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Selective precipitation of calcium ion from seawater desalination reverse osmosis brine

Molinari, Raffaele ; Avci, Ahmet Halil LU ; Argurio, Pietro ; Curcio, Efrem ; Meca, Sandra ; Plà-Castellana, Mireia and Cortina, Jose Luis (2021) In Journal of Cleaner Production 328.
Abstract

The near zero liquid discharge (NZLD) approach, by recovering water and dissolved valuable salts, is the most attractive clean solution for the valorisation of brines from seawater desalination reverse osmosis (SWD-RO) plants. In this perspective, a key aspect is calcium removal/recovery, to avoid scaling problems in the successive advanced separation units for recovering other valuable salts. In this work sodium citrate (Na3C6H5O7), carbonate (Na2CO3) and hydrogencarbonate (NaHCO3) were tested as calcium precipitation reagents. Different pH, temperature, ionic strength and reagent molar ratio were tested to maximize the Ca2+ precipitation and... (More)

The near zero liquid discharge (NZLD) approach, by recovering water and dissolved valuable salts, is the most attractive clean solution for the valorisation of brines from seawater desalination reverse osmosis (SWD-RO) plants. In this perspective, a key aspect is calcium removal/recovery, to avoid scaling problems in the successive advanced separation units for recovering other valuable salts. In this work sodium citrate (Na3C6H5O7), carbonate (Na2CO3) and hydrogencarbonate (NaHCO3) were tested as calcium precipitation reagents. Different pH, temperature, ionic strength and reagent molar ratio were tested to maximize the Ca2+ precipitation and minimize the Mg2+ loss. Aqueous solutions containing Ca and Mg ions with/without all major seawater electrolytes were used. The chemical basis of the precipitation processes were discussed based on the effective ion surface density (e.g. Slater rule), ion hydration and Eigen association process of the precipitate formation in the complex multicomponent brine. PhreeqC and Medusa equilibrium numerical codes were applied on some experimental data of the precipitation processes providing a good agreement between calculated and experimental values. Ca2+ removal efficiency higher than 90% coupled with an Mg2+ loss below 7% was obtained at 60 °C and controlled pH, by using NaHCO3. These results are very promising in view of designing a process for brines valorisation, thus mitigating the environmental problems related to SWD-RO brines disposal.

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author
; ; ; ; ; and
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Aragonite, Calcium precipitation by medusa equilibrium code, Calcium precipitation by PhreeqC modelling, Inhibition calcium precipitation by magnesium, Seawater desalination reverse osmosis brine valorisation, Selective calcium precipitation
in
Journal of Cleaner Production
volume
328
article number
129645
pages
10 pages
publisher
Elsevier
external identifiers
  • scopus:85119055909
ISSN
0959-6526
DOI
10.1016/j.jclepro.2021.129645
language
English
LU publication?
no
additional info
Publisher Copyright: © 2021
id
a5aa0c69-e8e9-4735-b669-176cd42d1845
date added to LUP
2022-05-13 10:41:58
date last changed
2022-05-13 11:06:09
@article{a5aa0c69-e8e9-4735-b669-176cd42d1845,
  abstract     = {{<p>The near zero liquid discharge (NZLD) approach, by recovering water and dissolved valuable salts, is the most attractive clean solution for the valorisation of brines from seawater desalination reverse osmosis (SWD-RO) plants. In this perspective, a key aspect is calcium removal/recovery, to avoid scaling problems in the successive advanced separation units for recovering other valuable salts. In this work sodium citrate (Na<sub>3</sub>C<sub>6</sub>H<sub>5</sub>O<sub>7</sub>), carbonate (Na<sub>2</sub>CO<sub>3</sub>) and hydrogencarbonate (NaHCO<sub>3</sub>) were tested as calcium precipitation reagents. Different pH, temperature, ionic strength and reagent molar ratio were tested to maximize the Ca<sup>2+</sup> precipitation and minimize the Mg<sup>2+</sup> loss. Aqueous solutions containing Ca and Mg ions with/without all major seawater electrolytes were used. The chemical basis of the precipitation processes were discussed based on the effective ion surface density (e.g. Slater rule), ion hydration and Eigen association process of the precipitate formation in the complex multicomponent brine. PhreeqC and Medusa equilibrium numerical codes were applied on some experimental data of the precipitation processes providing a good agreement between calculated and experimental values. Ca<sup>2+</sup> removal efficiency higher than 90% coupled with an Mg<sup>2+</sup> loss below 7% was obtained at 60 °C and controlled pH, by using NaHCO<sub>3</sub>. These results are very promising in view of designing a process for brines valorisation, thus mitigating the environmental problems related to SWD-RO brines disposal.</p>}},
  author       = {{Molinari, Raffaele and Avci, Ahmet Halil and Argurio, Pietro and Curcio, Efrem and Meca, Sandra and Plà-Castellana, Mireia and Cortina, Jose Luis}},
  issn         = {{0959-6526}},
  keywords     = {{Aragonite; Calcium precipitation by medusa equilibrium code; Calcium precipitation by PhreeqC modelling; Inhibition calcium precipitation by magnesium; Seawater desalination reverse osmosis brine valorisation; Selective calcium precipitation}},
  language     = {{eng}},
  month        = {{12}},
  publisher    = {{Elsevier}},
  series       = {{Journal of Cleaner Production}},
  title        = {{Selective precipitation of calcium ion from seawater desalination reverse osmosis brine}},
  url          = {{http://dx.doi.org/10.1016/j.jclepro.2021.129645}},
  doi          = {{10.1016/j.jclepro.2021.129645}},
  volume       = {{328}},
  year         = {{2021}},
}