Heavy metal removal, wastewater aqueous solutions

For purification of aqueous solutions the use of adsorption processes for cationic impurities is also common. As economical adsorbents, montmoriUonite, tober-morite, magnetite and silica gel were found sufficient for the removal of Cd(II), Cr(VI) and Cu(II) in rinsing wastewater from a plating factory [104], From this investigation, it was found that the removal efficiency tended to increase with increasing pH and decrease with increasing metal concentration. This method allows the realization of a rapid, simple and cheap rinse water treatment system for the removal of heavy metals. 

Not only the efficient removal of toxic heavy metals like hexavalent chromium (Cr(VI)), cadmium (Cd), zinc (Zn), nickel (Ni), etc., and other contaminants like phenol from industrial wastewaters [8-18] but also the recovery of valuable solutes from aqueous phases, for example, citric acid, carboxylic acids, amino acids, L-phenylalanine, etc. [19,20], are well-demonstrated applications of this technique. 

The removal of heavy metal ions from both natural water supplies and industrial wastewater streams is becoming increasingly important as awareness of the environmental impact of such pollutants is fiilly realized. In particular, the likelihood of such metal ions precipitating out of solution and/or coating other materials can have a profound effect on both aqueous and nonaqueous environments. There is considerable evidence in the literature that the primary mechanism for transportation of metal contaminants in aquatic systems is the movement of suspended particulate material containing the adsorbed pollutant metals [1,2]. It is also known that a strong correlation exists between the concentration of trace metals in the (aquatic) environment and the extent to which those metal ions adsorb onto colloidal substrates present in the environment [2,3], A similar correlation between the concentration of trace metals in the (aquatic) environment and their precipitation behavior is not so clear. There is, then, a well-founded need to study adsorption-related phenomena in order to understand and predict the behavior of toxic metals in the environment. 

A composite adsorbent was prepared by entrapping crosslinked chitosan and nano-magnetite (NMT) on heulandite (HE) surface to remove Cu(II) and As(V) in aqueous solution [47], Recently, chitosan composites have been developed to adsorb heavy metals and dyes from wastewater. A series of polyurethane (PU)/chitosan composite foams were prepared with different chitosan content of 5 20 wt.% and investigated their adsorption performance of acid dye (Acid Violet 48) [74], The adsorption of lead (II) from aqueous solutions onto ehitosan was investigated [46]. Chitosan can be modeled in several shapes gels, flakes, powders, beads, membranes and particles. 

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