State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China E-mail:
Water Sci Technol. 2013;68(5):1137-43. doi: 10.2166/wst.2013.356.
To investigate the possibility of removing titanium dioxide nanoparticles (TiO2 NPs) from water by coagulation, as well as to find the optimal coagulant and experimental conditions for TiO2 NP removal, four types of coagulant were adopted: polyferric sulfate (PFS), ferric chloride (FeCl3), polyaluminum chloride (PACl), and alum (Al2(SO4)3). It was found that the removal of TiO2 NPs by coagulation was affected by ionic strength, alkalinity, as well as types and dosages of coagulants. PFS and FeCl3 achieved much higher removal efficiency of TiO2 NPs than PACl and Al2(SO4)3 did. For 30 mg/L TiO2 NPs, a dosage of 0.3 mM PFS (as Fe) achieved 84% removal after coagulation followed by 30 min settlement. Optimal ionic strength (0.1 M NaCl or 0.03 M CaCl2) is of vital importance for the performance of PFS. Na2SO4 is unfavorable for the performance of PFS. Optimal alkalinity (0.01-0.03 M NaHCO3) is necessary for FeCl3 to remove TiO2 NPs. Natural organic matter, as represented by humic acid (HA) up to 11 mg/L, reduces the removal of TiO2 NPs by coagulation. These findings indicate that coagulation is a good option for the removal of TiO2 NPs from water, and more attention should be paid to the effects of water quality when using coagulation to remove TiO2 NPs from aqueous matrices. This provides a possible solution to alleviate the potential hazard caused by TiO2 NPs.
为了研究通过混凝去除水中纳米二氧化钛（TiO2 NPs）的可能性，并找到去除 TiO2 NPs 的最佳混凝剂和实验条件，采用了四种混凝剂：聚合硫酸铁（PFS）、三氯化铁（FeCl3）、聚合氯化铝（PACl）和硫酸铝（Al2(SO4)3）。研究发现，混凝去除 TiO2 NPs 的效果受到离子强度、碱度以及混凝剂类型和剂量的影响。PFS 和 FeCl3 对 TiO2 NPs 的去除效率远高于 PACl 和 Al2(SO4)3。对于 30 mg/L 的 TiO2 NPs，投加 0.3 mM 的 PFS（以 Fe 计），混凝后沉降 30 min，去除率达到 84%。最佳离子强度（0.1 M NaCl 或 0.03 M CaCl2）对 PFS 的性能至关重要。Na2SO4 不利于 PFS 的性能。最佳碱度（0.01-0.03 M NaHCO3）是 FeCl3 去除 TiO2 NPs 所必需的。天然有机物（以腐殖酸（HA）为例，浓度高达 11 mg/L）会降低混凝去除 TiO2 NPs 的效果。这些发现表明，混凝是去除水中 TiO2 NPs 的一种较好的选择，在使用混凝去除水相中的 TiO2 NPs 时，应更加注意水质的影响。这为缓解 TiO2 NPs 带来的潜在危害提供了一种可能的解决方案。
