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1. Remediation of Aqueous Phosphate Agricultural Runoff Using Slag and Al/Mg Modified Biochar

   https://doi.org/10.3390/pr10081561  

   Crisler, Glenn B. ; Hernandez, Cintly Guzman ; Orr, Andre ; Davis, Roger ; Schauwecker, Timothy ; Johnson, J. Casey ; Sparks, Darrell ; Brown, Ashli ; Wilding, Kelcie ; Navarathna, Chanaka ; et al ( August 2022 , Processes)

   Slag and Al/Mg oxide modified Douglas fir biochar (AMOB) were compared for their phosphate adsorbing abilities for use individually or in combination for simulated agriculture run-off remediation in wetlands. Aqueous batch and column sorption experiments were performed for both low-cost materials. AMOB was prepared in bulk using a novel green method. Material analyses included XRD, elemental analysis, SEM, EDX, and BET. Biochar and slag have different phosphate removal mechanisms. In short residence times (≤2 h), adsorption phenomena dominate for both adsorbents. Surface area likely plays a role in adsorption performance; slag was measured to be 4.1 m2/g while biochar’s surface area was 364.1 m2/g. In longer residence times (>2 h), the slow leaching of metals (Ca, Al, and Mg) from slag continue to remove phosphate through the precipitation of metal phosphates. In 24 h, slag removed more free phosphate from the solution than AMOB. Preliminary fixed bed column adsorption of slag or AMOB alone and in tandem was performed adopting a scaled-up model that can be used to remediate agricultural runoff with high phosphate content. Additionally, a desorption study was performed to analyze the efficiency of material regeneration. While AMOB does not release any adsorbed phosphates, slag slowly releases 5.7% adsorbed phosphate over seven days. 

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2. Material properties and environmental potential of developing world-derived biochar made from common crop residues

   https://doi.org/10.1016/j.envc.2021.100137  

   Howell, Nathan ; Pimentel, Andy ; Bhattacharia, Sanjoy ( August 2021 , Environmental Challenges)

   Biochar is frequently made using high-tech, high-control methods which will no doubt better optimize the final material for its intended purpose and increase its value. In contrast, we used low-tech, low-control methods to produce a developing world biochar (DWB) from two common crop wastes, cottonseed (CS) and pecan shell (PS). We created DWB biochar using a top-lit updraft microgasifier (TLUD) made from paint cans, and compared it to a biochar created in a muffle furnace held at 450 °C (MF450). We first used modern material characterization methods (yield, BET, SEM/EDS, TGA, XRD, FTIR) to understand the difference in biochar production methods on the feedstock. We then used batch equilibrium adsorption with cationic and anionic dyes (methyl orange, MO and crystal violet, CV) to examine environmental performance. The TLUD method generally has a lower biochar production yield than MF450 because we believe much of the material in the TLUD achieves temperatures > 450 °C and is sometimes difficult to retain in the device. The higher temperatures in the TLUD device lead to a biochar which is more microporous, has greater surface area, has less surface functional groups, has greater ash content, is more carbonized, and has lower residual cellulose crystallinity. There were differences in adsorption performance whereby the MF450 biochar adsorbs CV more strongly than the TLUD. For MO, PS-TLUD is less effective at adsorbing the dye when compared to PS-MF450, while CS-TLUD has a much higher adsorption strength than CS-MF450. We are not certain why the two methods show opposite effects in different feedstock but speculate that it may have to do with the much higher mineral content in the PS-TLUD compared to its MF450 counterpart. Out of many isotherms examined Freundlich and Langmuir isotherms provide a best-fit to our data only about half the time. Sometimes an S-shaped isotherm was the best fit or still fit the data reasonably well. Comparing the dye adsorption to other studies, the DWB does not adsorb as well, yet it is still effective for removal at environmental dye concentrations of relevance. Overall, we conclude that DWB, made in this uncontrolled fashion, can make a reasonably high quality biochar based on material properties and environmental performance. We suggest that additional research be done on other low-tech biochar production methods to see how to scale-up and optimize them according a developing world community's intended use. 

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3. Synthesis of Graphitic Mesoporous Carbon from Metal Impregnated Silica Template for Proton Exchange Membrane Fuel Cell Application

   https://doi.org/10.1002/fuce.201800034  

   Sultana, K. N. ; Worku, D. ; Hossain, M. T. Z. ; Ilias, S. ( January 2019 , Fuel Cells)

   High surface area graphitic mesoporous carbons (M‐mGMC; M=Ni, Fe, Co or Ni‐Fe) were synthesizedviacatalytic graphitization using a hard template based synthesis method. In house prepared SBA‐15 silica material was impregnated with metal precursors to obtain M/SBA‐15, template for M‐mGMC synthesis. These materials were studied using different material characterization techniques, such as nitrogen adsorption desorption (BET), X‐ray diffraction (XRD) analysis, Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Specific surface area ranging from 1,227.9 m²g⁻¹to 1,320.7 m²g⁻¹was observed for four M‐mGMCs. Raman spectroscopy, XPS and wide angle XRD suggested presence of graphitic structure in these materials along with disorders. Electrocatalytic performance of these materials along with conventional carbon black (Vulcan XC‐72) were evaluated in a single‐stack proton exchange membrane fuel cell (PEMFC). Pt/NiFe‐mGMC exhibited enhanced electrocatalytic activity compared to Pt/Ni‐mGMC, Pt/Fe‐mGMC and Pt/Co‐mGMC electrocatalysts. However, Pt/NiFe‐mGMC lacked adequate proton transport in membrane electrode assembly (MEA) compared to Pt/Vulcan XC‐72. This exploratory study showed that NiFe‐mGMC may find application as electrocatalyst support material in PEMFC.

    

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4. Study the Use of Activated Carbon and Bone Char on the Performance of Gravity Sand-Bag Water Filter

   https://doi.org/10.3390/membranes11110868  

   Fung, Eric ; Johnson, Ken I. ; Li, Wenqi ; Borges, William ; Chi, Kai ; Sharma, Sunil K. ; Madan, Yogita ; Sharma, Priyanka R. ; Hsiao, Benjamin S. ( November 2021 , Membranes)

   In this study, granulated activated charcoal (GAC) and bio charcoal (BC) is used as a filler in P3 biosand bag filter to study their filtration performance against a range of fluoride impurities from 1–1400 mg/L. A set of experiments are done to analyze the filtration efficiency of the sandbag filter against fluoride impurities after incorporating different amounts (e.g., 0.2, 2 kg) and a combination of GAC and BC. A combination of filler GAC and BC (1 kg each) have exhibited excellent results with 100% fluoride removal efficiency against 5 mg/L fluoride impurities for an entire experimental time of 165 min. It is because of the synergetic effect of adsorption caused by the high surface area (739 m2/g) of GAC and hydroxyapatite groups in BC. The data from remediation experiments using individual GAC and BC are fitted into the Langmuir and Freundlich Isotherm Models to check their adsorption mechanism and determine GAC and BC’s maximum adsorption capacity (Qm). The remediation data for both GAC and BC have shown the better fitting to the Langmuir Isotherm Model with a high R2 value of 0.994 and 0.970, respectively, showing the excellent conformity with monolayer adsorption. While the GAC and BC have presented negative Kf values of −1.08 and −0.72, respectively, for Freundlich Model, showing the non-conformity to multilayer adsorption. The Qm values obtained from Langmuir Model for GAC is 6.23 mg/g, and for BC, it is 9.13 mg/g. The pH study on adsorption efficiency of individual GAC and BC against 5 mg/L of fluoride impurities indicates the decrease in removal efficiency with an increase in pH from 3 to 9. For example, BC has shown removal efficiency of 99.8% at pH 3 and 99.5% at pH 9, while GAC has exhibited removal efficiency of 96.1% at pH 3 and 95.9% at pH 9. Importantly, this study presents the significance of the synergetic application of GAC and BC in the filters, where GAC and BC are different in their origin, functionalities, and surface characteristics. 

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5. Adsorption of Tetrathiomolybdate to Iron Sulfides and Its Impact on Iron Sulfide Transformations

   https://doi.org/10.1021/acsearthspacechem.0c00176  

   Miller, Nathan ; Dougherty, Maura ; Du, Ruochen ; Sauers, Tyler ; Yan, Candice ; Pines, Jonathan E. ; Meyers, Kate L. ; Dang, Y M. ; Nagle, Emily ; Ni, Ziqin ; et al ( November 2020 , ACS Earth and Space Chemistry)

   null (Ed.)

   Molybdenum (Mo) in marine sediments has been used as a paleoproxy to provide evidence for past oceanic euxinic and sulfidic conditions through its association with pyrite. Here, we examine the adsorption of Mo to the pyrite precursors mackinawite and greigite and assess the robustness of this association during iron sulfide phase transformations. Tetrathiomolybdate (MoS42–) adsorption experiments were done using mackinawite and greigite that had been characterized using powder X-ray diffraction and Raman spectroscopy. Adsorption of tetrathiomolybdate to mackinawite and to a primarily greigite mixture was similar. Both showed little change to the mineral phase upon adsorption. Relative to previously published data on pyrite, there was a much greater amount of Mo adsorption and a different mode of adsorption. A mackinawite/greigite mixture was also synthesized through an alternative method that more closely mimicked environmental conditions with a brief in situ aging to form an initial phase of iron sulfide, likely highly disordered mackinawite, and the near-immediate addition of MoS42–. X-ray photoelectron spectroscopy results support the adsorption of tetrathiomolybdate and its concomitant reduction to Mo(IV). The Mo-adsorbed mackinawite/greigite mixture was transformed through heating into a greigite/pyrite mixture while monitoring Mo release to the aqueous phase. Here, the sorption of Mo on the solid phase promoted the transformation of mackinawite into pyrite upon heating without diagenetic loss of Mo to the aqueous phase. These results support the early capture of MoS42– to less-stable forms of iron sulfide with negligible diagenetic loss during subsequent transformation. This work continues to point to Mo(VI) as a plausible oxidant of FeS to FeS2 within natural euxinic settings. 

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