Author(s): COA, F.; CLEMENTE, Z.; LOPES, J. R.; RODRIGUES NETO, L. L.; ALVES, O. L.; CASTRO, V. L. S. S. de; BARBIERI, E.; MARTINEZ, D. S. T.

Summary: Nanomaterials (NM) are promising for environmental remediation due to their unreleased properties such as high surface area and reactivity. Chemical oxidations (H2SO4/HNO3) have been applied to carbon NM in order to favor their application, but these are expensive and hazardous. In this work, industrial grade multiwalled carbon nanotubes (raw-MWCNT) were coated with humic acid (HA) by a ball milling processing (solid state). The aim was to apply a green mechanochemical process to improve the colloidal stability of MWCNTs and their removal capacity of metals. The HA-MWCNT complex was studied by atomic force microscope (AFM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), dynamic light scattering (DLS), electrophoretic light scattering (ELS) and ultraviolet-visible spectroscopy (UV-Vis). Cu2+ sorption from water by HA-MWCNT, MWCNT-COOH and milledMWCNT were compared. Acute bioassays (96h) were performed with Daphnia magna exposed to 0.0; 0.1; 1.0; 5.0 and 10.0 mg/L of HA-MWCNT. Our results showed that the coating process enhanced the zeta potential of raw-MWCNT of -25.4±0.2 mV to -37.4±0.7 mV and reduced their hydrodynamic diameter of 393.2±27.3 nm to 212.5±5.6 nm in ultrapure water. AFM images of HA-MWCNT showed that it has an irregular surface, due to the humic acid coating. The complex was 4 times (84±1.8%) more efficient to remove Cu2+ than MWCNTCOOH (20.0±1.4%) and 11 times compared to milled-MWCNT (7.6±3.1%). The increases in Oxygen and the reductions in Carbon on surface of HA-MWCNT relative to raw-MWCNT and milled-MWCNT indicated the introduction of functional oxygenated groups on MWCNT. The HA-MWCNT did not show acute toxicity against D. magna. These results suggest that the coating changes the MWCNT surface, resulting in a material with potential to metal remediation, prepared without oxidizing acids and that did not show toxicity on D. magna.

Publication year: 2016

Types of publication: Abstract in annals or event proceedings

Unit: Embrapa Environment

Keywords: Ecotoxicologia, Nantubes