Heterogeneous Fenton-like surface properties of oxygenated graphitic carbon nitride.

The photo-Fenton activity of graphitic carbon nitride (g-C3N4) has been widely studied, nevertheless, its Fenton-like catalytic behavior in the dark has not yet been demonstrated. In the present work, it is shown that oxygenated g-C3N4 obtained at different temperatures (500-600 °C) can degrade indigo carmine with hydrogen peroxide in the dark by a reaction similar to a conventional Fenton's reaction. Based on an extensive characterization of g-C3N4, we conclude that Fenton-like activity is directly related to the oxygenated functional groups on g-C3N4 structure, mainly by -OH functional groups. Oxygenated functional groups (e.g., hydroquinone-like groups) can reduce the H2O2 and generate oxidizing hydroxyl radicals, just like in the Fenton reaction performed by metals. In addition to new information on g-C3N4 surface reactivity revealed by this study, the metal-free oxygenated g-C3N4 catalyst may be an alternative to traditional metal catalysts used in Fenton-like reactions for advanced oxidation.

Development of non-enzymatic glucose sensor using recycled cobalt from cell phone Li-ion batteries.

This article aims to present an alternative to recycling of spent Li-ion batteries applied to electrochemical sensor manufacturing. The cobalt, from cathode of Li-ion batteries, was recovered by electrodeposition onto AISI 430 stainless steel substrate and applied as glucose sensor. The composition of cathode utilized was obtained by AAS measures and corresponds to LiNi0,40Co0,60O2. Despite this composition, in the cobalt electrodeposition onto AISI 430 stainless steel the Ni is less of 1.7% (w/w) due the anomalous electrodeposition. The sensitivity of cobalt electrode for glucose detection is 70.2 µA/mmol cm(2) and the linear range is 1-10 mmol/L. This result shows that the Co electrodeposited onto AISI 430 stainless steel is a promissory and low-cost non-enzymatic glucose sensor.

Chemical recycling of cell phone Li-ion batteries: Application in environmental remediation.

This paper presents, for the first time, the recycling and use of spent Li-ion battery cathode tape as a catalyst in the degradation of an organic dye. In our proposal, two major environmental problems can be solved: the secure disposal of cell phone batteries and the treatment of effluents with potentially toxic organic dyes. The spent Li-ion battery cathode investigated in this paper corresponds to 29% of the mass of Li-ion batteries and is made up of 83% LiCoO2, 14.5% C and less than 2.5% Al, Al2O3 and Co3O4. The use of spent Li-ion battery cathode tape increased the degradation velocity constant of methylene blue in the absence of light by about 200 times in relation to pure H2O2. This increase can be explained by a reduction in the activation energy from 83 kJ mol(-1) to 26 kJ mol(-1). The mechanism of degradation promoted by LiCoO2 is probably related to the generation of superoxide radical (O2(-)). The rupture of the aromatic rings of methylene blue was analyzed by ESI-MS.