Applied Research on the Resource Recovery of Formaldehyde in Pesticide Wastewater

Applied research on the technology of resource recovery of formaldehyde in pesticide wastewater through compression distillation was accomplished intensively in this study. Vaporliquid equilibrium data of the low-molar fraction formaldehyde aqueous solution were measured accurately in experiments. The results were in high accordance with the theoretical values through data association. It filled in a gap in data at the zone of low formaldehyde molar fraction (particularly below 0.006) and also provided theoretical basis for the distillation column design for recycling formaldehyde. Systematic experimental research investigated the recovery of formaldehyde in pesticide wastewater by compression distillation. The distillation column was operated under a top pressure of 0.2 to 0.4 MPa and with feed formaldehyde molar fraction range of approximately 0.006 to 0.03. The formaldehyde molar fractions at the top and bottom of column were 0.15 and 0.00072, respectively. Therefore, concentrated formaldehyde solution can be obtained for recycling, whereas the formaldehyde composition of residual wastewater reached the standard of biochemical treatment. Therefore, compression distillation was a feasible approach to the treatment of wastewater with low-molar fraction formaldehyde.