Magnetic cobalt ferrites (CoFe 2 O 4 ) were synthesized by sol-gel method. These nanoparticles were ultra-sonicated with surface modified multi-walled carbon nanotubes (SM-MWCNTs) to form CoFe 2 O 4 /SM-MWCNTs nanocomposites. The as-prepared materials were used as an adsorbent for the removal of hexavalent chromium (Cr(VI)) arising from the presence of dichromate ions (Cr 2 O 7 2− ) in the electroplating effluent. The synthesized nanocomposites were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-Ray diffraction (XRD), Fourier transmission infrared spectroscopy (FT-IR), raman spectroscopy, thermo-gravimetric analysis (TGA), and zeta analyzer. The effect of the environmental chemistry of the solution on the adsorption has been discussed. The adsorption isotherm of Cr(VI) adsorption onto the as-synthesized CoFe 2 O 4 /SM-MWCNTs best fitted the Langmuir Adsorption Isotherm model. The high adsorption capacity of 100mg/g was achieved at 40°C under optimized conditions. Besides, the magnetic properties of synthesized CoFe 2 O 4 /SM-MWCNTs nanocomposites allow them to separate from the aqueous solution by magnetization easily. Even after seven consecutive adsorption-desorption cycles, the CoFe 2 O 4 /SM-MWCNTs nanocomposites presented an efficiency loss of less than 20% for the removal of Cr(VI) ions. This study clearly shows that cobalt nanocomposites are promising candidates in environmental applications.

中文翻译：

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磁性钴铁氧体纳米复合材料的制备：一种去除电镀废水中有毒重铬酸盐离子的先进方法

通过溶胶-凝胶法合成了磁性钴铁氧体（CoFe 2 O 4 ）。这些纳米粒子与表面改性的多壁碳纳米管 (SM-MWCNTs) 进行超声处理，形成 CoFe 2 O 4 /SM-MWCNTs 纳米复合材料。所制备的材料用作吸附剂，用于去除电镀废水中因重铬酸根离子 (Cr 2 O 7 2- ) 的存在而产生的六价铬 (Cr(VI))。通过场发射扫描电子显微镜（FESEM）、透射电子显微镜（TEM）、X射线衍射（XRD）、傅里叶透射红外光谱（FT-IR）、拉曼光谱、热重分析（TGA）对合成的纳米复合材料进行表征, 和 zeta 分析仪。已经讨论了溶液的环境化学对吸附的影响。Cr(VI) 吸附在合成的 CoFe 2 O 4 /SM-MWCNT 上的吸附等温线最符合朗缪尔吸附等温线模型。在优化条件下，在 40°C 下实现了 100mg/g 的高吸附容量。此外，合成的CoFe 2 O 4 /SM-MWCNTs 纳米复合材料的磁性使它们很容易通过磁化从水溶液中分离出来。即使经过七个连续的吸附-解吸循环，CoFe 2 O 4 /SM-MWCNTs 纳米复合材料在去除 Cr(VI) 离子方面的效率损失也低于 20%。这项研究清楚地表明，钴纳米复合材料在环境应用中是很有前景的候选材料。此外，合成的CoFe 2 O 4 /SM-MWCNTs 纳米复合材料的磁性使它们很容易通过磁化从水溶液中分离出来。即使经过七个连续的吸附-解吸循环，CoFe 2 O 4 /SM-MWCNTs 纳米复合材料在去除 Cr(VI) 离子方面的效率损失也低于 20%。这项研究清楚地表明，钴纳米复合材料在环境应用中是很有前景的候选材料。此外，合成的CoFe 2 O 4 /SM-MWCNTs 纳米复合材料的磁性使它们很容易通过磁化从水溶液中分离出来。即使经过七个连续的吸附-解吸循环，CoFe 2 O 4 /SM-MWCNTs 纳米复合材料在去除 Cr(VI) 离子方面的效率损失也低于 20%。这项研究清楚地表明，钴纳米复合材料在环境应用中是很有前景的候选材料。