Fabrication And Oil-water Emulsion Separation Performance Of Polyaniline Modified Porous Membrane

The acceleration of industrialization, frequent oil spills and daily life can generate large quantities of oily wastewater, which not only is harmful to environment and human health but also has a very bad influence on ecosystem. Therefore it is extremely urgent to recycle oily wastewater. Oil-water separation membrane has attracted much attention in oily wastewater treatment owing to its high separation efficiency. However, existing oil-water separation membrane can’t offer a satisfying result, let alone achieve a direct intelligent separation of oil-water emulsion. To this end, polyaniline-modified porous membrane was prepared via in-situ polymerization in this dissertation. An efficient intelligent separation of both oil-in-water emulsion and water-in-oil emulsion was realized by changing substrate surface roughness and surface wettability.To improve surface roughness and surface wettability, filter paper and polypropylene fiber membrane were used as support materials, on which aniline polymerization in-situ was performed through slow addition of oxidant. It was found that the amount of polyaniline in the base raised along with the aniline monomer concentration, polymerization duration and times of polymerization, which resulted in an obvious increase of surface roughness. After polyaniline modifying, the under-water oil contact angle and under-oil water contact angle of the substrate were both greater than 150°, rendering under-water superoleophobic and under-oil superhydrophobic properties.Polyaniline-modified filter paper can separate water-in-oil emulsion successfully when aniline monomer concentration was 0.2 mol/L and polymerization time was 5 h. The separation efficiency was above 99% and the liquid droplet size was less than 1 μm after separating. Water-in-oil emulsion can be still separated by polyaniline-modified filter paper after 10 separation cycles and the separation efficiency was over 99%, demonstrating a good cycle performance. Nevertheless, polyaniline-modified filter paper was easily swelled in water and can’t separate of oil-in-water emulsion effectively.In order to further realize an intelligent separation of oil-water emulsion, polypropylene fiber membrane was chosen as support material and modified with polyaniline. The as-fabricated polyaniline membrane can separate both oil-in-water emulsion and water-in-oil emulsion successfully when aniline monomer concentration was 0.2 mol/L and a 4-hour polymerization was repeated over twice, achieving an efficient intelligent separation of oil-water emulsion. For oil-in-water emulsion, its filtrate liquid droplet size was so small that oil phase in filtrate can’t be detected by spectrum after polyaniline-modified membrane separating. While for water-in-oil emulsion, the filtrate liquid droplet size was smaller than 1 μm, leaving very few water in filtrate and offering a separation efficiency over 99%. Polyaniline-modified membrane had a good cycle performance both for oil-in-water emulsion and water-in-oil emulsion and its filtrate remained transparent after 10 cycles, showing an excellent cycle stability.