Preparation Of Zeolite4A Using Residue Of Acid Leaching Pyrolusite

Manganese is a strategic metal in a lot of fields for its various applications such as chemical industry, light industry, steel production, non-ferrous alloys, carbon-zinc batteries, fertilizers, and so on. Large market demand of manganese products result in increasing emissions of pyrolusite slags. Therefore, pyrolusite slags should be reused as a kind of secondary materials in order to preserve natural resources and obtain an important economical and ecological benefit. In this paper, because of high silica content of pyrolusite slags, leaching technology and kinetics of pyrolusite with alkali were studied, but also synthesis of the4A molecular sieve using pyrolusite slags as raw materials was researched. More details were described as follows:Through leaching silicon process in the residue of pyrolusite with alkali, The effects of sodium hydroxide concentration, reaction temperature, reaction time and liquid-solid ratio on the leaching ratio of SiO2were studied using orthogonal and single-factor experiments. The results showed that an optimum condition was determined:sodium hydroxide concentration of20mol·L-1, reaction temperature of120℃, reaction time of5.5h, liquid-solid ratio of2:1. The leaching ratio of SiO2was70.9%on the optimum condition.In addition, the kineties of the leaching silicon was researched. The results indicated that the leaching process follows unreacted skrinking core model and is controlled by the chemical reaction, what is more, the apparent activation energy was77.69kJ·mol-1and the apparent activation order were0.34.The4A molecular sieve was hydrothermally synthesized using pyrolusite slags as raw materials, applying aluminum source and regulating the ratio of silicon and aluminum. The works studied the investigation of the water-sodium ratio, crystallization time and crystallization temperature on the influence of4A molecular sieves. At the same time, the best process parameters in the preparation of Zeolite4A were determined. The parameters were that water-sodium ratio was40, the crystallization temperature was85℃and the crystallization time was5h. Under these conditions the calcium exchangeability of the products was285.65mgCaCO3·g-1and the pH was10.4. The products were characterized by XRD, SEM, FTIR, and so on. The results demonstrated that the products accord with the characteristics of4A molecular sieves, the shape of the products is in rules, the size of the products is uniform.