ÉTUDE DE MÉCANISMES DE TRANSFERT DES ORTHOPHOSPHATES À TRAVERS UNE MEMBRANE DE NANOFILTRATION EN MODE BATCH. EFFET DE LA MATRICE EXPÉRIMENTALE SUR LA SÉLECTIVITÉ ET MODÉLISATION PHÉNOMÉNOLOGIQUE.

Abstract

The levels of phosphates in urban and industrial wastewater in the Annaba region have reached a very alarming level and too often exceed the accepted standard. The increasing demand for the use of phosphates is that it becomes a scarce natural resource. For this the recovery of these species of water is essential. Against conventional methods of treatment, nanofiltration could present an interesting alternative. It is in this context that we conducted our thesis work to contribute to a better understanding of the mechanisms of transport of phosphate through a charged membrane of type Nanomax-50. Indeed the present study examines the potential of selective retention of orthophosphate anions H2PO4 - , HPO4 2- and PO4 3- in synthetic solutions through this membrane. The first part of this research is a review of literature on the current understanding of membrane techniques and models of transport as well as issues of discharges sewage phosphates in general and industrial in particular in the natural environment. The second part of this study presents the experimental device with a systematic characterization of the membrane used in our testing of filtration and the effects of the experimental matrix on the selectivity of the membrane. The results obtained shows that the membrane is negatively charged for pH 5, its pore radius is around 0.45 nm and its hydraulic permeability is 24.6.10-12 m.s -1 .Pa-1 . The retentions of orthophosphate anions are in the order of 93% for H2PO4 − and 98% for HPO4 2− .The rejection of orthophosphate anions, particularly the monovalent species, depend on the chemical parameters (feed concentration, ionic strength, and pH) and physical (transmembrane pressure). The third part applies and confronts Spiegler-Kedem transfer models and derivatives based on the Thermodynamics of irreversible processes. Modelling results are adjusted to the experimental values .The data were analyzed using the model and the transport parameters of orthophosphate anions, i.e., the reflection coefficient (σ) and solute permeability (Ps) have been determined.