Upcycling of the Used Cigarette Butt Filters through Pyrolysis Process: Detailed Kinetic Mechanism with Bio-Char Characterization

Abstract

Thermo-chemical conversion via the pyrolysis of cigarette butt (CB) filters was successfully valorized and upcycled in the pre-carbonization and carbonization stages. The pre-carbonization stage (devolatilization) of the precursor material (cellulose acetate filter, r-CAcF) was analyzed by micro-scale experiments under non-isothermal conditions using TG-DTG-DTA and DSC techniques. The results of a detailed kinetic study showed that the decomposition of r-CAcF takes place via complex mechanisms, including consecutive reaction steps and two single-step reactions. Consecutive stages include the α-transition referred to as a cellulose polymorphic transformation (cellulose I → II) through crystallization mechanism changes, where a more thermodynamically ordered system was obtained. It was found that the transformation rate of cellulose I → II (‘cellulose regeneration’) is strongly affected by the presence of alkali metals and the deacetylation process. Two single-step reactions showed significant overlapping behavior, which involves a nucleation-controlled scission mechanism (producing levoglucosan, gaseous products, and abundant radicals) and hydrolytic decomposition of cellulose by catalytic cleavage of glycosidic bonds with the presence of an acidic catalyst. A macro-scale experiment showed that the operating temperature and heating rate had the most notable effects on the total surface area of the manufactured carbon. A substantial degree of mesoporosity with a median pore radius of 3.1695 nm was identified. The presence of macroporosity on the carbon surface and acidic surface functional groups was observed.

Combustion Behavior of Cellulose Ester Fibrous Bundles from Used Cigarette Filters: Kinetic Analysis Study

“…The reactions may proceed to a termination stage, ultimately resulting in the toxic carbonyl-containing products. However, observing our case, the termination phase can be concluded according to the values of the activation energies (Ea) obtained in the later part of Region A. Namely, the presence of oxygen clearly enables chemical transitions that are not possible in an inert atmosphere, referring to our previously published work [12]. In line with this, the thermo-chemical conversion study may confirm an ability for oxygen to unlock an entirely new network of chemical conversions, which proceed through a lowtemperature reaction pathway.…”

Transforming Cigarette Wastes into Oxygen Reduction Reaction Electrocatalyst: Does Each Component Behave Differently? An Experimental Evaluation

“…These elements come from additives introduced in cigarette components for different purposes. For instance, Ti derives from the introduction of TiO 2 as a whitening agent in the paper or to reduce the luster among the filter fibers, [49,58] while Ca and K from CaCO 3 and potassium carboxylates are added as flame retardants. [58][59][60] The presence of Fe in the pristine materials is justified by the addition of iron oxide additives as catalysts to convert CO into CO 2 , [51] whereas the occurrence of Cr can have multiple origins, including the fertilizers used for tobacco cultivation.…”

“…For instance, Ti derives from the introduction of TiO 2 as a whitening agent in the paper or to reduce the luster among the filter fibers, [49,58] while Ca and K from CaCO 3 and potassium carboxylates are added as flame retardants. [58][59][60] The presence of Fe in the pristine materials is justified by the addition of iron oxide additives as catalysts to convert CO into CO 2 , [51] whereas the occurrence of Cr can have multiple origins, including the fertilizers used for tobacco cultivation. [61] Anyway, in the XRF of the final electrocatalysts (Figure S4), Fe results to be almost the only metal, obviously derived from FePc precursor whereas most of the aforementioned impurities do not appear in the final electrocatalysts, probably due to the acid washing, which leached out many metals found in the pristine materials.…”

Chemical Recycling of Cellulose Acetate Eyewear Industry Waste by Hydrothermal Treatment

“…Hydrothermal treatments (HT) are thermochemical processes occurring at medium temperature and high pressure in the presence of water as solvent/reagent in sub and supercritical states. , The hydrothermal liquefaction process has been successfully applied in the chemical recycling of plastics to produce monomers, chemicals, and fuels . The recycling of cellulose acetate by thermochemical processes was already addressed by many authors, especially the pyrolysis of cigarette filters which are mainly made of cellulose acetate with the aim of producing chemicals, fuels, and porous carbon material. − Pyrolysis of cigarette butt filters was investigated by Jankovic et al for the production of porous char having characteristics of a macroporous material with developed mesoporosity suitable to be used in wastewater treatments . The thermochemical degradation of cellulose acetate by HT is poorly investigated, Combs and Woodstone filed a patent on the recovery of a general cellulose acetate waste by hydrolysis in the presence of a hydrolyzing agent, acetic acid, to obtain valuable products such as glucose molecules and reduce the amount of solid which needs to be landfilled .…”

“…13−16 Pyrolysis of cigarette butt filters was investigated by Jankovic et al for the production of porous char having characteristics of a macroporous material with developed mesoporosity suitable to be used in wastewater treatments. 17 The thermochemical degradation of cellulose acetate by HT is poorly investigated, Combs and Woodstone filed a patent on the recovery of a general cellulose acetate waste by hydrolysis in the presence of a hydrolyzing agent, acetic acid, to obtain valuable products such as glucose molecules and reduce the amount of solid which needs to be landfilled. 18 However, to the best of the authors' knowledge, no works are present on the chemical recycling of the cellulose acetate waste of the eyewear industry with the aim of diethyl phthalate and acetic acid recovery.…”