Work

Selective leaching and crystallization methods to produce potassium and phosphate fertilizers from poultry litter fly ash

Year: 2025

Type: article

Abstract: Potassium and phosphate salts are essential in agriculture playing a vital role in the production of fertilizers, which are crucial for global food security. Their conventional production relies heavily on mining, a practice subjected to economic, geopolitical and environmental constraints. Consequently, alternative methods to recover potassium and phosphate salts from secondary sources are receiving increased attention. Agricultural waste is a promising material, especially after incineration, which significantly reduces its volume, concentrates the contained nutrients, and eliminates organic contaminants. Poultry litter is one such important source of potassium and phosphorus nutrients. Poultry litter fly ash containing 24.4 wt% potassium and 3.0 wt% phosphorus was used for selective production of potassium and phosphorus salts using a combination of water leaching, and cooling and evaporative crystallization. Optimal leaching at liquid to solid ratio 2.75 w:w, 70 °C for 30 min resulted in >90 % potassium and > 99 % sulphate dissolution; and produced a solid residue with >10 wt% phosphorus, present mainly as calcium phosphate. Cooling crystallization recovered 25 % of the aqueous potassium as high purity potassium sulphate (> 99 % purity). Further recovery of potassium as glaserite with very low chloride content (< 0.5 wt%) was possible using evaporative or antisolvent crystallization. Leftover aqueous chlorides were separated by exploiting the different solubilities of potassium and sodium chlorides at different temperatures. The crystal morphology of potassium sulphate was significantly influenced by cooling parameters, including endpoint temperature and agitation, while the morphology of glaserite varied depending on the crystallization method.

Source: Separation and Purification Technology

DOI: 10.1016/j.seppur.2025.136276

Authors: Ehsan Moslehi, Elin Larsson, Yariv Cohen, Gulaim A. Seisenbaeva, Cristian Tunsu

Institutions: Swedish University of Agricultural Sciences, EasyMining (Sweden)

Language: English

Topic: Phosphorus and nutrient management

Subfield: Waste Management and Disposal

Field: Environmental Science

Domain: Physical Sciences

SDGs: Responsible consumption and production, Zero hunger

Open Access status: hybrid

Estimated APC paid: $4,060