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Simultaneous Determination of Copper, Iron, Zinc and Nickel in Metal Pickling Wastewater by Flame Atomic Absorption Spectrometry
Key words: flame atomic absorption spectrometry; metal pickling waste copper, copper, iron, zinc and nickel; analysis instrument ; According to statistics, the annual quality of metal products that can no longer be used due to corrosion in the world is as high as the annual output of metal materials. 1/4 to 1/3 of the total. The oxides formed on the metal surface seriously affect the mechanical properties and chemical properties of the metal materials. Therefore, the metal surface is usually cleaned with acid before use, and the washed waste liquid is usually discharged directly into the environment, which pollutes the environment and wastes resources. A large number of steel pickling waste liquids produced by metallurgy, machinery and other industries have not been economically and rationally disposed of. It has been reported in the literature that the use of steel pickling waste liquid to treat printing and dyeing plant wastewater is effective, and finds a reasonable utilization route for steel pickling waste liquid to achieve the purpose of comprehensive management [1, 2] . By analyzing the four elements of copper, iron, zinc and nickel in 11 batches of metal pickling waste liquid, it is found that the amount of copper, iron, zinc and nickel contained in such metal pickling waste liquid is high. It has a certain value of recycling or utilization. If it is directly discharged into the environment, it will inevitably cause serious environmental pollution. 1 Test part 1.1 Instruments and reagents AA-1800C atomic absorption spectrophotometer (Shanghai Meifang Instrument Co., Ltd.); copper, iron, zinc, nickel hollow cathode lamps. The standard solution of zinc, nickel, copper and iron was purchased from the National Standards Research Center. When used, it was diluted to the standard working solution according to actual needs. The HNO 3 used for the experiment was analytically pure and the water was double distilled water. 1.2 Instrument determination Working conditions Determination conditions are shown in Table 1. Table 1 Working conditions of flame atomic absorption spectrometry
Element wavelength l/nm Lamp current I/mA Slit l/nm Air flow q V /L·min -1 Acetylene flow q V //L·min -1 Cu Fe Ni Zn 324.8 248.3 232.0 213.9 8.0 8.0 8.0 8.0 0.2 0.2 0.2 0.2 5.0 5.0 5.0 5.0 0.5 0.5 0.5 0.5
1.3 Analysis method Transfer a certain amount of copper, iron, nickel and zinc standard working solution in a 25 mL volumetric flask, dilute to the mark with water; dry the metal pickling waste liquid into a clean container, discard the first filter out A few milliliters of the solution, after dilution of the appropriate multiple; according to the 1.2 instrument working conditions for the determination of the standard series and metal pickling waste. At the same time, make a blank experiment. The concentration c (μg/25 mL) was linearly regressed by absorbance A, and after subtracting the blank value, the content of each element in the metal pickling waste liquid was determined. 2 Results and discussion 2.1 The detection limit is determined by the detection limit of A=0.010 [3] , and the results are shown in Table 2. 2.2 The standard curve is not interfered with each other due to the measured elements [4] , therefore, in a set of standard series The absorbance values ​​of the measured elements were measured simultaneously. The regression equation, the correlation coefficient r value and the linear range are shown in Table 2. Table 2 Method regression equation, correlation coefficient, detection limit and linear range Element regression equation correlation coefficient r Detection limit r/μg·mL -1 linear range / μg·mL -1 Cu A = 0.0047 c -0.0008 0.9998 0.092 0~1.5 Fe A =0.0029 c +0.0023 0.9992 0.106 0~3.0 Ni A =0.0033 c -0.0015 0.9997 0.139 0~0.9 Zn A =0.0145 c +0.0094 0.9990 0.0017 0~1.2
2.3 Method Accuracy In order to investigate the reliability of the method, spiked recovery and precision experiments were performed. The results are shown in Table 3. Table 3 Standard recovery and precision (n=6) Element sample No. Sample content m /mg·g -1 Addition amount m /mg Recovery amount m /mg Recovery rate /% Standard deviation /% Cu Fe Ni Zn 6 2 6 2 6 2 6 2 7.5 16.9 154069 79586 30.9 38.2 7.6 3787 4.5 4.5 7.5 7.5 4.5 4.5 1.5 1.5 4.20 4.16 7.10 7.47 4.49 4.52 1.42 1.23 93.3 92.5 94.7 99.6 99.8 100.4 94.6 82.2 3.6 2.3 4.7 3.8 2.8 2.9 8.4 8.4
2.4 Sample determination results Table 4 Analysis results of four metal elements in pickling waste liquid (n=8) mg/L Element Cu Fe Zn Ni 1 4.4 13.74 0.16 1.4 2 2.2 9.36 2.65 2.2 3 1.4 7.49 5107.4 6.0 4 3.6 9.36 1.79 3.6 5 3.09 10.74 6.67 4.20 6 4.03 14.72 6458.3 35.56 7 2.16 10.36 3.07 11.17 8 1.89 12.40 3.67 7.83 9 0.83 16.24 4.48 10.11 10 0.83 14.72 3.88 28.59 11 0.69 16.38 4.12 9.05
After analyzing the four elements of copper, iron, zinc and nickel in 11 batches of metal pickling waste liquid, it is found that the amount of copper, iron, zinc and nickel contained in such metal pickling waste liquid is high. Certain recycling value or utilization value, if directly discharged to the environment, will inevitably cause serious environmental pollution.
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