Investigation On Enrichment And Separation Of Silver Nanoparticles By Magnetic And Carbon Material

Nanotechnology, an emerging technology, is mainly applied in environment,catalysis, medicine, biology, chemistry and so on. And metal nanoparticles are used in medical and industrial disinfection because of their antibacterial properties. However,the toxicity of metal nanoparticles can not be neglected on human health and environment, which has been one of the focuses of the world. In the paper, the adsorption properties of magnetic materials such as polyethyleneimine modified magnetic silica nanoparticles（PEI-Fe₃O₄@SiO₂） and polyethyleneimine functionalized iron oxide nanoparticles（PEI-Fe₃O₄） toward citrate-Ag NPs from aqueous water were studied, and we investigated adsorption properties of CS@SBA-15 on gum Arabic silver nanoparticles.1. In the experiment, we firstly synthesize magnetic silica（Fe₃O₄@SiO₂）, then they was modified with PEI by electrostatic interactions. The as-prepared PEI-Fe₃O₄@SiO₂ adsorbent was characterized by TEM, FT-IR, XRD and TG,indicating that PEI was successfully modified onto Fe₃O₄@SiO₂. And the materials were used as adsorbent for the removal of citrate-Ag NPs. The experiment results showed that adsorption capacity was the best at pH=6.0 and adsorption processreached adsorption equilibrium at 18 h. The adsorption kinetic was found to follow the pseudo-second-order rate equation and the adsorption process could be fit well by the Freundlich adsorption isotherm. With the increase of NaNO3 and KNO3 concentration, the adsorption capacity of citrate-Ag NPs also increased slightly.However, the addition of humic acid（HA） caused that the adsorption capacity of citrate-Ag NPs cut down. The results reveal that the PEI-Fe₃O₄@SiO₂ was an excellent adsorbent on citrate-Ag NPs.2. CS@SBA-15 composites were successfully synthesized and characterized by FT-IR, SEM, XRD, TG and zeta potential, and their application as an adsorbent for GA-Ag NPs from water solution has been investigated. We studied the influences of solution pH, the salt concentration, concentration of humic acid, contact time and initial GA-Ag NPs concentration. As the water pH was close to 7.0 in natural environment and the adsorption capacity was maximum at pH=9.0 and 10.0, selecting the pH values has done a series of experiment. The adsorption kinetics could all be fit well by pseudo-second-order rate model at pH=7.0, 9.0, and 10.0. The equilibrium isotherm was fit well with the Langmuir adsorption isotherm at pH=7.0 and 10.0, and the maximum adsorption capacities towards GA-Ag NPs can be reach up to 38.88mg/g and 80 mg/g. However, the adsorption process was fit well by Freundlich isotherm at pH=9.0. The presence of humic acid and ion had minor effect on adsorption of GA-Ag NPs. The removal principle was mainly due to larger specific surface area and pore volume. The results indicated that CS@SBA-15 has great potential to remove GA-Ag NPs.3. This study shows a simple approach to fundctionalize Fe₃O₄ with branched-chain polyethyleneimine by electrostatic interactions, when Fe₃O₄ was prepared by the co-precipitation method. The as-synthetic PEI-Fe₃O₄ was used to the removal of citrate-Ag NPs from aqueous water. During the experiment, through the concentration of PEI optimized, it is found that when the content of PEI is 0.6wt.%,the highest adsorption capacity for citrate-Ag NPs was obtained. Therefore, this concentration was selected in experiment. The results revealed that the highest adsorption capacity for citrate-Ag NPs was obtain at pH=6.0 and the adsorption process reached the equilibrium at 28 h. And the adsorption of citrate-Ag NPs on PEI-Fe₃O₄ was well in line with the pseudo-second-order-model. The equilibrium isotherm was well described by the Langmuir adsorption isotherm, with maximum equilibrium adsorption capacity of 502.51 mg/g. Due to its magnetic property,PEI-Fe₃O₄ can be easily separated under external magnetic field and be able to avoid secondary pollution. Therefore, PEI-Fe₃O₄ material is a green adsorbent, which can make good use of the removal of citrate-Ag NPs.