As a new type of pollutant, microplastics are widely distributed in printing and dyeing wastewater. Coagulation performance, floc characteristics and mechanisms for synchronous removal of reactive orange and polyethylene terephthalate (PET) microplastics using magnesium hydroxide and polyacrylamide (PAM) were investigated in this paper. The floc properties were evaluated by laser particle size analysis and on line intelligent photometric dispersion analysis. Coagulation mechanism was investigated by scanning electron microscope (SEM), Fourier transform infrared spectroscope (FTIR) and Zeta analyzer. The results showed that the removal efficiencies for reactive orange and PET were 98 % and 93 % under the optimal conditions of magnesium ion 100 mg/L, PAM 4 mg/L with pH value 11.75. The increase of pH, coagulant and PAM dosage would significantly enhance the removal efficiency. The average floc size reached 61.90 µm and these flocs aggregated together for fast sedimentation. Meanwhile, electrical neutralization and adsorption for reactive orange by magnesium hydroxide, PAM bridging for PET were the main mechanisms. The removal behavior of reactive orange and PET microplastics during coagulation has potential applications for the removal of printing and dyeing wastewater.

微塑料作为一种新型污染物，广泛分布于印染废水中。本文研究了使用氢氧化镁和聚丙烯酰胺(PAM) 同步去除活性橙和聚对苯二甲酸乙二醇酯 (PET) 微塑料的混凝性能、絮体特性和机理。通过激光粒度分析和在线智能光度分散分析评估絮体性质。用扫描电镜研究凝血机制(SEM)、傅里叶变换红外光谱仪 (FTIR) 和 Zeta 分析仪。结果表明，在镁离子100 mg/L、PAM 4 mg/L、pH值为11.75的最佳条件下，活性橙和PET的去除率分别为98%和93%。pH、混凝剂和PAM用量的增加会显着提高去除效率。平均絮体尺寸达到 61.90 µm，这些絮体聚集在一起以实现快速沉降。同时，氢氧化镁对活性橙的电中和吸附、PAM对PET的架桥是主要机理。混凝过程中活性橙和PET微塑料的去除行为在印染废水去除方面具有潜在的应用价值。