The effects of hydroxylated multiwalled carbon nanotubes on the toxicity of nickel to Daphnia magna under different pH levels

Abstract

Hydroxylated multiwalled carbon nanotubes (OH-MWCNTs), with large amounts of hydrophilic groups attached on the nanoparticle surface, have caused considerable concern because of their inevitable release into aquatic environments. They may interact with other contaminants such as heavy metals and even influence their toxicity, fate, and transport. In the present study, the stability of OH-MWCNTs suspended in aerated Nanjing tap water (moderately hard) was evaluated using the spectrophotometric method. The toxicity of OH-MWCNTs to Daphnia magna was determined, and nontoxic concentrations were used in acute toxicity, accumulation, and sorption tests. It was found that OH-MWCNTs increased the Ni toxicity in a concentration-dependent manner under different pH levels. Nickel adsorption onto the OH-MWCNTs and the uptake of OH-MWCNTs increased the exposure of D. magna to Ni, which was verified by sorption and accumulation tests conducted under different pH levels. The lower pH level contributed to a higher overall toxicity, which could be interpreted by the increasing amount of Ni adsorption onto OH-MWCNTs with the decreasing pH levels.

Impact of carbon nanotubes on the toxicity of inorganic arsenic [AS(III) and AS(V)] to Daphnia magna: The role of certain arsenic species

“…Therefore, the presence of OH‐MWCNTs could enhance the toxicity of arsenic. The results were consistent with those reported by other researchers .…”

“…It was found that stability was reduced during the exposure period, and the CNT solutions with higher concentrations had lower stabilities. This was consistent with experimental results for OH‐MWCNTs .…”

“…It was found that stability was reduced during the exposure period, and the CNT solutions with higher concentrations had lower stabilities. This was consistent with experimental results for OH-MWCNTs [20,44]. Figure 2 shows the distribution of As(III) and As(V) species in the natural water within the pH range of 5.0 to 9.0.…”

“…The hydroxyl content of the OH‐MWCNTs was determined to be 1.82% , suggesting a high dispersion stability of OH‐MWCNTs in an aquatic environment. Absorbance of the stable OH‐MWCNTs solutions was measured at 255 nm (Supplemental Data, Figure S1), and the absorbance values have a highly linear correlation with the OH‐MWCNTs concentrations (Supplemental Data, Figure S2).…”

Role of graphene oxide in mitigated toxicity of heavy metal ions on Daphnia magna

“…It was also reported that, traditional carbon nanomaterials (carbon nanotubes and nC 60 ) increased the toxicity of heavy metal ions in D. magna by adsorbing metal ions and increasing metals accumulation as carriers. 23,24 Although GO is also a kind of carbon nanomaterial, its effect on biotoxicity of heavy metal ions may be a totally different case. According to Yu and Wang, although the physical properties of different carbon nanomaterials were similar in some ways, their inuences on metals accumulation and biotoxicity depend largely on the chemical properties.…”