Effect of temperature on the heat treatment to recover green solvent from emulsion liquid membranes used in the extraction of Cr(VI)

One of the main difficulties to achieve a good performance with the emulsion liquid membranes technique for metal extraction is the solvent phase recovery. In the present work, heating is proposed as an efficient and easy method to destabilize extraction liquid membranes (ELM) used to recover Cr(VI) from wastewaters. The formulated ELM consists of sunflower oil as vegetable green solvent, PGPR and Tween 80 as surfactants, tri-n-octylphosphine oxide (TOPO) as an extractant and a sodium carbonate Na2CO3 (0.5 M) solution as the internal water phase. The effect of the temperature during demulsification process was investigated. The membrane phase was successfully demulsified by heating at 80 degrees C during 2 h, with a water content less than 4%. Emulsion were reformulated with recovered oil up to four times to extract Cr(VI) with an extraction efficiency (EE) up to 99 %. Physical properties of water-in-oil (W-1/O) and ELMs formulated, using fresh and recovered oil, were characterized by dynamic light scattering (DLS) and multiple light scattering (MLS). Emulsions reformulated with recovered sunflower demonstrated to have not oil degradation, evaluated by dynamic scanning calorimetry (DSC) and Fourier transform infrared (FTIR), and were appropriate to form stable W-1/O with high Cr(VI) removal capacity.