Rott Eduard, Reinhardt Tobias, Wasielewski Stephan, Raith-Bausch Ellen, Minke Ralf
Institute for Sanitary Engineering, Water Quality and Solid Waste Management, University of Stuttgart;
Institute for Sanitary Engineering, Water Quality and Solid Waste Management, University of Stuttgart.
J Vis Exp. 2018 May 18(135):57618. doi: 10.3791/57618.
This paper introduces a procedure to investigate the adsorption of phosphonates onto iron-containing filter materials, particularly granular ferric hydroxide (GFH), with little effort and high reliability. The phosphonate, e.g., nitrilotrimethylphosphonic acid (NTMP), is brought into contact with the GFH in a rotator in a solution buffered by an organic acid (e.g., acetic acid) or Good buffer (e.g., 2-(N-morpholino)ethanesulfonic acid) [MES] and N-cyclohexyl-2-hydroxyl-3-aminopropanesulfonic acid [CAPSO]) in a concentration of 10 mM for a specific time in 50 mL centrifuge tubes. Subsequently, after membrane filtration (0.45 µm pore size), the total phosphorus (total P) concentration is measured using a specifically developed determination method (ISOmini). This method is a modification and simplification of the ISO 6878 method: a 4 mL sample is mixed with H2SO4 and K2S2O8 in a screw cap vial, heated to 148-150 °C for 1 h and then mixed with NaOH, ascorbic acid and acidified molybdate with antimony(III) (final volume of 10 mL) to produce a blue complex. The color intensity, which is linearly proportional to the phosphorus concentration, is measured spectrophotometrically (880 nm). It is demonstrated that the buffer concentration used has no significant effect on the adsorption of phosphonate between pH 4 and 12. The buffers, therefore, do not compete with the phosphonate for adsorption sites. Furthermore, the relatively high concentration of the buffer requires a higher dosage concentration of oxidizing agent (K2S2O8) for digestion than that specified in ISO 6878, which, together with the NaOH dosage, is matched to each buffer. Despite the simplification, the ISOmini method does not lose any of its accuracy compared to the standardized method.
本文介绍了一种以低成本且高可靠性的方式来研究膦酸盐在含铁过滤材料，特别是颗粒氢氧化铁（GFH）上的吸附情况的程序。将膦酸盐，如次氮基三甲基膦酸（NTMP），在50 mL离心管中与GFH于由有机酸（如乙酸）或Good缓冲液（如2-(N-吗啉代)乙磺酸 [MES] 和N-环己基-2-羟基-3-氨基丙烷磺酸 [CAPSO]）缓冲的溶液中，在浓度为10 mM的情况下于旋转器中接触特定时间。随后，经过膜过滤（孔径0.45 µm）后，使用专门开发的测定方法（ISOmini）测量总磷（总P）浓度。该方法是对ISO 6878方法的改进和简化：将4 mL样品与硫酸和过硫酸钾在螺帽小瓶中混合，加热至148 - 150 °C 1小时，然后与氢氧化钠、抗坏血酸和酸化的含锑(III)钼酸盐（最终体积10 mL）混合以产生蓝色络合物。通过分光光度法（880 nm）测量与磷浓度呈线性比例的颜色强度。结果表明，在pH 4至12之间，所用缓冲液浓度对膦酸盐的吸附没有显著影响。因此，缓冲液不会与膦酸盐竞争吸附位点。此外，与ISO 6878规定相比，相对较高浓度的缓冲液需要更高剂量浓度的氧化剂（过硫酸钾）进行消解，并且氢氧化钠的用量与每种缓冲液相匹配。尽管进行了简化，但与标准化方法相比，ISOmini方法并未损失任何准确性。
