The Importance Of Heavy Metals

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Heavy metals are elements having atomic weights between 63.5 and 200.6, and a specific gravity greater than 5.0 [1]. With the rapid development of industries such as metal plating facilities, mining operations, fertilizer industries, tanneries, batteries, paper industries and pesticides, etc., heavy metals wastewaters are directly or indirectly discharged into the environment increasingly, especially in developing countries. Unlike organic contaminants, heavy metals are not biodegradable and tend to accumulate in living organisms and many heavy metal ions are known to be toxic or carcinogenic. Toxic heavy metals of particular concern in treatment of industrial wastewaters include zinc, copper, mercury, cadmium, chromium, lead and nickel.…show more content…
Although a number of cellular effects of nickel have been documented, a deficiency state in humans has not been described [14-18]. Nickel and nickel compounds have many industrial and commercial uses, and the progress of industrialization has led to increased emission of pollutants into ecosystems. Although Ni is omnipresent and is vital for the function of many organisms, concentrations in some areas from both anthropogenic release and naturally varying levels may be toxic to living organisms [6-8]. All of this review for nickel problems in human and industrial pollution had to be a way to look for nickel extraction and recovery. Sludge waste from many plating operations is classified as a hazardous waste [19,20] . The tried have complexation-ultrfiltration method for nickel removal[21] . They used complexation enhanced ultrfiltration method with polymer sulphone membranes with different cut offs and complxating agents. They concluded that bottleneck of the process was regeneration. [22].Have investigated the removal of heavy metals by using a polymer inclusive membrane. This method was found to be useless for nickel but very effective for zinc methods are found to be effective for nickel removal. The recovery of nickel from this biomass is…show more content…
The solute in the external phase penetrates through the membrane phase, in which carrier is added to solubilise otherwise insoluble solute in the membrane phase. The transferred solute by the carrier reacts with a stripping agent at the interface of the membrane and internal phases and will be trapped in internal phase. The emulsion phase is then broken in a demulsifier and the oil phase is recycled for reusing in the emulsification process. Various types of membrane processes are employed to remove cadmium from aqueous solutions such as liquid membrane, [30] hollow fiber supported liquid membrane, [31] supported liquid membrane, [32] emulsion liquid membrane[33]. But these processes tend to suffer from the instability of the membranes in salty or acidic conditions and fouling by inorganic and organic substances present in

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