| Summary: | This research aims to investigate the effects of ferric ions on hydroxide precipitation
of copper; zinc, lead, chromium and nickel metals individually as well as in mixed
metals. The treatment method used was chemical precipitation using calcium
hydroxide as the precipitation agent in the existence of ferric ions as one of the
pollutants. The experiment was initially performed with the preparation of synthetic
wastewater stocks that were diluted according to the experimental requirements. pH
values of the solution were then initially reduced to pH 2 using nitric acid. 50 mL
aliquots of sample were obtained at each pH increment and filtered through 0.45 mm
porous cellulose nitrate membranes. The procedure was then repeated by adding ferric
chloride solutions as a polluting metal. The alkaline medium was found to be the most
suitable for metal precipitation purposes since all the optimum pH for all five metals
occurred at alkaline medium. The minimum solubility of individual hydroxide
precipitation for Cu, Ni, Zn, Pb and Cr were 2.34-5.4 mgL-1, 0-10.78 mgL-1, 1.35-
16.51 mgL-1, 2.34-10.89 mgL-1 and 1.09-5.38 mgL-1 respectively. With the presence
of 50 mgL-1 ferric ions, the minimum solubility for Cu, Ni, Zn, Pb and Cr decreased to
2.00-9.44 mgL-1 and 0-4.17 mgL-1 respectively. Hence, the presence of ferric ions was
able to effectively increase the metal precipitation as the formation of ferric hydroxide
acted as an intermediate kinetic during metal hydroxide precipitation process. The
precipitation effect if the presence of ferric ions was more noticeable in mixed metal
solutions
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