Desulfurization of Vulcanized Rubber Particles Using Biological and Chemical Methods

Abstract

Currently, recycling or degradation treatments for tires are an enormous challenge. Despite efforts to dispose of or recycle it, rubber waste is increasing year by year worldwide. To create a rubber-recycling system, several researchers have proposed tire desulfurization. In this study, we compare two methods: one biological, using Acidobacillus ferroxidans in shake 250 mL flask experiments, and one chemical using, for the first time, microwaves and an aqueous solution. The results of these methods were analyzed through sulfate quantification, cross-linking differences, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy disperse spectroscopy (SEM-EDS). We observed that the amount of sulfates generated by the chemical system was 56 mg / L, which was 10-times higher than the biological system, which generated 5.3 mg / L. Similarly, after cross-linking studies, a 36% higher decrease after the chemical treatment was observed. When using FTIR analysis, the disappearance of characteristic bands corresponding to functional groups containing sulfur bonds was observed by treating the sample with both desulfurization mechanisms. Morphological changes on the rubber surface structure was also demonstrated by SEM-EDS analysis with the appearance of holes, cracks and changes in the porosity of the material. This work analyzed two different non-aggressive desulfurization mechanisms that might be used as sustainable methods for rubber recycling processes.

The value of different recycling technologies for waste rubber tires in the circular economy—A review

“…In the same study the selectivity of samples treated at 140-160 • C was much improved but the decrease in the crosslink density was only moderate. Another study showed promising desulfurization rates at temperatures of 200 • C or more, but again also experienced shortening of the polymer as a result of C-C bond breakage (Valdés et al, 2021). Another apparent limitation of the microwave method is that only rubber with sufficient polarity is susceptible to the microwave radiation (Asaro et al, 2018).…”

Degradable Elastomers: Is There a Future in Tyre Compound Formulation?

“…Progress in biobased rubber has been reported [ 20 , 21 , 22 ]. Moreover, interesting research has been carried out on rubber desulfurization [ 23 , 24 , 25 , 26 ].…”