Efficient and reversible absorption of low pressure NH3 by functional type V deep eutectic solvents based on phenol and hydroxypyridine

Abstract

The efficient capture and separation of ammonia (NH₃), a fundamental raw material as well as widespread pollutant, is significant in the fertilizer industry and for environmental protection protocols. In this work, several new type V deep eutectic solvents (DESs), composed of hydroxypyridine and phenol, were designed as efficient and reversible NH₃ absorbents. All the DESs have low viscosity, good NH₃ absorption performance and high NH₃/CO₂ selectivity. The optimal 3-hydroxypyridine/phenol (1 : 5) ratio could respectively capture 10.00 mol kg⁻¹ and 4.63 mol kg⁻¹ NH₃ at pressures of 101.3 kPa and 10.0 kPa, better than most other DESs and ILs reported in the literature. The prepared DESs show satisfactory thermal stability and highly reversible absorption performance. By comprehensively analyzing the absorption behavior and spectroscopic results, the effective NH₃ absorption ability of DESs was deduced being due to a relatively strong interaction between multiple weak acidic hydroxyl groups and basic NH₃.