AIR GAS SEPARATION The invention relates to the separation of industrial gases into (V)PSA, in particular the separation of nitrogen and oxygen contained in the air, a quite suitable application being the preparation of medical oxygen , other possible applications being VPSA applications for the preparation of industrial oxygen. More specifically, the present invention relates to the use of specific adsorbent materials for the separation of air gases and industrial gases, and more particularly for the separation of nitrogen by adsorption in gas streams such as than air, as well as the preparation of oxygen (0 2 ) of high purity by adsorption of nitrogen (N 2 ), and more particularly for the preparation of oxygen for medical use from air. [0003] The separation of nitrogen from gas mixtures is the basis of several non-cryogenic industrial processes, including the production of oxygen from air by the PSA process ("Pressure Swing Adsorption", in English, either “Pressure Swing Adsorption”) or VPSA (“Vacuum and Pressure Swing Adsorption”, in English, or “Pressure Swing Adsorption”), the PSA process being one of the most important. [0004] In this application, the air is compressed and sent over a column of adsorbent having a marked preference for the nitrogen molecule. Thus, during the adsorption cycle, oxygen is produced with a purity of about 94-95% and argon. After a certain time, the column is depressurized and then maintained at low pressure, during which time the nitrogen is desorbed. A recompression is then ensured by means of a part of the oxygen produced and/or by air, then the cycle continues. The advantage of this process compared to commonly used cryogenic processes lies in the greater simplicity of the installations, greater ease of maintenance, and consequently more efficient uses and more economical implementations, [0005] However, the quality of the adsorbent used remains the key to an efficient and competitive process. The performance of the adsorbent is linked to several factors, among which we can notably cite the nitrogen adsorption capacity and the selectivity between nitrogen and oxygen which will be decisive for sizing the column sizes and optimizing the production yield (ratio between oxygen produced and oxygen entered), the kinetics of adsorption which will make it possible to optimize the duration of the cycles and to improve the productivity of the installation. [0006] Patent US6596256 B1 discloses a process for the preparation of sodium LSX and sodium MSX zeolites, without adding potassium. The zeolites thus prepared are then subjected to a cation exchange with lithium ions, calcium ions, rare earth cations, or mixtures of these cations, before being used, for example for the nitrogen/oxygen separation, in the case of LSX zeolite exchanged with lithium. [0007] Patent US5464467 A describes a process for preparing nitrogen from a gas mixture comprising passing said gas mixture through at least one adsorption zone containing an X zeolite comprising from 50% to about 95% lithium ions. Such lithium zeolites have quite advantageous oxygen production capacities, and in particular better than the adsorption capacities obtained with the zeolites of the prior art, or comprising other cations. [0008] Zeolite adsorbents based on faujasite-type zeolites (FAU) are also known, and in particular adsorbents based on zeolites with a low molar ratio silicon/aluminum exchanged with lithium (LiLSX) which are for example described in the international application W02018100318. These adsorbents have proven to be not only quite suitable but also very effective for oxygen/nitrogen separation, and in particular for the preparation of medical oxygen from air. [0009] The prior art therefore teaches those skilled in the art that the production of oxygen from gas mixtures (for example from a nitrogen/oxygen mixture or even from air) is optimized by using zeolite adsorbents based on X zeolites, better still based on LSX zeolites, and which contain lithium ions. [0010] In fact, lithium-exchanged zeolite adsorbents are now marketed for nitrogen/oxygen separation, which are considered to be the most efficient. However, adsorbents exchanged with lithium suffer from a relatively high manufacturing cost due in particular to the cost inherent in that of metallic lithium, which is a metal whose natural resources are constantly decreasing. [0011] In order to overcome these drawbacks and in particular to reduce the use of zeolitic adsorbents comprising lithium, US Pat. Despite the relatively low performance of adsorbents of the NaX type compared to those of the adsorbents of the LiX type, the multilayer adsorbents described in this document are of moderate cost and are presented as allowing an attractive cost/performance ratio. [0012] Indeed, it is well known that adsorbents of the NaX type can sometimes be used because of their low cost of manufacture/marketing compared with adsorbents exchanged with lithium. Adsorbents of the NaX type are however less efficient in terms of nitrogen adsorption capacity and nitrogen/oxygen selectivity. [0013] There therefore remains a need for products that remain inexpensive and exhibit good performance in terms of nitrogen adsorption capacity and nitrogen/oxygen selectivity. Thus, a first objective of the present invention is to provide inexpensive zeolite adsorbents with good performance or even very good performance in terms of gas separation, in particular in terms of nitrogen/oxygen separation, and more particularly in terms of production. oxygen and in particular medical oxygen. [0014] As a particularly targeted objective, a low-cost zeolite adsorbent is proposed which is very selective in the nitrogen/oxygen separation, and in particular which has the capacity to retain nitrogen without retaining oxygen, more particularly a zeolitic adsorbent which selectively adsorbs nitrogen, by not adsorbing oxygen or only very weakly. One of the objectives of the present invention consists in particular in improving the zeolitic adsorbents (also called "sieves") existing sodium grades for the separation of nitrogen and oxygen, by proposing solids which do not retain or which very little oxygen and very preferentially nitrogen. Still other objects will become apparent from the description of the invention which follows. [0016] The applicant has now discovered that the aforementioned objectives can be achieved in whole, or at least in part, thanks to the present invention which follows and which is described below. [0017] It has now been discovered that it is possible to prepare zeolitic adsorbent materials, from FAU type zeolite crystals, for the non-cryogenic separation of industrial gases into (V)PSA, in particular for the separation of nitrogen and oxygen (N 2 /0 2 ), and more particularly for the preparation of medical oxygen from air, as well as for the industrial preparation of oxygen by (V)PSA. Thus, and according to a first aspect, the present invention relates to the use of a zeolite adsorbent material: - based on faujasite (FAU) zeolite(s) crystals, the Si/Al molar ratio of which is between 1.00 and 1.20, better still between 1.00 and 1.15 and preferably 1.00 and 1 ,12, terminals included, - and a non-zeolite phase (PNZ) content such that 0