Revealing the sorption mechanisms of carbamazepine on pristine and aged microplastics with extended DLVO theory

Yunhai Zhang; Zihao Chen; Yuexiao Shi; Qing Ma; Haoran Mao; Ying Li; Hao Wang; Yongjun Zhang

doi:10.1016/j.scitotenv.2023.162480

Revealing the sorption mechanisms of carbamazepine on pristine and aged microplastics with extended DLVO theory

Sci Total Environ. 2023 May 20:874:162480. doi: 10.1016/j.scitotenv.2023.162480. Epub 2023 Feb 28.

Authors

Yunhai Zhang¹, Zihao Chen¹, Yuexiao Shi¹, Qing Ma¹, Haoran Mao¹, Ying Li¹, Hao Wang¹, Yongjun Zhang²

Affiliations

¹ School of Environmental Science and Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China.
² School of Environmental Science and Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China. Electronic address: y.zhang@njtech.edu.cn.

PMID: 36858211
DOI: 10.1016/j.scitotenv.2023.162480

Abstract

The co-occurrence of microplastics (MPs) and organic contaminants in aquatic environment can complexify their environmental fate via sorption interactions, especially when the properties of MPs can even vary due to the aging effect. Thus, quantitatively clarifying the sorption mechanisms is required to understand their environmental impacts. This study selected popularly occurring carbamazepine (CBZ) and four types of MPs as model systems, including polyethylene, polyvinyl chloride, polyethylene terephthalate and polystyrene in their pristine and aged forms, to investigate the sorption isotherms, kinetics, and desorption. The variation of MPs during the aging process were analyzed with scanning electron microscopy, contact angle, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. It was found that the aging process elevated the sorption capacity and intensified the desorption hysteresis of CBZ on MPs via increasing the surface roughness, decreasing the particle size, and altering the surficial chemistry of all MPs. The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory was innovatively applied hereby to calculate the interfacial free energies and revealed that the hydrophobic interaction was significantly lessened after aging for all MPs with the slightly enhanced van der Waals interaction. Then the total interfacial free energies were dropped down for all MPs, which resulted in their declined specific sorption capacity. This work reveals the sorption mechanisms of CBZ on pristine and aged MPs with XDLVO and provides a useful reference to study the sorption of other neutral organics onto MPs.

Keywords: Aging; Carbamazepine; Desorption; Microplastics; Sorption; XDLVO.