The effect of organic acids and alcohols on precipitation of phosphate using calcined seashell powder

Abstract

This study elaborates on the use of calcined seashell powder (SP) for the precipitation of phosphate from solutions containing high concentrations of organic compounds. Precipitation of phosphate was carried out in pure phosphate solution containing 0.1, 0.5 or 1 g L−1 phosphate or pure phosphate solutions containing ethanol, propanol, propionic acid or lactic acid. The concentration of each organic compound was 1 M and the amount of calcined SP added to each batch was 2 g L−1. This amount of SP was sufficient to remove 0.5 g L−1 phosphate. Interestingly, at 1 g L−1 phosphate and in presence of propanol, propionic acid or lactic acid the precipitation was finished within 10 min. Contrarily, 120 min was needed in water or ethanol. In 1 M lactic acid and 0.1 or 0.5 g L−1 phosphate no or inhibited phosphate removal, respectively, was observed. The outcomes of this study revealed that organic acids and alcohols can have a positive or negative effect on the precipitation of phosphate. The effect is not only dependent on the organic compound, but also on the concentration of phosphate.