TiO2 and SiO2 Nanoparticles Combined with Surfactants Mitigate the Toxicity of Cd2+ to Wheat Seedlings

Engineered nanoparticles (NPs) could be coated by surfactants and modify the bioavailability and toxicity of heavy metals. In this study, the single and combined effect of sodium dodecyl benzene sulfonate (SDBS) and NPs on the toxicities of Cd 2+ to wheat seedlings was investigated by a root elongation, and the underlying influence mechanism was further discussed. The results showed that the presence of SDBS improved the Cd 2+ adsorption capacity of TiO 2 and SiO 2 NPs. The reaction of SDBS and TiO 2 and SiO 2 NPs could increase TiO 2 and SiO 2 NPs dispersion stability and produced more available adsorption sites. The adsorption coefficients of Cd 2+ on TiO 2 and SiO 2 NPs were enhanced from 3.84 to 4.52 mg/g and from 4.51 to 7.16 mg/g after SDBS coating. Both SDBS-coated TiO 2 and SDBS-coated SiO 2 NPs reduced Cd 2+ phytotoxicity. The presence of bare TiO 2 and SiO 2 NPs at 1000 mg/L promoted root length of the wheat seedlings by 31.2% and 39.3%; however, SDBS-coated TiO 2 and SiO 2 NPs increased the root length by 41.2% and 51.4%, which demonstrated that SDBS-coated NPs had a much better effect on reducing the toxicity of Cd 2+ than bare NPs. The results indicated the mitigation of Cd 2+ toxicity was due to a decrease in bioavailable soluble Cd 2+ which was adsorbed by NPs through electrostatic attraction.