Study on Preparation of Poly Aluminum Ferric Sulfate Flocculant from Municipal Solid Waste Incineration Fly Ash

Abstract

In this study, an inorganic flocculant poly-aluminum sulfate flocculant (PAFS) was prepared with municipal solid waste incineration (MSWI) fly ash. By using XRD and FTIR, the shape and structure of PAFS were examined. The effects of the polymerization duration, temperature, stirring rate, and polymerization pH on the preparation of PAFS were investigated using a single-factor flocculation experiment. It was found that the maximum removal rate of 32.75% for kaolin turbidity with a polymerization time of 60 min, stirred rate of 100 r/min, temperature of 40℃, and polymerization pH of 10. To further improve the turbidity removal effect of the PAFS, an upgraded experiment was carried out on the fly ash, FeSO4·7H2O was used as an upgraded additive in this experiment. The results showed that the upgraded flocculant had the best turbidity removal effect, which was 74.95%, under identical conditions, with the pH being 3.5 and the amount of FeSO4·7H2O added being 1g (the ratio of added FeSO4·7H2O to fly ash mass was 1:5). Additionally, it was revealed by the findings of the flocculant characterization that PAFS is a composite flocculant made up of hydroxyl groups, iron ions, and chloride ions. It was a macro molecular polymer with a network structure made of staggered molecular connections and a compact structure. In addition, adsorption bridging of high molecular iron sulfate polymers with branchlike structures is essential for the elimination of turbidity. This work offers a fresh approach to achieving "waste to waste" of MSWI fly ash.