Preparation And Application Of Magnetic Nano - Cobalt And Its Composites

Nanosized magnetic cobalt is attracting a growing interest because of the potential applications in medical diagnostics, high-density magnetic recording media, sensor, catalysts and so on. In this paper, magnetic Co nanoparticles and Co/MWCNTs, Co/GRs, Co/HNTs composites were prepared by using a one-step high temperature liquid phase reduction method. The as-prepared composites were used for adsorption of anionic dyes and catalyzing the hydrolysis of NaBH4 for production of H2. These composites can be conveniently separated from the aqueous solution by an external magnetic field. The contents of the present study are listed as the following:1. Uniform sphere-like Co MNPs were prepared with high saturation magnetization, where the high temperature liquid phase reduction method was used with ethylene glycol (EG) as the solvent and hydrazine hydrate as the reductant. In the process, we control the morphology of Co nanoparticles by changing the concentration of ethylenediamine (EDA). And Co/MWCNTs composites were synthesized by using the same method. The as-obtained Co/MWCNTs composite was used as an adsorbent for adsorption of methyl orange (MO) from the aqueous solution and the maximum adsorption capacity reaches about 169.5 mg/g.2. To enhance the dispersibility of Co nanoparticles, Co/GRs composites with high saturation magnetization were synthesized through the method as described aforementioned, in which ethylene diamine (EDA) was used as an additive, and bis (2-ethylhexyl) sulfosuccinate sodium salt (AOT) was applied to adjust the morphology and size of the Co nanoparticles. The as-prepared Co particles were uniformly dispersed on the GRs, and the catalytic activity of the composite for hydrolysis of NaBH4 solution to produce H2 was studied, which is up to 188.3 mL·min-1·g-1. Furthermore, the effects of initial concentration of NaBH4 and experimental temperature on catalytic activity were investigated.3. To reduce the cost of the composites, more inexpensive natural nano-tube materials-halloysite (HNTs) were choosed as a supporter. Magnetic Co/HNTs composites were prepared by using a one-step high temperature liquid phase reduction method as described above. In the process, ethylene dimine (EDA) and AOT were used to control the nucleation and growth of particles along a particular crystallographic direction by selective adsorption, which affect the dispersibility of Co nanoparticles on the HNTs. And 3-Aminopropyltriethoxysilane (APTES) was used for the functionalization of the surface of the HNTs. By this way, the catalytic capacity was enhanced, and the optimal catalytic rate can reach 343.9 mL·min-1·g-1. The effect of APTES amount and the contact time of HNTs and Co2+ on the catalytic performance were discussed.