5种不同晶型的纳米二氧化钛对金属铜生物积累的影响

纳米二氧化钛(nTiO_2)作为一种具有独特物理化学性质的纳米材料被广泛应用。然而,在生产、使用的过程中,nTiO_2会不可避免地进入于水环境中。重金属是水体中常见的污染物之一,nTiO_2进入水体后是否会与水体中的重金属发生相互作用,进而影响重金属的生物积累,目前相关报道还很少。本论文以大型溞为模式生物,考察了5种不同晶型nTiO_2对常见的重金属铜生物积累影响。结果表明,nTiO_2对Cu2+的吸附降低了试验液中Cu2+浓度。但5种不同晶型nTiO_2的吸附能力并不一样,其中锐钛矿晶型(A-S)的吸附能力最高,这可能是由于结构缺陷和表面羟基的存在,为Cu2+提供了更多的结合位点,从而提高了A-S的吸附能力。nTiO_2的存在降低了金属铜在大型溞体内的积累,这可能是由于nTiO_2对金属铜的吸附,降低了自由Cu2+的生物可利用性。由于nTiO_2样品之间比表面积的差异,不同晶型之间单位nTiO_2引起的铜积累有显著性差异性(P0.05),其中锐钛矿和金红石之比为4:1混合晶型(M1)最高,A-S最低。

Effects of Five TiO2 Nanoparticles with Different Crystalline Phases on the Bioaccumulation of Metallic Copper

Due to its phy-chemical property, the Nano-titanium dioxide (nTiO2) is widely utilized. Definitely, the nTiO2 is released in the aquatic environment during itslife cycle (such as production, use and waste). The heavy metals are typical contaminants in aquatic environment, however, the influence from nTiO2 on heavy metal, as well as impact on bioaccumulation of heavy metals remains uncertain. In this study, the Daphnia magna was selected as the case to address the influence from different crystalline phases of nTiO2 on the bioaccumulation of copper. The results showed that nTiO2 reduced the concentrations of Cu2+ in the test solution. Meanwhile, the copper adsorption capacities of the five crystalline nTiO2 were different, among which anatase (A-S) was observed with the highest adsorption capacity. This may be explained by the presence of structural defects and surface hydroxyl groups of A-S can provide more binding sites for Cu2+ and correspondingly increase the adsorption capacity of A-S. On another aspect, in our study, the nTiO2 particles reduced the accumulation of copper in D. magna, since the adsorption of Cu by nTiO2 probably minimize the bioavailability of free copper ions. Also, as the variability of surface areas, the significant differences for the Cu accumulation per nTiO2 were observed amongst the five nTiO2 (P<0.05). In particular, the Cu accumulation for the 4:1 mixture of anatase/rutile (M1) was the highest, whilst that for the A-S was the lowest.