New Materials Synthesized by Sulfuric Acid Attack Over Power Plant Fly Ash

Loredana Forminte (Litu),Gabriela Ciobanu,Gabriela Buema,Maria Harja,Horia Chiriac,Nicoleta Lupu,Consuelo Gomez De Castro

doi:10.37358/rc.20.7.8224

Abstract

In the current work, the preparation of a complex wastewater coagulant based on polymeric sulfates of aluminum/iron from fly ash is presented. The performance of the coagulation�flocculation process is mostly influenced by the coagulant type, which enhances the aggregation of particles and leads to formation of fast-settling flocs by charge neutralization or chain-bridging mechanisms. Within the preparation process, the reaction temperature was controlled at 80�C and 90�C for 4 h, the synthesized materials being characterized through different techniques (SEM, EDAX, FTIR, and XRD) and further used as coagulants for real wastewater treatment. As a novelty of this study, it can be mentioned that there were analyzed the possibilities of capitalization of Romanian fly ash collected from Iasi area and its transformation into complex based on aluminum - iron sulfates. Fly ash containing different concentrations of Fe2O3 and Al2O3 was successfully used in producing complex coagulants by reacting with 10% technical sulfuric acid solution. The produced complex coagulants contain both polymeric ferric sulfate (PFS) and polymeric aluminum sulfate (PAS) (demonstrated by complex characterization) and proved to be effective in wastewater treatment. These sustainable materials exhibited a good performance in coagulation�flocculation process (e.g. it was obtained a TSS removal efficiency of 84% at the coagulant dosage of 60 mg/L).

Highlights

Coagulation process is a simple and economic wastewater treatment technology, recommended for domestic and industrial wastewater, in the primary purification treatment [1, 2]
The mixture aluminium sulfate + 71221 provided better results; the removal efficiencies were over 88% for all real wastewater tested
X-ray diffraction (XRD) patterns shown that the major phase structures are non-stoichiometric iron sulfate salt, but the presence of aluminum leads to formation of complex compounds as sulfo-aluminate-ferric crystals

Summary

Introduction

Coagulation process is a simple and economic wastewater treatment technology, recommended for domestic and industrial wastewater, in the primary purification treatment [1, 2]. The influence of type, respectively the dosage of flocculant and coagulant should be investigated at laboratory scale, especially for real wastewaters, pilot plant studies being necessary before implementation of new materials. If for the commercial coagulant, the dosage and mechanism are known, the investigations are focused on the synthesis of new coagulants able to improve the coagulation–flocculation process for wastewater treatment. These new materials must be low cost, but to have the advantage of improving the coagulation–flocculation process, such as inorganic and composite coagulants. Low cost coagulants, obtained from fly ash have been proposed for application in water treatment plant, as a result of their efficiency comparative with that of commercial coagulants. The influence of type and dosage were investigated for the determination of flocculation efficiency of the obtained materials compared with commercial materials

Materials and methods

Results and discussions

Conclusions