Adsorption of cadmium and lead from palm oil mill effluent using bone-composite: optimisation and isotherm studies

ABSTRACT

The adsorption of Cd and Pb ions from palm oil mill effluent on a mesoporous-activated cow bone composite powder has been investigated. Adsorbent was developed from cow bones, coconut shells and zeolite. The composite examined in the present work has a BET surface area of 248.398 m²/g. The optimisation of the removal efficiency of the heavy metals was investigated using central composite design and analysed using response surface methodology. The analysis of variance of the quadratic model signified that the model suitably predicted the uptake of the heavy metal ions at a 95% confidence level. The optimal operating condition was recorded at pH 4, 50 rpm, within 24 h and 1 mm of particle size and 12.5 gL⁻¹ of adsorbent dosage. The characteristics of the composite were investigated using the Fourier transform irradiation. The morphology and chemical composition of composite was examined using the scanning electron microscopy equipped with energy dispersive x-ray. Characterisation study was conducted before and after the adsorption process. The results obtained illustrated that the removal of cadmium and lead from POME was influenced by the functional groups available on the surface of the composite. The carboxyl and hydroxyl groups are mainly responsible for the removal of cadmium and lead through chelating process. The point of zero charge (pH_pzc) revealed that the adsorbent contained acidic sites with negatively charge surface which influenced the adsorption process. The experimental data of the heavy metals of Cd and Pb investigated were fitted to the Langmuir and Freundlich models. The result revealed that the adsorption equilibrium data fitted better to the Langmuir model for the adsorption Cd and to the Freundlich model for the adsorption of Pb.

KEYWORDS:

• Bone composite
• heavy metals
• palm oil mill effluent
• optimisation
• adsorption isotherm

Acknowledgments

The authors wish to fully acknowledge the Ministry of Higher Education Malaysia for fully supporting this work under the Fundamental Research Grant Scheme (Vot FRGS 1571, 2016). Special gratitude to the Division of Environmental Technology, School of Industrial Technology, Universiti Sains Malaysia for the contribution to this work.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was fully supported by the Ministry of Higher Education Malaysia under the scheme Fundamental Research Grant Scheme FRGS [Grant number FRGS 1571].