Biosorption Potential of Saraca asoca Bark Powder for Removal of Cr (VI) Ions from Aqueous Solution
2022
Lall, Anurag Samson | Pandey, Avinash Kumar | Mani, Jyoti Vandana
Saraca asoca bark has long been used in traditional Indian medicine. Considering its low cost and non-toxic nature, it can find application as a biosorbent. This article explores the application of Saraca asoca bark powder (SABP) for biosorption of hexavalent chromium. Various analytical techniques including Field emission scanning electron microscope (FESEM) attached with energy dispersive spectrometer (EDS), Fourier transform infrared spectroscopy (FTIR) and point of zero charge (pHpzc) were adopted in order to identify the physico-chemical features of SABP. Factors such as pH (2-8), contact time (for 3 hours), initial Cr (VI) concentration (10 – 250 mg/l) and temperature (15 - 35°C) were examined for their influence on Cr (VI) biosorption via batch studies. Biosorption data clearly followed Redlich-Peterson isotherm model as compared to Langmuir and Freundlich models. The Langmuir monolayer adsorption capacities (Qm) at 15, 25 and 35°C were 123.4, 125.0 and 175.4 mg/g respectively. Biosorption followed pseudo-second-order kinetics and the mechanism of diffusion was governed by both surface sorption and pore diffusion as demonstrated by the plot for Intraparticle diffusion model and the pore diffusion coefficient (Dp~10-9 cm2/s). The nature of biosorption was found to be spontaneous and endothermic as reflected through various thermodynamic parameters such as the free energy change (ΔG = -3.0 to -3.7 kJ/mol), entropy change (ΔS = 37.8 J/K/mol) and enthalpy change (ΔH = 7.9 kJ/mol). The study recommends that SABP may be utilized as a potential biosorbent for Cr(VI) ions.
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