Study of Mercury Adsorption by Low-Cost Sorbents Using Kinetic Modeling

摘要

In order to make further progress in the field of reducing mercury emissions to the atmosphere, it is necessary to develop efficient and economically viable technologies. Low-cost solid sorbents are a candidate technology for mercury capture. However, kinetic models are required to predict the adsorption mechanism and to optimize the design of the process. In this study, several low-cost materials (biomass chars) were evaluated for the removal of gas-phase elemental mercury and kinetic studies were performed to investigate the mechanism of mercury adsorption. These kinetic studies were also used to predict the behavior of a fixed-bed column. The models applied were pseudo-first-order and pseudo-second-order equations, Fick’s intraparticle diffusion model, and the Yoon–Nelson model. The chars obtained from the gasification of plastic-paper waste demonstrated the best behavior for mercury capture because of their high Brunauer–Emmett–Teller surface area, large total pore volume (mainly micropore volume), and high chlorine content. The Yoon–Nelson model provided a better fitting for the samples with low mercury retention capacities, while in the case of the plastic-paper chars, all of the models provided relatively accurate predictions because their highly microporous structure retarded the internal diffusion process and their increased chlorine content enhanced chemisorption on their surface.