亚/超临界水中典型硫酸盐Na_(2)SO_(4)和K_(2)SO_(4)的溶解特性及机理  

Dissolution characteristics and mechanisms of typical sulphates Na_(2)SO_(4)and K_(2)SO_(4)in sub-/supercritical water

作　　者：冯鹏 徐东海[1] 何冰 刘欢腾 杨立杰 王攀 刘青山 FENG Peng;XU Donghai;HE Bing;LIU Huanteng;YANG Lijie;WANG Pan;LIU Qingshan(School of Energy and Power Engineering,Xi’an Jiaotong University,Xi’an 710049,Shaanxi,China)

机构地区：[1]西安交通大学能源与动力工程学院,陕西西安710049

出　　处：《化工进展》2025年第3期1706-1715,共10页Chemical Industry and Engineering Progress

基　　金：国家自然科学基金(22078258);西安交通大学青年拔尖人才支持计划(ND6J018);中央高校基本科研业务费(xtr052022009);西安科学家和工程师团队建设项目(23KGDW0001-2023)。

摘　　要：超临界水氧化是一种能够高效无害化处理有毒和复杂有机废物的前沿技术。然而,无机盐溶解度在水临界点附近急剧降低而发生盐沉积,导致反应器堵塞,已成为了该技术大规模推广应用的基础性瓶颈问题。因此,本文对亚/超临界水中典型硫酸盐Na_(2)SO_(4)和K_(2)SO_(4)的溶解特性及机理进行了研究。获得了更宽温度和压力范围内Na_(2)SO_(4)和K_(2)SO_(4)在水中的溶解度数据。在84.13~540.46kg/m^(3)水密度范围内Na_(2)SO_(4)和K_(2)SO_(4)溶解度分别增加了约8931倍和36211倍,相同条件下K_(2)SO_(4)溶解度高于Na_(2)SO_(4)。溶解度并非严格随水密度增加而增加,Na_(2)SO_(4)在25MPa和663.15K的高密度(215.18kg/m^(3))下溶解度(64.375mg/L)明显低于在21MPa和643.15K的低密度(195.73kg/m^(3))下溶解度(906.141mg/L),近似水密度下溶解度相差了约13倍,因为前者处于超临界态而后者处于亚临界态。溶解度在643.15~663.15K范围内下降速率远高于663.15~723.15K,与水密度和介电常数随温度的变化趋势一致。通过分子动力学揭示了Na_(2)SO_(4)和K_(2)SO_(4)二元盐水体系中的离子成核特性等微观机理。Cl^(−)的电荷/半径比低于SO_(4)^(2−)并且多原子离子结构的SO_(4)^(2−)的配位层比单原子离子结构的Cl^(−)多,所以氯盐溶解度高于硫酸盐。常温常压下会形成水合Na^(+)、K^(+)和SO_(4)^(2−)离子,水分子对盐离子的静电屏蔽作用较强。超临界条件下水分子的静电屏蔽效应减弱,离子碰撞聚集形成团簇,从而产生盐晶体。研究结果能够为超临界水技术的进一步发展提供指导。Supercritical water oxidation is an effective technology capable of efficiently and harmlessly treating toxic and complex organic wastes.However,inorganic salt solubility decreases dramatically near the critical point of water,and deposited salt can lead to reactor clogging,which has become a fundamental bottleneck for the large-scale application of this technology.Therefore,the dissolution characteristics and mechanisms of typical sulphates Na_(2)SO_(4)and K_(2)SO_(4)in sub-/supercritical water were investigated in this study.Na_(2)SO_(4)and K_(2)SO_(4)solubilities in water were obtained over a wider temperature and pressure range.It was found that the solubilities of Na_(2)SO_(4)and K_(2)SO_(4)increased about 8931 times and 36211 times in the water density range of 84.13—540.46kg/m^(3),respectively.The solubility of K_(2)SO_(4)was higher than that of Na_(2)SO_(4)under the same conditions.Solubility did not strictly increase with increasing water density.Na_(2)SO_(4)solubility(64.375mg/L)at high density(215.18kg/m^(3)at 25MPa and 663.15K)was significantly 13 times lower than that(906.141mg/L)at low density(195.73kg/m^(3)at 21MPa and 643.15K).Because the former was in the supercritical state while the latter was in the subcritical state.The decreasing rate of solubility at 643.15—663.15K was much higher than that at 663.15—723.15K,which was consistent with the trend of water density and dielectric constant with temperature.Micro-mechanisms such as ion nucleation properties in the binary brine system of Na_(2)SO_(4)and K_(2)SO_(4)were revealed by molecular dynamics.Cl^(−)had a lower charge/radius ratio than SO_(4)^(2−)and SO_(4)^(2−)with polyatomic ionic structure had more coordination layers than Cl^(−)with monatomic,thus the solubility of chloride salts was higher than that of sulphate salts.Hydrated Na+,K^(+)and SO_(4)^(2−)ions could be formed at room temperature and pressure,and water molecules had a strong electrostatic shielding effect on salt ions.The electrostatic shielding effect was weake

关 键 词：超临界水 硫酸钠 硫酸钾 溶解度 分子动力学模拟 

分 类 号：X7[环境科学与工程—环境工程]