Adsorption mechanism of typical monohydroxyphenanthrene on polyvinyl chloride microplastics

doi:10.3724/SP.J.1123.2020.09005

Abstract

Abstract:

To enrich data related to the interaction mechanism between microplastics and organic pollutants, in this study, 3-hydroxy-phenanthrene (3-OHP, C₁₄H₁₀O), a phenanthrene derivative, was selected as a representative pollutant, and polyvinyl chloride (PVC) microplastics were chosen as the research objects. We investigated the adsorption behavior of 3-OHP on PVC microplastics in aqueous solutions and explored the adsorption mechanism in detail. The PVC microplastics were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The standard curves of the ultraviolet (UV) absorption spectrum of the target pollutant were obtained using a UV spectrophotometer. The fitting coefficient values of all standard curves were higher than 0.99 (R²>0.99). To ensure the accuracy of the UV absorption spectrum, the pollutant concentration gradient was set according to the absorbance (Abs) values, which were higher than 0.438. The measured concentrations were calculated using a standard curve equation. The adsorption mechanism of 3-OHP on PVC microplastics in an aqueous solution was studied by combining adsorption models (adsorption kinetics model, adsorption isotherm model, and adsorption thermodynamics model) and density functional theory (DFT) calculations. The results are as follows: (1) From the adsorption kinetics experiment, the pseudo-second-order kinetic model had the best fitting degree, and the fitting coefficient of adsorption kinetics was 0.998 (R²=0.998). Hence, 3-OHP adsorption on PVC microplastics may be attributed to surface adsorption and external liquid film diffusion; the equilibrium adsorption amount was 36.866 μg/g after 24 h. (2) The adsorption isotherm experiment showed that the Langmuir and Freundlich isotherm models were more suitable for describing the adsorption mechanism of 3-OHP adsorption on PVC microplastics because of the satisfactory fitting coefficient (R ²=0.956 and 0.907), suggesting that the adsorption mode was mainly single-layer adsorption with a small amount of multilayer adsorption. The maximum adsorption amount of 3-OHP adsorption on PVC microplastics was 408 μg/g; (3) the adsorption thermodynamics results showed that the adsorption efficiency of 3-OHP adsorption on PVC microplastics decreased with increasing temperature, indicating that the adsorption of 3-OHP on PVC microplastics was a spontaneous and exothermic adsorption process; (4) the salinity experiment results showed that salinity had little effect on the adsorption efficiency of 3-OHP on PVC microplastics; (5) DFT calculations showed that PVC had a relatively low binding energy to 3-OHP. Therefore, we suggest that the main adsorption mechanism of 3-OHP on PVC microplastics may be the hydrophobic effect; weak hydrogen bonding, halogen bonding, and π-π conjugate action could also play a role in 3-OHP adsorption on PVC. These results reveal the interaction mechanism between PVC microplastics and organic chemicals, and enhance our understanding of the environmental behavior of PVC microplastics in aqueous solutions. To serve as a reference in scientific evaluations of the environmental impact of microplastics, future studies should focus on obtaining toxicological data for the microplastics.

Key words: polyvinyl chloride, 3-hydroxyphenanthrene, ultraviolet spectrophotometry (UV), adsorption, mechanism

CLC Number:

O658

BAO Zhenzong, CHEN Zhifeng, QI Zenghua, WANG Guangzhao, CAI Zongwei. Adsorption mechanism of typical monohydroxyphenanthrene on polyvinyl chloride microplastics[J]. Chinese Journal of Chromatography, 2021, 39(8): 870-877.

Figures/Tables 8

Fig. 1 Characterization of polyvinyl chloride (PVC) microplastics a, b: SEM images of PVC microplastics; c. X-ray diffraction (XRD) pattern of PVC microplastics; d. FT-IR image of PVC microplastics before and after adsorption of 3-hydroxy-phenanthrene (3-OHP).

Table 1 Fitting parameters for adsorption isotherm of PVC microplastics and 3-OHP

Langmuir				Freundlich				Temkin						Dubinin-Radushkevich
R²	K_L	q_m/(mg/g)		R²	q_m/(mg/g)	β		ε	B	a_T	b_T	n		R²		q_m/(mg/g)	β	ε
0.956	3×10^-4	0.408		0.907	0.094	4.89×10^-4		211.838	0.826	0.057	2999	1.21		0.871		0.094	4.89×10^-4	211.838

Fig. 2 Adsorption kinetics of PVC microplastics and 3-OHP a. pseudo-first order kinetics model; b. pseudo-second order kinetics model; c. intra-particle diffusion model; d. liquid film diffusion model. Temperature: 298 K; speed: 150 r/min. Mass concentration of the initial pollutant: 1.5 mg/L; mass concentration of PVC: 15 g/L.

Table 2 Fitting parameters for adsorption kinetics of PVC microplastics and 3-OHP

Kinetics model	q_e,exp /(μg/g)	equation	R²	k	q_e,cal/(μg/g)
Pseudo-first order	36.866	y=34.336×(1-0.238x)	0.917	1.436 g/(mg·min)	34.336
Pseudo-second order	36.866	y=26.538x+22.19	0.998	0.0279 g/(mg·min)	37.764
Intra-particle diffusion		y=2.140x+23.311	0.791	2.140 mg/(g·min^0.5)
Liquid film diffusion		y=0.190x+2.060	0.602	-

Fig. 3 Adsorption thermodynamics of PVC microplastics and 3-OHP (n=3) Speed: 150 r/min; mass concentration of the initial pollutant: 1.5 mg/L; mass concentration of PVC=15 g/L.

Table 3 Fitting parameters for adsorption thermodynamics of PVC microplastics and 3-OHP

ln k_c				ΔG/(kJ/mol)			ΔH/ (kJ/mol)	ΔS/ (kJ/mol)
25 ℃	35 ℃	45 ℃		25 ℃	35 ℃	45 ℃	ΔH/ (kJ/mol)	ΔS/ (kJ/mol)
4.389	4.426	4.611		-10.875	-11.334	-12.192	-10.15	-0.65831

Fig. 4 Adsorption mechanism of PVC microplastics and 3-OHP a. Interaction pattern between PVC microplastics and 3-OHP; b. effect of salinity on the adsorption of 3-OHP on PVC microplastics (n=3).

Table 4 Theoretical calculation parameters of PVC microplastics and 3-OHP

Molecule	Total DFT energy (DFT-E)/eV	Binding energy (ΔE)/eV
PVC	-165.692
3-OHP	-170.417
PVC+3-OHP	-336.584	-0.475

References

[1]	Mani T, Hauk A, Walter U, et al. Sci Rep-UK, 2015,5:17988
[2]	Deng Y X, Lei K, An L H, et al. Bulletin of Chinese Academy of Sciences, 2018,33(10):1042
[2]	邓义祥, 雷坤, 安立会, 等. 中国科学院院刊, 2018,33(10):1042
[3]	Avio C G, Gorbi S, Regoli F. Mar Environ Res, 2017,128:2
[4]	Wright S L, Kelly F J. Environ Sci Technol, 2017,51(12):6634
[5]	Jambeck J R, Geyer R, Wilcox C, et al. Science, 2015,347(6223):768
[6]	Derraik J G B. Mar Pollut Bull, 2002,44(9):842
[7]	Huffer T, Hofmann T. Environ Pollut, 2016,214:194
[8]	Barnes D K, Galgani F, Thompson R C, et al. Philos Tr Soc B, 2009,364(1526):1985
[9]	Vaughan R, Turner S D, Rose N L. Environ Pollut, 2017,229:10
[10]	Xiong X, Zhang K, Chen X, et al. Environ Pollut, 2018,235:899
[11]	Gray A D, Wertz H, Leads R R, et al. Mar Pollut Bull, 2018,128:223
[12]	Tuncer S, Artuz O B, Demirkol M, et al. Mar Pollut Bull, 2018,135:283
[13]	Zhu X T, Yi J, Qiang L Y, et al. Environmental Science, 2018(5):2067
[13]	朱晓桐, 衣俊, 强丽媛, 等. 环境科学, 2018(5):2067
[14]	Zhang K, Su J, Xiong X, et al. Environ Pollut, 2016,219:450
[15]	Free C M, Jensen O P, Mason S A, et al. Mar Pollut Bull, 2014,85(1):156
[16]	Wang W, Ndungu A W, Li Z, et al. Sci Total Environ, 2017,575:1369
[17]	Su L, Xue Y, Li L, et al. Environ Pollut, 2016,216:711
[18]	Caron A G M, Thomas C R, Berry K L E, et al. Mar Pollut Bull, 2018,127:743
[19]	Rainieri S, Conlledo N, Larsen B K, et al. Environ Res, 2018,162:135
[20]	Boerger C M, Lattin G L, Moore S L, et al. Mar Pollut Bull, 2010,60(12):2275
[21]	Murray F, Cowie P R. Mar Pollut Bull, 2011,62(6):1207
[22]	Brillant M G S, MacDonald B A. J Exp Mar Biol Ecol, 2000,253(2):211
[23]	Anderson J C, Park B J, Palace V P. Environ Pollut, 2016,218:269
[24]	Liu L, Fokkink R, Koelmans A A. Environ Toxicol Chem, 2016,35(7):1650
[25]	Mizukawa K, Takada H, Ito M, et al. Mar Pollut Bull, 2013,70(1):296
[26]	Karapanagioti H K, Endo S, Ogata Y, et al. Mar Pollut Bull, 2011,62(2):312
[27]	Narvaez Valderrama J F, Baek K, Molina F J, et al. Environ Sci-Proc Imp, 2016,18(1):87
[28]	Brennecke D, Duarte B, Paiva F, et al. Estuar Coasta Shelf S, 2016,178:189
[29]	Abdel-Shafy H I, Mansour M S M. J Petro Egyp, 2016,25(1):107
[30]	Choi S D, Kwon H O, Lee Y S, et al. J Hazard Mater, 2012,241/242:252
[31]	He M C, Sun Y, Li X R, et al. Chemosphere, 2006,65(3):365
[32]	Li J, Luo C, Song M, et al. Environ Sci Technol, 2017,51(6):3391
[33]	Liu G, Zhu Z, Yang Y, et al. Environ Pollut, 2019,246:26
[34]	Wan T, Lu S H, Cheng W, et al. Environ Pollut, 2019,249:398
[35]	Qiao J S, Kong X, Hu Z X, et al. Nat Commun, 2014,5:4475
[36]	Dong X F, Zheng M G, Qu L Y, et al. Mar Pollut Bull, 2019,144:129
[37]	Liu R X, Tian J Y, Gong X X, et al. Desalin Water Treat, 2017,91:287
[38]	Weng S F. Fourier Transform Infrared Spectroscopy Analysis. 2nd ed. Beijing: Chemical Industry Press, 2010
[38]	翁诗甫. 傅里叶变换红外光谱分析. 2版. 北京: 化学工业出版社, 2010
[39]	Hyder A H M G, Begum S A, Egiebor N O J. Environ Chem Eng, 2015,3(2):1329
[40]	Utomo H D, Hunter K A. Environ Technol, 27(1), 25
[41]	Weber W J, McGinley P M, Katz L E. Water Res, 1991,25(5):499
[42]	Wu J, Xu P, Chen Q, et al. Chemosphere, 2020,253:126706
[43]	Bakir A, Rowland S J, Thompson R C. Mar Pollut Bull, 2012,64(12):2782
[44]	Wang W, Wang J. Chemosphere, 2018,193:567
[45]	Wang F, Shih K M, Li X Y. Chemosphere, 2015,119:841
[46]	Guo X, Yin Y, Yang C, et al. Ecotox Environ Safe, 2018,152:16
[47]	Liu F, Guo Z, Zheng S, et al. Chem Eng J, 2012,183:244
[48]	Li H Q, Huang G H, An C J, et al. Ind Eng Chem Res, 2013,52(45):15923
[49]	Hao J, Zhang Q X, Chen P, et al. Environ Sci Nano, 2019,6(11):3374
[50]	Huffer T, Weniger A K, Hofmann T. Environ Pollut, 2018,236:218
[51]	Zhang H, Wang J, Zhou B, et al. Environ Pollut, 2018,243(Pt B):1550
[52]	Zhang K N, Li J, Li X Q, et al. Environmental Chemistry, 2017,36(12):2531
[52]	张凯娜, 李嘉, 李晓强, 等. 环境化学, 2017,36(12):2531
[53]	Pan B, Ning P, Xing B S. Environ Sci Pollut Res, 2008,15(7):554
[54]	Wang Y Q, Zhang H M, Cao J, et al. J Photoch Photobio B, 2014,138:182
[55]	Li Q, Han C, Horton S R, et al. ACS Nano, 2012,6(1):566
[56]	Velzeboer I, Kwadijk C J, Koelmans A A. Environ Sci Technol, 2014,48(9):4869
[57]	Zhou D, Chen B, Wu M, et al. Sci Total Environ, 2014,497/498:665
[58]	Zhou X, Wei J, Liu K, et al. Langmuir, 2014,30(46):13861
[59]	Shah M B, Liu J B, Zhang Q H, et al. ACS Chem Biol, 2017,12(5):1204
[60]	Yamate T, Kumazawa K, Suzuki H, et al. ACS Macro Letters, 2016,5(7):858
[61]	Liu X, Zheng M, Wang L, et al. Mar Pollut Bull, 2018,135:581
[62]	Wu P F, Cai Z W, Jin H B, et al. Sci Total Environ, 2019,650:671