Comparative analysis of floating and submerged macrophytes for heavy metal (copper, chromium, arsenic and lead) removal: sorbent preparation, characterization, regeneration and cost estimation

In this study, a comparative evaluation of floating and submerged macrophytes was performed. Azolla filiculoides (free floating) and Hydrilla verticillata (submerged) aquatic macrophytes were utilized for arsenic, copper, chromium and lead removal from the respective metallic ion solutions. Batch experiments were performed initially with optimization of different physical parameters viz., pH, initial heavy metal concentration, biosorbent dosage, contact time, temperature and agitation speed. Submerged (Hydrilla verticillata) had depicted better removal efficiency in comparison to the floating macrophyte (Azolla filiculoides). Field emission scanning electron microscopy equipped with energy dispersive spectroscopy and Fourier transform infrared spectroscopy analysis was performed for the characterization of the metal loaded biosorbents. Biosorption of the respective heavy metal was clearly depicted in the FESEM-EDX spectrum, although not much change in the morphology of the biosorbents were examined. FTIR spectra of the biosorbents obtained after the experiments confirmed the involvement of C–H bend, –CH2–(C=O), N–H, –C–O, R2–C= bending and –C–C=O on the biomass. Furthermore, the biosorbent regeneration followed by heavy metal biosorption confirmed the reusability of the prepared biosorbent for at least two consecutive cycles without much significant change in the heavy metal biosorption capacity