Solventless Extraction of Phenol Using TOPO-Impregnated Hollow Fiber Membranes

Phenol and its derivatives are toxic pollutants which are often found in the effluents emanating from various industries. Since these are useful raw materials in various chemical processes, recovery of phenol from wastewater through adsorption or solvent extraction is quite attractive. While both of these technologies exhibit high solute retention capacity, adsorption tends to be a slower process and fixed beds are difficult to operate continuously. On the other hand, extraction is rapid but it requires large quantities of organic solvent and is more expensive. Besides, dispersion-based solvent extraction also results in emulsions and downstream separation problems.

The objective of this research was to obviate the limitations of adsorption and extraction by impregnating trioctylphosphine oxide (TOPO) - a solid extractant, into the pores of hydrophobic hollow fiber membranes. While hollow fiber support provide large interfacial area to the resulting extractant impregnated hollow fiber membranes (EIHFMs), high affinity of TOPO for phenol resulted in large adsorption capacity. EIHFMs exhibited excellent adsorption/desorption performance at 500-2000 mg/L phenol and equilibrium was achieved within 15 minutes of contact. Adsorption kinetics was described by pseudo-second-order model, while Langmuir model was used to plot the isotherm. Phenol was desorbed using sodium hydroxide and EIHFM performance remained quite stable during repeated operations. These results indicate that the use of EIHFMs in phenol recovery from wastewater is quite promising, and the EIHFMs can be a promising alternative to the conventional adsorbents.