Abstract
Sustainability and greenness are the concepts of growing interest in the area of research as well as industries. One of the frequently encountered challenges faced in research and industrial fields is the solubility of the hydrophobic compound. Conventionally organic solvents are used in various applications; however, their contribution to environmental pollution, the huge energy requirement for separation and higher consumption lead to unsustainable practice. We require solvents that curtail the usage of hazardous material, increase the competency of mass and energy and embrace the concept of recyclability or renewability. Hydrotropy is one of the approaches for fulfilling these requirements. The phenomenon of solubilizing hydrophobic compound using hydrotrope is termed hydrotropy. Researchers of various fields are attracted to hydrotropy due to its unique physicochemical properties. In this review article, fundamentals about hydrotropes and various mechanisms involved in hydrotropy have been discussed. Hydrotropes are widely used in separation, heterogeneous chemical reactions, natural product extraction and pharmaceuticals. Applications of hydrotropes in these fields are discussed at length. We have examined the significant outcomes and correlated them with green engineering and green chemistry principles, which could give an overall picture of hydrotropy as a green and sustainable approach for the above applications.
Funding source: Science and Engineering Research Board
Award Identifier / Grant number: EMR/2017/003893
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Author contribution: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
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Research funding: We are thankful to the Science and Engineering Research Board (SERB) (project no: EMR/2017/003893) under the Department of Science and Technology (DST), India, for financial support.
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Conflict of interest statement: The authors declare no conflicts of interest regarding this article.
Appendix: Toxicological information of hydrotrope
| Sr. no. | Hydrotrope | Toxicity |
|---|---|---|
| 1. | Sodium cumene sulfonate (NaCuS) | Oral LD50: >7000 mg/kg |
| Dermal LD50: >2000 mg/kg | ||
| Inhalation LD50: >770,000 mg/m3 | ||
| 2. | Sodium p-toluene sulfonate (NaPTS) | Oral LD50: 6500 mg/kg |
| Intravenous LD50: 1700 mg/kg | ||
| 3. | Sodium xylene sulfonate (NaXS) | Oral LD50: >5000 mg/kg |
| Dermal LD50: 182–727 mg/kg | ||
| 4. | Sodium benzoate (NaB) | Oral LD50: 4070 mg/kg |
| 5. | Sodium salicylate (NaS) | Oral LD50: 540 mg/kg |
| 6. | Nicotinamide | Oral LD50: 2500 mg/kg |
| 7. | Urea | Oral LD50: 8471 mg/kg |
| 8. | p-Toluene sulfonic acid (p-TsOH) | Oral LD50: 1410 mg/kg |
| 9. | Maleic acid | Oral LD50: 708 mg/kg |
| Dermal LD50: 1560 mg/kg | ||
| Inhalation LD50: >720 mg/m3 | ||
| 10. | Ethanol | Oral LD50: 7060 mg/kg |
| Dermal LD50: 20000 mg/kg | ||
| Inhalation LD50: 66000 mg/Lit | ||
| 11. | Methanol | Oral LD50: 1187–2769 mg/kg |
| Dermal LD50: 17100 mg/kg | ||
| Inhalation LD50: 128 mg/L | ||
| 12. | Acetone | Oral LD50: 5800 mg/kg |
| Dermal LD50: 20000 mg/kg | ||
| Inhalation LD50: 71 mg/L |
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