Kong Yuan, Huang Yangrui, Meng Chenrui, Zhang Zhi
Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University Chongqing 400045 China
School of Environmental Studies, China University of Geosciences Wuhan 430074 Hubei China.
RSC Adv. 2018 Sep 6;8(55):31440-31454. doi: 10.1039/c8ra05726e. eCollection 2018 Sep 5.
Modified MgAl layered double hydroxide (LDH) intercalated with dodecylsulfate anion composites, which were designated as SDS-LDH composites, were synthesized by coprecipitation. The samples were characterized using SEM, EDX, FT-IR, zeta potential analysis, and XRD. The results showed that the SDS-LDH composites contain a thicker and larger porous interconnected network than inorganic LDH due to the enlarged inter-layer distance. The outstanding adsorption performance of SDS-LDH composites toward 17β-estradiol (E2) was investigated under different conditions, including solution pH, adsorbent dosage, ion strength, reaction time, and temperature. When the solution pH was 7 and the adsorbent dosage was 2 g L, the removal rate of E2 reached the maximum at 94%, whereas inorganic LDH displayed a poor E2 removal rate of 10%. The presence of various ions (Na, SO , CI, and HPO ) in aqueous solution exerted no significant adverse effects on the adsorption process. The adsorption equilibrium was reached within 20 min, and the adsorption fitted well with the pseudo-second-order model and the Freundlich isotherm. The thermodynamic test revealed that the adsorption process was spontaneous and endothermic. Phosphorus was selected as the index for evaluating the adsorption capacity of SDS-LDH composites for inorganic ions. The removal rates of total phosphorus and PO were 43.71% and 55.93% for SDS-LDH composites at 2 g L. The removal rate of PO reached up to 85% when the contact time was 120 min and the dosage was 3 g L for SDS-LDH composites, which were approximately close to those of inorganic LDH of 30 min and 2 g L, respectively. This finding indicates that the removal capacity of SDS-LDH composites for PO decreased after the dodecylsulfate anions intercalated into the interlayer. The composites retained their high efficiency and stability after desorption and regeneration with alkali treatment. This study demonstrated that SDS-LDH composites are a promising adsorbent for the recovery and abatement of trace-level E2 in secondary effluents of wastewater treatment plants.
通过共沉淀法合成了插层有十二烷基硫酸根阴离子的改性镁铝层状双氢氧化物（LDH）复合材料，即十二烷基硫酸钠-LDH复合材料（SDS-LDH复合材料）。使用扫描电子显微镜（SEM）、能量散射X射线光谱（EDX）、傅里叶变换红外光谱（FT-IR）、zeta电位分析和X射线衍射（XRD）对样品进行了表征。结果表明，由于层间距增大，SDS-LDH复合材料比无机LDH含有更厚且更大的多孔互连网络。研究了SDS-LDH复合材料在不同条件下对17β-雌二醇（E2）的优异吸附性能，这些条件包括溶液pH值、吸附剂用量、离子强度、反应时间和温度。当溶液pH值为7且吸附剂用量为2 g/L时，E2的去除率达到最大值94%，而无机LDH的E2去除率仅为10%，效果较差。水溶液中各种离子（Na⁺、SO₄²⁻、Cl⁻和HPO₄²⁻）的存在对吸附过程没有显著的不利影响。吸附在20分钟内达到平衡，吸附过程符合准二级模型和Freundlich等温线。热力学测试表明，吸附过程是自发的且吸热的。选择磷作为评估SDS-LDH复合材料对无机离子吸附能力的指标。对于2 g/L的SDS-LDH复合材料，总磷和PO₄³⁻的去除率分别为43.71%和55.93%。当接触时间为120分钟且用量为3 g/L时，SDS-LDH复合材料对PO₄³⁻的去除率高达85%，这分别与无机LDH在接触时间30分钟和用量2 g/L时的去除率相近。这一发现表明，十二烷基硫酸根阴离子插入层间后，SDS-LDH复合材料对PO₄³⁻的去除能力下降。经过碱处理解吸和再生后，复合材料仍保持其高效性和稳定性。本研究表明，SDS-LDH复合材料是一种有前景的吸附剂，可用于回收和去除污水处理厂二级出水中痕量水平的E2。
