Abstract
Mercury pollution has become one of the most concerned environmental issues in the world because of its high toxicity, non-degradability, and bioaccumulation. Attapulgite adsorbents modified by magnetic manganese-copper (MnxCuy-MATP) were fabricated by co-precipitation and ultrasonic impregnation method, aiming at removing Hg0 from coal-fired flue gas. BET, SEM, XRD, VSM, and XPS were used to systematically explore the physical and chemical properties of the adsorbents, the effects of manganese and copper additions, reaction temperature, and various components in the flue gas on the efficiency of Hg0 removal were investigated. Mn8Cu5-MATP exhibited the optimal properties, and excessive copper loadings led to the aggregation of the active components. The efficiency of mercury removal can be effectively improved by NO and HCl regardless of the absence and presence of O2, because the NO+, NO3, NO2, and Cl* produced during the reaction can promote the adsorption and oxidation of Hg0. SO2 and H2O inhibited the oxidation of Hg0 because of the competitive adsorption at the active sites, while a large amount of sulfite and sulfate were formed to block the pores. However, the introduction of copper caused the sample to obtain SO2 resistance, which resulted in a mercury removal efficiency of 84.3% even under 1500 ppm SO2. In addition, after 5 cycles of adsorption and regeneration, Mn8Cu5-MATP can still maintain excellent Hg0 removal ability. The fabricated adsorbent can save the actual production cost and effectively improve the mercury removal efficiency in sulfur-containing flue gas.
Highlights
Mercury has attracted widespread public attention due to its high toxicity, persistence, high volatility, and bioaccumulation (Li et al 2017a, Wang et al 2019a, Yang et al 2020b)
When the O2 concentration improved from 0–6%, the mercury removal efficiency significantly increased to 91.1%, which can be ascribed to the regeneration of OA and OB consumed during the removal process and the replenishment of gas-phase oxygen (Chen et al 2018)
The effects of manganese and copper additions, reaction temperature and various components in the flue gas on the efficiency of Hg0 removal were investigated by the fixed-bed system
Summary
Mercury has attracted widespread public attention due to its high toxicity, persistence, high volatility, and bioaccumulation (Li et al 2017a, Wang et al 2019a, Yang et al 2020b). Activated carbon adsorbent has become a research hotspot in the field of mercury removal from flue gas owing to its excellent adsorption performance (Huang et al 2019). The pollution of fly ash has a negative impact on the resource utilization due to the incorporation of activated carbon containing mercury (Zhao et al 2017) Such technology cannot achieve the ultimate centralized control for mercury pollution in coal-fired flue gas. Yang et al successfully synthesized a magnetic activated carbon for Hg0 removal by co-precipitation method, and the mercury removal performance was optimal when the mass fraction of magnetic substance was 25% (Yang et al 2020a) These magnetic adsorbents can effectively remove mercury and regenerate, the synthesis process is usually complex and costly. The results of this work can provide valuable guidance for the development of mercury removal adsorbents with SO2 resistance
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