyes have been increasingly used in the textile, leather, paper, rubber, plastics, cosmetics, pharmaceutical and food industries. The extensive use of dyes often poses pollution problems in the form of colored wastewater discharged into environmental water bodies. For some dyes, the dye concentration of less than 1 ppm in receiving water bodies is highly visible, so that even small quantities of dyes can color large water bodies. This not only affects aesthetic merit but also reduces light penetration and hydrophyte photosynthesis. In addition, some dyes or their metabolites are either toxic or mutagenic and carcinogenic.As a new member of Fullerene family, Carbon nanotubes (CNTs) have been extensively concerned from their discovery by lijima in 1991.Because of their unique physical and chemical properties, carbon nanotubes have been one of the hotspots in the nanomaterial field. In recent years, with their preparation in batches carbon nanotubes have been applied in many fields, such as hydrogen storage, quantum nanowires, superior adsorbent, catalyst suports and chemical sensors, etc.Multi-wall carbon nanotubes / iron oxide magnetic composite was prepared using chemical co-precipitation after multi-wall carbon nanotubes (MWNTs) were purified by nitric acid solution. The magnetic composite obtained was characterized by SEM, powder XRD , ZETA SIZER and and BET surface areas measurements to estimate the composite’s physical and chemical characters. In addition, the adsorption kinetics, adsorption isotherm, effects of adsorbent dosage and pH on magnetic composite adsorption ability of four ionic dyes of Methylene Blue trihydrate, Brilliant cresy blue, Neutral red and Rhodamine B were discussed in detail.The result showed that the removal rate of four ionic dyes of the composites is good. The adsorption percentages of four dyes decreased with the increase of initial dye concentrations. To three ionic dyes of Methylene Blue trihydrate, Brilliant cresy blue and Neutral red the isothermal date of adsorption followed the Freundlich models and the adsorption processes conformed the pseudo-second-order rate kinetics, to Rhodamine B the isothemal date of adsorption followed the Langmuir model and the adsorption processes coincided with pseudo-first-order kinetics equation. The adsorption percentages of four dyes increased with the increase of adsorbent dosage.The pH value had few influence for adsorption percentages of all four dyes.