Journal
JOURNAL OF THE TAIWAN INSTITUTE OF CHEMICAL ENGINEERS
Volume 78, Issue -, Pages 378-385Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jtice.2017.06.040
Keywords
Calcium; Carbonate; Softening; Calcite; Aragonite; Crystallization
Categories
Ask authors/readers for more resources
Calcium is one of the divalent ions contributing to the hardness level of the water. This work describes the removal of calcium ions from aqueous solution using carbonate salts as precipitants and the recovery of homogeneous calcium carbonate crystals via a fluidized-bed homogeneous crystallization (FBHC) process without a heterogeneous seed material. The considered parameters were effluent pH, initial molar ratio of carbonate salt to Ca, up-flow velocity, and cross-section loading. The removal efficiency of Ca hardness reached 95% at the optimal pH of 10-11 and the corresponding crystallization ratio was 88% for initial concentrations of Ca of 50-330 ppm. The FBHC process was effective with a cross-section loading of calcium in the water of up to 4.5 kg/m(2)/h. The efficiency of Ca immobilization as the crystal grew on the fluidized pellets was greatly improved by adjusting the degree of supersaturation in the range 2-3, resulting in the crystallization ratio (CR) and total removal of Ca (TR) of 88% and 92%, respectively. XRD analysis revealed that the formed crystals comprised two calcium carbonate (CaCO3) phases-calcite and aragonite. SEM images of the surface morphology revealed that calcium carbonate particles (around 1-2 mm) were formed by the aggregation of fine crystals (around 5 mu m). (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available