Study On Environmentally Responsive Textile-Based Adsorbent Materials For Efficient Oil/Water Separation

With the development of global economic and industry, the environment problem caused by oily wastewater and oil slick pollution has attracted worldwide attention. The traditional oil/water separation technologies have many limitations, including high cost, low efficiency, secondary pollution etc. Nowadays, scientists haves developed an efficient method for oil/water separation by using materials with special wettability. Our work focused on preparing a series of smart cotton fabric via atom transfer radical polymerization(ATRP) technique for oil/water separation.(1) Although a large amount of hydroxyl groups exist in cellulose fiber, they are not reactive enough to be used as grafting sites. In this paper, three methods were developed to introduce amino groups on the surface of cotton, including the amino silicone finishing, silane coupling agents modification and the dye intermediates reaction. The surface chemistry, topography, surface wettability were investigated through infrared spectroscopy(IR), ultraviolet spectroscopy(UV), scanning electron microscopy(SEM) and contact angle measurement(CA). And then the durability during washing, softness and whiteness were characterized. It is found that the dye intermediates reaction method could produce a lot of amino groups on cotton fabric. And the fabric had a better washing stability, superior softness and other performance comparing to those treated with other methods. Thus, the dye intermediates modification method was used in the following studies.(2) Poly(methacrylic acid)(PMAA) was grafted onto amino-functionalized cotton surface via surface initiated ATRP technology. The pH responsive performance was characterized by IR and water/oil contact angle measurements(WCA/OCA). With the rising pH, the surface transited from superhydrophobic(WCA~150°) to superhydrophilic(WCA=0°) and underwater superoleophobic, and the wetting time correspondingly reduced from 120 s to 0 s. It is caused by the variation of ionization state of PMAA at different pH. At low pH, the protonated polymers prevented the fabric from being wetted by water and attained high affinity to oil. At high pH, PMAA chains were ionized and showed strong interaction with water. In this way, either oil-removing or water-removing with high efficiency can be achieved by this fabric by modulating the pH.(3) To improve the oil/water separation efficiency, a dual-responsive polymer(poly(N, Ndimethylaminoethyl methacrylate), PDMAEMA) was grafted onto cotton by ATRP. SEM, IR and CA measurement and other analytical techniques were employed to characterize the surface morphology, chemical composition and pH/thermo-responsibility. The results indicated that the fabric showed high temperature and pH responsive performance, which is strongly dependent on pDMAEMA grafting ratio. The fabric is hydrophilic at low temperature/pH, while it became hydrophobic at high temperature/pH. The transition pH was 5~7 and transition temperature was 40~50 oC at pH6.5. At high pH, the materials could absorb oil nearly 4 times about its own weight and the oil could almost desorption at low pH.