Optimization of Organic Nitrogen Compounds Removal in Pymetrozine Production Wastewater Using Complex Extraction with Response-Surface Methodology

Abstract

Production wastewater of pymetrozine leads to producing a lot of highly concentrated saline organic wastewater so that the related environmental aspects must be studied. In this study, a response surface methodology (RSM) was employed to investigate the effects of different operating conditions on the removal organic nitrogen compounds in pymetrozine production wastewater by a complex extraction with a mixed extractant containing di(2-ethylhexyl) phosphate and benzene. The Box-Behnken design (BBD) was used to optimize the extraction process and to evaluate the individual and interactions effects of the pH, diluent volume fraction, water to organic phase (W/O), temperature, and extraction time on organic nitrogen compounds removal. An optimized extraction efficiency of 78.91% from the RSM was obtained at a pH of 12.7, diluent volume fraction of 54.8%, W/O of 0.8, temperature of 24°C, extraction time of 35 min. Also, 2.94 mol/L of HCl solution was used as stripping agent in the back extraction process. The back extraction efficiency of organic nitrogen compounds reached 88.9% when the W/O was 1∶1 and the extraction time was 15 min. An extractant after stripping can be repeatedly used by test verification.