Magnesium Dross and Ground Granulated Blast Furnace Slag Utilisation for Phosphate Elimination from Water

Alwash, R, Andredaki, M, Carnacina, I ORCID: 0000-0001-5567-7180, Sadique, M ORCID: 0000-0001-7967-2659 and Amoako-Attah, J ORCID: 0000-0002-2353-4131 (2025) Magnesium Dross and Ground Granulated Blast Furnace Slag Utilisation for Phosphate Elimination from Water. Applied Sciences, 15 (23). ISSN 2076-3417

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Abstract

It is well known that elevated phosphate concentrations in water bodies trigger the eutrophication process, posing adverse environmental, health, and economic consequences that necessitate effective removal solutions. Phosphate removal has therefore been widely studied using various methods, including chemical precipitation, membrane filtration, and crystallisation. However, most of these methods are often expensive or inefficient for low phosphate concentrations. Therefore, in this study, an eco-friendly, sustainable and biodegradable adsorbent was manufactured by extracting calcium ions from an industrial by-product, ground granulated blast furnace slag (GGBS) and magnesium ions from magnesium dross (MgD), then immobilising them on sodium alginate to form Ca-Mg-SA beads. The new adsorbent was applied to remove phosphate from water under different flow patterns (batch and continuous flow), initial pH levels, contact times, agitation speeds and adsorbent doses. Additionally, the degradation time of the new adsorbent, recycling potential, its morphology, formation of functional groups and chemical composition were investigated. The results obtained from batch experiments demonstrated that the new adsorbent achieved 90.2% phosphate removal efficiency from a 10 mg/L initial concentration, with a maximum adsorption capacity of 1.75 mg P/g at an initial pH of 7, a contact time of 120 min, an agitation speed of 200 rpm and an adsorbent dose of 1.25 g/50 mL. The column experiments demonstrated a 0.82 mg P/g removal capacity under the same optimal conditions as the batch experiments. The findings also showed that the adsorption process fitted well to the Freundlich and Langmuir isotherm models and followed a pseudo-second-order kinetic model. Characterisation of Ca-Mg-SA beads using EDX, SEM and FTIR confirmed successful ion immobilisation and phosphate adsorption. Furthermore, the beads fully biodegraded in soil within 75 days and demonstrated potential recycling as a fertiliser.

Item Type:	Article
Uncontrolled Keywords:	phosphate elimination; adsorption; sodium alginate; water remediation; industrial waste recycling; 41 Environmental Sciences; 40 Engineering; 4104 Environmental Management; 4011 Environmental Engineering
Subjects:	Q Science > Q Science (General) T Technology > TD Environmental technology. Sanitary engineering
Divisions:	Engineering and Built Environment
Publisher:	MDPI AG
Date of acceptance:	2 December 2025
Date of first compliant Open Access:	15 September 2026
Date Deposited:	15 Sep 2026 09:20
Last Modified:	15 Sep 2026 09:20
DOI or ID number:	10.3390/app152312844
URI:	https://researchonline.ljmu.ac.uk/id/eprint/29421

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