Chemical Precipitation of Nickel Species from Waste Water
G. Ramiro Escudero *
Institute of Research in Metallurgy and Materials, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, México
E. Eunice Espinoza
Institute of Research in Metallurgy and Materials, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, México
Feng Rao
Institute of Research in Metallurgy and Materials, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, México
*Author to whom correspondence should be addressed.
Abstract
In liquid-liquid and solid-liquid systems, it is possible to promote chemical precipitation of certain species by controlling the physicochemical conditions of the liquid media. In the case of solid-liquid interactions the chemical precipitates can absorb on the surface of particles modifying their surface properties (i.e. during milling), whereas for liquid-liquid system precipitation contributes to the removal (cleaning) of contaminated water (wastewater).
In this work nickel sulfate hexahydrate (NiSO4 ∙ 6H2O) was dissolved in distilled water, to establish the physicochemical conditions (pH, electrochemical potential, ionic strength, activity coefficient) that enhance the chemical precipitation of nickel species.
The experimental results show that nickel precipitates as nickel hydroxide (Ni(OH)2) starting at pH 3, being more evident at pH 9. Nickel precipitates completely at pH 11. From these results, it is possible to propose a decontamination mechanism for wastewater containing nickel.
Keywords: Wastewater treatment, heavy metals, chemical precipitation, Pourvaix diagrams, amorphous nickel