The heavy metal lead will cause serious effects on human living environment and personal health when it enters the ecosystem, and the wastewater produced during the production of lead–chromium pigments may cause lead pollution to the environment. The heavy metals in wastewater can be further treated by studying the thermodynamic properties and phase diagrams of the NaNO₃ and Pb(NO₃)₂ systems. The cell potential method and the Pitzer model were used to evaluate the activity coefficients of the NaNO₃-Pb(NO₃)₂-H₂O system at 298.2 K. The Pitzer mixed ion parameters were fitted by the activity coefficient data and solubility data, and the theoretical prediction of the solubility of the NaNO₃-Pb(NO₃)₂-H₂O system at 298.2 K was made based on the obtained parameters (θ_Na,Pb= 0.0462, ψ_Na,Pb,NO3= −0.0056). Phase diagrams predict better results. From the phase diagram, an isothermal evaporation process can be designed to separate NaNO₃. By conservation calculations, the percentage of NaNO₃ recovered was 71.07%, where NaNO₃ solution can be used to produce KNO₃ products, and the solution after isothermal evaporation has a high Pb(NO₃)₂ content, which can be reused in the production of lead–chromium pigments.

中文翻译：

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NaNO3-Pb(NO3)2-H2O体系在298.2 K下的活度系数、相图及其应用

重金属铅进入生态系统会对人类生存环境和人体健康造成严重影响，铅铬颜料生产过程中产生的废水可能对环境造成铅污染。_{通过研究NaNO 3}和Pb(NO ₃ ) ₂体系的热力学性质和相图可以进一步处理废水中的重金属。采用细胞电位法和Pitzer模型评价了NaNO ₃ -Pb(NO ₃ ) ₂ -H ₂ O体系在298.2 K下的活度系数。通过活度系数数据和溶解度数据拟合Pitzer混合离子参数。 ，并根据得到的参数(θ _{Na ,} Pb ₌ 0.0462, ψ Na _{, Pb, NO3} = - 0.0056）。相图预测更好的结果。从相图可以看出，可以设计等温蒸发工艺来分离NaNO ₃。_{经守恒计算，NaNO 3}回收率为71.07%，其中NaNO ₃溶液可用于生产KNO _{3产品，且等温蒸发后的溶液Pb(NO 3} ) ₂含量较高，可重复使用于生产铅铬颜料。