Adsorption of Cr(VI) onto Azadirachta indica stem bark extract modified dolerite composite adsorbent

ABSTRACT

This study assessed the adsorptive uptake of Cr(VI) onto eco-friendly adsorbent fabricated via the surface coating of pristine dolerite (PD) using the extract ofAzadirachta indica stem bark. The materials were characterised using the XRD, FESEM, FTIR, EDX, BET and Raman analysis. Optimum adsorption of Cr(VI) onto AMD was achieved at pH = 2, contact time of 180 min and dosage of 0.03 g. The adsorption equilibrium data for PD and Azadirachta indica extract modified dolerite (AMD)fitted well with the Langmuir and Redlich-Peterson models respectively at 318 K.Also, a good correlation between the experimental data and the Elovich kinetic model was achieved. The diffusion mechanisms were both controlled by film diffusion and intraparticle diffusion.The uptake of Cr(VI) onto PD and AMD was feasible, endothermic (ΔH: PD = 14.14 kJ mol⁻¹ and AMD = 37.67 kJ mol⁻¹) and entropy-driven (ΔS: PD = 17.69 J K⁻¹ mol⁻¹ 204.3 J K⁻¹ mol⁻¹). Besides, the recyclabilitypropensity of AMD afterseveral cycles projects AMD as a fibrousbasedmaterialwithsustainablepotential for the decontamination of Cr(VI) polluted water.

KEYWORDS:

• Azadirachta indica
• dolerite
• isotherm model
• kinetic model
• waste water treatment

Acknowledgments

The authors are grateful to Michael OkparaUniversity of Agriculture, Umudike Nigeria for providingenablingresearchenvironment for thisstudy.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors gratefully acknowledge the financial support from TETFund National Research Fund grant [TETF/DR&D/CE/NRF/STI/66/VOl.I].