Abstract
Cement is the most widely used construction material in the world. However, its manufacture is high energy consumption and high carbon emission owing to the high temperature calcination process. Geopolymer is an ideal alternative material for cement because it has a similar structure and performance to cement. In addition, it can be synthesized at room temperature and thus has the advantages of energy saving and carbon emission reduction. Sewage sludge (SS) can be used as raw material for geopolymer synthesis. However, the high organic matter content in SS lowers the mechanical strength of geopolymer. Although the organic matter in SS can be removed by incineration at high temperature, this consumes energy and emits carbon dioxide, which diminishes the advantages of geopolymer. In this study, the Fenton method was applied for the removal of organic matter in SS at room temperature. The parameters of the Fenton method, including the dosages of hydrogen peroxide (H2O2) and Fe2+ reagent (FeSO4·7H2O), reaction time, and initial pH value, were investigated. The results indicated that 83.7% of the organic matter in SS could be removed at room temperature by using 5.15 M H2O2 and 5.15 mM FeSO4·7H2O at pH 7, which suggested the possibility of sewage sludge reclamation through geopolymer synthesis as an alternative material for cement toward sustainability.
Highlights
Cement is made from limestone, clay, silica sand, and iron slag
The Thermogravimetry/Differential Thermal Analyzer [32] (TG/DTA) analysis was applied to determine the thermal characteristics of sewage sludge (SS)
600 ◦C was chosen as the temperature to determine the removal of organic matter in SS
Summary
Cement is made from limestone, clay, silica sand, and iron slag. They are ground and mixed with appropriate ingredients, followed by sintering in a rotary kiln at high temperature to become clinker, which is ground with an appropriate amount of gypsum. Geopolymer is thought of as an ideal alternative material for cement because it has a similar structure and performance to cement. It can be synthesized at room temperature and has the advantages of energy saving and carbon emission reduction. Geopolymer can be synthesized by solid wastes containing silicon and aluminum, such as fly ash, slag, sewage sludge (SS), etc. Raw materials containing high contents of silicon (Si) and aluminum (Al) can be used for the synthesis of geopolymer, such as blast furnace stone powder [3], met-kaolin and volcanic ash [4], coal-fired fly ash [5], and reservoir sludge [6]
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