Enhancing biochar redox properties through feedstock selection, metal preloading and post-pyrolysis treatments

Chacón, Francisco J.; Sánchez-Monedero, Miguel Á.; Lezama, Luís; Cayuela, María Luz

doi:10.1016/j.cej.2020.125100

Cited by 108 publications

(39 citation statements)

References 67 publications

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“…This result suggested that both modification methods may improve the Cr(VI) removal efficiency, but the HTT had a slight effect on the Cr(VI) removal efficiency of modified biochars, although HTT was key for the production of biochar with the desired surface area, pore characteristics, surface functional groups, and crystalline structure. 23 …”

Section: Resultsmentioning

confidence: 99%

Influence of Synthesis Methods on the High-Efficiency Removal of Cr(VI) from Aqueous Solution by Fe-Modified Magnetic Biochars

Jian

Feng

et al. 2020

ACS Omega

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Fe-modified biochars have been widely used in removal of Cr(VI) from water due to the resulting modified surface functional groups and magnetization property. However, few studies have synthetically investigated modification methods and synthesis parameters on the improvement of the removal efficiency of Cr(VI) by Fe-modified biochars. Herein, 10 types of corn straw-based magnetic biochars were produced using pre-modification and post-modification methods with various modifier ratios, and the highest heating temperature (HHT). Cr(VI) removal results suggest that the removal efficiency of pre-modified biochars ranged from 50.7 to 98.6%, which was much higher than that of post-modified (6.6–21.6%) and unmodified biochars (0.4–7.6%). The effect of synthesis methods on Cr(VI) adsorption was in the following order: Fe-modification method > modifier ratio > HHT. The adsorption kinetics and isotherm results of three types of pre-modified biochars were well fitted with the pseudo-second-order model (R 2 > 0.99) and the Langmuir adsorption model (R 2 > 0.99), respectively, indicating the surface homogeneity of the pre-modified biochars and unilayer chemisorptions of Cr(VI). Characterization results show that iron oxides or zerovalent iron particles were successfully deposited onto the surface of biochars and magnetism was introduced. A good Pearson correlation (r = −0.9694) between the removal efficiency and pH value in modified biochar suggests that the lower pH value may offer more positive charges and promote electrostatic attraction. Therefore, the dominant mechanism for enhanced Cr(VI) adsorption on pre-modified biochar was electrostatic attraction, resulting from its distinguished acidity nature. Our findings provide new insights into the high-efficiency removal of Cr(VI) onto Fe-modified magnetic biochars and will benefit future design of more efficient magnetic biochars.

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Section: Resultsmentioning

confidence: 99%

Influence of Synthesis Methods on the High-Efficiency Removal of Cr(VI) from Aqueous Solution by Fe-Modified Magnetic Biochars

Jian

Feng

et al. 2020

ACS Omega

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“…[ 74 ] During pyrolysis, organic constituents of the biomass are decomposed at 300–1200 °C in an oxygen‐limited environment without solvent involvement. [ 75–77 ] In an oxygen‐free atmosphere, biomass can be heated to a temperature above its thermal stability limit to form solid residues and stable products. The key parameters for the raw materials include pyrolysis temperature, heating rate, pressure, and residence time.…”

Section: Conversion Of Biomasses Into Biochar Catalystsmentioning

confidence: 99%

Hydrothermal and Pyrolytic Conversion of Biomasses into Catalysts for Advanced Oxidation Treatments

Zheng

et al. 2020

Adv Funct Materials

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Biomasses are very important natural products. Transferring biomass into catalysts for the advanced oxidation process (AOP) via heat treatment has attracted extensive attention. This review systematically introduces and summarizes two kinds of innovative biomass‐based catalysts according to the treating temperature. At low temperature (<300 °C), biomasses are converted into hydrothermal carbonation carbon (HTCC) with semiconductive properties for photocatalysis application. At high temperature (>300 °C), by contrast, the products lose their semiconductive nature and become a conductive carbon‐based conductor (biochar). They usually work as AOP catalysts by activating oxidant of O2, H2O2, and peroxysulfate for environmental treatment. This review summarizes and compares HTCC and biochar according to their formation process, structure, catalytic mechanism, and key points for the activity enhancement. The active units in HTCC are the sp2‐hybridized polyfuran unit while those in biochar are the persistent free radicals, nitrogen‐containing unit, or defects. HTCC converts water into OH radicals by using the photoexcited electron/hole pairs induced by solar illumination, while biochar activates oxidants via the active unit on its surface. More importantly, this review summarizes and demonstrates the key points to obtain high‐efficiency HTCC and biochar catalysts. Finally, conclusions are drawn and the future aspects for biomass‐based catalysis are given.

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“…A 0.5 mL volume of liquid phase was taken and measured for 100 s in a well-type NaI (Tl) scintillation detector NKG-314 with a single-channel analyzer spectrometric assembly NV-3120 (all Tesla, Zbidy, Czechoslovakia,). The data has been processed by Equations ( 15)- (18).…”

Section: Batch Sorption Studymentioning

confidence: 99%

“…Then, mixtures were filtered under pressure through a glass microfiber filter Whatman GF/C. These data were processed by Equations ( 15)- (18) and relationships (19) and (20). To describe the dependence of the solute amount on its equilibrium concentration, Freundlich adsorption isotherm was used (21).…”

Section: Batch Sorption Studymentioning

confidence: 99%

“…However, most of the traditionally produced have limited ability to sorb anionic species. Recently a new concept, engineered biochar has gained interest, in which engineered biochar is prepared by biochar surface impregnation with montmorillonite or other clay minerals [ 3 , 17 , 18 , 19 , 20 ]. Therefore, technetium in the most environmentally stable form—pertechnetate is sorbed, while others, mostly metals flow through this material if pH is smaller than approx.…”

Section: Introductionmentioning

confidence: 99%

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Surface Complexation Models of Pertechnetate on Biochar/Montmorillonite Composite—Batch and Dynamic Sorption Study

et al. 2020

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The study summarizes the results of monitoring the properties of two types of sorbents, BC1 (biochar sample 1) and BC2a (biochar sample 2), prepared by pyrolysis of bamboo biomass (BC1) and as its composite with montmorillonite K10 (BC2a). The main goal was to study their applicability to the Tc (VII) separation from liquid wastes, using NH4ReO4 as a carrier. The research was focused on determining the sorbents surface properties (by XRF (X-ray fluorescence) method and potentiometric titration in order to determine the properties of surface groups—Chemical Equilibrium Model (CEM) and Ion Exchange Model (IExM) models were applied here). As well as monitoring Tc (VII) (+Re(VII)) sorption, especially to determine equilibrium isotherm, the influence of pH and kinetics. The subject of research was also the dynamics of sorption, including its mathematical–physical modeling. Both sorbents have good properties against Tc (VII), however BC2a, due to the presence of montmorillonite, is more advantageous in this respect. It has a higher sorption capacity and faster kinetic investigation. An important finding is that the optimal pH is 2–3, which is related not only to the protonation of surface groups (they have a positive charge), but also to the negative form of the existence of Tc (VII) and Re (VII): TcO4− and ReO4−.

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Enhancing biochar redox properties through feedstock selection, metal preloading and post-pyrolysis treatments

Cited by 108 publications

References 67 publications

Influence of Synthesis Methods on the High-Efficiency Removal of Cr(VI) from Aqueous Solution by Fe-Modified Magnetic Biochars

Influence of Synthesis Methods on the High-Efficiency Removal of Cr(VI) from Aqueous Solution by Fe-Modified Magnetic Biochars

Hydrothermal and Pyrolytic Conversion of Biomasses into Catalysts for Advanced Oxidation Treatments

Surface Complexation Models of Pertechnetate on Biochar/Montmorillonite Composite—Batch and Dynamic Sorption Study

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