Preparation Of Imidazole Ionic Liquid-polyvinylidene Fluoride Membrane And Its Separation Of VOCs In Pharmaceutical Wastewater

The pharmaceutical industry is one of the important sources of volatile organic compounds(VOCs)pollution.Organic solvents generate a large amount of VOCs in the pharmaceutical production process(biosynthesis,chemical synthesis of pharmaceuticals)The pharmaceutical production process is complicated and the VOCs pollutants produced are numerous,endangering people’s lives.Therefore,researchers have been working hard to develop effective separation techniques to deal with VOCs in the pharmaceutical industry.As a new and efficient separation technology,membrane separation technology has received widespread attention due to its strong processing capacity and simple operation Driven by pressure difference and concentration difference,membrane separation technology can achieve the separation effect of low energy consumption and high flux of pollutants.The membrane is a key part of membrane separation technology.In practical applications,membranes are susceptible to fouling and lead to reduced flux.Therefore,proper modification of the membrane to increase the service life of the membrane has become the main research direction of scientists.In this paper,imidazole-based ionic liquids are used as modified materials to modify polyvinylidene fluoride membranes(PVDF)to prepare IL/PVDF membranes,and the IL/PVDF membranes are used to separate VOCs(toluene,phenol,naphthalene).The main contents of the study are summarized as follows:Part Ⅰ Preparation and characterization of imidazole-based ionic liquid modified polyvinylidene fluoride membraneThe ionic liquid(IL)is prepared by a classical two-step synthesis method and characterized by infrared.In the process of membrane preparation,non-solvent-induced phase separation(NIPS)is one of the most widely used membrane preparation methods compared to thermally induced phase separation(TIPS).The NIPS method was used to prepare PVDF membrane and IL/PVDF membrane.[PMIM][BF4],[BMIM][BF4],[HMIM][BF4],[OMIM][BF4]four kinds of imidazole ionic liquids were synthesized to prepare corresponding IL/PVDF membranes.The methods of FT-IR,DSC,XRD and SEM have proved that IL/PVDF has been successfully prepared.Compared with PVDF film,IL/PVDF film has improved thermal stability and increased crystallinity.SEM results show that there are two phase separation competitions(delayed liquid-liquid phase separation and transient liquid-liquid phase separation)during the formation of IL/PVDF membrane.With the increase of IL dosage,the transient liquid-liquid phase separation process of the membrane Intensified,more macroporous structures appeared on the surface of the membrane.Part Ⅱ Study on the separation performance of imidazole-based ionic liquid modified polyvinylidene fluoride membraneThrough the meas’urement of specific surface area,contact angle,pure water flux,mechanical strength and other parameters,the effect of IL on the separation performance of IL/PVDF membrane was compared.The results show that the IL/PVDF membrane has a larger specific surface area;the hydrophobicity of the membrane increases as the length of the imidazole IL carbon chain increases;the flux of pure water increases by about 5-6 times;the mechanical strength of the membrane is higher than that of the PVDF membranePart Ⅲ Application of IL/PVDF membrane in the separation of VOCs in pharmaceutical wastewaterFrom the data of PVDF membrane and IL/PVDF membrane to VOCs rejection rate,multi-cycle rejection rate and flux recovery rate,the performance of membrane separation VOCs was investigated.Studies have shown that:for toluene:when toluene is retained,although the PVDF membrane has a better removal rate for toluene,its flux is lower.Under high-flux treatment,the IL/PVDF membrane performs better;for phenol:change The membrane rejection rate does not increase significantly after the resistance,and the IL/PVDF membrane has an unsatisfactory separation effect on phenol;for naphthalene when it retains naphthalene,the IL/PVDF membrane has an excellent separation effect Under high-throughput processing,the IL/PVDF membrane performs still outstanding.In the multi-cycle experiment,the IL/PVDF membrane showed good stability.When removing toluene and naphthalene,the flux recovery rate of the IL/PVDF membrane exceeded 90%,and the repeat effect was good.A simulated pharmaceutical wastewater treatment experiment was done,and the results showed that the interception rate of IL/PVDF membrane was 93.10%,and the interception effect was good.