University of Oulu

Simões dos Reis, G., Bergna, D., Tuomikoski, S., Grimm, A., Lima, E. C., Thyrel, M., Skoglund, N., Lassi, U., & Larsson, S. H. (2022). Preparation and characterization of pulp and paper mill sludge-activated biochars using alkaline activation: A box–behnken design approach. ACS Omega, 7(36), 32620–32630.

Preparation and characterization of pulp and paper mill sludge-activated biochars using alkaline activation : a Box–Behnken design approach

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Author: Simões dos Reis, Glaydson1; Bergna, Davide2,3; Tuomikoski, Sari2;
Organizations: 1Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, Biomass Technology Centre, SE-901 83 Umeå, Sweden
2Research Unit of Sustainable Chemistry, University of Oulu, PO Box 4300, FI-90014 Oulu, Finland
3Unit of Applied Chemistry, University of Jyvaskyla, Kokkola University Consortium Chydenius, Talonpojankatu 2B, FI-67100 Kokkola, Finland
4Institute of Chemistry, Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9500, Porto Alegre 91501-970, RS, Brazil
5Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University, SE-901 87 Umeå, Sweden
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 9.6 MB)
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Language: English
Published: American Chemical Society, 2022
Publish Date: 2022-12-28


This study utilized pulp and paper mill sludge as a carbon source to produce activated biochar adsorbents. The response surface methodology (RSM) application for predicting and optimizing the activated biochar preparation conditions was investigated. Biochars were prepared based on a Box–Behnken design (BBD) approach with three independent factors (i.e., pyrolysis temperature, holding time, and KOH:biomass ratio), and the responses evaluated were specific surface area (SSA), micropore area (Smicro), and mesopore area (Smeso). According to the RSM and BBD analysis, a pyrolysis temperature of 800 °C for 3 h of holding and an impregnation ratio of 1:1 (biomass:KOH) are the optimum conditions for obtaining the highest SSA (885 m2 g–1). Maximized Smicro was reached at 800 °C, 1 h and the ratio of 1:1, and for maximizing Smeso (569.16 m2 g–1), 800 °C, 2 h and ratio 1:1.5 (445–473 m2 g–1) were employed. The biochars presented different micro- and mesoporosity characteristics depending on pyrolysis conditions. Elemental analysis showed that biochars exhibited high carbon and oxygen content. Raman analysis indicated that all biochars had disordered carbon structures with structural defects, which can boost their properties, e.g., by improving their adsorption performances. The hydrophobicity–hydrophilicity experiments showed very hydrophobic biochar surfaces. The biochars were used as adsorbents for diclofenac and amoxicillin. They presented very high adsorption performances, which could be explained by the pore filling, hydrophobic surface, and π–π electron–donor–acceptor interactions between aromatic rings of both adsorbent and adsorbate. The biochar with the highest surface area (and highest uptake performance) was subjected to regeneration tests, showing that it can be reused multiple times.

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Series: ACS omega
ISSN: 2470-1343
ISSN-E: 2470-1343
ISSN-L: 2470-1343
Volume: 36
Issue: 7
Pages: 32620 - 32630
DOI: 10.1021/acsomega.2c04290
Type of Publication: A1 Journal article – refereed
Field of Science: 116 Chemical sciences
Funding: This research was funded by Bio4Energy─a Strategic Research Environment appointed by the Swedish government and the Swedish University of Agricultural Sciences. The Fourier transform infrared (FTIR) spectroscopy and Raman measurements were performed at the Vibrational Spectroscopy Core Facility (ViSp), Chemical Biological Centre (KBC), Umeå University. The Umeå Core Facility for Electron Microscopy (UCEM-NMI node) at the Chemical Biological Centre (KBC), Umeå University, is gratefully acknowledged. E.C.L. thanks FAPERGS and CNPq for financial support.
Dataset Reference: The Supporting Information is available free of charge at
Copyright information: © 2022 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.