Abstract:
Elemental mercury (Hg
0) and chlorinated volatile organic compounds (CVOCs), which are highly toxic, exhibit significant migration and transformation capabilities, making them prone to forming various secondary pollutants in the atmosphere. This poses severe threats to human and environmental health, attracting widespread global attention. Despite numerous studies, controlling mercury and CVOCs in industrial flue gas remains a significant research challenge. Notably, there are few reports on the impact of CVOCs on the low-temperature adsorption of Hg
0. This study investigated the low-temperature adsorption performance of various common adsorbents for Hg
0, specifically assessing the effect of CVOCs using chlorobenzene as a model compound. We prepared three types of materials: activated carbon and its modified materials, sulfide, and metal oxides, and evaluated their Hg
0 adsorption activity at low temperature (80−120 ℃). The adsorption performance was ranked as follows: CuS/AC>CuS>Mn
2O
3>AC>HCl/AC. Brunauer-Emmett-Teller (BET) analysis indicated no direct relationship between the specific surface area or pore type of the adsorbents and their Hg
0 adsorption performance. In contrast, X-ray photoelectron spectroscopy (XPS) results revealed that oxidizing species such as \mathrmCu^2+ , \mathrmS_n^2- , and \mathrmMn^3+ in CuS and Mn
2O
3 served as the primary active sites for the chemisorption of Hg
0. After adding chlorobenzene, the adsorption performance of CuS/AC and AC remained unchanged, while the other three materials exhibited inhibited performance, particularly Mn
2O
3, whose adsorption efficiency decreased by over 50%. Hg
0 temperature-programmed desorption (TPD) experiments demonstrated that HgS was the predominant form of mercury in CuS/AC and CuS when only mercury was present in the flue gas. In Mn
2O
3, HgO was the primary form, accompanied by some physically adsorbed mercury, whereas AC only facilitated physical adsorption of Hg
0. In HCl/AC, both HgCl
2 and physically adsorbed Hg
0 were detected. Following the addition of CVOCs, the main form of mercury in CuS remained HgS, while physically adsorbed mercury appeared in CuS/AC. Additionally, Mn
2O
3 exhibited a new adsorption component, HgCl
2. Kinetic analyses indicated that the adsorption process of Hg
0 across different adsorbent materials conformed to a pseudo-first-order kinetic model (
R2>0.99), highlighting the dominant role of external diffusion. The presence of chlorobenzene further enhanced the chemisorption of Hg
0 by HCl/AC and Mn
2O
3. Moreover, the Hg
0 adsorption capacities of AC, HCl/AC, CuS, and Mn
2O
3 decreased significantly in the presence of chlorobenzene, dropping from 842.5, 573.4, 5
5 505.6, and 3 352.6 μg/g to 730.3, 181.7, 5 504.1, and 434.0 μg/g, respectively. By exploring the effects of CVOCs on the adsorption of Hg
0, this study contributes valuable insights for future research on low-temperature co-adsorption methods involving Hg
0 and CVOCs.