Particulate copper electrodeposited on carbon felt for degradation of low concentration of methyl iodide in liquid radioactive wastes.

In this work, the study of copper particles deposition on to carbon felt was presented by pulse electrodeposition method to electrochemically degrade methyl iodide (CH3I, 1 mg L-1) in aqueous solution. In order to solve the problems linked to the heterogeneous potential distribution in the 3-D porous structure, which lead to the so-called 'black core', we successfully used low concentration of copper salt (1 mM) and negative deposition potential (-2.5 V) to obtain Cu-nanoparticles/carbon felt (Cu-nano/CF) electrode, the copper coating improved the specific surface area of carbon felt from ∼0.07 to 0.7 m2 g-1 with high catalytic activity. Results show that 98.1% of CH3I can be removed with the Cu-nano/CF electrode in 120 min.

Electrochemical behaviors and influence factors of copper and copper alloys cathode for electrocatalytic nitrate removal.

The electrocatalytic activities of a series of copper alloys, Cu/Ni/Zn (Cu60 Ni15 Zn25 ) and Cu/Zn (Cu62 Zn38 ), toward the reduction of nitrate were investigated, in comparison with that of pure copper. Electrochemical analysis showed that the copper alloy electrode exhibited higher electrochemical reduction rate of nitrate. The extreme difference (R) between the orthogonal experiments revealed that the NO 3 - - N concentration was the main determinant of the removal percentage, followed by the current density and electrolyte concentration, while the impact of the initial pH was minimal. The conditions of the electrolysis experiments with Cu/Ni/Zn and Cu/Zn cathodes were optimized as follows: a current density of 8 mA/cm2 , a NaCl concentration of 2.0 g/L, and an initial pH of 3.0. The nitrate reduction reaction process with copper alloy cathodes was confirmed by electrochemical analysis and electrolysis experiments. Therefore, copper alloyed with Zn and Ni is a feasible option for practical application to the electrocatalytic reduction of nitrate. PRACTITIONER POINTS: Alloy of Cu, Zn, and Ni improved electrochemical nitrate reduction reaction. Electrochemical reduction of nitrate was confirmed in the presence of NaCl. The optimized current density with copper alloy cathodes was 6 mA/cm2 . A feasible strategy was provided for the improving nitrate removal and minimizing by-products.

pH-Dependent Structure-Activity Relationship of Polyaniline-Intercalated FeOCl for Heterogeneous Fenton Reactions.

In this study, we prepared polyaniline-intercalated iron oxychloride (FeOCl-PANI) by aqueous intercalation method to use it as a Fenton-like catalyst that was then assessed in terms of behavior of intercalation, structural evolution, Fenton-like activity, and catalytic mechanism. Gel-permeation chromatography demonstrated that the molecular weight (polymerization extent) of polyaniline fragment gradually increased with the increase of intercalation time. Interestingly, the polyaniline-intercalated materials with varying intercalation times exhibited distinctly different Fenton-like activity trends under acidic (pH 4) and neutral (pH 7) conditions. Specifically, Fenton-like degradation is favored with a shorter intercalation time under acidic conditions, while it is preferred with a longer intercalation time under neutral pH values. We propose that an additional pH-dependent charging of FeOCl-PANI with different polymerization extents of the intercalated polyaniline promotes a switch in the contaminant degradation pathway, leading to opposite trends in observable activity at different pH values. As a class of typical layered metal chalcogenohalides (MeAX, A = O, S, Se, X = Cl, Br, I), FeOCl-PANI is expected to provide new insights into the development of other similar materials. This work could be useful to further understand the H2O2 heterogeneous activation behavior, which is of significance to the application of iron-based heterogeneous Fenton oxidation.

Decrease of dissolved sulfide in sewage by powdered natural magnetite and hematite.

Natural magnetite and hematite were explored to decrease sulfide in sewage, compared with iron salts (FeCl3 and FeSO4). A particle size of magnetite and hematite ranging from 45 to 60µm was used. The results showed that 40mgL-1 of powdered magnetite and hematite addition decreased the sulfide in sewage by 79%and 70%, respectively. The achieved decrease of sulfide production capacities were 197.3, 210.6, 317.6 and 283.3mgSg-1Fe for magnetite, hematite, FeCl3 and FeSO4 at the optimal dosage of 40mgL-1, respectively. Magnetite and hematite provided a higher decrease of sulfide production since more iron ions are capable of being released from the solid phase, not because of adsorption capacity of per gram iron. Besides, the impact on pH and oxidation-reduction potential (ORP) of hematite addition was negligible; while magnetite addition resulted in slight increase of 0.3-0.5 on pH and 10-40mV on ORP. Powdered magnetite and hematite thus appear to be suitable for sulfide decrease in sewage, for their sparing solubility, sustained-release, long reactive time in sewage as well as cost-effectiveness, compared with iron salts. Further investigation over long time periods under practical conditions are needed to evaluate the possible settlement in sewers and unwanted (toxic) metal elements presenting as impurities. CAPSULE ABSTRACT: Powdered magnetite and hematite were more cost-effective at only 30% costs of iron salts, such as FeCl3 and FeSO4 for decreasing sulfide production in sewage.

Biological capacitance studies of anodes in microbial fuel cells using electrochemical impedance spectroscopy.

It is known that cell potential increases while anode resistance decreases during the start-up of microbial fuel cells (MFCs). Biological capacitance, defined as the apparent capacitance attributed to biological activity including biofilm production, plays a role in this phenomenon. In this research, electrochemical impedance spectroscopy was employed to study anode capacitance and resistance during the start-up period of MFCs so that the role of biological capacitance was revealed in electricity generation by MFCs. It was observed that the anode capacitance ranged from 3.29 to 120 mF which increased by 16.8% to 18-20 times over 10-12 days. Notably, lowering the temperature and arresting biological activity via fixation by 4% para formaldehyde resulted in the decrease of biological capacitance by 16.9 and 62.6%, indicating a negative correlation between anode capacitance and anode resistance of MFCs. Thus, biological capacitance of anode should play an important role in power generation by MFCs. We suggest that MFCs are not only biological reactors and/or electrochemical cells, but also biological capacitors, extending the vision on mechanism exploration of electron transfer, reactor structure design and electrode materials development of MFCs.