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

Abstract

To elucidate the physicochemical properties of the artificial silicate composite material, K-feldspar and lime were reacted in mild hydrothermal conditions (different reaction temperatures and various K-feldspar/lime ratios). Formed phases were investigated using various techniques, such as X-ray powder diffraction, the Rietveld method, scanning electron microscopy (SEM), and inductively coupled plasma-optical emission spectrometry. The analysis revealed that tobermorite, grossular (hydrogarnet), alpha-dicalcium silicate hydrate (α-C2SH), amorphous calcium silicate hydrate, potassium carbonate, bütschliite, calcite, and calcium hydroxide formed with various conditions. Both the temperature and the Ca/Si molar ratio in the starting material greatly affected the formation of phases, especially the generation of tobermorite and α-C2SH. The substitution of H4O4 ↔ SiO4 proceeded with the increase of the Ca/Si molar ratio rather than the reaction temperature and the reaction time. More hydrogen was incorporated in hydrogarnet through the substitution of H4O4 ↔ SiO4 with the increase of the Ca/Si molar ratio in the starting material. Due to the properties of tobermorite as a cation exchanger and its potential applications in hazardous waste disposal, experimental parameters should be optimized to obtain better performance of the artificial silicate composite material from K-feldspar and lime hydrothermal reaction. The dissolution mechanism of K-feldspar was also discussed.

Effect of sintering temperature of potassium feldspar‐limestone/dolomite on composition and microstructure of silicate fertilizers

“…To break the K‐feldspar crystal structure and produce a multi‐nutrient fertilizer with the aids of calcareous/magnesia materials, two main approaches have been put into operation, namely hydrothermal treatment and high‐temperature treatment. Hydrothermal methods typically operate at lower temperatures (150~300°C) and elevated pressure (0.5~2 Mpa) for several hours and utilize water as the reagent. Hydrothermal methods aim to accelerate the natural decomposition of K‐feldspar by aqueous fluids, a reaction that is responsible for soil formation on the geological timescale.…”

“…Hydrothermal methods aim to accelerate the natural decomposition of K‐feldspar by aqueous fluids, a reaction that is responsible for soil formation on the geological timescale. The minerals in the final product cover tobermorite (Ca 2.25 (Si 3 O 7.5 (OH) 1.5 )(H 2 O)]), grossular (Ca 3 Al 2 (SiO 4 ) 1.53 (OH) 5.88 ), alpha‐dicalcium silicate hydrate (α‐C 2 SH, Ca 2 (SiO 3 OH)(OH)), amorphous calcium silicate hydrate, and so on . For the latter, namely the high‐temperature treatment, the process temperature ranges between 600 and 1400°C, including gypsum‐limestone sintering and limestone/dolomite sintering .…”

Fertilizer derived from alkaline hydrothermal alteration of K-feldspar: A micrometer to nanometer-scale investigation of K in secondary reaction products and the feldspar interface

“…The former two phases are Ca-Al-silicate hydrate minerals (CASH), whereas tobermorite is a Ca-silicate hydrate (CSH). In addition, the studies by Liu et al (2015Liu et al ( , 2018Liu et al ( , 2019Liu et al ( , 2020 also noted the significant formation of carbonate phases, such as CaCO 3 , K 2 CO 3 , and K 2 Ca(CO 3 ) 2 . Another study (Su et al, 2015) presents data from hydrothermal alteration of K-feldspars in NaOH solutions at 240 and 280 °C.…”

“…Overall, the net reaction can be thought of as dissolution of the primary feldspar and classical precipitation of secondary phases. In related studies at similar conditions, Liu et al (2018Liu et al ( , 2019 postulated that the initial dissolution of primary feldspar is progressively slowed down by the formation of secondary phases on the surface (t > 20 hours), which ultimately results in a diffusioncontrolled alteration process. The formation of hibschite, katoite, and tobermorite was universal in these studies (Liu et al, 2015(Liu et al, , 2018(Liu et al, , 2019.…”

Editorial for Special Issue “Modeling, Design and Optimization of Multiphase Systems in Minerals Processing”

“…These effects can be explained by the change of properties within the settler produced by the temperature profiles. Simulation of kinetic phenomena in multi-phase reactions are also present in this special issue [20,21], although the simulation of the phenomena in these papers have followed traditional methodologies using unreacted shrinking core and progressive conversion models, which have been shown to be unsuitable in several cases [22]. In this sense, it is necessary to move towards multiscale simulation using mesoscale simulation techniques to describe, for example, diffusion and reactive molecular dynamics [23] tools to describe the processes occurring within the interface in order to generate a procedure that can be used to increase our understanding of the heterogeneous gas-solid, liquid-solid, or other multiphase reactions in mineral processing.…”