Treatment of high-concentration phenolic wastewater by pyridine–coal tar complexation extraction system

AbstractTo effectively and economically separate and recycle the useful phenols from industrial effluents, as well as provide a comprehensive method for reutilization of coal tar to improve its economic value, the pyridine–coal tar originating from lignite gasification process was innovatively developed as a promising extractant. The extraction characteristics of the pyridine–coal tar were studied via treatment of 4,000 mg/L phenolic wastewater. Maximum extraction power of phenol on the extractant was obtained with 8% pyridine, 1.4:1 of phase ratio, 160 rpm of rotary speed at weak acid or neutral pH, which the dephenolization efficiency was as high as 90% within 5 min at 50°C. The extracted phenol in pyridine–coal tar could be recovered, and the regenerated extractant can be reused for at least 5 cycles with no obvious loss in the dephenolization efficiency. The pyridine–coal tar was also used to extract phenol from practical phenolic wastewater, and the dephenolization efficiency was 86.7%. Based on the ...