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Article

Comparison of the Properties of Activated Carbons Produced in One-Stage and Two-Stage Processes

1
Research Unit of Sustainable Chemistry, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland
2
Unit of Applied Chemistry, University of Jyvaskyla, Kokkola University Consortium Chydenius, Talonpojankatu 2B, FI-67100 Kokkola, Finland
*
Author to whom correspondence should be addressed.
Received: 11 June 2018 / Revised: 5 July 2018 / Accepted: 6 July 2018 / Published: 16 July 2018
(This article belongs to the Special Issue Carbons from Biomasic Waste and Their Applications)
Activated carbons (ACs) can be produced from biomass in a thermal process either in a direct carbonization-activation process or by first carbonizing the biomass and later activating the bio-chars into activated carbons. The properties of the ACs are dependent on the type of process used for production. In this study, the properties of activated carbons produced in one-stage and two-stage processes are considered. Activated carbons were produced by physical activation of two types of starting materials: bio chars produced from spruce and birch chips in a commercial carbonization plant and from the corresponding raw chips. The activated carbons produced were characterized regarding specific surfaces, pore volumes, and pore size distributions. The un-activated bio chars had varying surface areas, 190 and 140 m2 g−1 for birch and spruce, respectively, and pore volumes of 0.092 and 0.067 cm3 g−1, respectively. On the other hand, 530–617 and 647–679 m2 g−1 for activated bio chars from birch and spruce, respectively, and pore volumes 0.366–0.509 and 0.545–0.555 cm3 g−1, respectively, were obtained. According to the results obtained, two slightly different types of activated carbons are produced depending on whether a one-stage or a two-stage carbonization and activation process is used. The ACs produced in the one-stage process had higher specific surface areas (SSA), according to the BET-model (Brunauer–Emmett–Teller), compared to the ones produced in a two-stage process (761–940 m2 g−1 vs. 540–650 m2 g−1, respectively). In addition, total pore volumes were higher in ACs from the one-stage process, but development of micro-pores was greater compared to those of the two-stage process. This indicates that the process can have an influence on the ACs’ porosity. There was no significant difference in total carbon content in general between the one-stage and two-stage processes for spruce and birch samples, but some differences were seen between the starting materials. Especially in the one-stage procedure with 2 and 4 h steam activation, there was nearly a 10% difference in carbon content between the spruce and birch samples. View Full-Text
Keywords: biomass; bio-char; activation; activated carbon; thermal treatment; physical activation; porosity; specific surface areas biomass; bio-char; activation; activated carbon; thermal treatment; physical activation; porosity; specific surface areas
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MDPI and ACS Style

Bergna, D.; Varila, T.; Romar, H.; Lassi, U. Comparison of the Properties of Activated Carbons Produced in One-Stage and Two-Stage Processes. C 2018, 4, 41. https://0-doi-org.brum.beds.ac.uk/10.3390/c4030041

AMA Style

Bergna D, Varila T, Romar H, Lassi U. Comparison of the Properties of Activated Carbons Produced in One-Stage and Two-Stage Processes. C. 2018; 4(3):41. https://0-doi-org.brum.beds.ac.uk/10.3390/c4030041

Chicago/Turabian Style

Bergna, Davide, Toni Varila, Henrik Romar, and Ulla Lassi. 2018. "Comparison of the Properties of Activated Carbons Produced in One-Stage and Two-Stage Processes" C 4, no. 3: 41. https://0-doi-org.brum.beds.ac.uk/10.3390/c4030041

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