Special Issue "Advances in Ultrasound Stimulated Crystallization"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystal Engineering".

Deadline for manuscript submissions: 30 June 2018

Special Issue Editor

Guest Editor
Dr. Judy Lee

Chemical and Process Engineering, University of Surrey, UK
Website | E-Mail
Interests: acoustic cavitation; sonoluminescence; ultrasound processing; sonocrystallisation; membrane filtrations

Special Issue Information

Dear Colleagues,

It is my great pleasure to introduce to you all the exciting Special Issue on “Advances in Ultrasound Stimulated Crystallization”. Crystallization is an important industrial process and the benefits of ultrasound in crystallization is well known but poorly understood. No doubt to the researchers in this field, the mechanism behind sonocrystallization is still contentious. This is not surprising considering ultrasound induce cavitation and crystallization processes are two complex dynamic systems, and when coupled together this complexity is compounded. 

This Special Issue hopes to bring together research which showcases the advances in the application of ultrasound in crystallization processes and in particular any work which could shed some light on the mechanism behind sonocrystallization.

Dr. Judy Lee
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Sonocrystallization
  • Polymorphism
  • Crystal Nucleation
  • Acoustic Cavitation

Published Papers (3 papers)

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Research

Open AccessArticle The Effect of Ultrasound on the Crystallisation of Paracetamol in the Presence of Structurally Similar Impurities
Crystals 2017, 7(10), 294; doi:10.3390/cryst7100294
Received: 17 August 2017 / Revised: 14 September 2017 / Accepted: 26 September 2017 / Published: 30 September 2017
PDF Full-text (18121 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Sono-crystallisation has been used to enhance crystalline product quality particularly in terms of purity, particle size and size distribution. In this work, the effect of impurities and ultrasound on crystallisation processes (nucleation temperature, yield) and crystal properties (crystal size distribution determined by Focused
[...] Read more.
Sono-crystallisation has been used to enhance crystalline product quality particularly in terms of purity, particle size and size distribution. In this work, the effect of impurities and ultrasound on crystallisation processes (nucleation temperature, yield) and crystal properties (crystal size distribution determined by Focused Beam Reflectance Measurement (FBRM), crystal habit, filtration rate and impurity content in the crystal product by Liquid Chromatography-Mass Spectroscopy (LC-MS)) were investigated in bulk suspension crystallisation experiments with and without the use of ultrasound. The results demonstrate that ultrasonic intervention has a significant effect on both crystallisation and product crystal properties. It increases the nucleation rate resulting in smaller particles and a narrower Particle Size Distribution (PSD), the yield has been shown to be increase as has the product purity. The effect of ultrasound is to reduce the level acetanilide impurity incorporated during growth from a 2 mol% solution of the selected impurity from 0.85 mol% to 0.35 mol% and likewise ultrasound reduces the uptake of metacetamol from 1.88 mol% to 1.52 mol%. Full article
(This article belongs to the Special Issue Advances in Ultrasound Stimulated Crystallization)
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Open AccessArticle Ultrasound Assisted Particle Size Control by Continuous Seed Generation and Batch Growth
Crystals 2017, 7(7), 195; doi:10.3390/cryst7070195
Received: 10 April 2017 / Revised: 16 June 2017 / Accepted: 22 June 2017 / Published: 29 June 2017
PDF Full-text (4752 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Controlling particle size is essential for crystal quality in the chemical and pharmaceutical industry. Several articles illustrate the potential of ultrasound to tune this particle size during the crystallization process. This paper investigates how ultrasound can control the particle size distribution (PSD) of
[...] Read more.
Controlling particle size is essential for crystal quality in the chemical and pharmaceutical industry. Several articles illustrate the potential of ultrasound to tune this particle size during the crystallization process. This paper investigates how ultrasound can control the particle size distribution (PSD) of acetaminophen crystals by continuous seed generation in a tubular crystallizer followed by batch growth. It is demonstrated that the supersaturation ratio at which ultrasound starts seed generation has a substantial effect on the final PSD while the applied power is insignificant in the studied conditions. The higher the supersaturation ratio, the smaller the final crystals become up to a supersaturation ratio of 1.56. Furthermore, it was shown that ultrasound can also impact the final PSD when applied during the growth phase. Frequencies of 850 kHz or below reduce the final particle size; the lower the applied frequency, the smaller the crystals become. In conclusion, one could state that ultrasound is able to control the particle size during seed generation and subsequent growth until the final particle size. Full article
(This article belongs to the Special Issue Advances in Ultrasound Stimulated Crystallization)
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Open AccessArticle Agglomeration Control during Ultrasonic Crystallization of an Active Pharmaceutical Ingredient
Crystals 2017, 7(2), 40; doi:10.3390/cryst7020040
Received: 16 January 2017 / Revised: 1 February 2017 / Accepted: 2 February 2017 / Published: 8 February 2017
Cited by 2 | PDF Full-text (30154 KB) | HTML Full-text | XML Full-text
Abstract
Application of ultrasound during crystallization can efficiently inhibit agglomeration. However, the mechanism is unclear and sonication is usually enabled throughout the entire process, which increases the energy demand. Additionally, improper operation results in significant crystal damage. Therefore, the present work addresses these issues
[...] Read more.
Application of ultrasound during crystallization can efficiently inhibit agglomeration. However, the mechanism is unclear and sonication is usually enabled throughout the entire process, which increases the energy demand. Additionally, improper operation results in significant crystal damage. Therefore, the present work addresses these issues by identifying the stage in which sonication impacts agglomeration without eroding the crystals. This study was performed using a commercially available API that showed a high tendency to agglomerate during seeded crystallization. The crystallization progress was monitored using process analytical tools (PAT), including focus beam reflectance measurements (FBRM) to track to crystal size and number and Fourier transform infrared spectroscopy (FTIR) to quantify the supersaturation level. These tools provided insight in the mechanism by which ultrasound inhibits agglomeration. A combination of improved micromixing, fast crystal formation which accelerates depletion of the supersaturation and a higher collision frequency prevent crystal cementation to occur. The use of ultrasound as a post-treatment can break some of the agglomerates, but resulted in fractured crystals. Alternatively, sonication during the initial seeding stage could assist in generating nuclei and prevent agglomeration, provided that ultrasound was enabled until complete desupersaturation at the seeding temperature. FTIR and FBRM can be used to determine this end point. Full article
(This article belongs to the Special Issue Advances in Ultrasound Stimulated Crystallization)
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