Synthesis of a novel slow-release potassium fertilizer from modified Pidgeon magnesium slag by potassium carbonate

ABSTRACT

A novel slow-release potassium fertilizer (SPF) was synthesized using Pidgeon magnesium slag (PMS) and potassium carbonate, which could minimize fertilizer nutrient loss and PMS disposal problems. Orthogonal experiments were conducted to determine the optimum conditions for synthesis. The potassium (K)-bearing compounds of SPF existed mainly in the form of crystalline phases Ca_1.197K_0.166SiO₄, K₂MgSiO₄, and K₄CaSi₃O₉, and in the noncrystalline phase. The active silicon content of SPF was 2.09 times as much as that of magnesium slag, and the slow-release character of SPF met the requirement for partly slow-release fertilizer in the national standard (GB/T23348-2009). The best models for describing the K release kinetics in water and 2% citric acid were the Elovich model and the first-order model, respectively. The heavy metal contents of SPF conformed to the national standard for organic–inorganic compound fertilizers, and the leaching mass concentrations of heavy metals and Fluorine were far lower than the limit values of the identification standard for hazardous waste identification for extraction toxicity (GB5085.3-2007), and also met the class II quality standard for ground water. The environmental risk of SPF is therefore very low, but because SPF is alkaline, its effect on soil pH should be taken into account.

Implications: PMS is the solid waste resulting from the production of magnesium metal by Pidgeon’s reduction process. Utilization of PMS in the high-technology and high-value areas may promote the high-efficiency development of worldwide collection metallic magnesium industry and contribute to the reduction of emissions of fine dust to air. This paper presents one of the new techniques in the use of PMS as a slow-release fertilizer by adding K₂CO₃. The product can serve as a very cost-effective and reliable artificial fertilizer.

Funding

This work was supported by the National 863 High-Tech Research and Development Program of China (2012AA061602) and the Coal-Base Scientific and Technological Key Project of ShanXi Province (MC2014-06).

Additional information

Funding

This work was supported by the National 863 High-Tech Research and Development Program of China (2012AA061602) and the Coal-Base Scientific and Technological Key Project of ShanXi Province (MC2014-06).

Notes on contributors

Yongling Li

Yongling Li is a doctoral candidate at the State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal-waste Resources, Institute of Resource and Environment, Shanxi University, Taiyuan City, People’s Republic of China, and an associate professor at the College of Arts and Science, Shanxi Agricultural University, Taigu, Shanxi Province, People’s Republic of China.

Fangqin Cheng

Fangqin Cheng is a professor at the State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal-waste Resources, Institute of Resource and Environment, Shanxi University, Taiyuan City, People’s Republic of China.