Activated carbons (ACs) are widely used in different industrial processes as adsorbents for pollutant removal or as catalytic material support. The parameters and methods of activation can vary, and they affect the final characteristics of ACs, e.g., specific surface area, pore size distribution, and surface functional groups. The results of this study show that microporosity and mesoporosity can be modified, variating these parameters. ACs from Northern Finland Region peat have been prepared through physical activation with steam. The process has been evaluated using the design of experiment approach. Different parameters have been considered as factors, including holding time, oven temperature, heating rate, steam flow, nitrogen flow, kiln rotation, and biomass initial mass. Based on these factors, several responses characterizing the porosity and the elemental analysis of ACs have been selected. All the data collected have been processed statistically using the Fractional Factorial Resolution IV design linear model in a screening configuration fitted with a partial least squares regression using MODDE 9.1 by Umetrics Software.

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.

The process for producing activated carbon from peat was optimized. The peat was impregnated with different ratios of ZnCl2, and the impregnated biomass was activated at different temperatures. The specific surface area, pore size distribution, total carbon content, and yield of the activated carbon were investigated. The best results for the specific surface area and mesoporosity of the activated peat were obtained by using a high impregnation ratio (2) and high activation temperature (1073 K). Highly porous activated carbon was produced that had a specific surface area of approximately 1000 m2/g and total pore volume that was higher than 0.5 cm3/g for most samples. The activated carbon had a high degree of mesoporosity. The adsorptive properties of the activated carbon were determined with methylene blue and orange II dyes.