Struvite Grown in Gel, Its Crystal Structure at 90 K and Thermoanalytical Study

Jolanta Prywer,Lesław Sieroń,Agnieszka Czylkowska

doi:10.3390/cryst9020089

Jolanta Prywer, Lesław Sieroń + Show 1 more

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https://doi.org/10.3390/cryst9020089

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Journal: Crystals	Publication Date: Feb 8, 2019
Citations: 18	License type: CC BY 4.0

Affiliation: Lodz University of Technology, Institute of Physics

Abstract

In this article, we report the crystallization of struvite in sodium metasilicate gel by single diffusion gel growth technique. The obtained crystals have a very rich morphology displaying 18 faces. In this study, the habit and morphology of the obtained struvite crystals are analyzed. The crystals were examined and identified as pure struvite by single X-ray diffraction (XRD). The orthorhombic polar noncentrosymmetric space group Pmn21 was identified. The structure of the crystal was determined at a temperature of 90 K. Our research indicates a lack of polymorphism, resulting from the temperature lowering to 90 K, which has not been previously reported. The determined unit cell parameters are as follows a = 6.9650(2) Å, b = 6.1165(2) Å, c = 11.2056(3) Å. The structure of struvite is presented here with a residual factor R1 = 1.2% at 0.80 Å resolution. We also present thermoanalytical study of struvite using thermal analysis techniques such as thermogravimetry (TG), derivative thermogravimetry (DTG) and differential thermal analysis (DTA).

Highlights

Practical attempts to obtain crystals in the gel environment were made in the 1960s [1]
In this article we present the structure of the struvite crystal examined at 90 K
The grown struvite crystals show different morphologies, namely dendritic, and prismatic and rectangular platelet depending on the growth site

Summary

Introduction

Practical attempts to obtain crystals in the gel environment were made in the 1960s [1]. A gel is a two-component system with mechanical properties of a solid body, containing a large number of microscopic liquid phase. This structure provides adequate stiffness, eliminating convection, while maintaining the mobility of ions close to that observed during crystal growth from solutions. Gel techniques have been found to be useful for obtaining crystals of compounds that are sparingly soluble in water and metal crystals, due to the difficulty of obtaining these crystals from solutions and melts. The progress in technology has led to such development of gel techniques that nowadays one can obtain crystals of many inorganic and organic substances, including substances well soluble in water and metals. Another important reason for the increasing interest in gel methods is that the course of many processes occurring in the gel is very similar to the course of processes

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