Abstract
The removal of sulfate ions from natural waters, as well as from industrial effluents of different origins, is a problem, considering that most of the proposed processes are inefficient and have a high cost, mainly when reducing the sulfate ion concentration to values below 500 mg.L−1 is required. The flotation technique, combined with precipitation, has proven to be efficient for the removal of heavy metal ions. However, there is not enough research to confirm its efficiency for the removal of sulfate ions. This article presents the results of sulfate ion removal from synthetic solutions prepared in an acidic medium, applying the co-precipitation techniques with polyaluminum chloride (PAC) and solid/liquid separation by dissolved air flotation (DAF). The effect of the pH, the [PAC: sulfate ions] ratio, the effect of saturated water flow with air, and the flocculant and collector doses were studied. The achieved results confirm that it is possible to reduce the concentration of sulfate ions from 1 800 to 350 mg.L−1 (80% removal) from synthetic solutions by applying the flotation technique combined with precipitation.
Highlights
Sulfate ions are contaminants found in high concentrations in natural waters, as well as in effluents from different industrial processes, including mining acid drainage, acid effluents from copper smelters, water recovered from tailings ponds, and solutions for hydrometallurgical processes (Guerrero-Flores, Uribe-Salas, Dávila-Pulido, and Flores-Alvarez, 2018; Runtti et al, 2017; Silva, Lima, and Leão, 2012)
Effects of pH: Figure 1 shows the effect of pH on sulfate ion removal via precipitation using a [polyaluminum chloride (PAC): sulfate ions] ratio of 8:1
Silva et al (2010) and Xu et al (2004) reported that, at pH 4,5, a higher proportion of sulfate ions is precipitated since Alb the is predominant species
Summary
Sulfate ions are contaminants found in high concentrations in natural waters, as well as in effluents from different industrial processes, including mining acid drainage, acid effluents from copper smelters, water recovered from tailings ponds, and solutions for hydrometallurgical processes (Guerrero-Flores, Uribe-Salas, Dávila-Pulido, and Flores-Alvarez, 2018; Runtti et al, 2017; Silva, Lima, and Leão, 2012).
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