The kinetics of dissolution of octacalcium phosphate II. The combined effects of pH and solution Ca/P ratio

Cultivation of Green Algae Chlorella sp. in Different Wastewaters from Municipal Wastewater Treatment Plant

“…Recovery of phosphorus as calcium phosphates than other forms is far more promising from the industry's viewpoint [40]. However, there are still a lot of obstacles from the technological side [41] because a lot of factors influence the precipitation of calcium phosphates, such as the concentrations of phosphate and calcium, the pH value [42], the ionic strength, the temperature, and the impurities of the solution [43,44]. If the precipitation of calcium phosphorus by growing algae in the centrate is validated in the future, it would add one more side benefit to the centrate treatment by the algal process.…”

pH-Dependent surface properties of perlite: Effects of plant growth

“…4 clearly indicate that dissolution of a Ca-P mineral (probably βTCP) contributed most of the P present in the Up suspension. Although HAP is the most thermodynamically stable Ca-P mineral, it does not precipitate directly from aqueous solutions (Verbeeck and Devenyns, 1992) and, therefore, more soluble compounds such as βTCP or even OCP temporarily controlled P in perlite solutions. This interpretation is supported by the data of Imas et al (1996) and Salinger et al (1993), who found that on a time scale of a few days, P solubility in the Ca-CO 3 -PO 4 system was controlled by a metastable Ca phospho-carbonate phase, and Sanyal and De Datta (1991) conclusion that βTCP governed P dissolution in neutral and basic soil solutions.…”

Unexpected pH Dependence of Dissolution Kinetics of Dicalcium Phosphate Dihydrate

“…This is quite surprising because the rate could be expected to increase with decreasing pH due to proton catalysis, as was the case for HAP dissolution.6 Although a minimum rate near neutral pH has been found for the dissolution of a number of clay minerals,8-10 the increase in rate at higher pH is attributed to an increased adsorption of OHions which promote the detachment of surface cations.8 **However, in the present case, OHadsorption is unlikely to be significant at pH values of 5.0-6.4, and a different theoretical approach is required to interpret the results. 7 Present address: Department of Inorganic, Analytical and Applied Chemistry, University of Geneva, Sciences II, 30 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland.…”