University of Oulu

Sylwan, I.; Runtti, H.; Westholm, L.J.; Romar, H.; Thorin, E. Heavy Metal Sorption by Sludge-Derived Biochar with Focus on Pb²⁺ Sorption Capacity at μg/L Concentrations. Processes 2020, 8, 1559.

Heavy metal sorption by sludge-derived biochar with focus on Pb²⁺ sorption capacity at μg/L concentrations

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Author: Sylwan, Ida1; Runtti, Hanna1,2; Johansson Westholm, Lena1;
Organizations: 1School of Business, Society and Engineering, Future Energy Center, Mälardalen University, P.O. Box 883, SE-721 23 Västerås, Sweden
2Research Unit of Sustainable Chemistry, University of Oulu, P.O. Box 8000, FI-90014 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.8 MB)
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Language: English
Published: Multidisciplinary Digital Publishing Institute, 2020
Publish Date: 2021-02-08


Municipal wastewater management causes metal exposure to humans and the environment. Targeted metal removal is suggested to reduce metal loads during sludge reuse and release of effluent to receiving waters. Biochar is considered a low-cost sorbent with high sorption capacity for heavy metals. In this study, heavy metal sorption to sludge-derived biochar (SDBC) was investigated through batch experiments and modeling and compared to that of wood-derived biochar (WDBC) and activated carbon (AC). The aim was to investigate the sorption efficiency at metal concentrations comparable to those in municipal wastewater (<1 mg/L), for which experimental data are lacking and isotherm models have not been verified in previous works. Pb²⁺ removal of up to 83% was demonstrated at concentrations comparable to those in municipal wastewater, at pH 2. SDBC showed superior Pb²⁺ sorption capacity (maximum ~2 mg/g at pH 2) compared to WDBC and AC (<0 and (3.5 ± 0.4) × 10⁻³ mg/g, respectively); however, at the lowest concentration investigated (0.005 mg/L), SDBC released Pb²⁺. The potential risk of release of other heavy metals (i.e., Ni, Cd, Cu, and Zn) needs to be further examined. The sorption capacity of SDBC over a metal concentration span of 0.005–150 mg Pb²⁺/L could be predicted with the Redlich–Peterson model. It was shown that experimental data at concentrations comparable to those in municipal wastewater are necessary to accurately model and predict the sorption capacity of SDBC at these concentrations.

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Series: Processes
ISSN: 2227-9717
ISSN-E: 2227-9717
ISSN-L: 2227-9717
Volume: 8
Issue: 12
Pages: 1 - 23
Article number: 1559
DOI: 10.3390/pr8121559
Type of Publication: A1 Journal article – refereed
Field of Science: 116 Chemical sciences
Funding: This work was supported by VA-kluster Mälardalen, Eskilstuna Energi och Miljö, Vafab Miljö, Mälarenergi, Maa-ja Vesitekniikan tuki ry, and the Walter Ahlström Foundation.
Copyright information: © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (