Preparation of Slow-Release Fertilizer from Fly Ash and Its Slow-Release and Metal Immobilization Properties

Yingqin Wang, Hao Chen, Dongyu Tian, Liyun Yang and Hao Bai ()
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Yingqin Wang: State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, 30# Xueyuan Road, Haidian District, Beijing 100083, China
Hao Chen: State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, 30# Xueyuan Road, Haidian District, Beijing 100083, China
Dongyu Tian: State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, 30# Xueyuan Road, Haidian District, Beijing 100083, China
Liyun Yang: State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, 30# Xueyuan Road, Haidian District, Beijing 100083, China
Hao Bai: State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, 30# Xueyuan Road, Haidian District, Beijing 100083, China

Sustainability, 2023, vol. 15, issue 14, 1-20

Abstract: In this study, SRPF with metastable KAlSiO 4 as the main slow-release substance was prepared by the sintering method using fly ash and K 2 CO 3 as raw materials, and an orthogonal experiment was conducted to optimize the raw material ratio and preparation parameters of SRPF. The optimum parameters for preparing SRPF are as follows: the potassium carbonate content is 15%; the sintering temperature is 1100 °C; heat preservation time is 60 min; cooling mode is furnace cooling, and the particle size of raw materials is not less than 150 μm. Initial leaching rates in water and 2% citric acid solution were 4.64% and 47.07%, respectively, and cumulative leaching rates at 28 days were 11.17% and 85.86%, respectively, showing that the SRPF prepared from fly ash and K 2 CO 3 meets the standard GB/T 23348-2009 of China. A soil column leaching test was carried out to study the slow-release behavior of SRPF in soil. When the leaching medium is water, the 70-day cumulative leaching rate of SRPF in soil is about 4%, while when the leaching medium is citric acid, depending on the soil type, the 70-day cumulative leaching rate of SRPF can reach 21.2% and 43.5%. The results of the soil column leaching test showed that the total potassium content in the soil was negatively correlated with the slow-release rate of SRPF. Finally, the immobilization effect and mechanism of SRPF on lead ion immobilization was studied, and it was found that SRPF still had a considerable effect on lead ions immobilization. The BET results showed that, compared with fly ash, the BET surface area of SRPF was reduced by 48.3%, the total pore volume was reduced by 16.0%, and the average pore diameter had a small change. The decrease in total pore volume was mainly concentrated in the micropore volume and mesopore volume, which are reduced by 50% and 20% respectively, while the macropore volume hardly changes. In summary, fly ash can be used to prepare SRPF with a good release effect and similar heavy metal ions immobilization ability.

Keywords: fly ash; slow-release fertilizers; metal immobilization (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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