الفهرس 
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Abstract
A widely used definition of pollution is the introduction by man into the environment of substances or energy liable to cause hazards to human’s health, harm to living resources and ecological systems, damage to structures or amenity, or interference with legitimate uses of the environment(1). Some experts make a distinction between contamination and pollution, contamination is used for situations where a substance is present in the environment, but not causing any obvious harm, while pollution is reserved for cases where harmful effects is apparent(2).
Pollutants are basically of two types; primary pollutants, which exert harmful effects in the form in which they enter the environment and secondary pollutants, which are synthesized as a result of chemical processes, often from less harmful precursors, in the environment. Although highly toxic substances are responsible for many cases of environmental pollution, under some circumstances materials which are normally considered harmless may cause pollution if they are present in excessive quantities or in the wrong place at the wrong time and this makes definitions difficult(3).
Heavy metal pollution is an environmental problem of world concern. Actually, the contamination by wastes from electroplating industries, mining activities, metal finishing plants, and natural erosion are some of the sources of toxic metals found in water, soil and air(2).
There are a variety of methods used for metal ions removal, however most are expensive or do not remove the metals at trace levels, which are required for drinking water regulations. The development of an economical-general sorbent material is necessary to remove these pollutants from the environment (3).
1.1.1. Water pollution
Cities and industries discharge their untreated or only partially treated sewage and industrial wastewaters into neighboring streams and thereby remove waste matter from their own neighborhood. But in doing so, they create intense pollution in streams and rivers and expose the downstream riparian population to dangerously unhygienic conditions. With the expending industries that discharging their wastewater in neighboring streams, the latter get all the more polluted and become progressively unsuitable as sources of potable water. Such streams also become unfit as sources of industrial water supply. Very often putrefying solids are deposited along their channels and sides. Fish life is ruined, recreation facilities are restricted i.e. the natural biological balance is severely upset and in some cases totally disrupted. The problems are becoming increasingly serious with higher degrees of industrialization and higher standards of living (4).
Many metals are of concern because of their toxic properties and some metals are also essential for survival and health of animals and humans. In risk assessments concerning toxicity of essential metals, their essentiality should also be taken into account to avoid too low intakes. This has not always been done in a proper way and authorities responsible for.