铁(氢)氧化物对金纳米粒子的吸附行为研究

Study of the adsorption behaviour of iron(hydr)oxidess and gold nanoparticles

随着纳米技术的应用越发广泛,大量纳米粒子(NPs)进入到环境中,对环境和人类健康构成潜在风险。研究NPs与环境中普遍存在的铁(氢)氧化物的吸附过程和机制,对于理解NPs在环境中的迁移与转化具有重要意义。另一方面,在一些红土型金矿和卡林型金矿的氧化带中发现了以铁(氢)氧化物为载体的天然金纳米粒子(AuNPs),研究NPs与铁(氢)氧化物的相互作用,也可以为相关矿床中的天然NPs的成因提供一定参考。本研究以应用较为广泛的柠檬酸盐包覆的AuNPs为例,以赤铁矿、磁铁矿、针铁矿作为铁(氢)氧化物代表,研究在含柠檬酸盐体系中不同pH、离子强度(IS)下铁(氢)氧化物-AuNPs的吸附规律和作用机制。发现在酸性条件下(初始pH在4~6时),铁(氢)氧化物-AuNPs的吸附行为由静电作用力主导;在碱性条件下(初始pH在7~10时),不同铁(氢)氧化物对AuNPs的吸附行为有较大差异,赤铁矿、磁铁矿与AuNPs由于静电斥力几乎不发生吸附,但针铁矿与AuNPs发生了较为强烈的吸附作用。我们认为针铁矿的吸附差异可能是柠檬酸盐在碱性条件下发挥的促进作用以及针铁矿的结构羟基导致的。研究也表明,总体上IS的增加会促进铁(氢)氧化物与AuNPs的吸附。所得结果将为AuNPs的环境归趋提供新的见解,同时也将为红土型金矿和卡林型金矿的氧化带中天然AuNPs的成因提供一定参考依据。

As the increasing application of nanotechnology,a large number of nanoparticles(NPs)entered the environment and pose potential risks to the environment and human health.The study of the processes and mechanisms of adsorption of NPs on iron(hydr)oxides which are prevalent in the environment will contribute to the understanding of the transport and transformation of NPs in the environment.On the other hand,natural gold nanoparticles(AuNPs)with iron(hydr)oxides as carriers have been found in laterite and oxidation zones of Carlin-type gold deposits.The study of the interaction between NPs and iron(hydr)oxides can also provide some reference for the genesis of natural NPs in the related deposit.In this paper,we take the more widely used citrate-coated AuNPs as an example,and use hematite,magnetite and goethite as representatives of iron(hydr)oxides to study the adsorption behaviour and mechanism of iron(hydr)oxides-AuNPs under different pH and ionic strength(IS)in the citrate-containing system.We find that under acidic conditions(at an initial pH of 4~6),the adsorption behaviour of iron(hydr)oxides-AuNPs was dominated by electrostatic forces;under alkaline conditions(at an initial pH of 7~10),the adsorption behaviour of AuNPs on different iron(hydrogen)oxides varied considerably.AuNPs hardly adsorbed on hematite and magnetite because of electrostatic repulsion,but AuNPs underwent more intense adsorption on goethite.We consider that the difference in adsorption of goethite may be due to the facilitating effect of citrate in alkaline conditions and the structural hydroxyl group of goethite.Our study also shows that an overall increase in IS promotes the adsorption of iron(hydr)oxides with AuNPs.The results of this paper will provide new insights into the environmental fate of AuNPs,and will also provide some reference for the genesis of natural AuNPs in the oxide zones of lateritic and Carlin-type gold deposits.