Study On The Treatment Process Of Oily Wastewater Using Coagulation-hydrophilic And Oleophobic PVDF Membrane Filtration

In recent years,the pollution of wastewater on environment and the wastewater quality are getting more and more serious,conventional oily wastewater treatment processes cannot meet well with the emission standards.So in this study,a coagulation-ultrafiltration combined process was investigated on oily wastewater treatment.In this study,the dithiocarbamate coagulant-DTC(D230),was prepared by the Jeffamine-D230.The product was characterized by elemental analysis and IR spectra,and the product yield was calculated.The effects of DTC dosage,pH and water temperature on the performance of coagulation were investigated.The optimum operation conditions were confirmed as 20 ℃ of water temperature,without water pH adjustment,DTC concentration of 0.3 g/L,Fe2 + concentration of 0.06 g/L,quick stirring speed of 200 r/min for 10 s and slow stirring speed of 50 r/min for 10 min.The removal efficiency of CODcr,oil content,suspended solids and turbidity could be achieve at 91.77%、90.48%、98.14%、93.81%。 respectively.After the coagulation experiment,the flocs in the oily wastewater were characterized by IR spectra.The same type of functional groups were observed in the flocs and DTC,which implied the possible produced flocs were originated from DTC.The attachment of the oil droplets on the flocs and the fill of the pores were observed under SEM,which confirmed the flocs produced by the complexation process between DTC and Fe2 + do have the oil-removing effects.In the ultrafiltration experiment,the water contact angle,n-hexadecane contact angle,porosity,average pore diameter and the mechanical strength of a hydrophilic and oleophobic PVDF membrane were characterized.The results showed that the modified membrane had an excellent hydrophilic and oleophobic performance,which is suitable for the low pressure operation.After settling for 60 min,the treated water under the liquid level of 3 cm in the coagulation experiment was used as the feed water of the ultrafiltration process.The oily water flux was degradated to 55.74%,the remaining oil concentration was 2.86 mg/L and the turbidity was close to 0 after one cycle operation under the optimum operation conditions in transmembrane pressure of 0.1 Mpa and a run cycle of 80 min.The ultrasonication-submerging method was adopted to regenerate the polluted modified membrane after one cycle operation.The polluted membrane was submerged into pure water and sonicated for 30 min,the black pollutants on membrane surface were completely cleaned,and the relative flux recovery rate was 97.13%.The self-resistance Rm,the reversible pollution resistance R1 and the irreversible pollution resistance R2 of the membrane were analyzed according to the darcy formula.The results showed that the R1 occupied the largest percentage of all.