Biosorption of some pharmaceutical compounds from aqueous medium by Luffa cylindrica fibers: application of the linear form of the Redlich-Peterson isotherm equation

This study is focused on the removal of dextropropoxyphene (DPP) and paracetamol (PAR) from aqueous solutions by sorption on a low-cost biosorbent such as Luffa cylindrica fibers, which was initially characterized using Fourier-transform infrared spectroscopy and scanning electron microscopy and X-ray diffraction techniques. Luffa cylindrica fibers specific surface area was determined using adsorption/desorption isotherms of the N-2 gas method. The sorption study was realized by the batch method with the effect of the biosorbent amount, initial concentration, medium pH, and batch temperature. The modeling of the sorption phenomenon was based on the mathematical approach of the modified equation of Redlich-Peterson isotherm proposed by FengChin-Wu, in which the dimensionless form of this isotherm, corresponding to the optimal curve, allows us to evaluate the alpha parameter. The same value of alpha was obtained for both pharmaceutical compounds, in which the b(RP )C(e)(a) values are 2 for DPP and 10 for PAR. The linear regression of the Redlich-Peterson isotherm equation was also confirmed by analysis of variance. The obtained outcomes show that the probability value (p-value) is less than 0.05, with correlation coefficients (R-adj(2)) 0.9515 for DPP and 0.9283 for PAR. The kinetics modeling analysis indicates that the biosorption mechanism can confirm pseudo-second-order and intraparticle diffusion. The adsorption of DPP and PAR is characterized by spontaneous and exothermic characters, in which the molecules of the two pharmaceutical products have a random behavior on the Luffa cylindrica active sites.

Automated summary

This study focused on the removal of DPP and PAR from aqueous solutions using Luffa cylindrica fibers as a biosorbent. The biosorption process was modeled using the Redlich-Peterson isotherm, with further analysis confirming a pseudo-second-order kinetics and intraparticle diffusion mechanism. The results showed spontaneous and exothermic adsorption of DPP and PAR molecules onto the Luffa cylindrica active sites.