浒苔多糖强化聚合氯化铝对水体微塑料的去除效能及机制研究

Removal Efficiency and Mechanism of Microplastics in Water by Enteromorpha Polysaccharide Enhanced Polymeric Aluminum Chloride

摘要:

水环境中的微塑料污染日益严重，微塑料污染治理已成为有待解决的问题。传统絮凝剂聚合氯化铝(Polyaluminum chloride，PAC)在去除微塑料时存在效率有限、投加量较高以及潜在生态环境风险等问题。浒苔多糖(Enteromorpha prolifera polysaccharide，EP)作为一种阴离子型天然多糖，展现出良好的絮凝潜力。本研究在系统对比PAC对不同类型不同粒径微塑料去除效果的基础上，针对较难去除的100 μm的微塑料聚乙烯(Polyethylene，PE)，系统探究了PAC和EP复合添加对其的去除效率及内在作用机理，并阐明了环境因素对该絮凝效率的影响。结果表明，添加适量的EP可提高PAC对PE微塑料的絮凝效率，当PAC和EP的投加量分别为300 mg/L和20 mg/L时，PAC单独使用和PAC-EP复合使用对PE微塑料的去除率分别达到76.3%和94%。Zeta电位、FTIR傅里叶红外光谱等多种表征手段共同揭示PAC和EP复合添加可通过金属聚合物的电中和作用和高分子聚合物的吸附架桥等协同作用，实现对PE微塑料的有效去除。此外，水体pH、共存阴离子浓度、天然有机物浓度等环境因素均可能会影响PAC-EP复合絮凝剂对PE的去除效果。本研究采用湖水和水产养殖水进一步评估了真实水体中PAC-EP复合絮凝剂对PE的去除效能，发现300 mg/L PAC和20 mg/L EP复合使用对PE的去除率仍可达到80%以上。本研究为利用生物多糖增强传统絮凝剂对微塑料的去除效果提供了理论依据，为拓展多糖类物质在水体新兴污染物控制中的应用前景提供数据参考。

Abstract:

Microplastic pollution in aquatic environments has become increasingly severe, and its effective control remains a pressing challenge. Conventional flocculants such as polyaluminum chloride (PAC) exhibit limited removal efficiency for microplastics and often require relatively high dosages, which may pose potential ecological risks. Enteromorpha polysaccharide (EP), an anionic natural polysaccharide, has demonstrated promising flocculation potential. In this study, based on a systematic comparison of the removal performance of PAC for microplastics with different types and particle sizes, polyethylene (PE) microplastics with a particle size of 100 μm, which are relatively difficult to remove, were selected as the target pollutant. The removal efficiency and underlying mechanisms of PE microplastics by PAC combined with EP were systematically investigated, and the effects of environmental factors on the flocculation performance were also elucidated.The results showed that the addition of an appropriate amount of EP significantly enhanced the flocculation efficiency of PAC for PE microplastics. When the dosages of PAC and EP were 300 mg/L and 20 mg/L, respectively, the removal efficiencies of PE microplastics reached 76.3% for PAC alone and 94.0% for the PAC–EP composite system. Multiple characterization techniques, including zeta potential analysis and Fourier transform infrared (FTIR) spectroscopy, revealed that the enhanced removal of PE microplastics was achieved through the synergistic effects of charge neutralization by polymeric aluminum species, adsorption–bridging by the polysaccharide, and the reconstruction of the aluminum coordination environment.In addition, environmental factors such as water pH, the concentrations of coexisting anions, and natural organic matter were found to influence the removal performance of PE microplastics by the PAC–EP composite flocculant. Further evaluations using lake water and aquaculture water demonstrated that the PAC–EP system maintained removal efficiencies exceeding 80% for PE microplastics at dosages of 300 mg/L PAC and 20 mg/L EP. This study provides a theoretical basis for enhancing the removal of microplastics using bio-based polysaccharides in combination with conventional flocculants and offers valuable data to support the expanded application of polysaccharide materials in the control of emerging contaminants in aquatic environments.