Development of low-carbon and porous biochar-slag composites for efficient phosphorus removal.

Ren, Zongqiang, Xu, Yaowen, Sapsford, Devin ORCID: https://orcid.org/0000-0002-6763-7909 and Jin, Fei ORCID: https://orcid.org/0000-0003-0899-7063 2026. Development of low-carbon and porous biochar-slag composites for efficient phosphorus removal. Journal of environmental management 412 , 130240. 10.1016/j.jenvman.2026.130240

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Abstract

A CO -sequestering porous biochar-slag composite was fabricated via carbonation coupled with biochar modification for phosphorus (P) removal. Carbonation created meso-/macropores and increased surface area from 0.32 m /g to 5.13 m /g, biochar addition further raised surface area to 7.24 m /g and enhanced CO uptake from 82.07 mg/g to 141.29 mg/g, likely by promoting CaCO nucleation and improving CO diffusion. In batch tests, carbonation improved effluent quality (pH 11.51 to 9.93; electrical conductivity 1074.90 to 116.90 μS/cm) but lowered P uptake. An optimised 10 wt% biochar-carbonated composite (BC _C) balanced capacity and leaching, achieving 3.16 mg/g at P  = 10 mg/L. P removal was sensitive to solution chemistry: humic acid and added Ca enhanced P removal, whereas CO most strongly inhibited it. Column study showed that BC _C maintained ∼100% P removal over 930 bed volumes without surface ponding observed for BC _UC, while exhibiting more moderated effluent chemistry, including lower and more stable electrical conductivity (∼600 μS/cm), lower TOC release, and post-operational P immobilisation of 38.91 mg/g. SEM-EDS mapping and fractionation revealed Ca-P precipitation was the dominant removal mechanism. This study proposed a scalable, low-carbon route for sustainable P remediation. [Abstract copyright: Copyright © 2026 The Authors. Published by Elsevier Ltd.. All rights reserved.]

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Schools > Engineering
Date of First Compliant Deposit:	29 June 2026
Date of Acceptance:	13 June 2026
Last Modified:	29 Jun 2026 10:00
URI:	https://orca.cardiff.ac.uk/id/eprint/187768

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