Enhanced heavy metal removal from produced water using metal-incorporated iron oxyhydroxide (FeO(OH)) nanomaterials: adsorption kinetics and isotherm studies

Abstract

Environmental contamination with heavy metal ions poses a major public health challenge, particularly groundwater contamination affecting drinking, agricultural, and industrial water supplies. Goethite (FeO(OH)) and metal-incorporated goethite (Ca, Co, Mn, Al) nanomaterials were synthesized via simple precipitation (pH = 12, aging time 7 days) for adsorptive removal of cadmium and chromium ions. Samples were characterized by XRD, FTIR, HR-TEM, N₂ adsorption–desorption isotherms, and thermal analyses. Results showed that metal incorporation increased surface hydroxyl group content relative to pure goethite. Al incorporation dispersed the goethite needles, reducing their length and width compared to other metal-incorporated variants. Al-goethite achieved the highest adsorption capacity, improving from 72.9 to 86 mg L⁻¹ for Cr and 28 to 38 mg L⁻¹ for Cd. Adsorption kinetics followed a pseudo-second-order model, confirming chemisorption. Cd adsorption obeyed the Langmuir isotherm (R² ≈ 0.99), indicating monolayer formation on the predominant goethite faces (001 and 010), while Cr adsorption followed both Langmuir and Freundlich models, suggesting mono- and/or multilayer formation. Goethite nanomaterials demonstrated high remediation efficiency for complete heavy metal removal from produced water samples, confirming their promise as effective adsorbents.