ORIGINAL RESEARCH article
Front. Environ. Chem.
Sec. Sorption Technologies
This article is part of the Research TopicNanostructured Sorbents for Sustainable Environmental Management: Pioneering Next-Gen Solutions for Complex Contaminant RemovalView all articles
Selective phosphate uptake in the presence of sulfate with granular spent coffee grounds-based adsorbents via metal oxide modification
Provisionally accepted
- 1University of Saskatchewan, Saskatoon, Canada
- 2Saskatchewan Polytechnic, Saskatoon, Canada
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Selective phosphate remediation from saline aquatic environments is crucial in combating eutrophication. Herein, biocomposite adsorbents with 80% spent coffee grounds, variable chitosan content and either 1% or 5% metal oxide (MO) content (-A = 1 wt.%; -B = 5 wt.%) were evaluated. The type of MO was either Fe2O3 (Fe-B or Fe-A) or Al2O3 (Al-B or Al-A). The materials characterization of these biocomposites was achieved via thermogravimetry and spectroscopic (13C NMR, FT-IR, XRD) techniques. Composite formation and coordination between functional groups was evidenced by FT-IR spectral and XRD results. The role of sulfate as a competitor anion was evaluated due to its environmental significance. Single-component isotherm studies showed equilibrium adsorption capacities that range from ca. 13-20 mg/g for phosphate and 9-36 mg/g for sulfate. To investigate the selectivity of phosphate over sulfate, binary selectivity experiments (equal concentration) were conducted. The binary selectivity factor αt/c ranged from 14-16 for Al-based and 6-9 for Fe-based composites. The adsorption capacity ratio was ca. 2-3 for Al-based and ca. 4 for Fe-based composites, which favor phosphate over the presence of sulfate (at 100 mg/L for both anions). This was verified through adsorption experiments in binary, ternary, and quaternary anion systems, where different adsorption sites account for the concerted anion adsorption. Kinetic studies according to the Pseudo-nth order model for two selected composites that showed a reaction order of ca. 1.6-1.8 for Al-A and Fe-B. Adsorption of phosphate in spiked river water with 10 mg/L phosphate (spiked) and ca. 80 mg/L sulfate (natural) for Al-A and Fe-B resulted in ca. 0.4-0.5 mg/g uptake capacity of phosphate. Coordination of phosphate was inferred to follow inner-sphere complexation, in contrast to sulfate. In turn, this study demonstrates how granular adsorbents derived from food-waste with high lignocellulose content can be modified with MO to yield phosphate selective adsorption in saline aqueous media.
Keywords: River water, Environmental matrix, Adsorption, Granular adsorbents, Food waste, Chitosan
Received: 25 Sep 2025; Accepted: 14 Nov 2025.
Copyright: © 2025 Steiger, Faleye, Babalola and Wilson. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Lee D Wilson, lee.wilson@usask.ca
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