Abstract
Red mud and coal fly ash (CFA) are bulk aluminum-containing solid waste in the industrial production process, posing a great threat to the environment and ecological security. The present paper proposes a novel method for one-step producing potassium-containing fertilizer synergistically extracting Al2O3 by KOH hydrothermally treating red mud or CFA. In this paper, the dissolving ratio of Al2O3 in the K2O-Al2O3-H2O ternary system and the extraction of Al2O3 from red mud or CFA after hydrothermal treatment with KOH were investigated. The phase structure transformation of leaching residue obtained under various conditions was analyzed by X-ray diffraction and scanning electron microscopy, and the fertilization efficiency of the products was verified by potting experiments. The results show that the dissolving ratio of Al2O3 can reach the highest value of 85.04% at 120 °C with the K2O mass fraction of 24.90% in the ternary system. When red mud or CFA was hydrothermally leached with 240 g/L K2O at 240 ℃, the Al2O3 extraction rates of 25.50% and 31.42% could be separately obtained, and the leachate could be reused. The main phases of the leaching residue were kaliophilite, illite, and megakalsilite, and the content of K2O was 7.83% and 26.89%, which can be applied as potassium-containing fertilizer to improve soil fertility and effectively promote the growth of pakchoi. The process improves the comprehensive utilization of red mud and CFA without secondary pollution, reduces the negative impact on the environment, and opens up a new way to apply bulk solid waste in the agricultural field.
Published Version
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