Aggregation Of CuO Nanoparticles Research Articles

Effect of clay colloid – CuO nanoparticles interaction on retention of nanoparticles in different types of soils: role of clay fraction and environmental parameters

The extensive application of metal oxide nanoparticles (NPs) in various sectors has raised concern about their subsequent release and potentially harmful impacts on the soil system. The present study has addressed the interaction of CuO NPs with bentonite clay colloids (CC) under varying environmental parameters as a model to represent the soil pore water scenario. Based on CuO – CC interaction in model and natural soil solution extracts (SSE), the role of clay fraction and their stability on CuO retention in various types of soils have been evaluated.Results suggested that increasing ionic strength (IS) in the system caused aggregation of CuO NPs, and in the presence of CC, critical coagulation concentration decreased drastically from 27.8 and 17.3 mM to 10.7 and 0.33 mM for NaCl and CaCl2 respectively, due to heteroaggregation in the system. Interestingly, in the SSE, the dominating role of ionic valency, dissolved organic carbon (DOC), and CC was observed in colloidal stabilization over IS. No significant impact of temperature was observed on the stability of CuO NPs both in model and SSE. Further, stability studies in the SSE were correlated with NPs retention behavior in soils. Observations suggest that retention of CuO NPs in soils is a function of binding of the colloidal fraction to the soil, which in turn depends on the colloidal stability. The highest retention was observed in black and laterite soils, whereas lower binding of clay fraction in red soil caused the least retention. A decrease in Kd values after a certain application concentration provided maximum sustainable application concentration of CuO NPs, which may vary with soil properties. Results suggest that the binding of clay and organic matter with a sandy matrix of soil plays a prime role in deciding the overall fate of CuO NPs in the soils.

Exogenous Fe2+ alleviated the toxicity of CuO nanoparticles on Pseudomonas tolaasii Y-11 under different nitrogen sources.

Extensive use of CuO nanoparticles (CuO-NPs ) inevitably leads to their accumulation in wastewater and toxicity to microorganisms that effectively treat nitrogen pollution. Due to the effects of different mediums, the sources of CuO-NPs-induced toxicity to microorganisms and methods to mitigating the toxicity are still unclear. In this study, CuO-NPs were found to impact the nitrate reduction of Pseudomonas tolaasii Y-11 mainly through the action of NPs themselves while inhibiting the ammonium transformation of strain Y-11 through releasing Cu2+. As the content of CuO-NPs increased from 0 to 20 mg/L, the removal efficiency of NO3− and NH4+ decreased from 42.29% and 29.83% to 2.05% and 2.33%, respectively. Exogenous Fe2+ significantly promoted the aggregation of CuO-NPs, reduced the possibility of contact with bacteria, and slowed down the damage of CuO-NPs to strain Y-11. When 0.01 mol/L Fe2+ was added to 0, 1, 5, 10 and 20 mg/L CuO-NPs treatment, the removal efficiencies of NO3- were 69.77%, 88.93%, 80.51%, 36.17% and 2.47%, respectively; the removal efficiencies of NH4+ were 55.95%, 96.71%, 38.11%, 20.71% and 7.43%, respectively. This study provides a method for mitigating the toxicity of CuO-NPs on functional microorganisms.

Aggregation kinetics and surface charge of CuO nanoparticles: the influence of pH, ionic strength and humic acids

Environmental context The high demand and use of nanomaterials in commercial products have led to increased concerns about their effect on the environment and human health. Because CuO nanoparticles are widely used in several products, it is necessary to understand and predict their behaviour and fate in the environment. We report a study on the aggregation and surface charge of CuO nanoparticles under environmentally relevant conditions to better predict the mobility and bioavailability of these materials in natural waters. Abstract In this study, the role of pH, ionic strength and humic acids (HAs) on the aggregation kinetics and surface charge of commercial copper oxide (CuO) nanoparticles were examined. Results show that the aggregation of CuO nanoparticles is favoured near pH 10, which was determined as the isoelectric point where the hydrodynamic diameter of the aggregates is the greatest. The aggregation of CuO nanoparticles is also ionic strength dependent. The increase in the ionic strength reduces the zeta potential, which leads to an increase in aggregation until 0.15M. After this point an increase in ionic strength has no influence on aggregation. In the presence of HA for concentrations below 4mgCL–1, aggregation was enhanced for acidic to neutral pH, whereas for higher concentrations, at all pH tested, aggregation does not change. The influence of HA on CuO nanoparticles is due to steric and electrostatic interactions. The sedimentation rates of CuO nanoparticles showed a relation between particle diameter and zeta potentials values confirmed by Derjaguin–Landau–Verwey–Overbeek calculations. The results obtained have important implications for predicting the stability and fate of CuO nanoparticles in natural water.

Methane oxidation over catalytic copper oxides nanowires

Copper oxide (CuO) is one of the promising catalysts for the catalytic oxidation of methane (CH 4). Previous studies have focused on CuO nanoparticles (NPs) dispersed on other supporting oxides. However, aggregation of CuO NPs under large loadings and solid state reactions between CuO and supports hinder the understanding and further improvement of the catalytic properties of CuO. Here, we report the first study of the catalytic oxidation of CH 4 over CuO nanowires (NWs). The CuO NWs were prepared by the thermal annealing of copper meshes and grew perpendicularly to the mesh surface with a high surface coverage density. The percentage of CH 4 converted to CO 2 over the CuO NWs was experimentally measured in a flow reactor over a range of temperatures. First, the conversion percentage of CH 4 over the catalytic CuO NWs is almost 40% (a total flow rate of 100 sccm with 1.5 vol.% of CH 4) at 500 °C, which is comparable to that measured over supported CuO NPs. Second, the conversion percentage of CH 4 increases with increasing CuO NW loading. Third, the catalytic activity of the CuO NWs remains constant for at least 24 h at 500 °C. Moreover, the CuO NWs can be easily regenerated in situ by thermal annealing. Finally, when the CuO NWs are briefly reduced in hydrogen RF plasma, their catalytic activity is enhanced, such that the CH 4 conversion percentage is increased by approximately 7% over the tested temperature range. The hydrogen plasma treatment changes the oxidation state of surface copper species from Cu(II) to Cu(I), suggesting that Cu(I) is more active than Cu(II) in the catalytic process. These CuO NWs have great potential to be economical and effective catalysts for the oxidation of CH 4 and, possibly, hydrocarbons as well.