A two-step method for the integrated removal of HCl, SO2 and NO at low temperature using viscose-based activated carbon fibers modified by nitric acid

Abstract Activated carbon fibers (ACFs) have been widely used as cost-effective integrated processes for the removal of nitrogen oxides, sulfur oxides and hydrogen chloride (HCl), while the competitive adsorption behaviors and the detailed interaction mechanisms have not been comprehensively investigated. In the current work, the adsorption capacities with one-step process and two-step method were compared, and the effects of HNO 3 modification and ambient O 2 concentration were simultaneously studied. Furthermore, the relative ratios of surface nitrogen groups, sulfur and chlorine compounds, as well as the soluble species on the ACFs surface, were respectively characterized by X-ray photoelectron spectroscopy and ion chromatography techniques. The results indicated that HCl, SO 2 and NO were not able to be effectively removed with only one reactor due to the strong competitive adsorption behaviors, while the adsorption capacities of HCl, SO 2 and NO were significantly improved by 30%, 280%, 230% in the two-stage reactors with HNO 3 modification. Further investigation indicated interactions between HCl, SO 2 and NO in the two-stage reactors are very complicated. The primary reactor can remove HCl and facilitate the catalytic removal of SO 2 /NO in the secondary reactor since HCl can severely inhibit the adsorptions of SO 2 and NO, yet HCl adsorption can be suppressed by SO 2 . Simultaneously, nitro/nitroso groups derived of HNO 3 treatment and NO oxidation can promote the chemisorption of HCl.