1. Activated Carbons from Herbaceous Bioenergy Crops
Oluwatosin Oginni and Kaushlendra Singh
School of Natural Resources, West Virginia University
Northeast Agricultural and Biological Engineers Conference
Orono, Maine
July 31 - August 3, 2016

2. Background

3. Activated carbon is an amorphous solid with large internal surface area/pore structure that absorbs molecules from both the liquid and gas phase.
It is has been proven to be an effective adsorbent for the removal of a wide variety of organic and inorganic pollutants dissolved in aqueous media, or from gaseous environment, wastewater treatment and soil amendment.
Biochar, a product of biomass pyrolysis due to its properties such as porosity, surface area, pore structure, volatile and carbon contents, has been identified as a precursor for activated carbon production.
Activated carbon production involves activation process and it is classified into two types: Physical and Chemical Activation.

4. Physical Activation Chemical Activation
Physical activation involves carbonization of the raw material in an inert atmosphere.
Thereafter, the carbonized material is partially gasified with steam, CO2 or a mixture of both at temperatures in the range 800 – C to form a complex array of micropores and mesopores.
Chemical Activation
The biochar is impregnated with chemical compounds such as KOH, H3PO4 or ZnCl2.
The impregnated product is carbonized and then washed to remove the activating agent.
Some possible advantages of chemical activation are: (a) simplicity, (b) good development of the porous structure and (c) easy recovery of some of the impregnated chemicals

5. MOTIVATION
Recent studies had shown that conventional wastewater treatments are not effective to eliminate majority of the pharmaceutical active compounds.
A residual quantities are found in the treated water and have been found to accumulate in drinking water.
However, adsorption has become a well-established technique in removing pollutants and hence activated carbon finds an application in this area.
With the abundant biomass resources available for conversion into liquid, the resulting biochars can serve as a low cost resource for production of activated carbon.
In West Virginia, there are herbaceous bioenergy crops grown on reclaimed mining lands and the use of these resources for activated carbon can serve as a source of income for the plant growers

6. OBJECTIVE
To investigate activated carbon production via chemical activation of biomass and biochar samples of two herbaceous bioenergy crops (switchgrass and miscanthus) harvested from a reclaimed mining land in West Virginia.

7. Batch Pyrolysis Reactor
METHODOLOGY
Two biomass samples (namely Switchgrass and Miscanthus) harvested from a reclaimed mining land in West Virginia were used in this study. The samples were dried and ground through a sieve of size 1.00 mm.
About 50 g of the ground samples were impregnated with 200 ml of phosphoric acid (85% wt.) using a parr reactor at a temperature of 85 0C continuously stirred for 24 hours.
Pyrolysis of the biomass samples were carried in a batch pyrolysis reactor at temperature of 500 0C for 30 minutes under constant flow of nitrogen. The biochar produced from the two samples were also subjected to similar impregnation.
The impregnated samples were oven dried and thereafter heat-treated using thermogravimetric analyzer at 900 0C.
The carbonized samples were washed using distilled water to remove the acid, oven dried for 24 hours at 103 0C and thereafter characterized.
Batch Pyrolysis Reactor
Parr Reactor System

8. Characterization of Biochar and Activated Carbon
Properties
Sulfur
Porosity
Hydrogen
Nitrogen
SEM
Volatile Matter
Proximate Analyzer
Elemental surface composition
(XPS)
Characterization of Biochar and Activated Carbon
CHNS/O Analyzer

9. RESULTS
Fig 1: Carbon, Hydrogen, Nitrogen and Sulfur content of Biomass and Biochar
Fig 2: Van Krevelen diagram of H/C and O/C atomic ratios for biomass, bio-oil and biochar
The carbon content of the biochars in comparison to the parent feedstock is significantly high (p<0.05). The high carbon content of the biochars makes it a good precursor for activated carbon production (Fig 1).
Biochars have a relatively low H/C and O/C ratio which depicts a high concentration of carbon which makes it a good candidate for carbon sequestration and activated carbon production.

10. Properties
Switchgrass
Miscanthus pH
Volatile (%)
Fixed Carbon
Atomic C/N
145.64
85.64
Atomic O/C
0.15
0.17
Atomic H/C
0.41
0.45
Porosity
0.83
0.85

11. XPS Elemental Surface Composition
Carbon Oxygen Aluminum Silicon Phosphorus %
Fig 3: Activated Carbon from Impregnated Switchgrass Biochar

12. Carbon Oxygen Aluminum Silicon Phosphorus Iron%
Fig 4: Activated Carbon from Impregnated Switchgrass Biomass

13. Carbon Oxygen Silicon Phosphorus Iron%
Fig 5: Activated Carbon from Impregnated Miscanthus Biochar

14. Carbon Oxygen Aluminum Silicon Phosphorus%
Fig 6: Activated Carbon from Impregnated Miscanthus Biomass

15. SEM Micrograph of Biochar and Activated Carbons
Fig 7a: SEM Micrograph of Switchgrass Biochar
Fig 7b: SEM Micrograph of Activated Carbon from Impregnated Switchgrass Biochar

16. Fig 8a: SEM Micrograph of Miscanthus Biochar
Fig 8b: SEM Micrograph of Activated Carbon from Impregnated Miscanthus Biochar

17. Ongoing Work
Adsorption of two pharmaceutical compounds (Acetaminophen and Caffeine) using the produced activated carbons.
Determination of surface area, pore size distribution, total pore volume, micropore and mesopore volume.
Performance comparison of commercial activated carbon with carbon from herbaceous bioenergy crop.
Techno-economic analysis of activated carbon production from herbaceous bioenergy crops harvested on reclaimed mining lands in West Virginia.

18. SUMMARY
The low H/C and O/C ratio of the biochars compared favorably with reported lignite coal composition hence making it a good candidate for carbon sequestration and activated carbon production
Impregnation and carbonization of the biomass samples yielded an activated carbon with high surface carbon, low oxygen and other minerals as compared to the activated carbons produced from the biochar.
Activated carbon produced from impregnated Miscanthus biomass has the best surface elemental composition.
The SEM micrographs of the activated carbons showed the amorphous nature of the carbons.

19. THANK YOU FOR YOUR TIME.