Activity coef ficients o f major ions in Lake Urmia b rine at different temp eratures

Lake Urmia in the n orthwestern corner of Iran is one of the largest permanen t hypersali ne lakes in the world and is a t erminal lak e meaning that water leaves the lake only b y evaporation. As is generally the case, this l eads to a saltwater bod y and in the case of La ke Urmia, salinity is q uite high. The lake has dramatically decreased in volume over the past decade-and-a-half, further conce ntrating salts in the la ke, raising salinity to m ore than ۳۰ ۰ g/L. The main cations in the lake water inclu de Na+, K+, Ca۲+, Li+ a nd Mg۲+, wh ile Cl–, SO۴۲– , HCO۳– are the m ain anions. The Na+ and Cl– concentration is roughly ۴ times t he concentration of natural seawater. Sodium ions are at slightly hi gher concentration in t he south compared to t he north of the lake, wh ich could result from t he shallower depth in t he south, a nd a higher net evaporation rate. Convention al single io n activity coefficients of major io ns in Lake U rmia brine have been estimated using Pitzer's thermodynamic treatment of mixed electrolyte solutions. It has been shown that Pitzer's equations are applicable to suc h natural concentrated brines. Th e system of equations d eveloped by Pitzer for conventional single ion activity coefficients makes it possible to extend the specific ionic interaction model over a range of solution compos itions, temp eratures and pressures. It is known that one of t heprincipal thermodynamic properties for th e prediction of mineral solubilities in brinesis activity coefficients. The number of possible neutral species in nat ural brines is much larger than the number of single ions. Therefore it is convenient for s uch comple x mixtures to calculate the conventional single ion activity coefficien ts, because these values can then be combined to obtain the activity coefficient for any neutral species represented i n brines. T he purpose of this paper is to study the conventional single ion activity coefficients of major io ns in the Lake Urmia brine body under different temperatures

کلیدواژه ها:

Activity coefficients ، Pitzer equations ، Electrolyte ، Lak e Urmia brin e