Chemical speciation in natural and brine sea waters

Abstract

A combined approach consisting of monitoring and thermodynamic modeling was used in order to calculate the concentration of trace element species in water samples of a broad salinity range and to explain their chemical behaviour. The study was performed on water samples (fresh, marine, hyper-saline) taken from the area of Burgas Bay, Bulgaria. The ion association model based on Debye-Hückel theory using the sst2008.dat database and the ion interaction model based on Pitzer theory using a new pit2010.dat database were compared and combined for the purposes of this study. The new pit2010.dat database combines the sst2008.dat database and the pitzer.dat database of the PHREEQCI computer program as well as the thermodynamic data for the elements Fe, Mn, Cu, Zn, Cd and Pb and their Pitzer ion interaction parameters. The results showed that: (1) the predominant species in fresh waters were free ions of Mn(2+) (73.6%), Zn(2+) (58.0%) and Cd(2+) ions (78.3%) as well as carbonate species CuCO⁰₃ (81.8%), PbCO⁰₃ (77.2%) and hydroxy species Fe(OH) ⁰₃(55.2%) and Fe(OH)+₂(35.6%); (2) an increase in chloride species MeCl²(n)-(n)(n = 1-4, Me = Mn, Zn, Cu, Pb and Cd) and of the hydroxy species Fe(OH)⁺₂ for Fe was calculated for sea and hyper-saline water.

Chemical speciation in fresh, saline and hyper-saline waters

“…dat enriched by us with the Pitzer parameters for the ions Fe 3+ , Mn 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Pb 2+ and the major anions Cl -, SO 4 2- [19][20][21][22][23][24][25][26][27]. The highly coordinated sulfate complexes M(SO 4 ) 3 4-and M(SO 4 ) 4 6-of Zn and Cd are of low probability and are therefore excluded from our database [8]. Thus, along with the main components behavior described by the ion interaction model, our combined model also describes the behavior of the trace metal ions Fe 2+ , Mn 2+ , Cu 2+ , Zn 2+ , Cd 2+ and Pb 2+ in the studied waters even at very low concentrations (10 -3 -10 -10 mol.kg).…”

“…Surface waters of two different regions of Bulgaria were the subject of our previous monitoring and thermodynamic modeling studies [7,8]. The studied areas were chosen so as to include waters with different type (urban and mining) and level of pollution (reference stations registering the background in the examined region, the pollution sources and the affected areas), as well as surface waters of different ionic strength (fresh, saline and hyper-saline waters).…”

“…Detailed information on the sampling stations, chemical analysis and results of the studies of the fresh, saline and hyper-saline waters from the Bourgas bay, the Atanassovsko lake, the Ropotamo and Aheloi rivers, Bulgaria, can be found elsewhere [8]. In the present work, these waters are modeled by the ion association model (A) and the combined ion association/ion interaction model (B) (Fig.…”

“…Thus, thermodynamic modeling can be a useful tool for non-expensive and effective evaluation of inorganic chemical species in natural waters [2,7,8]. Two basic thermodynamic methods, differing in activity coefficient calculation of the species, have been developed -the ion association model [9,10] and the ion interaction model [11,12].…”

Dewatering methanotrophic enrichments intended for single cell protein production using biomimetic aquaporin forward osmosis membranes

“…Eight different DS were prepared including NaCl, MgCl2, synthetic brine and glycerol (Sigma Aldrich, USA). Synthetic representation of brine from seawater desalination was made by dissolving NaCl and MgCl2 in a mass ratio of 5.4:1, which gives a Mg 2+ to Na + mass ratio of 0.12 [31]. The initial volume of both FS and DS was 2 L.…”