Remediation of copper contaminated sediments by granular activated carbon-supported titanium dioxide nanoparticles: Mechanism study and effect on enzyme activities.

After much effort, the remediation of heavy metal contaminated sediments still remains physically hard and technically challenging issue to resolve. In this study, granular activated carbon-supported titanium dioxide nanoparticles (GAC-TiO NPs) are synthesized to remedy heavy metal copper (Cu) contaminated sediments. The concentration and chemical speciation of Cu in overlying water, interstitial water and contaminated sediments are fully assessed to examine the remediation effect of GAC-TiO NPs. The GAC-TiO NPs are separated from GAC-TiO NPs-remedied sediments and characterized by X-ray photoelectron spectra (XPS), which reveals the mechanism of GAC-TiO NPs remedy Cu Contaminated sediments. The results show that after 35 days adding 20% GAC-TiO NPs to contaminated sediments, the Cu concentration in the overlying water and interstitial water decreases 89.47% and 83.52%, respectively, and the exchangeable fraction (F-1) of Cu in sediments decreases from 43.91% to 7.49%. The percentage of residual fraction (F-4) increases sharply from 42.79% to 80.30%. XPS results show that hydroxyl (-OH) plays an important role in the remediation process. The synergistic effects of pH, phosphorus concentration and organic matter (OM) content on the remediation effect are explored. When the pH value is 8, phosphorus concentration is 0.32 mg/L and OM content is 151.2 g/kg, adding 20% GAC-TiO NPs achieves the best remediation effect on Cu contaminated sediment. Biological enzyme-activity experiments prove that GAC-TiO NPs not only reduce the bioavailability and biotoxicity of Cu, but also effectively suppress the negative effects of granular activated carbon (GAC) on enzyme activities. All these results indicate that GAC-TiO NPs is an environmentally friendly remediation material for Cu contaminated sediments with high-potential applications.