Increasing the chlorine active sites in the micropores of biochar for improved mercury adsorption

Wang, Tao; Wu, Jiawen; Zhang, Yongsheng; Liu, Jun; Sui, Zifeng; Zhang, Huicong; Chen, Wei-Yin; Norris, Pauline; Pan, Wei‐Ping

doi:10.1016/j.fuel.2018.05.028

Cited by 87 publications

(25 citation statements)

References 47 publications

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“…Compared with the B, the adsorption capacity of the MB to Hg 2+ (Qmax, 9.152 mg·g −1 ) was also relatively high, indicating that potassium hydroxide and hydrochloric acid etching may have been key factors for an increase in the CB adsorption capacity after composite modification. Some studies have shown that hydrochloric acid and sodium hydroxide etching can increase the specific surface area and the number of micropores in the biochar adsorbent, thus improving the adsorption effect [ 18 , 19 , 28 ]. It has also been shown that the high-energy adsorption sites of metal ions are primarily located on the edges, defects, and vacancies of the oxide interlayers [ 29 , 30 , 31 ].…”

Section: Resultsmentioning

confidence: 99%

Preparation of a Novel Millet Straw Biochar-Bentonite Composite and Its Adsorption Property of Hg2+ in Aqueous Solution

Bai¹,

Hong²

2021

Materials

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The remediation of mercury (Hg) contaminated soil and water requires the continuous development of efficient pollutant removal technologies. To solve this problem, a biochar–bentonite composite (CB) was prepared from local millet straw and bentonite using the solution intercalation-composite heating method, and its physical and chemical properties and micromorphology were then studied. The prepared CB and MB (modified biochar) had a maximum adsorption capacity for Hg2+ of 11.722 and 9.152 mg·g−1, respectively, far exceeding the corresponding adsorption value of biochar and bentonite (6.541 and 2.013 mg·g−1, respectively).The adsorption of Hg2+ on the CB was characterized using a kinetic model and an isothermal adsorption line, which revealed that the pseudo-second-order kinetic model and Langmuir isothermal model well represented the adsorption of Hg2+ on the CB, indicating that the adsorption was mainly chemical adsorption of the monolayer. Thermodynamic experiments confirmed that the adsorption process of Hg2+ by the CB was spontaneous and endothermic. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and a thermogravimetric analysis (TGA) showed that after Hg2+ was adsorbed by CB, functional groups, such as the –OH group (or C=O, COO–, C=C) on the CB, induced complexation between Hg and –O–, and part of Hg (ii) was reduced Hg (i), resulting in the formation of single or double tooth complexes of Hg–O– (or Hg–O–Hg). Therefore, the prepared composite (CB) showed potential application as an excellent adsorbent for removing heavy metal Hg2+ from polluted water compared with using any one material alone.

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Section: Resultsmentioning

confidence: 99%

Preparation of a Novel Millet Straw Biochar-Bentonite Composite and Its Adsorption Property of Hg2+ in Aqueous Solution

Bai¹,

Hong²

2021

Materials

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“…Different mercury compounds correspond to different decomposition temperatures. Therefore, it is necessary to use a temperature-programmed-desorption (TPD) method to appraise the mercury compounds’ desorption properties on the surface of the sorbent traps. − Figure is a TPD experimental platform used by the authors in this study. The carrying gas N 2 flowed at 1 L/min.…”

Section: Methodsmentioning

confidence: 99%

Experimental and Kinetic Analysis of H₂O on Hg⁰ Removal by Sorbent Traps in Oxy-combustion Atmosphere

Wang

Shen

et al. 2021

Ind. Eng. Chem. Res.

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Oxy-combustion technology is under development for CO2 capture. H2O could influence the Hg0 removal by sorbent traps in an oxy-combustion atmosphere. A study of the effects of H2O on Hg0 removal by biomass char under oxy-combustion conditions is presented in this paper. The kinetic model analysis was conducted to study the adsorption process of Hg0, which included a pseudo-first-order kinetic model, a pseudo-second-order kinetic model, and intraparticle diffusion kinetic model. Experimental results showed that a low-level of H2O had a promoting effect on the adsorption of Hg0, and high-level of H2O had an inhibiting effect. A high concentration of H2O would form a water film on the surface of sorbent traps to hinder the removal of external mass transfer on Hg0. Although the adsorption rate of Hg0 depended both on external mass transfer and intraparticle diffusion, external mass transfer was a more important controlling factor. It was found that physical adsorption was one of the main forms of Hg0 removal on the surface of sorbent traps, owing to the large specific surface area and good pore structure of the modified corn straw char. The removal of Hg0 was mainly attributed to capture by physical adsorption and the formation of HgO by chemisorption.

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“…3. The MIL101-Cr sorbent has presented the type-IV adsorption isotherm, according to the IUPAC classification, indicating that the sample has a mesoporous structure which is beneficial to mercury removal 37 . The BET specific surface area and total pore volume of the sample is 2368 m 2 /g and 1.48 cm 3 /g, respectively.…”

Section: Experimental Methodsmentioning

confidence: 99%

Investigation of Elemental Mercury Removal from Coal-Fired Boiler Flue Gas over MIL101-Cr

et al. 2019

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In this work, the MIL101-Cr sorbent with a large BET surface area was prepared and used to remove Hg 0 from the simulated coal-fired boiler flue gas. The chemical and physical properties of the prepared sorbent were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS). A range of experiments was conducted in a fixed-bed reactor to investigate the effects of reaction temperature, Hg 0 inlet concentration, gas hourly space velocity (GHSV) and flue gas composition on the Hg 0 removal for the prepared sorbent. The mechanisms and kinetics of the Hg 0 adsorption were also studied. The results showed that the MIL101-Cr sorbent achieved the Hg 0 removal efficiency of more than 85% for 4 h at 200 o C under the condition of a relatively high Hg 0 inlet concentration (203 μg/m 3 ) and GHSV (8  10 5 h -1 ). The O2 in the flue gas was found to be beneficial to Hg 0 removal. The NO in the flue gas favoured Hg 0 removal both in the presence and absence of O2. The SO2 in the flue gas notably inhibited Hg 0 adsorption in the absence of O2, whereas a low concentration of SO2 slightly inhibited Hg 0 removal in the presence of O2.However, high concentrations of SO2 in the flue gas still significantly weakend Hg 0 removal ability even in the presence of O2 due to the competitive adsorption of SO2 with Hg 0 on the sorbent and the sulfation of the sorbent. A simultaneous presence of O2 and NO in the flue gas could overcome the adverse impact of SO2 on Hg 0 adsorption. The H2O has little influence on Hg 0 removal due to the competitive adsorption. The XPS analysis indicated that the surface Cr 3+ , oxygen species and C=O group in MIL101-Cr acted as the active adsorption/oxidation sites for Hg 0 . The Hg 0 removal by MIL101-Cr belonged to chemisorption and could be described by the pseudo-second-order model. The equilibrium adsorption capacity calculated for the sorbent amounted to 25656 μg/g at 200 o C, which indicated that MIL101-Cr could be used as a promising sorbent to removeHg 0 from the coal-fired boiler flue gas.

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Increasing the chlorine active sites in the micropores of biochar for improved mercury adsorption

Cited by 87 publications

References 47 publications

Preparation of a Novel Millet Straw Biochar-Bentonite Composite and Its Adsorption Property of Hg2+ in Aqueous Solution

Preparation of a Novel Millet Straw Biochar-Bentonite Composite and Its Adsorption Property of Hg2+ in Aqueous Solution

Experimental and Kinetic Analysis of H₂O on Hg⁰ Removal by Sorbent Traps in Oxy-combustion Atmosphere

Investigation of Elemental Mercury Removal from Coal-Fired Boiler Flue Gas over MIL101-Cr

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Increasing the chlorine active sites in the micropores of biochar for improved mercury adsorption

Cited by 87 publications

References 47 publications

Preparation of a Novel Millet Straw Biochar-Bentonite Composite and Its Adsorption Property of Hg2+ in Aqueous Solution

Preparation of a Novel Millet Straw Biochar-Bentonite Composite and Its Adsorption Property of Hg2+ in Aqueous Solution

Experimental and Kinetic Analysis of H2O on Hg0 Removal by Sorbent Traps in Oxy-combustion Atmosphere

Investigation of Elemental Mercury Removal from Coal-Fired Boiler Flue Gas over MIL101-Cr

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Experimental and Kinetic Analysis of H₂O on Hg⁰ Removal by Sorbent Traps in Oxy-combustion Atmosphere