Chemometric Ways of Improvement of Heavy Metals Recovery Yields from Toxic Wastes using Mixtures of Strong Acids

摘要

Chemometrical tools for experimental design were used to study ways of improvement of cadmium(II) and lead(II) ions recovery yields from toxic wastes using mixtures of strong acids. We report here a technique that takes advantage of the predictable electrochemical behavior of cadmium(II) and lead(II) ions in several strong acidic media and the effect of these strong acids to collect cadmium(II) and lead(II) ions from toxic wastes. The anodic peak intensity was used to compare the free forms of cadmium(II) and lead(II) in different aqueous mineral acids media. The experimental screening design show that only the sulfuric acid exhibits significant positive effects on cadmium(II) and lead(II) ions, therefore the free forms of cadmium(II) and lead(II) ions in this media are the highest. In perchloric and phosphoric acids media the cadmium(II) and lead(II) ions generate more stable, electroinactive ionic species of the heavy metals due to their different solvation properties and also probably by favoring the formation of insoluble colloidal particles of cadmium and lead, which gave lower electrochemical signals and also the shift of redox peak potentials recorded by square wave polarography. On the other hand, according to the designs coefficient plot, the influence of hydrochloric and nitric acid is not at all significant. Considering the anodic peak intensity as response of the screening experimental design, we can conclude that the nature and concentration of acid used in mixture with metallic ions exhibits positive, negative or no effect on the the formation of free, electroactive ionic complexes of the studied cations.