Nitrate sorption by modified Lagenaria vulgaris biomass: Kinetic and equilibrium studies

Abstract

In order to prevent the occurrence of eutrophication, the efficiency of a new alternative sorbent based on a chemically modified Lagenaria vulgaris shell for nitrates removal from aqueous solution was analyzed in batch conditions. The sorption experiments were performed from aqueous solutions of different initial nitrate concentrations (2 - 100 mg N dm-3), with a sorbent dose of 2 g dm-3 at optimal conditions. Kinetic and equilibrium studies to predict the nitrate sorption mechanism and to evaluate characteristic sorption parameters were applied. Modeling the equilibrium data was performed using the typical sorption isotherms: Langmuir, Freundlich and Temkin, by a linear regression method. The nitrate sorption followed the Langmuir isotherm model (R2 0,994) with the maximum sorption capacity of 16,67 mg N g-1. For the kinetic studies, pseudofirst order and pseudo-second order equatios, as well as the Weber-Morris model of intra-particle diffusion were applied. The sorption process was found to be best fitted by the pseudo-second order kinetic model. The multilinear Weber-Morris model suggests that the surface physisorption mechanism, in addition to intra-particle diffusion, controls the total process rate.