Leite Samara T, do Nascimento Fernando H, Masini Jorge C
Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, 05508-000, São Paulo, SP, Brazil.
Heliyon. 2020 Apr 28;6(4):e03868. doi: 10.1016/j.heliyon.2020.e03868. eCollection 2020 Apr.
Since phosphate is strongly related to eutrophication of environmental waters, several research groups quest for materials that can efficiently remove phosphate from wastewaters before it contaminates lakes and reservoirs. In the present work, a commercial clay mineral (K10 montmorillonite) modified with Fe polyhydroxy cations was investigated as an adsorbent for phosphate. The incorporation of the polycations did not alter the main conformational characteristics of the montmorillonite, as verified by specific surface area measurements, X-ray diffractometry, FTIR, electron microscopy, and zeta potential titrations. On the other hand, the materials supporting Fe polyhydroxy cations exhibited a significant enhancement of adsorption capacity, as determined by Langmuir-Freundlich isotherms, from 39 ± 2 to 104 ± 15 μmol g. The different ratios of OH to Fe did not affect the adsorption capacities. The adsorption kinetics was best described by the pseudo 2 order model, approaching the equilibrium after 120 min of contact time. A variation of pH between 4.6 and 8.5 did not affect the adsorption percentages. The adsorption capacities increased with the increase of the ionic strength, thus suggesting that the formation of inner-sphere complexes prevails over electrostatic interactions as the adsorption mechanism. The materials removed phosphate from three polluted water samples having phosphate concentrations between 0.0919 and 1.211 mg L. The remaining phosphate concentration was below the limit of quantification of the analytical method (0.063 mg L in P, or 2.0 μmol L). The presence of 10 mg L humic of fulvic acid did not affect the performance of the materials. In conclusion, the modification of clay minerals with Fe polyhydroxy cations is useful in producing low-cost adsorbents for phosphate.
由于磷酸盐与环境水体的富营养化密切相关，几个研究小组一直在寻找能够在磷酸盐污染湖泊和水库之前有效从废水中去除它的材料。在本研究中，对一种用铁多羟基阳离子改性的商业粘土矿物（K10蒙脱石）作为磷酸盐吸附剂进行了研究。通过比表面积测量、X射线衍射、傅里叶变换红外光谱、电子显微镜和zeta电位滴定法验证，聚阳离子的掺入并未改变蒙脱石的主要构象特征。另一方面，负载铁多羟基阳离子的材料表现出吸附容量的显著提高，通过朗缪尔-弗伦德利希等温线测定，从39±2增加到104±15 μmol/g。不同的OH与Fe比例不影响吸附容量。吸附动力学最好用伪二级模型描述，接触120分钟后接近平衡。pH在4.6至8.5之间的变化不影响吸附百分比。吸附容量随离子强度的增加而增加，因此表明内球络合物的形成作为吸附机制比静电相互作用更占优势。这些材料从三个磷酸盐浓度在0.0919至1.211 mg/L之间的污染水样中去除了磷酸盐。剩余的磷酸盐浓度低于分析方法的定量限（P为0.063 mg/L，或2.0 μmol/L）。10 mg/L腐殖酸或富里酸的存在并不影响材料的性能。总之，用铁多羟基阳离子改性粘土矿物有助于生产低成本的磷酸盐吸附剂。
