Aqueous Brilliant Blue Adsorption on Fe3O4@Kaolin: Adsorption Performance, Equilibrium, and Operational Parameters

ORCID

Oguntuyi: https://orcid.org/0000-0001-8784-0843; Ariwoola: https://orcid.org/0009-0008-6225-677X; Paul: https://orcid.org/0000-0002-6313-5848; Mlsna: https://orcid.org/0000-0002-4858-1372

MSU Affiliation

College of Arts and Sciences; Department of Chemistry; Department of Geosciences

Creation Date

2026-07-30

Abstract

Textile wastewater is a major contributor to global water pollution. Magnetically modified kaolin adsorbents calcined at 200-500 °C (Fe3O4@K) were prepared. They removed anionic dyes from water, raised neat kaolin’s capacity, supported Fe3O4, and reduced its aggregation. Calcination had minimal impact on surface area and pore structure. Fe3O4 was deposited onto kaolin via FeCl3 and FeSO4‧7H2O co-precipitation at pH 10 using 25 % NH4OH. After drying and calcined at 200 °C, it was characterized by XRD, FT-IR, SEM-EDX, BET-surface area, and . The adsorbent was magnetically removed from dye solutions. Fe3O4@K-200 and virgin-kaolin adsorbed Brilliant Blue (BB), Crystal Violet (CV), and Brilliant Green (BG), but only BB’s uptake significantly increased on Fe3O4@K-200 vs kaolin. Fe3O4 promoted this anionic BB uptake. BB adsorption was evaluated as a function of adsorbent dose, pH, initial concentration, temperature, and contact time. Virgin-kaolin had a surface area of 18.91 m2/g, while Fe3O4@K-200 increased to 27.07 m2/g. Respective pore volumes were 0.031 and 0.06 cm3/g with an improved Fe3O4 dispersion. Kaolin has a pore diameter of 1.08 nm while Fe3O4@K-200 has 1.01 nm. Adsorption isotherms from 283-318 K (R2 = 0.95-0.99) best fit the Langmuir model vs the Freundlich model. Maximum BB Langmuir capacities ranged from 88.48 to 103.23 mg/g at pH 5 and 1 g/L dosage after 90 min equilibrations under controlled conditions. Adsorption was spontaneous endothermic, with increased randomness, indicating favorable thermodynamic behavior for practical wastewater treatment applications. Fe3O4@K-200 is a promising low-cost, magnetically recoverable adsorbent for anionic dye removal.

Publication Date

7-3-2026

Publication Title

Journal of Environmental Sciences

Publisher

Elsevier

Rights

© 2026 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences

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Digital Object Identifier (DOI)

https://doi.org/10.1016/j.jes.2026.105591