This study focused on utilization of Leucaena leucocephala seeds’ extract and iron oxide nanoparticles (IONPs) under magnetic field to provide effective coagulation process. Leucaena seeds’ extract was obtained using 3 M NaCl solution as solvent at feed-to-solvent mass ratio of 1:20. IONPs were synthesized using co-precipitation method. The obtained IONPs were analyzed using scanning electron microscopy, X-ray diffraction and transmission electron microscopy. Based on analysis results, the obtained IONPs were the agglomerate of Fe₃O₄ phase with average particle diameter of 14.6 nm. The extract and IONPs were used as natural coagulant at various pHs (3–12), coagulant dosages (4–40 mL extract/L), and IONPs concentrations (0.5–3 mg/mL extract) under external magnetic field. It was obtained that pH 3 was the best pH because positively charged Leucaena protein at pH 3 acts to neutralize negatively charged Congo red molecules. The highest removal was obtained at coagulant dosage of 20 mL/L, and further increase in dosage was decreasing the removal due to colloid re-stabilization effect. The variation of IONPs concentration did not give any effect on the %removal and sludge volume. However, further investigation using pseudo-second-order kinetic model showed that the increase in IONPs concentration gave increase to the kinetic constant, signifying faster settling kinetics. The best condition was obtained at pH 3, coagulant dosage 20 mL/L, and IONPs concentration of 3 mg/mL extract that gave 90% Congo red removal, 30 mL/L sludge volume, and 30 min settling time.

中文翻译：

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氧化铁纳米粒子-白头翁种子提取物的磁辅助混凝处理合成刚果红废水

这项研究的重点是在磁场下利用银合欢种子提取物和氧化铁纳米粒子（IONPs）来提供有效的混凝过程。用3M NaCl溶液作为溶剂以进料与溶剂的质量比为1:20获得银合欢种子的提取物。使用共沉淀法合成了IONP。使用扫描电子显微镜，X射线衍射和透射电子显微镜对获得的IONP进行分析。根据分析结果，获得的IONPs为Fe ₃ O ₄的团聚体相的平均粒径为14.6 nm。提取物和IONPs在各种pH（3–12），凝固剂剂量（4–40 mL提取物/ L）和IONPs浓度（0.5–3 mg / mL提取物）下用作天然凝结剂。获得的pH为3是最佳pH，因为在pH 3下带正电荷的白桦蛋白起到中和带负电的刚果红分子的作用。凝结剂剂量为20 mL / L时，去除率最高，由于胶体的再稳定作用，剂量的进一步增加使去除率降低。IONPs浓度的变化对去除率和污泥量没有任何影响。但是，使用伪二级动力学模型进行的进一步研究表明，IONPs浓度的增加使动力学常数增加，这表明沉降动力学更快。