| With the rapid development of China’s dyeing and printing industry, China accounts for more than 65% of world dye production in 2012, exports 40% of the total world output, being the world’s largest dye exports country. Wastewater comes from textile, leather, paper making, printing and dye industry. Compared with other industrial wastewater, dye wastewater is characterized by high organic matter content, complex components, chromaticity, high salinity, refractory material, etc. A large number of different natural and synthetic organic compounds can be found in such wasteweater, as a result of booming of dye production technoly. The remaining colored chemical compounds in wastewater can not only be aesthetically undesirable but also inhibit sunlight penetration into the stream, leading to the reduction of photosynthetic reaction. Furthermore, the aromatic amines generated from the enzymatic breakdown and cleave of azo dye linkage may cause disorders of living systems, including carcinogenicity.In recent years, many approahces such as flocculation precipitation, adsorption method, electrochemical method, chemical oxidation, photocatalytic, advanced oxidation, membrane treatment technology and biological treatment methods have been studied in dyeing wastewater treatment,. With inappropriate disposal, agricultural wastes such as straw, wood chips and peels can have negative influence on the environment. These agricultural products, consisting of structural components such as cellulose and hemicelluloses, can be potentially used as low-cost adsorbents for the treatment of dyeing wastewater. In such a way, the sustainable environmental disposal using one waste to treat another waste can be achieved.The study investigated the adsorption of hexadecylpyridinium chloride monohydrate (CPC) on wheat bran. The experiment results showed that, the adsorption rate of the CPC increased with the increase of adsorbent concentration., The optimum adsorbent dosage was 1g/L. The Freundlich and Dubinin-Radushkevich models could fit to the adsorption isotherm data. The pseudo-second-order model could be used for interoperating the kinetics. The maximum adsorption capacity was 216.784 mg/g and the adsorption process was dominated by physical adsorption process. Adsorption reaction was endothermic and spontaneous, The increase of ionic strength would reduce adsorption of CPC on the wheat bran.The study also investigated the specific surface area (BET), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) of wheat bran and Gemini 12-2-12 surfactant-modified wheat bran (MWB). Gemini surfactant-assisted modification couln significantly improve the adsorption capacity of wheat bran. The modification changed the surface configuration and the charged character of wheat bran. This study investigated the performance of Gemini 12-2-12 surfactant-modified wheat bran for removal of anionic azo dyes from aqueous solution. The equilibrium and kinetic studies on the adsorption of acid red 18 (AR-18), acid orange 7 (AO-7) and acid black 1 (AB-1) on MWB were conducted. The adsorption isotherm data could well fit to the Langmuir model. The adsorption process followed pseudo-second-order kinetics and two-step intra-particle diffusion models. The results of thermodynamic studies indicated the adsorption of AR-18 and AB-1 onto MWB was endothermic and spontaneous in nature, while the adsorption of AO-7 was exothermic. The optimum pH level for the adsorption of anionic azo dyes on MWB was at 3. The absorbed amount of anionic azo dyes onto MWB decreased when NaCl concentration ranged from 0 to 0.4 mol/L. The results can help understand the migration patterns of organic pollutants in wheat bran-water interface. |
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