Method for adjusting norfloxacin removal performance of ferrate based on buffer salt

Abstract

The invention relates to a method for adjusting the norfloxacin removal performance of ferrate based on buffer salts, and belongs to the technical field of novel pollutant environmental protection, and the method mainly comprises the following steps: preparing different types of buffer salts, and calculating the norfloxacin removal rate to evaluate the norfloxacin removal performance of ferrate in different buffer systems.

Description

(I) Technical field

[0001] The invention belongs to the technical field of environmental protection of new pollutants, and specifically relates to a method for degrading quinolone antibiotic norfloxacin by regulating potassium ferrate (K2FeO4) using common buffer salts. (II) Background technology

[0002] It is well known that trace organic pollutants (TrOCs) include a series of pharmaceuticals, personal care products (PPCPs), endocrine disrupting chemicals (EDCs), pesticides, algal toxins, and industrial solvents and precursors, which have made great contributions to production and life. However, their harm to human health and ecological safety has become increasingly prominent recently, with more and more reports on antibiotic-resistant bacteria, disturbances in the reproductive system of the aquatic biosphere, and bioaccumulative toxicity in the food chain. The molecular structure makes TrOCs persistent in environmental self-purification and traditional sewage treatment plant processes, so optimized TrOCs removal technology is urgently needed.

[0003] Norfloxacin is a third-generation quinolone antibiotic that can inhibit the action of DNA gyrase (DNA Gyrase) of pathogenic bacteria in the digestive tract and hinder bacterial DNA replication. Its concentration in municipal sewage is a few μg / L, while in the sewage of some hospitals or antibiotic production sites it can reach several milligrams, and the concentration in groundwater can reach 10 μg / L.

[0004] High-valent iron species (Fe VI O4 2- ;Fe V O4 3- ;Fe IV O4 4- ) is commonly known as ferrate, which has attracted widespread attention due to its strong oxidizing ability and non-toxicity. Ferrate has shown great potential in TrOCs oxidation, disinfection, heavy metal control, solid waste pretreatment and coagulation. Many excellent studies have reviewed the characteristics and contributions of ferrate. There are endless research reports on the treatment of various pollutants with ferrate, from inorganic substances such as halides / cyanides / N-containing compounds / S-containing compounds / selenium and arsenic, heavy metals to organic pollutants. Compared with traditional oxidants, ferrate has great advantages and can be used in a variety of environmental media such as water, sludge and soil.

[0005] However, potassium ferrate has poor stability and is greatly affected by pH and coexisting ions. In water environments, hexavalent iron is mainly present in the form of H2FeO4, H3FeO4 + 、HFeO4 - 、FeO4 2-There are four forms, with dissociation constants of 1.6, 3.5, and 7.2. When the pH is 3.5-7.2, hexavalent iron is mainly in the form of HFeO4 - When the pH is greater than 7.2, hexavalent iron mainly exists in the form of FeO4 2- It exists in the form of potassium ferrate. Studies have shown that the protonated ferrate has a larger spin density for the oxidized ligand, so it has a stronger oxidizing ability. When the system is acidic, the protonated ferrate is dominant, and Fe(VI) has a stronger oxidizing ability. In order to control the background pH value to stabilize and study the oxidizing ability of potassium ferrate, researchers often use some common buffer salts, such as phosphates, acetates, borates, etc., but these buffer salts have a significant effect on the oxidizing ability of potassium ferrate. (III) Summary of the invention

[0006] The purpose of the present invention is to use common buffered salt solution as a solvent background to accommodate potassium ferrate to oxidize norfloxacin, so as to provide technical support and guidance for ferrate oxidation water treatment technology, in order to promote the maturity and development of ferrate-based advanced oxidation technology.

[0007] The technical solution of the present invention is:

[0008] (1) Preparation of NOR stock solution: Dissolve NOR powder in ultrapure water and use a magnetic stirrer to help it dissolve completely.

[0009] (2) Preparation of pure phosphate buffer: Calculate the amount of phosphoric acid, sodium monohydrogen phosphate, and sodium dihydrogen phosphate used at pH = 3, 5, 7, 9, and 11 according to the formula. For pH = 11, adjust the sodium monohydrogen phosphate solution with 0.1 mol / L sodium hydroxide solution. Dissolve it in deionized water. The calculation formula is as follows:

[0010]

[0011]

[0012]

[0013]

[0014] Among them, pH is the target pH value, which is 3, 5, 7, 9, and 11 respectively, and pKa1=2.2 is the isoelectric point of the phosphoric acid / sodium dihydrogen phosphate buffer. is the concentration of sodium dihydrogen phosphate, a is the calculated constant, V is the volume of the buffer (L), C I =0.05M is the ionic strength, is the molar mass of sodium dihydrogen phosphate. To weigh the drug mass (g). And so on.

[0015] (3) Preparation of acetate buffer: Calculate the amount of acetic acid and sodium acetate used at pH = 3 and 5 respectively according to the formula. Dissolve them in deionized water. The calculation formula is as follows:

[0016]

[0017]

[0018]

[0019]

[0020] Wherein, pH is the target pH value of 3 and 5 respectively, pKa2=4.76 is the isoelectric point of sodium acetate / acetic acid buffer, b is the calculated constant, V is the volume of buffer (L), C I =0.05M is the ionic strength.

[0021] (4) Preparation of borate buffer: Calculate the amount of boric acid and sodium tetraborate used at pH = 7, 9 and 11 according to the formula. Dissolve in deionized water. The calculation process is the same as before, pKa3 = 9.24

[0022] (5) Preparation of borate phosphate mixed buffer: The pH was adjusted with 0.1 M sodium hydroxide or sulfuric acid.

[0023] (6) Start of reaction: Using the above different types of buffer solutions as the reaction system, add 1 mL of NOR stock solution and 1 mL of potassium ferrate stock solution to 18 mL of buffer solution respectively. The reaction starts.

[0024] (7) Determination of NOR residual concentration: Determined by high performance liquid chromatography.

[0025] (IV) Beneficial effects

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention improves the oxidation ability of potassium ferrate on norfloxacin by adjusting the type of buffer salt.

[0028] (2) The present invention discloses the removal ability of potassium ferrate for norfloxacin at different pH values. (V) Description of the drawings

[0029] Figure 1 This is a performance diagram of potassium ferrate removing norfloxacin in different buffer systems of the present invention. (VI) Specific implementation methods

[0030] The present invention is further described below through specific implementation examples. The implementation examples of the present invention are intended to enable those skilled in the art to better understand the present invention, and do not impose any limitation on the present invention.

[0031] The specific implementation modes of the present invention will be further described in detail below with reference to the accompanying drawings.

[0032] (1) Dissolve NOR powder in deionized water, add an appropriate amount of sodium hydroxide solution to assist dissolution, and use a 250 mL volumetric flask to make the final stock solution concentration 800 μM for later use.

[0033] (2) The reaction is carried out in a stoppered brown Erlenmeyer flask. 18 mL of a 50 mM buffer solution or deionized water adjusted to pH with 0.1 M sodium hydroxide / sulfuric acid is added in advance: A. pure water; B. pure phosphate; C. pH = 3-5 acetate / 7-11 borate; D. 40% boric acid / 60% phosphoric acid.

[0034] (3) Before the reaction begins, a potassium ferrate stock solution is prepared and used immediately. The concentration is measured by direct spectrophotometry at 510 nm. The calculation formula is as follows:

[0035] Abs 510 =ε×b×C[K2FeO4]

[0036] Among them, Abs 510 is the absorbance value measured at 510nm, ε=1150±25M -1 cm -1 , b=1cm is the thickness of the cuvette.

[0037] (4) First, add 1 mL of NOR stock solution to the flask to make its concentration 40 μM, then add 1 mL of potassium ferrate stock solution to make the potassium ferrate concentration 100 μM, start timing for 1 hour, and place the flask in a constant temperature shaker at 25°C for shaking.

[0038] (5) Determination of residual concentration of NOR: After the reaction, 1.5 mL of the sample was taken, and 75 μL of 1 M sodium thiosulfate was added to terminate the reaction. The sample was filtered through a 0.22 μm organic membrane and determined by liquid chromatography. The chromatographic conditions were 15% aqueous phase (0.1% formic acid aqueous solution), 85% organic phase (methanol), which increased to 25% aqueous phase (0.1% formic acid aqueous solution), 75% organic phase (methanol) in 4 minutes, and decreased to 15% aqueous phase (0.1% formic acid aqueous solution), 85% organic phase (methanol) in 6 minutes. The determination time was 13 minutes, and the peak time was 11 minutes.

[0039] Figure 1The performance diagram of potassium ferrate in different buffer systems for removing norfloxacin. It can be seen that, in general, under acidic and neutral pH conditions, potassium ferrate has good oxidation ability regardless of the buffer system. Except for the best effect of no buffer solution at pH = 3 (70%), the effect of buffer salts at other pH values ​​is better than that of no buffer salts. At pH = 5, the removal rate of pure phosphoric acid buffer system is the highest at 63%, and the mixed buffer effect of phosphate and boric acid is the same, but since acetic acid is an organic acid, it may compete with NOR for potassium ferrate here, resulting in a decrease in removal rate. At pH = 7, the effects of the three buffer systems are similar, but the removal rate of the no buffer system is reduced by about 60%. This is because potassium ferrate produces a large amount of hydroxide ions during the decomposition process, which increases the pH of the solution and inhibits the removal of NOR. This principle also applies to the case of pH = 9. However, at pH = 9, the removal rate of phosphoric acid buffer salt is lower than that of boric acid buffer, which may be due to the complexation of sulfuric acid with iron ions, which reduces the reaction activity of potassium ferrate with NOR and causes precipitation.

[0040] It should be understood that the embodiments and examples discussed here are for illustrative purposes only and may be modified or altered by those skilled in the art, and all such modifications and alterations should fall within the scope of protection of the appended claims of the present invention.

Claims

1. Preparation of pure phosphate buffer: Calculate the amount of phosphoric acid, sodium monohydrogen phosphate, and sodium dihydrogen phosphate used at pH = 3, 5, 7, 9, and 11 according to the formula. For pH = 11, adjust the sodium monohydrogen phosphate solution with 0.1 mol / L sodium hydroxide solution and dissolve it in deionized water. The calculation formula is as follows: in, pH is the target pH value, which is 3, 5, 7, 9, and 11 respectively, and pKa1=2.2 is the isoelectric point of the phosphoric acid / sodium dihydrogen phosphate buffer pair; is the concentration of sodium dihydrogen phosphate; a is the calculated constant; V is the volume of the buffer solution (L); C I =0.05M is the ionic strength; is the molar mass of sodium dihydrogen phosphate; To weigh the drug mass (g).

2. Preparation of acetate buffer: Calculate the amount of acetic acid and sodium acetate used at pH = 3 and 5 according to the formula, and dissolve them in deionized water. The target pH is 3 and 5 respectively; pKa2 = 4.76 is the isoelectric point of the sodium acetate / acetic acid buffer pair; b is the calculated constant; V is the volume of the buffer (L); C is the target pH value. I =0.05M is the ionic strength.

3. Preparation of borate buffer: Calculate the amount of boric acid and sodium tetraborate used at pH = 7, 9 and 11 according to the formula, and dissolve them in deionized water. The calculation process is the same as 1, pKa3 = 9.

24.

4. Preparation of borate phosphate mixed buffer: Preparation The pH was adjusted with 0.1 M sodium hydroxide or sulfuric acid.

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