Studies On New Liquid Membrane Treatment Of Phenolic Wastewater

Environmental pollution control of phenolic industrial wastewater is an important global research topic.The traditional method of treating phenol wastewater is complicated,and the secondary pollution is serious.The application of a novel polymer inclusion membrane(PIM)separation technology on treatment of phenol wastewater was discussed in this paper.The main research contents were as follows:(1)The PIM containing polyvinyl chloride(PVC),polyvinylidene fluoride(PVDF)and cellulose triacetate(CTA)as the base polymer,Dis-(2-ethylhexyl)phosphoric acid(D2EHPA)as the carrier was prepared by solvent evaporation casting technique.The effects of preparation conditions such as casting solution concentration,plasticizer content,carrier content and volatile temperature on the structure,morphology,mechanical strength and mass transfer performance of the polymer inclusion membrane were studied.The preparation process of PIM was further optimized.The special effects of the base polymer on the mass transfer behavior of phenol were discussed and analyzed.The application of the polymer inclusion membrane with D2 EHPA as the carrier was confirmed in the simulated phenol wastewater.(2)The series of PVC/OCT-polymer inclusion membrane(PO-PIM)was first prepared with n-octanol(OCT)as the carrier and PVC as the base polymer.The surface morphology of a series of PO-PIM membrane was investigated by scanning electron microscopy(SEM).The mass transfer behavior of PO-PIM on phenol was confirmed and optimized under the condition of weak acidity and strong alkaline solution as the feed phase and the stripping phase,respectively.The influence of membrane composition on mass transfer rate and mass transfer stability was discussed.The mass transfer kinetics and thermodynamic behavior of PO-PIM on phenol were established.The results showed that the mass transfer of PO-PIM on phenol followed the first-order kinetic equation,and the control step of mass transfer rate was diffusion process.With the increase of the carrier content,the membrane surface changed from homogeneous to porous,and the membrane porosity reached the maximum value and the highest mass transfer rate was formed when the carrier content was 81.5%.After the carrier content exceeded 81.5%,the porosity of membrane decreased due to the higher swelling degree.Under the optimum separation conditions,the feeding phase pH is 2 and the receiving phase contains 0.1 mol/L sodium hydroxide,the mass transfer coefficient of PO-PIM to phenol was 13.6?m/s.(3)The stability of PO-PIM was decreasing when the carrier content was more than 70.6%.The introduction of hydrophobic components kerosene,liquid paraffin and vegetable oil can improve the stability of PIM.The effects of three hydrophobic additives on the contact angle and the mass transfer stability of PO-PIM were investigated.The mass transfer behavior of kerosene-PO-PIM(KPO-PIM)under the optimum mass transfer conditions was discussed.The results showed that the hydrophobic component could significantly improve the stability of PO-PIM.The mass transfer efficiency of KPO-PIM could still be more than 90% when the addition amount of kerosene was 0.4g.Under the optimum conditions,the mass transfer coefficient of KPO-PIM to phenol could reach 14.21?m/s,which showed its potential application value in phenol wastewater.(4)The effects of KPO-PIM on the mass transfer selectivity of various phenolic compounds was investigated.And the application of KPO-PIM to phenol wastewater treatment was simulated when the concentration of phenol was 200-17500mg/L.The result showed that KPO-PIM with the octanol content of 69% and the kerosene content of 13% had different mass transfer selectivity for monatomic phenol,dihydric phenol,phenolic acids and phenolic aldehyde compounds.The mass transfer rate decreased with the increase of the number of hydrogen bonds formed between n-octanol and phenolic species.When the concentration of phenol was less than 12000 mg/L,the mass transfer flux of KPO-PIM increased with the increase of the phenol concentration.However,the permeation flux was no longer increasing when the concentration of phenol was more than 12000 mg/L.The enrichment ratio of KPO-PIM to phenol was 3.51 times within 48 h,which provided basic research data for the comprehensive management of phenol wastewater.