Research Of High Pwf Cellulose Membrane Preparation And Application In Oil/Water Separation

Efficient processes for food oily wastewater separation are highly desired yet still challenging, because of its complex component and high emulsibility. The filtration membranes especially hydrophilic membranes have been acknowledged as an effective technology for treating emulsified oil/water mixtures, even the separation of dissolved oil. Hydrophilic membranes have the excellent performances of oil/water separation and antifouling for oil. But the high cost has became the restricted condition of their industrial applications. Cellulose is the most abundant natural raw material in the world. Apart from being biodegradable and hydrophilic, cellulose possesses excellent thermal and chemical stability and low cost. So, it is a desired material for the preparation of hydrophilic membranes. Facing global environmental pollution and resource depletion, new materials research and development has been focusing in natural raw materials.The native cellulose was completely dissolved in low-temperature 7wt%NaOH/12wt% urea aqueous solution. We altered the conditions of additive and coagulation, for obtaining suitable structure and property of RC membranes which with high pure water flux (PWT). Finally, evaluating their performance in separating food oily wastewater. The main contents and conclusions in this thesis are divided into the following parts:1. RC membranes were prepared by immersion precipitation phase inversion method, and polyethylene glycol (PEG) or others were mixed in cellulose solution as additives. Effects of PEG molecular weight and addition ratio, coagulant components and temperature on structure and properties of RC membranes were investigated systematically. The higher molecular weight and proportion of additives, the looser structure and higher PWF of RC membranes coagulated from high temperature 5%Na2SO4 aqueous solution. It has been confirmed that the optimal preparation conditions of RC membranes with high PWF were as follows: cellulose casting solutions added PEG 1000 as the additive and proportion (PEG1000:cellulose) was 1.5, coagulated from 5%Na2SO4 aqueous solution of 40℃.2. Exploring the formation mechanism of RC membrane in the low-temperature solvent. Low-temperature 7wt%NaOH/12wt% urea aqueous solution is solvent, and PEG/cellulose casting solution is a system that dissolved at low temperature, but occurred phase separation at high temperature. The structure and performance of RC membranes are influenced by nonsolvent induced phase separation (NIPS) and thermally induced phase separation (TIPS). The results show that the formation mechanism dominated by NIPS at low-temperature coagulants, but dominated by TIPS at high-temperature coagulants.3. Studies of evaluating the performance of RC membranes with high PWF in treating oil/water emulsions. Results show that the membrane can effectively separate oil-in-water emulsions with high separation efficiency and has excellent anti-fouling ability. The membrane performed more than 98% oil retention in treatment of the peanut oil/water emulsion and the food oily wastewater. The oil concentration of filtrates is less than 10 mg/L that meet emissions standards. Permeate flux recovery ratio of membranes are closed to 90% after cleaning that can ensure their reusability.