| Recently, mass of waste water and wastes containing heavy metal ion have been produced consequently with the rapid development of Electroplating, pharmaceutical, papermaking, non-ferrous metal smelting and processing industries, etc. Such waste water is toxic and hard to remove, so it can bring about great harm when discharged into water bodies at will.Manganese is abundant in nature, which is also essential to organisms as an trace element. But excessive intake of aluminum is even harmful to human body according to many researches. Thus, the Remediation of heavy metal wastewater containing Manganese ions have aroused enthusiasm in experts majoring in Environmental Science and Engineering and is worth regarding and scientifically anatomizing in industrial community.Traditional basifying, oxidizing and biochemical treatment methods are often difficult to achieve the emission standards. Manganese ion-bearing waste water can be efficiently treated with activated carbon absorption, but the granular or powder activated carbon is easy to fill loose or close together in the oscillation, forming grooves or settlement during processing. However, activated carbon fiber (ACF) has much more adsorption capacity and better adsorption dynamics performance than activated carbon. Modified PAN-activated carbon fiber (PAN-ACF) is employed as the adsorbent for removal of Mn2+in wastewater. Studies on PAN-ACF become a hot topic in the world due to its enormous surface area, the unique microstructure and surface chemical properties. Meanwhile, it can be made into various forms as needed, with certain intensity, and overcomes the problem of forming grooves and easier settlement of granular and powdered activated carbon in the operating process.This paper is to use the above characteristics of PAN activated carbon fiber, and to optimize the static adsorption effect of Mn2+in wastewater through a certain degree of modification, researching the adsorption kinetics characteristics of Mn2+by modified PAN-activated carbon fiber.In this paper, static adsorption experiments were carried out to investigate the adsorption of Mn2+, to explore the feasibility of using activated carbon fiber adsorption method to process heavy metal ions. The adsorption performance of Mn2+on unmodified PAN-ACF and the effect of the adsorption time, temperature, pH, dosage, Mn2+initial concentration on the adsorption were studied. The results indicated that the best conditions were:adsorption time (3h); adsorption temperature (30℃); pH (4.5); PAN-ACF dosage (1.0g). Kinetic data showed that the pseudo first order kinetic model is suitable to describe the adsorption process. The static experiment data also demonstrated that the sorption isotherm presented a good fit to Langmuir and Freundlich model. Meanwhile the Langmuir model was more suitable to describe the mechanism of the adsorption process of Mn2+, showing that the adsortption of Mn2+by PAN-ACF is mainly the result of physical adsorption.In order to obtain the PAN-ACF with desired surface chemical properties to determine the best modification method, in the best adsorption conditions, various methods of chemical modification were applied, such as nitrate impregnation, hydrogen peroxide impregnation and air thermal oxidation. And the surface character of the activated carbon was studied by means of FTIR spectroscopy, Boehm acid-base titration, as well as BET surface area to get micro-structural features of the surface of the main experimental material, BET surface area and other relevant data and parameter values. Result indicated that the main factors affecting the quality of modification and the best conditions were:dipping temperature (80℃); Oxidants (68%HNO3); dipping time (3h).The Roughness structure of PAN-ACF3became clearer with surface roughness also increased. Compared with untreated PAN-ACF, experimental results indicated that:Trench etch of surface Microstructure is in favor of improving the adsorption capacity of PAN-ACF; Specific surface area increased; PAN-ACF3developed a tremendous Pore Structure.The results of Boehm acid-base titration show that the numbers of phenolic group、carboxyl and lacton of PAN-ACF3are increased. The more oxygen acidic functional groups the PAN-ACF3has, the stronger acidic it is. PAN-ACF3with acid groups has the cation exchange characteristic, which can effectively remove Mn2+Result indicated that the main factors affecting the regeneration of adsorption saturated PAN-ACF with microwave radiation and the best conditions were: microwave power(500W); irradiation time:(6min);PAN-ACF dosage (5.0g).Tests showed that the adsorption effect of Mn2+on PAN-ACF declined very slightly after microwave radiation regeneration by4times which indicated that PAN-ACF could be readily recycled. Microwave radiation regeneration of adsorption saturated PAN-ACF was carried out.The effect of Microwave power, Irradiation time, dosage of PAN-ACF on the adsorption were studied through orthogonal experiment. Microwave regeneration requires less energy and shorter time than conventional regeneration... |
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