Unlocking the potential of recycled waste cooking oil for a sustainable volatile organic compound absorption process

Finding suitable absorbents to remove volatile organic compounds (VOCs) from industrial polluted air remains a pressing scientific and industrial challenge. Most VOCs are hydrophobic and water demonstrates limited mass transfer in this case. In this study, we evaluated the feasibility of using recycled waste cooking oil (RWCO) to absorb VOCs for the first time. We compared the performance of RWCO with that of two deep eutectic solvents (DESs), including a hydrophobic DES prepared from decanoic and dodecanoic acids (C10:C12) and a supramolecular DES based on randomly methylated β-cyclodextrin (RAMEB) and levulinic acid, and with a conventional solvent, propylene glycol (PG), in absorbing four hydrophobic VOCs, toluene, limonene, siloxane D4, and decane. The vapor-liquid partition coefficients (K) of the VOCs alone and in mixture were determined using static headspace gas chromatography (SH-GC). A lab-scale bubbling device was used to measure absorption capacities under simulated industrial conditions. Results from the static method showed that RWCO performed similarly to the hydrophobic DES C10:C12, exhibiting the highest absorption affinities for the tested VOCs, with K values up to 208 000 times lower than in water. Dynamic absorption studies corroborated these results, highlighting RWCO and C10:C12 as the most effective absorbents, with an absorption capacity up to 0.884 mg/g for toluene at 100 ppm. This study also demonstrated that bubbling nitrogen in addition to heating at 60°C reduced regeneration time from 48 hours to 2.5 hours. The RWCO and C10:C12 absorbents retained over 99.5% of their initial absorption capacity after undergoing twelve consecutive absorption-desorption cycles. These results suggest that RWCO could be an effective and sustainable absorbent for VOCs abatement while complying with circular economy concept.