Effects of Temperature, Alkali Source, and Mg/Al Ratio on Phase Purity and Yield of Hydrothermal Synthesized Smectites

Bing-Sheng Yu,Yuh-Ruey Wang,Yi-Yu Liu,Wei Lo

doi:10.3390/min9090520

Abstract

Smectites are a major type of clay minerals. Hydrothermally synthesized smectites have become a major research topic because of the unstable quality or excessive impurity of natural smectites. The high-phase purity and yield of hydrothermally synthesized smectites are vital in advanced industries and materials applications. In this study, a Taguchi orthogonal array was integrated with eight factors to avoid biased experimental results, thus creating relatively robust factor portfolios to investigate the effects of temperature, alkali sources, and the magnesium (Mg)/aluminum (Al) ratio on the phase purity and yield of hydrothermally synthesized smectites. The synthesized environment was mainly established using trioctahedral smectites based on the formula Na2x(Al2(1−x)Mg2x□)Si4O10(OH)2X-ray diffraction and Rietveld refinement were used for the quantitative analysis of the products’ mineral facies and calculating the synthesized smectites’ phase purity and yield. The Taguchi method was employed to calculate each factor’s effect on the product quality. The results indicated that among the numerous factor portfolios, a relatively high temperature, ammonia solution as the alkali source, and a relatively high Mg/Al ratio were conducive to enhanced phase purity and yield of synthesized smectites. The optimized products of the synthesized smectites achieved a phase purity of 92.5% and a yield of 88.3%.

Highlights

The results indicated that among the numerous factor portfolios, a relatively high temperature, ammonia solution as the alkali source, and a relatively high Mg/Al ratio were conducive to enhanced phase purity and yield of synthesized smectites
Smectites are a major type of clay minerals commonly found on the Earth’s surface
Natural smectite clays vary in their structural composition, mineral facies, and impurities, all of which may limit their potential use without pretreatment purification because of differences in the geological environment of mineral deposits

Summary

Introduction

Smectites are widely applied in various fields, including use as drug carriers in biomedicine [1], as well as ceramics, metal casting clarifiers, drilling fluid materials, fillers, and supports for semiconductor nanoparticles in materials science because of their their high cation exchange capability, large specific surface area, and swelling [2,3,4,5]. They have been used in environmental rehabilitation as carriers for adsorbents and catalysts, hazardous material adsorbents, and barriers for highly radioactive waste [3,6,7,8,9]. This can be remedied by smectites synthesized under controlled conditions [10]

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Results

Conclusion