Separation of phenolic compounds from water by using monoterpenoid and fatty acid based hydrophobic deep eutectic solvents

Abstract

Nitrophenol-based chemicals are hazardous compounds that negatively impact human health and the environment. These pollutants are used in agriculture as fungicides and pesticides and contribute to groundwater contamination. These compounds are also commonly used for making dyes, rubber materials, and paint coloring. Nitrophenol compounds are known to cause problems with respiratory, ocular, and hematological-related health issues. Due to their environmental and health impacts, the World Health Organization has listed these compounds as one of the most widely observed pollutants that must be addressed. Hydrophobic deep eutectic solvents (HDES) are widely popular for water treatment as they are formed by combining non-toxic, renewable, and biodegradable materials. In this work, three different types of monoterpenoid and fatty acid-based HDES were used in liquid–liquid extraction to remove varying concentrations of 2- and 4-nitrophenol compounds from water. Liquid-liquid extractions were performed at various temperatures and mixing times to optimize the extraction performance. Ultraviolet–visible (UV–Vis) spectrophotometry and mass spectroscopy were utilized to determine and confirm the exaction efficiencies of the various HDES systems. In addition to experimental data, density functional theory (DFT) and classical molecular dynamics (MD) simulations were carried out to study close-range interactions and how HDES and phenolic contaminants interact with each other in the bulk phase. Radial and spatial distribution functions, hydrogen bonding distribution, and energy profiles were studied in detail. The results show high extraction efficiency of up to 95% at short HDES exposure time to contaminated water with both phenolic compounds considered in this work.