Effect Of Organic Complexing Agents On Removal Of Iron From Aluminum Sulfate

The primary aluminum sulfate can be used for papermaking, water purification, while the refined in the textile, food, carrier of catalyst production. The key quality index affecting the aluminum sulfate application is the iron content. Low-grade bauxite and coal gangue are divided by sulfuric acid. This is an easy and efficient method for producing aluminum sulfate. Because higher iron in the bauxite and coal gangue, so aluminum sulfate can not meet demands in the catalyst, high-quality fabric and papermaking fields. The hydrogenation catalyst based on nickel active unit was prepared with the carrier of aluminum sulfate in our group. This catalyst was investigated for the hydro-genation of maleic anhydride and producting1,4-butanediol aqueous. The application and catalytic activity were affected by concentration of iron in aluminum sulfate. Studying on iron removal technology from aluminum sulfate with nickel has very important theory significance and practical value.Recrystalization, extraction, inorganic precipitation, organic complex precipitation and organic complex adsorption were the mainly methods reported in the literature. Organic complex precipitation is a potential method, which has advantages of strong selectivity, less dosage, lager precipitation particles, easy separation, simple process and better effect for iron removing. Organic groups can be incorporated in the silica materials through grafting and co-condensation methods. With organic functional groups of the material has a wide application in the water pollution treatment, catalytic and biological chemistry.In this paper, organic complex precipitation and organic complex adsorption methods were used for removing iron from aluminum sulfate. The effect of organic precipitating agent dosage, acidity of solution, reaction time and reaction temperature on removing iron efficiency were investigated. The relationship between adsorption, complexation and separation was established, which based on the kinetics and thermodynamics model of organic adsorption. The main conclusions were summarized as follows:1. Organic complex precipitation was used for removing iron from aluminum sulfate.The effect of organic precipitating functional organic dosage, acidity of solution, reaction time and reaction temperature on iron removing efficiency were investigated with DDTC, CP, and BPHA.1) DDTC amount was0.88%, the pH value of solution was2.5-3.0, the reaction temperature was room temperature, and the reaction time was5min. Under the above condition, the removal rate of iron was94%, loss ratio of aluminum was about13%-15%, and iron content was below50mg/L;2) CP amount was1.4%, the pH value of solution was0.3, the reaction temperature was60℃, and the reaction time was one hour. Under the mentioned-above condition the removal rate of iron was above95%, loss ratio of aluminum was about10%, and the iron content was below50mg/L;3) BPHA amount was1.4%, the acidic concentrations was1.0mol/L, the reaction temperature was60℃, the reaction time was one hour. Under the mentioned-above condition the removal rate of iron was above96.1%, the loss ratio of aluminum was below5%, and the iron content was below50mg/L;2. Amino-modified adsorbents were used for removing iron from aluminum sulfate.Amino-functional groups can be incorporated on the silica materials through grafting, which obtained HN adsorbents and used for removing iron from aluminum sulfate. Adsorption kinetics were researched with different types of HN adsorbents and matched with pseudo-second-order equation. The Sips isotherm model was demonstrated to provide the ideal correlation for the adsorption of Fe (Ⅲ) ion on HN absorbents, with a maximum adsorption capacity of0.6196mg/g under30℃. With an increase about14times in initial concentration of iron ion, removal ratio and distribution coefficient decreased2times and9.6times respectively. 3. Amino-modified honeycomb adsorbents were applied for removing iron from nickel aluminum sulfate.Adsorption kinetics and isotherm were matched with pseudo-second-order equation and Sips model respectively, with a maximum adsorption capacity of0.784mg/g under30℃. With the increase of the amino on the adsorbents and the pH value of solution, the adsorption capacities of HN adsorbents decreased. The pH value of solution was higher than2.0and the reaction temperature was30℃. Under the above condition, with an increase about9.6times in initial concentration of iron ion, removal ratio and distribution coefficient decreased3.7times and26times respectively. But the concentration of nickel and aluminum were little changed.In summary, the different pH (hydrogen ion concentration10-2.5、10-3、0.5mol/L、1mol/L) and iron content (75-750mg/L) iron removal methods were established with DDTC, CP, BPHA. It can be found that organic complex precipitation and organic complex adsorption methods can effectively remove iron from aluminum sulfate, and provide the theoretical and practical significance for high-removing iron production.