The application of blended surfactant ionic liquid in emulsion liquid membrane for phenol removal from aqueous waste solution

Abstract

Emulsion liquid membrane (ELM) is a liquid membrane technology that has the capability to remove metals and organic compounds from aqueous waste solution in high efficiency. Phenol as one of organic compounds that is toxic and has carcinogenic effect. Phenol exists in industrial effluent especially from petrochemical, paint, pharmaceutical industries, and refineries. However, application of ELM in industries is still limited due to the instability of emulsion membrane during the process. Thus, this research investigates the significant use of blended surfactant in emulsion preparation and the effect of ionic liquid on emulsion stability and extraction performance of ELM process. Selection of liquid membrane components was carried out to determine the optimum ratio of palm oil to kerosene as a solvent and to determine the suitable stripping agent to be used. In this research, 7:3 ratio of palm oil to kerosene was selected as the liquid membrane phase and sodium hydroxide as the stripping agent phase. Then, blended surfactant emulsion liquid membrane was formulated using several composition of mixed surfactant of Span 80 and Tween 80. The stability of primary water-in oil (W/O) emulsion was studied by manipulating several parameters such as hydrophile-lipophile balance (HLB) range, blended surfactant concentration, homogenizer speed, emulsifying time, and organic membrane to internal (O/I) ratio using one factor at one-time method. The results showed that the most stable emulsion was obtained at HLB 5, 3% (w/v) of blended surfactant concentration, 8000 rpm homogenizer speed, 3 minutes emulsifying time and 3:1 O/I ratio. Using this stable W/O emulsion, the extraction performance of phenol was studied by manipulating several parameters such as agitation speed, extraction time, ionic liquid concentration and treat ratio (emulsion phase to feed phase ratio). This system was optimized using the response surface methodology. The results showed that the optimum conditions were obtained at 267 rpm agitation speed, 5 minutes extraction time, 0.107% (w/v) ionic liquid concentration and 1:7.3 treat ratio where 83% of phenol was extracted. At this condition, the recovered phenol obtained was about 11 times enrichment ratio as concentrated phenolate solution. In conclusion, blended surfactant ionic liquid has the potential to increase emulsion stability, phenol extraction and recovery.