Study on aging mechanism of waste polystyrene in landfill

doi:10.19491/j.issn.1001-9278.2024.08.016

Abstract

Abstract:

This study simulated the photo⁃thermal aging of discarded polystyrene （PS） in a landfill environment. Firstly， the molecular structure of the aged samples was characterized. The aging process of PS was then studied through X⁃ray diffraction， differential scanning calorimeter tests， and the tool⁃narayanaswamy⁃moynihan （TNM） model， along with molecular dynamics calculations of enthalpy relaxation processes.The results indicated that PS undergoes chain scission after photoaging， with the molecular weight decreasing from 112 200 to around 13 000. This process generates PS oligomers， benzoic anhydride， acetophenone， and methyl benzoate. Furthermore， aging leads to a reduction in PS crystallinity and the glass transition temperature. The enthalpy relaxation changes rapidly in the early stages of aging， gradually slowing down as aging progresses， with a corresponding enthalpy value of 4.2 J/g at equilibrium.

Key words: landfill, waste polystyrene, aging behavior, performance change, theoretical calculation

CLC Number:

TQ325.1⁺2

ZHU Chenxi, CHEN Chenhui, HU Guoming, ZHANG Lei, JIANG Wei. Study on aging mechanism of waste polystyrene in landfill[J]. China Plastics, 2024, 38(8): 100-105.

Figures/Tables 9

老化天数/d	数均分子量/g·mol^-1	重均分子量/g·mol^-1	分子量分布
0	112 200	261 400	2.330
5	34 900	176 300	5.040
10	31 600	162 800	5.147
20	19 800	107 700	5.416
30	17 700	87 000	4.905
40	13 700	63 100	4.606
50	13 400	73 100	5.439
60	13 000	60 100	4.609
70	13 000	55 600	4.270
80	12 900	45 600	3.518

Tab.1. Molecular weight distribution of the PS treated with UV accelerated aging for different time

Fig.1. FTIR spectra of the PS after UV accelerated aging for different time in wavenumber 4 000~500 cm-1

Fig.2. TG curves of the PS before and after UV accelerated aging

Fig.3. XPS spectra of the PS after UV accelerated aging for different time

Fig.4. （a）~（c） 1H⁃NMR and （d） GPC spectra of the PS after UV accelerated aging for different time

Fig.5. （a） WXRD and （b） DSC characterization of the PS after UV accelerated aging for different time

Fig.6. （a） changes of the specific heat at different aging time and （b） enthalpy loss of time function of the PS at 358 K

Fig.7. Molecular dynamics calculation of density change of the PS at 418.15 K and 1 atm

Fig.8. Molecular dynamic simulation of the volume relaxation changes in PS in isothermal process at 308 K and 353 K，respectively

References 31

1	刁晓倩，翁云宣，宋鑫宇，等. 国内外生物降解塑料产业发展现状［J］. 中国塑料，2020， 34 （5）：123⁃135.
	DIAO X Q， WENG Y X， SONG X Y，et al. Current development situation of biodegradable plastic industry In China and abroad［J］. China Plastics， 2020， 34 （5）：123⁃135.
2	Sundqvist⁃Andberg H， Akerman M. Sustainability governance and contested plastic food packaging e an integrative review［J］. Journal of Cleaner Production， 2021， 306：127111.
3	Chen Y， Awasthi A K， Wei F，et al. Single⁃use plastics： production， usage， disposal， and adverse impacts［J］. Science of the Total Environment， 2021， 752：141772.
4	Qi R， Jones D L， Li Z， et al.Behavior of microplastics and plastic film residues in the soil environment： A critical review［J］. Science of the Total Environment， 2020， 703：134772.
5	Jiang H， Zhang Y， Wang H. Surface reactions in selective modification： The prerequisite for plastic flotation［J］. Environmental Science & Technology， 2020， 54 （16）： 9 742⁃9 756.
6	Taghavi N， Udugama I A， Zhuang WQ， et al. Challenges in biodegradation of non⁃degradable thermoplastic waste： From environmental impact to operational readiness［J］. Biotechnology Advances， 2021， 49：107731.
7	Liang K， Liu L， Wang W， et al. Conversion of waste plastic into ordered mesoporous carbon for electrochemical applications［J］. Journal of Materials Research， 2019， 34 （6）： 941⁃949.
8	Ren Z， Gui X， Wei Y， et al. Chemical and photo⁃initiated aging enhances transport risk of microplastics in saturated soils： Key factors， mechanisms， and modeling［J］. Water Research， 2021， 202：117407.
9	Ito T， Hiraki A. Aging phenomena of light⁃emitting porous silicon［J］. Journal of Luminescence， 1993， 57 （1/6）： 331⁃339.
10	Jang B N， Wilkie C A. The thermal degradation of polystyrene nanocomposite［J］. Polymer， 2005， 46 （9）： 2 933⁃2 942.
11	Mao R， Lang M， Yu X， et al. Aging mechanism of microplastics with UV irradiation and its effects on the adsorption of heavy metals［J］. Journal of Hazardous Materials， 2020， 393：122515.
12	Song Y K， Hong S H， Jang M， et al. Combined effects of UV exposure duration and mechanical abrasion on microplastic fragmentation by polymer type［J］. Environmental Science & Technology， 2017， 51 （8）：4 368⁃4 376.
13	Liu X， Sun P， Qu G， et al. Insight into the characteristics and sorption behaviors of aged polystyrene microplastics through three type of accelerated oxidation processes［J］. Journal of Hazardous Materials， 2021， 407：124836.
14	Zhang L K， Chen W Y， Wang H M， et al. Growth factors regional patterned and photoimmobilized scaffold applied to bone tissue regeneration［J］. Journal of Materials Chemistry B， 2020， 8 （48）：10 990⁃11 000.
15	Lang M， Yu X， Liu J， et al. Fenton aging signi ficantly affects the heavy metal adsorption capacity of polystyrene microplastics［J］. Science of the Total Environment， 2020， 722：137762.
16	Narayanaswamy S. A model of structural relaxation in glass［J］. Journal of The American Ceramic Society⁃Narayanaswamy， 1971， 54：491⁃498.
17	Koh Y P， Simon S L. Enthalpy recovery of polystyrene： Does a long⁃term aging plateau exist？［J］. Macromolecules， 2013， 46 （14）：5 815⁃5 821.
18	Cangialosi D， Boucher V M， Alegria A， et al. Direct evidence of two equilibration mechanisms in glassy polymers. Physical Review Letters， 2013， 111 （9）：095701.
19	Weyer S， Huth H， Schick C. Application of an extended Tool⁃Narayanaswamy⁃Moynihan model. Part 2. Frequency and cooling rate dependence of glass transition from temperature modulated DSC［J］. Polymer， 2005， 46 （26）：12 240⁃12 246.
20	Salomon⁃Ferrer R， Case D A， Walker R C. An overview of the amber biomolecular simulation package［J］. WIREs Computational Molecular Science， 2013， 3 （2）：198⁃210.
21	Lü J T， Hu B Z， Hedegard P， et al. Semi⁃classical generalized Langevin equation for equilibrium and nonequilibrium molecular dynamics simulation［J］. Progress in Surface Science， 2019， 94 （1）：21⁃40.
22	Pikkemaat M G， Linssen A B M， Berendsen H J C， et al. Molecular dynamics simulations as a tool for improving protein stability［J］. Protein Engineering， Design and Selection， 2002， 15 （3）：185⁃192.
23	Sprenger K G， Jaeger V W， Pfaendtner J. The general amber force field （GAFF） can accurately predict thermodynamic and transport properties of many ionic liquids［J］. The Journal of Physical Chemistry B， 2015， 119 （18）：5 882⁃5 895.
24	Natali M， Nastasi F， Puntoriero F， et al. Mechanistic insights into light⁃activated catalysis for water oxidation［J］. European Journal of Inorganic Chemistry， 2019，（15）：2 027⁃2 039.
25	Wang C， Zhao Z， Deng X， et al. Ultrafast oxidation of emerging contaminants by novel VUV/Fe₂+/PS process at wide pH range： Performance and mechanism［J］. Chemical Engineering Journal， 2021， 426：131931.
26	Wang M， Yang L， Guo C， et al. Bimetallic Fe/Ti⁃based metal⁃organic framework for persulfate⁃assisted visible light photocatalytic degradation of orange II［J］. Chemistryselect， 2018， 3 （13）：3 664⁃3 674.
27	Mueller A， Becker R， Dorgerloh U， et al. The effect of polymer aging on the uptake of fuel aromatics and ethers by microplastics［J］. Environmental Pollution， 2018， 240：639⁃646.
28	Xiong Y， Zhao J， Li L， et al. Interfacial interaction between micro/nanoplastics and typical PPCPs and nanoplastics removal via electrosorption from an aqueous solution［J］. Water Research， 2020， 184：116110.
29	Wang H， Liu P， Wang M， et al. Enhanced phototransformation of atorvastatin by polystyrene microplastics： Critical role of aging［J］. Journal of Hazardous Materials， 2021， 408：124756.
30	Zhu K， Jia H， Zhao S， et al. Formation of environmentally persistent free radicals on microplastics under light irradiation［J］. Environmental Science & Technology， 2019， 53 （14）： 8 177⁃8 186.
31	Bottino F A， Cinquegrani A R， Di Pasquale G， et al. Chemical modifications， mechanical properties and surface photo⁃oxidation of films of polystyrene （PS）［J］. Polymer Testing， 2004， 23 （4）：405⁃411.

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