Adsorption of Estrogen Contaminants by Graphene Nanomaterials under Natural Organic Matter Preloading: Comparison to Carbon Nanotube, Biochar, and Activated Carbon

Adsorption of two estrogen contaminants (17β-estradiol and 17α-ethynyl estradiol) by graphene nanomaterials was investigated and compared to those of a multi-walled carbon nanotube (MWCNT), a single-walled carbon nanotube (SWCNT), two biochars, a powdered activated carbon (PAC), and a granular activate carbon (GAC) in ultrapure water and in the competition of natural organic matter (NOM). Graphene nanomaterials showed comparable or better adsorption ability than carbon nanotubes (CNTs), biochars (BCs), and activated carbon (ACs) under NOM preloading. The competition of NOM decreased the estrogen adsorption by all adsorbents. However, the impact of NOM on the estrogen adsorption was smaller on graphenes than CNTs, BCs, and ACs. Moreover, the hydrophobicity of estrogens also affected the uptake of estrogens. These results suggested that graphene nanomaterials could be used to removal estrogen contaminants from water as an alternative adsorbent. Nevertheless, if transferred to the environment, they would also adsorb estrogen contaminants, leading to great environmental hazards

Stabilized Nanoscale Zerovalent Iron Mediated Cadmium Accumulation and Oxidative Damage of <i>Boehmeria nivea</i> (L.) Gaudich Cultivated in Cadmium Contaminated Sediments

Nanoparticles can be absorbed by plants, but their impacts on phytoremediation are not yet well understood. This study was carried out to determine the impacts of starch stabilized nanoscale zerovalent iron (S-nZVI) on the cadmium (Cd) accumulation and the oxidative stress in <i>Boehmeria nivea</i> (L.) Gaudich (ramie). Plants were cultivated in Cd-contaminated sediments amended with S-nZVI at 100, 500, and 1000 mg/kg, respectively. Results showed that S-nZVI promoted Cd accumulation in ramie seedlings. The subcellular distribution result showed that Cd content in cell wall of plants reduced, and its concentration in cell organelle and soluble fractions increased at S-nZVI treatments, indicating the promotion of Cd entering plant cells by S-nZVI. In addition, the 100 mg/kg S-nZVI alleviated the oxidative damage to ramie under Cd-stress, while 500 and 1000 mg/kg S-nZVI inhibited plant growth and aggravated the oxidative damage to plants. These findings demonstrate that nanoparticles at low concentration can improve the efficiency of phytoremediation. This study herein develops a promising novel technique by the combined use of nanotechnology and phytoremediation in the remediation of heavy metal contaminated sites

Adsorption of Cu(II), Pb(II), and Cd(II) Ions from Acidic Aqueous Solutions by Diethylenetriaminepentaacetic Acid-Modified Magnetic Graphene Oxide

In this study, diethylenetriaminepentaacetic acid (DTPA)-modified magnetic graphene oxide (MGO) was synthesized for removal of Cu­(II), Pb­(II), and Cd­(II) ions from acidic aqueous solutions. The prepared DTPA/MGO composites were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared and X-ray photoelectron spectroscopies, and zeta potential. The results showed that DTPA successfully functionalized MGO. Adsorption experiments indicated that DTPA/MGO composites exhibited excellent adsorption property in acidic aqueous solutions. The adsorption processes were applicable for the Langmuir adsorption isotherm and the pseudo-second-order model. The maximum adsorption capacities at pH 3.0 for Cu­(II), Pb­(II), and Cd­(II) ions were 131.4, 387.6, and 286.5 mg/g, respectively. The thermodynamic studies demonstrated that adsorption processes were endothermic and spontaneous. Moreover, the DTPA/MGO composites could selectively adsorb Pb­(II) from multimetal mixed systems. Adsorption–desorption results showed that the DTPA/MGO composites exhibited excellent reusability. These results suggested that DTPA/MGO composites have great potential in removing heavy metals from acidic wastewater, especially for Pb­(II)

Ethylenediamine grafted to graphene oxide@Fe₃O₄ for chromium(VI) decontamination: Performance, modelling, and fractional factorial design - Fig 4

<p>(a) Time profiles of Cr(VI) adsorption with GO@Fe₃O₄ and EDA-GO@Fe₃O₄; Kinetics of Cr(VI) adsorption by fitting (b) pseudo-first-order and pseudo-second-order models, and (c) intraparticle diffusion model, respectively (initial Cr(VI) concentration = 10 mg/L; sorbent dose = 2 mL; temperature = 25°C; pH = 2).</p

HRTEM images of EDA-GO@Fe₃O₄ at different magnification.

<p>HRTEM images of EDA-GO@Fe₃O₄ at different magnification.</p

Effect of solution pH on Cr(VI) adsorption onto the EDA-GO@Fe₃O₄: (initial Cr(VI) concentration = 10 mg/L; sorbent dose = 2 mL; temperature = 25°C; time = 8 h).

<p>Effect of solution pH on Cr(VI) adsorption onto the EDA-GO@Fe₃O₄: (initial Cr(VI) concentration = 10 mg/L; sorbent dose = 2 mL; temperature = 25°C; time = 8 h).</p

Isotherm parameters for Cr(VI) ions adsorption onto EDA-GO@Fe₃O₄.

<p>Isotherm parameters for Cr(VI) ions adsorption onto EDA-GO@Fe₃O₄.</p

Adsorption kinetics parameters for Cr(VI) adsorption onto GO@Fe₃O₄ and EDA-GO@Fe₃O₄.

<p>Adsorption kinetics parameters for Cr(VI) adsorption onto GO@Fe₃O₄ and EDA-GO@Fe₃O₄.</p

Le Courrier

15 juillet 18341834/07/15 (N196)