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Role of Grinding Method on Granular Activated Carbon Characteristics
Citation:
Abulikemu, G., D. Wahman, G. Sorial, M. Nadagouda, E. Stebel, E. Womack, S. Smith, E. Kleiner, B. Gray, R. Taylor, C. Gastaldo, AND J. Pressman. Role of Grinding Method on Granular Activated Carbon Characteristics. Carbon Trends. Elsevier B.V., Amsterdam, Netherlands, 11:100261, (2023). https://doi.org/10.1016/j.cartre.2023.100261
Impact/Purpose:
A coconut shell based (AC1230CX) and a bituminous coal based (F400) granular activated carbon (GAC) were ground with mortar and pestle (MP), a blender, and a bench-scale ball milling unit (BMU). For particle size reduction, the blender was the most time efficient method. Four size fractions ranging from 20x40 to 200x325 were characterized along with the bulk GACs for specific surface area (SSA), pore size distribution, surface morphology, point of zero charge (pHPZC), surface elemental composition, and crystalline structure. Compared to bulk GACs, F400 blender and BMU 20x40 fractions decreased in SSA (–23% and –31%, respectively) while smaller variations (between –14% and 5%) occurred randomly for AC1230CX ground fractions across all grinding methods. For F400, the blender and BMU size fraction dependence were attributed to the combination of (i) radial variations in the F400 particle properties and (ii) importance of shear (outer layer removal) versus shock (particle fracturing) size reduction mechanisms. Compared to bulk GAC, surface oxygen content (At%-O1s) increased (up to 34%) for the F400 blender and BMU 20x40 fractions, whereas all AC1230CX ground fractions except for the blender 100x200 and BMU 60x100 and 100x200 fractions showed around 25–29% consistent increases. The At%-O1s gain was attributed to (i) the inherent radial trend in F400 properties and (ii) oxidization during grinding, both of which supported the shear mechanism of mechanical grinding. Relatively small to insignificant changes in pHPZC and crystalline structure were consistent with the changes in SSA and At%-O1s, further supporting the combined effect of GAC inherent properties and grinding mechanisms. The study findings provide guidance for informed selection of grinding methods based on GAC type and target particle sizes to improve the representativeness of adsorption studies conducted with ground GAC.
Description:
A coconut shell based (AC1230CX) and a bituminous coal based (F400) granular activated carbon (GAC) were ground with mortar and pestle (MP), a blender, and a bench-scale ball milling unit (BMU). For particle size reduction, the blender was the most time efficient method. Four size fractions ranging from 20x40 to 200x325 were characterized along with the bulk GACs for specific surface area (SSA), pore size distribution, surface morphology, point of zero charge (pHPZC), surface elemental composition, and crystalline structure. Compared to bulk GACs, F400 blender and BMU 20x40 fractions decreased in SSA (–23% and –31%, respectively) while smaller variations (between –14% and 5%) occurred randomly for AC1230CX ground fractions across all grinding methods. For F400, the blender and BMU size fraction dependence were attributed to the combination of (i) radial variations in the F400 particle properties and (ii) importance of shear (outer layer removal) versus shock (particle fracturing) size reduction mechanisms. Compared to bulk GAC, surface oxygen content (At%-O1s) increased (up to 34%) for the F400 blender and BMU 20x40 fractions, whereas all AC1230CX ground fractions except for the blender 100x200 and BMU 60x100 and 100x200 fractions showed around 25–29% consistent increases. The At%-O1s gain was attributed to (i) the inherent radial trend in F400 properties and (ii) oxidization during grinding, both of which supported the shear mechanism of mechanical grinding. Relatively small to insignificant changes in pHPZC and crystalline structure were consistent with the changes in SSA and At%-O1s, further supporting the combined effect of GAC inherent properties and grinding mechanisms. The study findings provide guidance for informed selection of grinding methods based on GAC type and target particle sizes to improve the representativeness of adsorption studies conducted with ground GAC.
