de Gennaro Bruno, Catalanotti Lilia, Bowman Robert S, Mercurio Mariano
Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università di Napoli Federico II, Piazzale V. Tecchio 80, 80125 Napoli, Italy.
New Mexico Institute of Mining and Technology, Department of Earth and Environmental Science, 801 Leroy Place, Socorro, NM 87801, USA.
J Colloid Interface Sci. 2014 Sep 15;430:178-83. doi: 10.1016/j.jcis.2014.05.037. Epub 2014 Jun 2.
Lately, the functionalization of industrial minerals with high technological properties, such as natural zeolites, is shaping as a promising approach in environmental sphere. In fact, under the specific conditions, the surface functionalization via adsorption of cationic surfactants reverses the surface charge of the mineral, enabling zeolites to simultaneously interact either with organic contaminants or inorganic anions. This aspect allows zeolites to be used in the remediation of contaminated fluids. The present research shed new light on some still not fully understood aspects concerning exchange kinetics such as anion-exchange mechanisms and selectivity of surface modified minerals. For this purpose the mineralogical characterization and the surface properties evaluation (X Ray Powder Diffraction, chemical analysis, thermal analysis, ECEC and AEC) of a clinoptilolite-rich tuff were performed, and the anion exchange isotherms of the sample, modified with hexadecyltrimethylammonium chloride or bromide (HDTMA-Cl/-Br), were determined. Ion-exchange equilibrium data of uni-uni valent reaction were obtained by solutions containing Br(-), Cl(-), NO3(-) or ClO4(-). Liquid phase was analysed via high performance liquid chromatography. Thermodynamic quantities (Ka and ΔG(0)) were determined and compared with the Hofmeister series. The value of the ECEC, calculated in batch conditions, was about 137 mmol/kg, in good agreement with that evaluated in dynamic conditions, while the AEC data were different for the SMNZ-Br and -Cl samples, amounting to 137 and 106 mmol/kg, respectively, thus indicating a different compactness of the bilayer formed in the two cases. Moreover, the anion isotherm results and the mathematical evaluation of the thermodynamic parameters, demonstrated the good affinity of SMNZ-Br towards chloride, nitrate and perchlorate, and of SMNZ-Cl for nitrate and perchlorate, also endorsing the possibility of using the same thermodynamic approach developed to describe cation exchange selectivity in zeolites. Finally, it was also verified that the zeolite modified with HDTMA-Cl is able to better exploit its anion exchange capacity compared to the same zeolite modified with HDTMA-Br.
最近，利用具有高科技性能的工业矿物（如天然沸石）进行功能化处理，正成为环境领域一种很有前景的方法。事实上，在特定条件下，通过阳离子表面活性剂吸附进行表面功能化会使矿物的表面电荷反转，使沸石能够同时与有机污染物或无机阴离子相互作用。这一特性使得沸石可用于受污染流体的修复。本研究为一些关于交换动力学（如阴离子交换机制和表面改性矿物的选择性）尚未完全理解的方面提供了新的线索。为此，对一种富含斜发沸石的凝灰岩进行了矿物学表征和表面性质评估（X射线粉末衍射、化学分析、热分析、阳离子交换容量和阴离子交换容量），并测定了用十六烷基三甲基氯化铵或溴化铵（HDTMA-Cl/-Br）改性后的样品的阴离子交换等温线。通过含有Br(-)、Cl(-)、NO3(-)或ClO4(-)的溶液获得了单价-单价反应的离子交换平衡数据。通过高效液相色谱分析液相。测定了热力学量（Ka和ΔG(0)）并与霍夫迈斯特序列进行了比较。在分批条件下计算的阳离子交换容量值约为137 mmol/kg，与动态条件下评估的值吻合良好，而SMNZ-Br和-Cl样品的阴离子交换容量数据不同，分别为137和106 mmol/kg，这表明两种情况下形成的双层结构紧密程度不同。此外，阴离子等温线结果和热力学参数的数学评估表明，SMNZ-Br对氯离子、硝酸根离子和高氯酸根离子具有良好的亲和力，而SMNZ-Cl对硝酸根离子和高氯酸根离子具有良好的亲和力，这也支持了使用相同的热力学方法来描述沸石中阳离子交换选择性的可能性。最后，还证实了与用HDTMA-Br改性的相同沸石相比，用HDTMA-Cl改性的沸石能够更好地发挥其阴离子交换能力。
