Removal of phenol from aqueous phenol solution using bio-emulsion

Abstract

• Emulsion prepared using Lecithin is used to remove phenol in aqueous phenol solution. • Operating parameters are optimized to obtain stable emulsion and maximum extraction. • Bio-emulsion is very stable and durable during extraction and has low removal rate. • Emulsion effective diffusivity decreases with increasing ELM process temperature. • The rate of removal process is controlled by diffusion over stripping. Emulsion liquid membrane, an efficient water treatment technique while leaving minimal residue, has major challenges in scaling up due to rapid emulsion swelling and disintegration during extraction. In this study, Lecithin, a biosurfactant is used to prepare an emulsion (bio-emulsion) with kerosene and aqueous NaOH solution to remove phenol from aqueous phenol solution. The experimental conditions are varied and optimised to obtain a possible maximum stability and removal efficiency. The stand-alone stability of the emulsion prepared at an optimum condition is more than 2 h. The maximum removal efficiency of ~90% at 20 °C is obtained with the bio-emulsion prepared with 45% lecithin, oil:water ratio of 2:1, and treatment ratio of 1:1. Thermodynamic studies revealed that the process is feasible, exothermic ( Δ H = −41 kJ/mol), spontaneous (ΔG < 0 J/mol), and ordered (ΔS = −124 J/mol·K). Rate of removal is controlled by the rate of phenol diffusion through the oil membrane rather than the reaction between phenol and NaOH in the internal phase. The effective diffusivity of the emulsion linearly decreases with an increase in temperature.