Waste citrus fruit peels for removal of Hg(II) ions

Abstract

Mercury is considered as a highly toxic and hazardous pollutant even in trace concentration. Severe consequence of mercury poisoning was observed as Minamata disease in Japan in 1956. Amongst the various techniques used for removal of Hg(II) ions from polluted waters, adsorption demonstrates most promising results. This paper focuses on adsorption of mercury using citrus fruit peels waste from Phyllanthus emblica (Indian gooseberry/amla), Citrus sinensis (orange), Mangifera indica (raw mango) and Citrus limetta (sweet lime). The citrus peels were naturally shade dried, powdered to an average particle diameter of 150–200 μ and used without any chemical modification. The impact of solution pH, Hg(II) ion concentration and initial Hg(II) concentration was evaluated in batch adsorption process. The order of Hg(II) adsorption was found to be as: P. emblica > C. sinensis > C. limetta > M. indica. Langmuir and Freundlich isotherm describes the equilibrium adsorption condition. The adsorption of Hg(II) followed the pseudo-second-order kinetic mechanism. The thermodynamic investigation showed that the adsorption is a spontaneous process.

Keywords:

• Mercury
• Adsorption
• Waste citrus fruit peels

Acknowledgements

The authors thank Dr Prahlada (Vice Chancellor, DIAT(DU)) for the support and help he extended to us in the research activities and Prof Om Parkash (Head of Department, Ceramic Engineering, IIT (BHU), Varanasi) for helping us in getting the internship and thereby, giving us the opportunity to work at DIAT. We would also thank Dr Renuka Gonte, DIAT and Vivek Verma IISER Pune for their continued technical support.