Efficient photo-assisted Fenton oxidation treatment of multi-walled carbon nanotubes

Abstract

In this paper, a new and efficient way to oxidize and functionalize the multi-walled carbon nanotubes (MWNTs) has been developed by using a combination of ultraviolet (UV) irradiation and Fenton oxidation process, namely UV/Fenton oxidation treatment. Comparing with conventionally individual Fenton oxidation treatment of MWNTs, UV/Fenton combined treatment improved the etching rates and efficiencies and hence reduced the time for surface modification of MWNTs, which was proved to be an effective method in etching and functionalizing CNTs. The formation of new functional groups, structural changes and thermal stability during oxidation period were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and could be clarified by thermogravimetric analysis (TGA), which showed that it was under UV irradiation conditions that MWNTs could be rapidly functionalized with hydroxyl, carbonyl and carboxyl groups in the presence of Fenton reagents, originating from the increase in the gross HO• concentration and the existent synergetic effect when using UV irradiation combing with Fenton oxidation process. Introduction of such new oxygen-containing functional groups was attributed to attacks of HO• on defect sites and unsaturated bonds of C=C in the MWNTs sample, which should play an important role in accounting for the FTIR and Raman spectral changes.multi-walled carbon nanotubes (MWNTs), functionalization, UV/Fenton combined oxidation treatment As a consequence of their superior physicochemical properties and large potential applications, carbon nanotubes (CNTs) have opened new frontiers in the field of nanotechnology and nanoscience [1][2][3] . However, graphite and similar graphene including CNTs are well known to be chemically quite inert and insoluble in most organic and aqueous solvents, which limit their solution-based manipulation and processability, greatly hindering their wide application in practical work. So recently the modification or functionalization of CNTs has attracted great attention, primarily to improve their solubility and dispersibility in various solvents especially in aqueous solutions. Several ways of dispersion and solubilization have been explored and can be roughly divided into two approaches. One is noncovalent functionalization of CNTs with surfactants, polymers and biological macromolecules, where the mechanism of dispersion is based on adsorption, wrapping, π-stacking and hydrophobic/ π-π interactions [4][5][6][7][8][9] ; the other to render CNTs soluble and dispersible is convalent attachment of organic functional groups, which can be referred to as convalent functionalization. Two main strategies are currently used to attach functional groups onto CNTs. In the first case, the required functional groups are attached directly onto CNTs by using 1,3-dipolar cycloaddition, Birch reduction, and reactions with nitrenes, radicals and carbenes, etc. [10][11][12][13][14] . In the second one, a simple bridgehead func-

Degradation of 14C-labeled few layer graphene via Fenton reaction: Reaction rates, characterization of reaction products, and potential ecological effects

“…These reactive oxygen species are considered the critical factor in the transformation of the FLG (Pignatello et al, 2006). These generated reactive oxygen species could attack and destroy FLG to form defect sites, and finally decompose FLG into CO 2 (Fan et al, 2007;Zhou et al, 2012). The H 2 O 2 concentration is directly proportional to the generation rate of ROS in Fenton-like reaction (Ensing et al, 2003;Neyens and Baeyens, 2003).…”

“…It has been developed and applied in wastewater treatment, especially in treating aromatic organic pollutants (Ensing et al, 2003;Neyens and Baeyens, 2003;Pignatello et al, 2006). Recently, the Fenton and photoFenton reactions were found to have significant implication on the treatment of carbon nanotubes (CNTs) (Allen et al, 2009;Fan et al, 2007) and GO (Bai et al, 2014;Zhou et al, 2012). Researchers have demonstrated that this simple and economical approach could effectively degrade CNTs and GO into CO 2 and some intermediate products which largely consist of adjacent aromatic rings with carboxylic acid groups (Allen et al, 2009;Bai et al, 2014;Zhou et al, 2012).…”

Environmental degradation of carbon nanomaterials and related degradation mechanisms

“…除此之 外, 含有大离域π键的CNTs具有较强的光反应活性, 吸 收光后表面电子发生跃迁, 并被氧气等物质接受形成 超氧自由基等活性氧促使CNTs降解转化 [85] . •OH是CNMs转化的关键因素 [67] . 以CNTs为例…”

“…CNTs在紫外光照作用下首先转化为氧化中间产物, 进一步反应形成残余碎片和小分子物质. 光照诱发 CNTs降解主要有两个途径: ① CNTs在光照作用下产生电子-空穴对导致CNTs还原 [66] ; ② 光芬顿反应产生羟基自由基, 与 CNTs发生亲电加成反应 [67] (网络版彩图) [66], including the reduction of CNTs; ② Electrophilic addition between CNTs and hydroxyl radicals, which are produced by photoassisted Fenton process [67] (color online).…”

Kinetic calculations for the thermal decomposition of calcium propionate under non-isothermal conditions

“…Thermogravimetric (TG) analysis [7][8][9] has been widely used for the preliminary assessment of the combustion/pyrolysis behavior of fossil fuel, biomass fuel, sewage sludge and other organic/inorganic compounds. From TG-DTG (differential thermogravimetry) curves, the initial and final mass loss temperatures, the maximum mass loss rate and its corresponding temperature can be deduced.…”