Simultaneous Removal of Molybdate and Chromate Ions from Industrial Wastewater using Biosorbents Derived from Stems of Murraya koenigii: Thermodynamics, Isothermal and Kinetic Investigations

Goriparthi Aparna Devi1, Kunta Ravindhranath1,*,, Sneha Latha Pala1,, Sudhakar Miriyala1 and Wondwosen Kebede Biftu1,2,

1Department of Chemistry, Koneru Lakshmaiah Education Foundation, Green Fields, Vaddeswaram-522502, India

2R&D Directorate, Ethiopian Radiation Protection Authority, Addis Ababa, Ethiopia

*Corresponding author: E-mail: ravindhranath.kunta@gmail.com

Abstract

The removal of molybdate and chromate from industrial wastewater is one of the major tasks of water remediation methods. The disposal of ill-treated effluents containing these toxic heavy metal oxyanions into aqueous environment, effects aquatic life, ecosystems and endogenous the human life. The adsorptive methods available so far are to removal either molybdate or chromate ions and not their simultaneous removal. In the present investigation, a bioadsorbent derived from Murraya koenigii plant has the potential to remove both molybdate and chromate ions simultaneously at pH 2.5. The adsorbent was characterized using XRD and FTIR besides the assessment of conventional physico-chemical parameters. Various extraction conditions were investigated and optimized using simulated solutions of individual as well as mixtures of molybdate and chromate ions. The optimum conditions for simultaneous removal are: pH: 2.5; dosage of adsorbent: 2.5 g/L; contact time: 120 min; rpm: 300; temp.: 30 ± 1 ºC. The extraction was marginally effected by common co-ions. The adsorbents can be regenerated and reused for three cycles. Thermodynamic parameters revealed that the adsorption of molybdate and chromate onto the surface of the adsorbent is endothermic and spontaneous. Further, the magnitude of ΔH values and IR data confirmed that the nature of adsorption is ‘ion exchange and/or a sort of surface complex formation’. Kinetics of adsorption was analyzed by various models and of them, pseudo-second-order model explains well. Of the various isotherm models analyzed, Langmuir model fits well and thereby indicating the homogeneity surface of the adsorbent and unform distribution of active sites. The developed method was applied to treat real wastewater samples collected from industrial and mining effluents and found to be highly effective. The novelty of the present investigation is that a simple and effective bioadsorbent is developed for the simultaneous removal of highly toxic molybdate and chromate ions from the industrial wastewaters.

Keywords

Water remediation methods, Bioadsorbents, Murraya koenigii, Molybdate ions, Chromate ions.

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