**1. Introduction**

Increased demands by limited water resources have triggered in worldwide for innovative water practices. Many processes are used to purify water contaminated with rare earths and heavy metals, such as solvent extraction, precipitation, ion exchange, absorption and liquid–liquid extraction. The underground water resources can be polluted by wastewaters [1].

There is a lot of proceed of separation which can be applied to the treatment of discharges, among these techniques we mention: chemical precipitation, coagulation–flocculation, flotation, ion exchange, and the membrane processes as supported membrane liquid [2–4], nanofiltration (NF) [5], ultrafiltration (UF) [6, 7], reverse osmosis (RO) [8] and microfiltration recently show by [9].

Nanofiltration has a lot of applications in industry [10]. Among membrane technologies, nanofiltration is the best opportunity to solve environmental problems, such as: desalination recently shown by [11], wastewater and ground water treatment [12, 13], and heavy metals elimination [14].

These methods are valid but have many drawbacks which require the use of organic solvents which are harmful to the environment and time consuming.

With technological development in industries and the differentiation in quantity and type of waste, the development of new, more efficient techniques has become necessary. Among these techniques, membrane processes.

Currently, membrane extraction is the most widely used method for treating industrial waste and purifying wastewater. It is a very active field in separation sciences and many companies are currently producing and developing new membrane extraction techniques.

Nanofiltration is ecological technique; this advantage is particularly linked to this operation without the need for organic solvents and also because the extraction requires little time to perform.

Currently, membrane techniques play a very important role in water purification and open up new possibilities for beneficial use for water sources. They were difficult to use before for technical and economic reasons.

Membrane methods are commonly used in the purification of water and the purification of wastewater [15, 16].

Using these techniques, every five years the creation of water purification plants is multiplied by ten [17].

The "naturalists" are the first who approached the selective transport of substances through membranes [18].

In order to explain the transfer of the solvent, Abbé Nollet supposes the presence of forces between the parts of the membrane, through the membranes the passage of substances is influenced by their molecular mass [19].

The use of membrane processes in industry began in the 1960s. There is a wide variety of membranes due to the existence of several fields of application for membrane processes.

The membranes are used in the separation and concentration of ionic species or molecules in the solution and/or to separate microorganisms (bacteria, viruses, etc.) or suspended matter.

Perm selective membranes are used in membrane processes [19, 20].

The selective displacement of certain components through a membrane, under the application of a force, is the concept of membrane separation [20–22].

All membrane processes use tangential filtration to limit the accumulation of material [20, 23].

The solution of the particles which do not pass through the membrane is called "retentat", and "permeat", the solution of the components which pass through the membrane [24].

Various advantages, among which:


For these reasons, the water treatment sectors use these technologies [30].
