Adsorption of naphthalene and its derivatives onto high-density polyethylene microplastic: Computational, isotherm, thermodynamic, and kinetic study

• Published in: Environmental pollution (1987) Vol. 318; p. 120919
• Main Authors: Funari, Ronaldo Antunes, Frescura, Lucas Mironuk, de Menezes, Bryan Brummelhaus, Bastos, Ana Flávia de Moraes, da Rosa, Marcelo Barcellos
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2023
• Subjects: Adsorption; Adsorption mechanisms; Environmental Pollutants; Functional groups; HDPE microplastics; Humans; Hydrogen-Ion Concentration; Kinetics; Microplastics - chemistry; Nap derivatives; Naphthalenes - chemistry; Plastics; Polycyclic Aromatic Hydrocarbons - analysis; Polyethylene; Thermodynamics; Water Pollutants, Chemical - analysis; Nap derivatives; Adsorption mechanisms; HDPE microplastics; Functional groups
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2022.120919

Microplastics (MP) have received great attention due to the mass-produced residues discharged into the environment. MP are ideal for adhering to organic pollutants that can be easily dispersed, thus posing risks to human health. Furthermore, little has been reported on how different functional groups in polycyclic aromatic hydrocarbons (PAH) derivatives influence the adsorption behavior on MP. To better understand this process, groups methyl (–CH3) and hydroxyl (–OH) were selected and commercial and waste high-density polyethylene (HDPE, ≤ 1 mm) were used as adsorbents, and Naphthalene (Nap), 1-Methyl-Naphthalene (Me-Nap) and α-Naphthol as adsorbates. The results showed different behaviors for nonpolar and polar adsorbates. Dispersion forces were the main type of interaction between HDPE and Nap/Me-Nap, while dipole-induced dipole forces and H-bonding were the chief interactions involving MP and polar compounds. Regardless the HDPE source, Nap and Me-Nap have a Type III isotherm, and α-Naphthol presents a Type II isotherm. Nap and Me-Nap fitted to Freundlich isotherm of an unfavorable process (n = 2.12 and 1.11; 1.87 and 1.31, respectively), with positive values of ΔH° (50 and 77.17; 66 and 64.63 kJ mol−1) and ΔS° (0.070 and 0.0145; 0.122 and 0.103 kJ mol−1) for commercial and waste MP, respectively. Besides, the adsorption isotherm of α-Naphthol on commercial and waste HDPE fitted to the Langmuir model (Qmax = 42.5 and 27.2 μmol g−1, respectively), presenting negative values of ΔH° (−43.71 and −44.10 kJ mol−1) and ΔS° (−0.037 and −0.025 kJ mol−1). The adsorption kinetic study presents a nonlinear pseudo-second-order model for all cases. The K2 values follow the order Me-Nap > Nap >α-Naphthol in both MP. Therefore, this experimental study provides new insights into the affinity of PAH derivatives for a specific class of MP, helping to understand the environmental fate of residual MP and organic pollutants. [Display omitted] •Methyl groups increase LogKow favoring adsorption on HDPE.•Polar groups make PAH adsorption favorable with increasing temperatures.•Nonpolar PAH adsorption is favored on low temperatures.•Polyethylene MP can accumulate and carry PAH in the aquatic environment.