Liu Xuewei,Gao Minling,Qiu Weiwen,Khan Zulqarnain Haider,Liu Nengbin,Lin Lina,Song Zhengguo
In this study, a novel Fe–Mn–Ce oxide-modified biochar composite (FMCBC) was synthesized via pyrolysis to enhance the adsorption capacity of biochar (BC). Scanning electron microscopy-energy-dispersive X-ray spectroscopy confirmed that Fe, Mn, and Ce were successfully loaded onto the surface of the BC. A series of adsorption experiments showed that the FMCBC exhibited improved adsorption of As(III) in an aqueous environment. The adsorption process was well expressed by the pseudo-second-order kinetic model. The adsorption capacity of FMCBC reached 8.74 mg L −1 , which was 3.27 times greater than that of BC. The pH of the solution significantly influenced the adsorption of As(III), where the amount of As(III) adsorbed by FMCBC was maximized at pH 3. A high phosphate concentration inhibited adsorption, whereas nitrate and sulfate ions promoted As(III) adsorption and increased the FMCBC adsorption capacity. Similarly, with increasing humic acid concentration, the adsorption capacity of FMCBC for As(III) decreased; however, a low concentration of humic acid promoted adsorption. X-ray photoelectron spectroscopy analysis revealed that the adsorption of As(III) by FMCBC occurred through redox and surface complexation reactions. Therefore, FMCBC has excellent potential for purifying arsenic-contaminated water.
The Fe–Mn–Ce/CP catalyst prepared by the incipient-wetness impregnation method was investigated for elemental mercury (Hg 0 ) removal in simulated coal-fired flue gas . The incorporation of Fe could remarkably enhance the SO 2 -resistance of Fe–Mn–Ce/CP catalyst at low temperature, and the existence of water vapor had negative impact on Hg 0 removal efficiency. More than 95% of Hg 0 could be removed at 100 °C under the conditions of 60 ppm HCl, 3% O 2 ( v/v ), 5% H 2 O ( v/v ) and 400 ppm SO 2 . Hg-TPD results indicated that Hg 0 adsorption amount decreased after the addition of H 2 O or SO 2 . The XPS results revealed that the incorporation of Fe could enhance the contents of high valence Mn x + (i.e., Mn 3+ /Mn 4+ ) and Ce 3+ species in the composite catalysts, which are favorable for the oxidation process of elemental mercury. The surface characteristics were not the primary factor determining the catalytic activity . Overall, the catalytic performance of the Fe–Mn–Ce/CP catalyst was closely related to the Fe 3+ state, high ratios of (Mn 4+ + Mn 3+ )/Mn 2+ and high content of not fully coordinated cerium species.
This study investigated the effects of sequential acid treatment and phosphorus incorporation on the performance of Fe–Mn-Ce composite metal oxide catalysts. The FeMnCeO x catalyst was prepared using the sol–gel method and modified through two methods: treatment with phosphoric acid alone and a sequential treatment with phosphoric acid followed by sulfuric acid. The results show that the sequentially acid-treated catalyst exhibited over 90% NO x conversion and N 2 selectivity in the temperature range of 200–350 °C, outperforming other catalysts. Characterization analyses such as XRD and NH 3 -TPD revealed that acid modification enhanced the surface acidity and redox properties of catalysts. XPS analysis showed that sequential acid treatment increased the surface chemisorbed oxygen content of the catalyst and optimized its surface structure. In-situ DRIFTS spectroscopy further elucidated that the catalytic reaction follows both Langmuir–Hinshelwood and Eley–Rideal mechanisms concurrently.
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