Preparation And Properties Of Trilobal Pitch-Based Activated Carbon Fibers Supporting Silver

Ordinary activated carbon fibers (ACF) can only adsorb bacteria on its'surface but cannot kill them when used in water disposal. The question of ACF made by soakage method is that most silver particles were simply absorbed on the surface, they would be easily dropped from the surface by water washing and the sterilizing capability would decreased notably. In order to avoid this disadvantage, nano-silver powders and silver nitrate were dispersed into spinnable pitch respectively, after melt spinning, curing, carbonization and activation trilobal pitch-based activated carbon fibers exhibited adsorptive and sterilizing capability were obtained, the ability of water washing resitance was enhanced too. .The influence of dispersing technics on spinnability of composites was studied. Preparing techniques of trilobal-shaped pitch fibers were studied by analyzing the influence of spinning temperature, spinning pressure and take-up rate on effective filament diameter (Edo) and degree of profile (Dp). Carbonization technics was investigated through the ways of analyzing the influences of carbonized temperature, heating velocity, carbonized time on weight reservation and tensile strength. Activation technics was also researched by analyzing the influences of activated time and CO2 flow rate on burn off and I2 adsorption. XRD and SEM were used to discuss the chemical state of silver and the morphologies of trilobal-shaped ACF. N2 adsorption at low temperature was used to test the surface area, pore size distribution were calculated based on H-K and BJH models. The influence of silver on surface area and pore parameters was analyzed. Three kinds of sewage were selected to test the sterilizing capability of ACF supporting silver. The sterilizing effects on Escherichia.coli (E.coli) were also compared between different ACF.The results showed that the composite of nano silver powder (1wt %) and pitch made by ultra-sonic processing had a good spinnability. The composite of silver nitrate and pitch which made by internal mix processing had a relatively bad spinnability, it's Average continuous time is shorter than 2 min.There was a gradual rise in Edo with the increasing of spinning temperature, the increasing of N2 pressure and the decreasing of take-up rate. The Dp of trilobal-shaped green fibers supporting silver remained nearly the same when changing N2 pressure, but it dropped sharply as spinning temperature increased, the influence of take-up rate on Dp was smaller than temperature.The suitable spinning parameters are: temperature 300~306℃, N2 pressure 1.0~1.8MPa, take-up rate 250~450rpm. Under these conditions, trilobal pitch fibers could be obtained with Edo 25~35μm and Dp 0.55~0.60.With the CO2 flow rate 0.2L/min and activated temperature 900℃, Burn off increased as activated time prolonged, I2 adsorption increased at first, then decreased sharply, and it reached to a maximum of 1080mg/g when activated time was 45min. The curves between I2 adsorption, Burn off and activated time could be divided into four stages: I2 adsorption and Burn off increased sharply at first; I2 adsorption and Burn off remained the same secondly; I2 adsorption and Burn off increased continually; I2 adsorption decreased notably and Burn off still increased at last. Keeping activated time 45min and activated temperature 900℃as constants, as the CO2 flow rate increased, I2 adsorption and Burn off increased rapidly at first, and then increased at a lower speed. When Burn off was lower than 45%, it was proportion to I2 adsorption approximately.The suitable activation parameters are: activated temperature 900℃; activated time 15~45min; CO2 flow rate 0.1~0.3 L/min and Burn off less than 45%. Under this condition, we could obtain trilobal ACF supporting silver with I2 adsorption higher than 1000mg/g.Face-centered cubic lattic silver particles in trilobal-shaped ACF was scattered both on the surface and in the interior. The addition of silver could accelerate activation. Silver could increase the pore volume and Surface area, but couldn't enlarge the avreage pore size.Qualitative analysis showed that ACF supporting silver had sterilizing capability while Ordinary ACF hadn't.Quantitative analysis showed that When 0.1g fibers acted with 25ml E.coli solution (~106cfu/ml) under 37℃for 4 hours, the Survived rate of E.coli of ordinary trilobal ACF, trilobal ACF supporting 1wt% silver and trilobal ACF supporting 3wt% silver were 117.3%,16.5%and 0. That was to say, ACF didn't have sterilizing capabilities when it didn't containing silver, and bacteria would propagate, when silver supporting was 3%, it could kill all the E.coli. As the Burn off increased, the sterilizing effect of carbon fibers supportting silver enhanced. The E.coli Survived rate of circular ACF (d=17.8μm) and trilobal ACF(Edo=22.5μm) were 13.9% and 16.5% when silver supporting was 1wt%.