Agro-Environmental Protection Institute, Ministry of Agriculture of China, Tianjin, 300191, China.
Department of Civil and Environmental Engineering, Shantou University, Shantou, 515063, China.
Environ Pollut. 2019 Nov;254(Pt A):112950. doi: 10.1016/j.envpol.2019.07.118. Epub 2019 Jul 23.
Microplastics exhibit active environmental behavior and unique surface characteristics, and act as carriers for the migration of trivalent arsenic (As(III)) in the environment. Herein, the mechanism by which polytetrafluoroethylene (PTFE) microplastic particles adsorb As(III) is systematically determined. The larger the size of PTFE particles, the smaller the specific surface area, the higher the point of zero charge (PZC), and the more unfavorable adsorption of As(III); the highest adsorption amount can reach 1.05 mg g. The adsorption process can be divided into three stages by the intraparticle diffusion model: external mass transfer, intraparticle diffusion, and dynamic equilibrium, of which the external mass transfer stage is the adsorption rate-limiting stage. The Langmuir isotherm model better represented the equilibrium adsorption results. The adsorption of As(III) by PTFE was an exothermic process, and because the increase in temperature broke the hydrogen bond, the amount of adsorption was decreased, which was not conducive to spontaneous adsorption. In the pH range of 3-7, as the pH value increased, the amount of As(III) adsorbed by PTFE gradually decreased, which may be related to the change in PZC for PTFE and the protonation of As(III). The H on the surface hydroxyl group of the PTFE exhibited a very large positive potential (+82.37 kcal mol). Thus, it can attract the arsenic oxyanion, and As(III) was subsequently adsorbed on the surface of the PTFE through the hydrogen bond on the hydroxyl group. Electrostatic force and non-covalent interaction were the key mechanisms affecting the PTFE adsorption.
微塑料表现出活跃的环境行为和独特的表面特性，并作为环境中三价砷（As(III)）迁移的载体。本文系统地确定了聚四氟乙烯（PTFE）微塑料颗粒吸附 As(III)的机制。PTFE 颗粒的粒径越大，比表面积越小，零电荷点（PZC）越高，对 As(III)的吸附越不利；最高吸附量可达 1.05mg/g。吸附过程可以通过颗粒内扩散模型分为三个阶段：外部传质、颗粒内扩散和动态平衡，其中外部传质阶段是吸附速率限制阶段。Langmuir 等温模型更好地表示了平衡吸附结果。PTFE 对 As(III)的吸附是一个放热过程，由于温度升高破坏了氢键，吸附量减少，不利于自发吸附。在 3-7 的 pH 范围内，随着 pH 值的升高，PTFE 吸附的 As(III)量逐渐减少，这可能与 PTFE 的 PZC 变化和 As(III)的质子化有关。PTFE 表面羟基上的 H 表现出非常大的正电势（+82.37 kcal/mol）。因此，它可以吸引砷含氧阴离子，随后通过羟基上的氢键将 As(III)吸附在 PTFE 表面上。静电力和非共价相互作用是影响 PTFE 吸附的关键机制。
