No abstract

The bioremoval efficiency of Opuntia biomass, a low-cost biosorbent and renewable resource, for cadmium ions from aqueous solutions was investigated using factorial design methodology. The functional groups involved in the sorption process were identified by FTIR spectroscopy. A factorial experimental design technique, the full factorial design 3 3 , has been used for enhanced cadmium ions bioremoval. Three factors were considered: protonation of the sorbent, initial cadmium concentration, and sorbent dosage at three markedly different levels. An empirical model was statistically developed using response surface methodology for its optimization. The model showed that cadmium ions bioremoval in aqueous solution was affected by all the three factors analyzed. The statistical model revealed a maximum sorption capacity (q e ) of 58.4 mg/g with sorbent protonated with 0.67 M HCl, initial Cd(II) concentration of 50 mg/L, and 0.55 g/L of sorbent dosage. Bioremoval kinetic data were properly fitted by chemical sorption of pseudo-second order. The Langmuir equation fits better the sorption isotherm (equilibrium data) than other classical models.Abbreviations: ANOVA, analysis of variance; DW, Durbin-Watson; FTIR, Fourier transform infrared; ICP, inductively coupled plasma; MAE, mean absolute error; PFORE, pseudo-first-order rate equation; PSORE, pseudosecond-order rate equation; SEM, scanning electron microscopy. 959