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Adsorption Removal of Phosphate Using Iron-modified Activated Carbon

Author: WangZhengFang
Tutor: ZhengZheng；LuoXingZhang
School: Nanjing University
Course: Environmental Engineering
Keywords: By Fe activated carbon Adsorption isotherm P ( V ) Thermodynamic Adsorption mechanism
CLC: X703
Type: Master's thesis
Year: 2011
Downloads: 188
Quote: 1
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Abstract

Load iron, iron-carrying activated carbon was prepared by direct evaporation method on activated carbon. The suitable conditions for the laboratory prepared: the concentration of nitric acid for 5 mol / L, the load when the pH of the solution is 2, the concentration of the iron salt as 0.2 mol / L, and the evaporation temperature of 110 ° C. Using more than the surface area and the hole tolerance analysis, electric mirror scanning (SEM), X Are ray diffraction (XRD), infrared spectrum (FT1R) and other modern analysis means the product carried out the analysis of characterization, results show that, the PAC / N-Fe Ⅱ surface of the iron component trend toward small disperses tiny particles, more uniform distribution; PAC / N-Fe Ⅲ surface of the iron component reunion, its irregular shape and sizes, the surface microstructure showed rough shape. Modified by the load, the ratio of the activated carbon surface area, pore volume is significantly reduced, this phenomenon is particularly evident for the PAC / N-Fe III. Iron load by PAC / N-Fe II as main components for the alpha-FeOOH, while the PAC / N-Fe III the load iron component mainly beta-FeOOH, the iron component of the load on the activated carbon was mainly microcrystalline, microcrystalline material consists of small grains. By after molysite modified, FTIR spectra at 903 cm-1 and 843 cm-1 and 680 cm-1 appears a new absorption peak, respectively, on behalf of the Fe-OH, Fe-O, and other reactive groups on the activated carbon iron uploader. Through small shaker experiments investigated the iron-carrying activated carbon under different conditions, in addition to the effect of P (V): Effect of pH on P (V) removal efficiency greater impact, PAC / N-Fe II and PAC / N-Fe on P (Ⅴ) removal effect with the rise of the pH value to significantly reduce the PAC / N-Fe III for the change of the pH value is more sensitive, the PAC / N-the FE II is in the relatively wide range of pH values ??(3.78 to 6.84) maintain a high removal rate (93.32% to 86.92%). Initial P (V) concentration of 11.82mg / L to 42.96mg / L the PAC / N-Fe II on P (V) the removal rate dropped to 62.89% from 95.99%; PAC / N-Fe III P (V) removal rate from 87.26% to 36.01%. In the case of lower concentration (11.82mg / L), the removal of both the P (V): and when P (V) at a high concentration level, the PAC / N-Fe II of the adsorption effect is significantly better than the PAC / N-Fe III. Cl-, NO3 on two adsorbents adsorption of the smaller P (V); significantly inhibited in the presence of SO42-adsorption of P (V). 0.1 mol / L NaOH desorption optimal. The thermodynamics studies show that in the studied concentration and temperature range are two main kinds of iron activated carbon adsorption of P (V) are in line with the Langmuir adsorption model, indicating that the surface of the activated carbon adsorption site energy distribution is uniform, the adsorption process is a uniform surface the monolayer adsorption. P (V) on activated carbon adsorption is spontaneous endothermic reaction, as the temperature increases, the absolute value of △ G0 increases, showed that at high temperatures the adsorption reaction is easier to carry out. Under the same temperature conditions, the the PAC / N-Fe II adsorbed on the adsorption properties of the P (V) is better than the PAC / N-Fe Ⅲ, PAC / N-Fe Ⅱ and PAC / N-Fe III adsorption of P (V) the activation energy E. Were 22.23 KJ / mol, 10.89 KJ / mol, and belongs to the chemical adsorption. Kinetic studies have shown that in the temperature and concentration of the study, the two carriers of iron activated carbon adsorption of P (V) are in line with the pseudo-second order kinetic equation; quasi-second-order reaction rate constant k2 increase as the temperature rises, large, indicating that the adsorption rate is accelerated with increasing temperature. The adsorption diffusion in the form of studies have shown that the P (V) on activated carbon adsorption process is divided into the continuous three phases: the first phase of the the adsorbate molecular diffusion through the water film surface to reach the surface of the adsorbent (film diffusion); second stage adsorbate diffusion within the adsorbent particles (particle diffusion); third stage of surface adsorption, the total rate of adsorption is controlled by film diffusion or particle diffusion. As the reaction temperature, the increasing influence of the boundary layer on the total adsorption rate conducive to the conduct of the interior of the particle mass transfer. Iron-carrying activated carbon adsorption process of P (V) is a chemical adsorption may be hydrogen bonding, the combined result of the electrostatic adsorption and chemical bond, chemical bond ancient dominance.

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