Biosorption of pharmaceuticals from aqueous medium by Luffa Cylindrica Fibres: Application of the linear form of Redlich-Peterson isotherm equation

Abstract This study is focused on the removal of Dextropropoxyphene (DPP) and Paracetamol (PAR) from aqueous solutions by sorption on Luffa Cylindrica fibres, as a low-cost biosorbent, that was initially characterized using BET, FTIR spectroscopy, and SEM analysis. The sorption study has been realized by the batch method with the effect of the biosorbent amount, initial concentration, solution pH and batch temperature. The modelling of the sorption phenomenon was based on the mathematical approach of the modified Redlich-Peterson isotherm equation (RP), where the dimensionless form of this isotherm, corresponding to the optimal curve, allows the α parameter evaluation. The same value of α was obtained for both pharmaceutical compounds, while the values where 2 and 10 for DPP and PAR, respectively. The linear regression of the Redlich-Peterson isotherm equation was also confirmed by analysis of variance (ANOVA). The obtained results show that p-value is less than 0.05, with correlation coefficients (Radj2) equal to 0.9515 and 0.9283 for DPP and PAR, respectively. The kinetics modelling shows that the sorption mechanism obeys the pseudo-second-order and intraparticular diffusion. The adsorption process is exothermic, spontaneous and the molecules of the two pharmaceutical products have a random behaviour on the Luffa Cylindrica active sites.