Progressive freezing and suspension crystallization methods for tetrahydrofuran recovery from Grignard reagent wastewater

Freezing methods, progressive freezing and suspension crystallization, were examined for treating Grignard reagent wastewater containing tetrahydrofuran (THF) used as a solvent. The effect of freezing temperature, addition of seed ice crystals, and stirring speed on performance were investigated. The addition of seed ice with appropriate temperature contributed to enhance the purity. The optimal operating conditions of freezing temperature and stirring speed were -6 degrees C and 300 rpm respectively while the removal efficiency of COD was above 90%. The suspension crystallization is superior to progressive freezing in terms of performance and energy consumption, with an estimation of about 38.26 kW h per ton of wastewater treated. Based on these results, a freezing/concentration concept for THF recovery from Grignard reagent wastewater is proposed. (C) 2017 Elsevier Ltd. All rights reserved.