Potassium fertilizer via hydrothermal alteration of K-feldspar ore

Abstract

A novel potassium fertilizer material is obtained via hydrothermal processing of K-feldspar ore in alkaline conditions.

Study of K-Feldspar and Lime Hydrothermal Reaction: Phase and Mechanism with Reaction Temperature and Increasing Ca/Si Ratio

“…All formed phases were concluded to be calcium silicate hydrate or calcium aluminosilicate hydrate by EDS analysis, and the amorphous phases were mainly composed of calcium silicate hydrates or some transition state compounds that were discussed in a previous work [19]. Here, ACSH may have contained other amorphous phases-except calcium silicate hydrates-and all of these phases were judged to be amorphous by XRPD [20]. Therefore, the authors did not further determine the chemical compositions of ACSH because it was still difficult to distinguish different crystal or amorphous phases, even using Electron Probe Micro-Analyzer (EPMA) due to small particles and quantities of intertwining phases [19,20].…”

“…Here, ACSH may have contained other amorphous phases-except calcium silicate hydrates-and all of these phases were judged to be amorphous by XRPD [20]. Therefore, the authors did not further determine the chemical compositions of ACSH because it was still difficult to distinguish different crystal or amorphous phases, even using Electron Probe Micro-Analyzer (EPMA) due to small particles and quantities of intertwining phases [19,20].…”

“…We further investigated the mechanism of the hydrothermal reaction between K-feldspar and different alkalis [including Ca(OH) 2 ] and identified minerals formed through an elaborative interface experiment [19]. Several researchers also studied the preparation of potassium fertilizer via the hydrothermal alternation of K-feldspar ore at 200 • C [20,21]. However, none of the abovementioned studies investigated the hydrothermal reaction of K-feldspar under alkaline conditions with reaction conditions, such as various reaction temperatures, various reactant ratios (the ratio of K-feldspar and lime in the starting material), and various reaction times.…”

Study of K‐Feldspar and Lime Hydrothermal Reaction at 190 °C: Phase, Kinetics and Mechanism with Reaction Time

“…Potassium carbonate and bütschliite, as potassium reservoirs, were distinguished by XRPD (Table ) and contributed to the water‐soluble potassium content by leaching tests (Table S1, Figures S1 and S2). Other potassium reservoirs, such as tobermorite or the amorphous phases (ACSH), were presumed to be water‐insoluble and acid‐soluble (0.5 mol L −1 HCl), and will release K at a slower and possibly more controllable rate than a water‐soluble species such as carbonate ,. In fact, the artificial silicate composite material is not only the reservoir of potassium but is also the reservoir of other medium elements, such as Si, Ca, and some trace healthy elements, such as sulfur (S), molybdenum (Mo), and boron (B), and these elements are very critical for crops.…”

Hydrothermal reaction of K‐feldspar powder in NaOHCa (OH)2 mixed medium

“…However, treating conditions and the crystallization zone for a certain product are huge different. Ciceri et al developed an approach to generate potassium fertilizer via hydrothermal alteration of K‐feldspar ore in Ca (OH) 2 medium at 200°C, but only about 17% of K‐feldspar truly reacted into calcium–silicate–hydrate compounds (CSHs: hydrogrossular, α‐dicalcium silicate hydrate, tobermorite, etc.). When treated in KOHNaOH mixed medium, kalsilite maintains as stable product within Na/(K + Na) molar ratio of 0.7 (240°C) or 0.6 (280°C) for the initial solution .…”