Lab-scale continuous flow studies for comparative biosorption of cadmium (II) on untreated and xanthated Ficus religiosa biomass

The present studies report the use of an ecofriendly biomass Ficus religiosa in untreated (UFR) and xanthate treated (XFR) forms for the Cd (II) ions removal in a fixed bed column. FTIR, SEM-EDS, BET surface area, and elemental analysis (CHNS) techniques were used to characterize the biosorbents. The acquired data supported FTIR findings regarding the nature of functional groups present in the materials. Packed bed continuous flow studies explored the effects of various parameters such as Cd (II) ion concentration (100 mg/L-300 mg/L), bed heights (5 cm-30 cm), pH (3-5), at a constant linear flow rate (~1.13 cm/min). The obtained S-shaped breakthrough curves indicated the efficiency of the packed bed for the Cd (II) removal. Breakthrough time and exhaust times increased (67.5 min-390 min and 292.5 min-1852.5 min) (97.5 min-442.5 min and 345 min-1920 min) for unmodified and modified respectively with bed heights. The BDST, Thomas, and Yoon-Nelson models were used to evaluate the experimental results. The Yoon-Nelson model describes the breakthrough data more efficiently compared to other models. Under similar conditions, the modified material exhibited 400% increased capacity (55.20 mg/g) than that of unmodified material (13.33 mg/g). Thus, xanthate modification significantly enhanced the capacity for Cd (II) ions from aqueous solutions. PRACTITIONER POINTS: Xanthate modification of Ficus religiosa is an environmentally friendly process. Modified and unmodified materials were utilized for Cd (II) removal in fixed bed column process which is industrially viable process. Low inlet Cd (II) concentration at pH 5 and higher bed height favored the continuous flow process at fixed flow rate. Modification caused an increase of about 400% in the capacity of material.