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SEAWATER NEUTRALISATION: FACTORS AFFECTING ADSORPTION OF ANIONIC CHEMICAL SPECIES

Smith, H.D. and Parkinson, G.M.

In situ reactions between the magnesium(II) ion and synthetic sodium aluminate have been used in our laboratory to mimic neutralization of supernatant liquor by seawater. This reaction produces fine white precipitates of hydrotalcite, which belong to the class of chemicals known as layered double hydroxides. These have interesting properties making them useful for amelioration of wastewater streams. Of particular importance is their capacity to adsorb a number of chemical species deemed toxic to the environment, including arsenates, oxalates and oxy-anions of transition metals such as vanadium and molybdenum.

Laboratory work has indicated that under conditions similar to those utilized by the seawater neutralization process, only a limited number of possible crystalline forms can be synthesized and that these particles are restricted in size. It has also been found that through adjustment of other physicochemical parameters it is possible to alter the crystalline form and the rate at which toxic chemical species can be adsorbed.