Malachite Green Adsorption on Fe3O4@Pinecone Biochar Formed in an Attempted CaFe2O4 Deposition

ORCID

Olabode: https://orcid.org/0000-0001-7966-1212; Mlsna: https://orcid.org/0000-0002-4858-1372

MSU Affiliation

College of Arts and Sciences; Department of Chemistry

Creation Date

2026-07-30

Abstract

Many metal-ferrite-based adsorbents are reported, encouraging this work. We investigated Fe3O4 formation during attempted CaFe2O4 deposition by a published method on pinecone biochar. Fe3O4@PCBC was formed without any confirmed evidence of CaFe2O4 formation. The resulting composite was magnetically recoverable after Malachite Green (MG) dye uptake. This adsorbent was characterized using XRD, FTIR, SEM-EDX, BET surface area, pHpzc, CHNS combustion, EDX surface, and bulk Ca and Fe analyses. MG adsorption parameters were evaluated. Crystalline CaFe2O4, neat Fe3O4, and Fe3O4@PCBC could not be distinguished by XRD, requiring elemental analysis for confirmation of all synthesized samples. Importantly, the identification of CaFe2O4 and other ferrites on supports in the literature sometimes depends only on XRD. Thus, the example we report is a warning to not depend exclusively on XRD. MG uptake data on Fe3O4@PCBC at 278, 298, 308, and 323 K fit the Langmuir isotherm (R2 = 0.97) with maximum capacities of 22.3, 32.0, 39.6, and 34.2 mg/g, respectively, at pH 5. Adsorption was spontaneous (ΔGo278 − 323 K = −23.5,   − 27.3,   − 29.2,   − 32.0 kJ/mol), endothermic (ΔH°278–323 K = 28.9 kJ/mol), and caused enhanced randomness (ΔSo278 − 323 K = 188.5 J/mol•K). Uptake followed both pseudo-first and pseudo-second order kinetics. Neat-PCBC has smaller maximum Langmuir MG capacities (278–323 K) of 7.88, 9.50, 20.02, and 3.40 mg/g. Magnetic separations were demonstrated.

Publication Date

6-19-2026

Publication Title

Surfaces and Interfaces

Publisher

Elsevier

Creative Commons License

Creative Commons Attribution-NonCommercial 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License

Rights

© 2026 The Author(s)

This document is currently not available here.

Share

COinS
 

Digital Object Identifier (DOI)

https://doi.org/10.1016/j.surfin.2026.109803