Biosorption - a case study of hexavalent chromium removal with raw pomegranate peel

Abstract

Biosorptive removal of heavy metals from water is an eco-friendly green technology. In this study, raw pomegranate (Punicagranatum L.) peel (RPP), without any modification or activation, was used as biosorbent for the removal of chromium (Cr(VI)). The influence of operating parameters such as pH, contact time, temperature and concentration of Cr(VI) were studied in batch mode. A maximum removal of 100% was achieved for a Cr(VI) solution of concentration 20 mg/L at an optimum pH and temperature of 2 and 313 K respectively in 3 min. Among the isotherms tested, Langmuir adsorption isotherm has good correlation with experimental data. A maximum Cr(VI) biosorption capacity of 370.4 mg/g was observed at 313K under equilibrium conditions. RPP is also effective in the removal of Cr(VI) at higher concentrations. Among the kinetic models, pseudo-second order kinetic model fits the data well. The thermodynamic study reveals that the endothermic biosorption taking place on RPP is physico-chemical in nature. The biosorption mechanism of RPP with Cr(VI) indicates that intra-particle diffusion is not the only rate limiting step and film diffusion also plays a major role in biosorption.

Characterization and adsorption of raw pomegranate peel powder for lead (II) ions removal

“…K L values reported in the aforementioned pertinent literature were less than unity, except for the K L = 2.76 reported by Giri, et al [13]. The dimensionless separation factor, R L , which is used to evaluate the feasibility and applicability of the process was found to be less than unity in the current study, as well as in the result presented by Salam, et al [14] and Ben-Ali, et al [19]. This finding is an indication of a favorable adsorption (since 0 < R L < 1).…”

“…Other authors also reported the presence of carbon, oxygen, nitrogen, and hydrogen as the major constituents of PMPP [13,19]. However, asides from the main constituents, traces of potassium, calcium, copper, zinc, manganese, iron were also observed by [13,14].…”

“…This finding coincides with the XRD and FTIR analyses result, thus confirming that the main components of the PMPP sample are non-cellulosic materials. Studies by Salam, et al [14] and Giri, et al [13] reported a coarse surface structure with hollow cavities and pore structure on the native/raw pomegranate peel. However, the coarse and rough surface structures metamorphized into a comparatively smoothened surface due to a possible occurrence of a redox reaction between the adsorbent active sites and adsorbed chromium ions.…”

“…For instance, the hydroxybenzoic (gallic and ellagic) acids, derivatives of flavones, and hydroxycinnamic acids are responsible for their superior heavy metal chelation properties [13]. The phenolic compounds and the anthocyanin derivatives contribute to the excellent surface adsorption of free metal ions [14]. In a previous phytochemical investigation of pomegranate peels, 10 phenolic compounds containing a common hexahydroxy diphenol moiety were isolated [15].…”

“…Within the last decade, several authors have investigated the heavy metal adsorption potentials of raw pomegranate peel powder (PMPP) [13,14,[19][20][21][22][23][24][25][26][27][28]. The novelty of the current study lies in the authors' succinct discussion of the experimental results in comparison with findings from pertinent publications.…”