Abstract
The pyrolysis of waste tire has been proposed as an alternative route to its recycling producing residual oils that can be used as fuels. In this work, a physicochemical process to obtain carbon-based dots (CBD) from carbon black (CBL) derivatives of tires is described. For this, the CBL was treated with different acids to produce CBL1 and CBL2 particles suspension. The pH of the suspension was adjusted to 5.6 to precipitate remaining impurities. Afterwards, the supernatant was ultra-centrifuged and the yellow pale solid, the purified CBD obtained by roto evaporation, was characterized by ultraviolet-visible spectrophotometer (UV-Vis), photoluminescence (PL) at 320-380 nm, high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared microscopy (mFTIR), and X-ray photoelectron spectroscopy (XPS). This material showed the typical excitation wavelength dependent emission and a PL quantum yield of 19.29% and was constituted by a well-defined spherical shaped and single sheets of “graphene quantum dots” with undefined shape, with potential applications in optoelectronic and fluorescence imaging devices.
Highlights
The accumulation of industrial, agricultural, and urban waste has substantially increased, while residues of tires are considered a major environmental issue due to the continuous and growing amount corresponding to approximately 50% of all products sold annually
These results show that the carbonbased dots (CBD) have abundant CH2 and CH3 groups, as well as several hydrophilic groups such as carboxyl and hydroxyl groups on their surface, which can explain the PL feature of this material and the presence of graphene quantum dots (GQDs) and carbon quantum dots (CQDs)
The pyrolysis of unserviceable tires has been an alternative to improper disposal of waste tire, as it may contribute to remove these residues from inappropriate locations
Summary
The accumulation of industrial, agricultural, and urban waste has substantially increased, while residues of tires are considered a major environmental issue due to the continuous and growing amount corresponding to approximately 50% of all products sold annually (around 1.5 billion tires) Another problem is the severe environmental damage caused by their inadequate disposal, affecting the environment, e.g., water contamination, emission of harmful pollutants such as SO2, (NO)x, and several organic compounds.[1,2]. In this context, the pyrolysis, a thermal degradation process carried out under an inert atmosphere from moderate to high temperatures (normally 400-900 °C) has proven to be a viable alternative to recycle such residues. Exploitation of such aspects can be a promising alternative for removing scrap tires from environment.[3]
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