Deep eutectic solvent-assisted bacterial devulcanization, detoxification, and degradation of waste tyre rubber

Area of Science:

• Materials Science
• Environmental Science
• Microbiology

Background:

• Waste tyre rubber (WTR) biodegradation is limited by sulfur compounds and additives.
• Microbial mineralization of rubber polymers is inefficient due to these constraints.
• Developing effective WTR recycling methods is crucial for environmental sustainability.

Purpose of the Study:

• To develop a hybrid chemi-biological approach for enhanced WTR biodegradation.
• To investigate the efficacy of choline chloride/urea (ChCl/Ur) deep eutectic solvent (DES) pretreatment.
• To improve the bioavailability of rubber polymers for microbial degradation.

Main Methods:

• Ground tyre rubber (GTR) underwent thermochemical pretreatment with a reusable ChCl/Ur DES.
• Pretreated GTR was subjected to biological treatment using *Rhodococcus rhodochrous* RPK1 for 28 days.
• Structural, elemental, and thermal analyses were performed to assess degradation.

Main Results:

• DES pretreatment significantly improved biodegradation efficiency compared to biological treatment alone.
• Partial devulcanization, sulfur crosslink cleavage, and zinc additive removal were confirmed.
• Crosslink density decreased by 43.6%, indicating enhanced rubber polymer accessibility.

Conclusions:

• The hybrid DES pretreatment effectively overcomes limitations in WTR biodegradation.
• This approach enhances rubber bioavailability for microbial action.
• The strategy offers a viable pathway for sustainable waste tyre rubber recycling.