Preparation And Application Of Viscose-based Activated Carbon Fibers

Activated carbon fibers (ACFs) were widely developed and applied as a highly efficient carbonaceous adsorbent during the 1960s. Compared to activated carbon (AC), the ACFs have the good characteristics of high specific surface area, abundant micropores, larger adsorption capacity, quick adsorption/desorption rate and easy regeneration and overcome the rocketed temperature and easier abrasion in the practical application. The viscose-based activated carbon fibers possessed multitudinous advantages, such as abundant precursor, reproducible precursor and mature technology, whereas its lower yield coefficient and poor performance, in other words, "double low" limited its applications.In the paper the composition of dipping solution, the process conditions of carbonization and activation, the heating rate, the cleanliness and adsorbed water of viscose fibers and so on, which influenced yield coefficient and adsorption properties of viscose-based activated carbon fibers were investigated for the purpose of the "double low" problem with viscose fibers as the precursor. At the same time, waste gas containing acrylic acid and toluene as adsorbent on viscose-based activated carbon fiber with dynamic adsorption method was studies. Moreover, the effect of activated carbon fiber pore structure, carrier gas flow rate, acrylic acid concentration in the waste gas and recycling times on the adsorption capacity were systematically discussed. The results and achievements were summarized as follows:Dipping agents and the heating rate affected the pyrolysis mechanism of viscose fibers, and complex dipping solution could give full play to advantages of different dipping gents. The optimum dipping solution formula of viscose fibers was A:B:C:D=40:7:7:1. Activated carbon fibers at majorized heating rate had better adsorption properties. Viscose-based activated carbon fibers with higher yield coefficient and high performance was prepared at 400℃and 30 min during carbonization process,900℃,20 min,3:1(water-carbon ratio),35 mL/min(carrier gas flow rate) in activation course. The optimal treatment way of viscose fiber before soaking craftwork was dried for 1h. The appropriate ACFs amount of iodine adsorption test and proper benzene adsorption time on activated carbon fiber were 0.3 g (correct to 0.1 mg) and 24 h, respectively. Surface functional groups of activated carbon fibers produced with optimized dipping solution formula and process, did not change, but ACFs possessed more developed microporous and better adsorption capacity. In addition, the specific surface area was up to 2110 m2·g-1. Fiber diameter became thinner, and cross section transformed from the solid to the hollow structure. Viscose-activated carbon fibers showed excellent absorption properties of toluene. Activated carbon fibers used for adsorbed acrylic acid was feasible, and had higher adsorption capacity and outstanding regeneration effect. The adsorption performance of waste gas including acrylic acid and toluene on activated carbon fibers was depended on the volume of pores having diameter in the range of 1-2 nm. The acrylic acid existed in waste gas would go against the adsorption of toluene on ACFs. And as acrylic acid increased, the side effect was more obvious. As acrylic acid increased, the adsorption capacity of waste gas increased firstly and then decreased. When the carrier gas flow was 1.6 L/min, the breakthrough and saturation adsorption capacities reached the maximum. The number of activated carbon fiber cycles increased, while the adsorption property on ACFs decreased. When activated carbon fiber was recycled up to 13 times, the capacity was stable.