Magnetic Fe.SUB.2.O.SUB.3 .nanospheres with PNH surface modification and application hereof in water treatment

Abstract

The present invention provides a magnetic Fe.sub.2O.sub.3 nanosphere with PNH surface modification and application thereof in water treatment. First, 2,2-bipyridyl-5,5′-dicarboxylic acid is reacted with thionyl chloride to obtain 2,2-bipyridyl-5,5′-diacid chloride; then 2,2-bipyridyl-5,5′-diacid chloride and 1,4,8,11-tetraazacyclotetradecane react in the presence of triethylamine to obtain a polynitrogen heterocyclic polymer; the polynitrogen heterocyclic polymer is added into an aqueous solution with iron salt to obtain a magnetic Fe.sub.2O.sub.3 nanosphere with PNH surface modification which has strong light absorption ability, which improves its ability to catalyze in degradation of tetracycline under visible light, so that the pollutants are removed from water.

Claims

1. A method for preparing a magnetic Fe.sub.2O.sub.3 nanosphere with PNH (polynitrogen heterocyclic polymer) surface modification, comprising the following steps: (1) reacting 2,2-bipyridyl-5,5′-dicarboxylic acid with thionyl chloride to obtain 2,2-bipyridyl-5,5′-diacid chloride; then, in the presence of triethylamine, reacting 2,2-bipyridyl-5,5′-diacid chloride with 1,4,8,11-tetraazacyclotetradecane to obtain a polynitrogen heterocyclic polymer; (2) adding the polynitrogen heterocyclic polymer to an aqueous solution of iron salt to obtain the magnetic Fe.sub.2O.sub.3 nanosphere with PNH surface modification.

2. The method according to claim 1, wherein in the step (1), said 2,2-bipyridyl-5,5′-dicarboxylic acid is dissolved in thionyl chloride, the reaction of 2,2-bipyridyl-5,5′-dicarboxylic acid with thionyl chloride is carried out at 110 to 115° C. for 10 to 12 hours to obtain the 2,2-bipyridyl-5,5′-diacid chloride.

3. The method according to claim 1, wherein in the step (1), the reaction time of said 2,2-bipyridyl-5,5′-diacid chloride and said 1,4,8,11-tetraazacyclotetradecane is 24 to 48 hours, and the reaction temperature is 45 to 50° C.

4. The method according to claim 1, wherein in the step (1), after the reaction of said 2,2-bipyridyl-5,5′-diacid chloride and said 1,4,8,11-tetraazacyclotetradecane, the reaction system is washed successively with KOH aqueous solution, chloroform and ethanol, then placed in DMF (Dimethylformamide) and heated at 140-150° C. for 12 hours, then filtered, and the obtained solid is dried to obtain a polynitrogen heterocyclic polymer.

5. The method according to claim 1, wherein in the step (2), the reaction temperature is 140 to 180° C., and the reaction time is 10 to 20 hours.

6. The method according to claim 1, wherein in the step (2), after the reaction is finished, the product is sequentially washed with ethanol and deionized water, and then dried to obtain the magnetic Fe.sub.2O.sub.3 nanosphere with PNH surface modification.

7. The method according to claim 1, wherein the molar ratio of said 2,2-bipyridyl-5,5′-diacid chloride and said 1,4,8,11-tetraazacyclotetradecane is 1:(2 to 2.1); the mass ratio of said polynitrogen heterocyclic polymer and said iron salt is 1:(0.5 to 2); and said iron salt is FeCl.sub.3.

8. The method according to claim 1, further comprising adding the magnetic Fe.sub.2O.sub.3 nanosphere with PNH surface modification into water containing organic pollutants, then adding hydrogen peroxide, under illumination to complete degradation of organic pollutants in water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a .sup.13C NMR spectra image of PNH in the example 1;

(2) FIG. 2 is transmission electron micrograph and scanning electron micrograph image of PNH in the example 1, a is a magnified view of b;

(3) FIG. 3 is transmission electron micrograph and scanning electron micrograph image of Fe.sub.2O.sub.3 in the example 2, a is a magnified view of b;

(4) FIG. 4 is transmission electron micrograph and scanning electron micrograph image of Fe.sub.2O.sub.3@PNH in the example 3, a is a magnified view of b;

(5) FIG. 5 is Power X-ray diffraction images of PNH, Fe.sub.2O.sub.3 and Fe.sub.2O.sub.3@PNH in the example;

(6) FIG. 6 is UV-vis diffuse reflectance spectra image of tetracycline in the example 6;

(7) FIG. 7 is an effect image of the degradation of tetracycline in the example 6.

DETAILED DESCRIPTION OF THE INVENTION

(8) The present invention utilizes the strong coordination ability of the bipyridyl group in 2,2′-bipyridyl-5,5′-dicarboxylic acid to Fe′ to let the polymer PNH pre-adsorb Fe′ in aqueous solution and synthesizes by a one step simple hydrothermal process to obtain organic polymer-coated magnetic nano-particle Fe.sub.2O.sub.3@PNH, which has strong light-absorbing ability and enhanced ability in the degradation of tetracycline in visible light so that the pollutants are removed from the water. The magnetic Fe.sub.2O.sub.3 nanosphere (Fe.sub.2O.sub.3@PNH) with surface modified PNH can be used as a composite material for photocatalytic degradation of organic pollutants. The preparation method is as follows:

(9) (1) Synthesis of Polynitrogen heterocycle polymer (PNH)

(10) 2,2′-bipyridine-5,5′-dicarboxylic acid is dissolved in a solution of thionyl chloride and refluxed to obtain 2,2-bipyridin-5,5′-diacid chloride. After spin-dried the solvent, chloroform is added, then a solution of 1,4,8,11-tetraazacyclotetradecane and triethylamine in chloroform is added dropwise, and then refluxed to obtain PNH.

(11) (2) Synthesis of PNH@ Fe.sub.2O.sub.3

(12) The iron salt is dissolved in water, and then PNH is added to carry out the reaction. After the reaction is completed, the product is washed with ethanol and deionized water respectively, and then dried under vacuum to obtain Fe.sub.2O.sub.3@PNH.

(13) The reaction process is as follows:

(14) ##STR00001##

Example 1

(15) 2,2′-bipyridine-5,5′-dicarboxylic acid (3 g) is dissolved in thionyl chloride (80 ml) and reacts for 8 h at 110° C., then the solvent is spin-dried to obtain 2,2′-bipyridine-5,5′-dicarboxylic acid chloride. Then, dissolving the obtained 2,2′-bipyridine-5,5′-dicarboxylic acid chloride in chloroform (120 ml), and then under ice bath, a chloroform solution of 1,4,8,11-tetraazacyclotetradecane (1.17 g) and triethylamine (10 ml) is added dropwisely. Then removing the ice bath, after stirring at room temperature for 30 min, the reaction is carried out at 45° C. for 2 days. In order to remove small molecules such as acid chloride in the crude product, the crude product is washed with KOH aqueous solution, chloroform and ethanol, and then placed in a DMF solution and refluxed at 140° C. for 12 hours. After filtration and drying, PNH is obtained as a light-yellow solid.

(16) FIG. 1 is a solid carbon spectrum of the above PNH, wherein the blue and green lines represent two raw materials, and the blue curve is the carbon spectrum data of 2,2-bipyridyl-5,5′-diacid chloride, the green curve is 1,4,8,11-tetraazacyclotetradecane carbon spectrum data, red is the carbon spectrum data of the polymer PNH. It can be obtained by analysis of SSC.sup.13-NMR that 2,2-bipyridyl-5,5′-dicarboxylic acid shows obvious sharp peaks at δ=121 pm, 124 pm, 139 pm, 152 ppm, 157 pm, 174 pm, 1,4,8,11-tetraazacyclotetradecane shows peaks at the positions of 6=29 ppm and 53 ppm, and the peak of PNH contained peaks of two monomers and shifted to some extent, and the results shows a significant chemical reaction took place between 2,2-bipyridyl-5,5′-dicarboxylic acid and 1,4,8,11-tetraazacyclotetradecane. FIG. 2 is a scanning electron micrograph and a projected electron micrograph of the above PNH, which proves that PNH is successfully synthesized and is disordered.

Example 2

(17) Dissolving 50 mg of FeCl.sub.3 in water (10 ml), placing the solution in a high pressure reaction kettle, reacting at 140° C. for 10 h, and washing the product three times with ethanol and deionized water, and vacuum drying in a drying oven at 60° C. for 12 hours. The reaction gets pure Fe.sub.2O.sub.3. FIG. 3 is a scanning electron microscope and a projection electron micrograph of Fe.sub.2O.sub.3, which proves that Fe.sub.2O.sub.3 is in irregular particles.

Example 3

(18) Dissolving 50 mg of FeCl.sub.3 in water (10 ml), adding 50 mg of PNH, stirring at room temperature for 6 hours and placing in a high pressure reaction kettle, reacting at 140° C. for 10 h, and washing the product three times with ethanol and deionized water, and vacuum drying in a drying oven at 60° C. for 12 hours to obtain the product Fe.sub.2O.sub.3@PNH, which is magnetic Fe.sub.2O.sub.3 nanosphere with PNH surface modification.

(19) FIG. 4 is a scanning electron micrograph and a projected electron micrograph of Fe.sub.2O.sub.3@PNH, which proves that Fe.sub.2O.sub.3@PNH is a regular sphere. FIG. 5 is an X-ray diffraction diagram of PNH, Fe.sub.2O.sub.3 and Fe.sub.2O.sub.3@PNH, which proves that the invention successfully synthesizes Fe.sub.2O.sub.3 and Fe.sub.2O.sub.3@PNH and mainly exhibits a crystal form of Fe.sub.2O.sub.3.

Example 4

(20) Dissolving 50 mg of FeCl.sub.3 in water, adding 25 mg of PNH, stirring at room temperature for 6 hours and placing in a high pressure reaction kettle, reacting at 140° C. for 10 h, and washing the product three times with ethanol and deionized water, and vacuum drying in a drying oven at 60° C. for 12 hours to obtain the product Fe.sub.2O.sub.3@PNH.

Example 5

(21) Dissolving 50 mg of FeCl.sub.3 in water, adding 100 mg of PNH, stirring at room temperature for 6 hours and placing in a high pressure reaction kettle, reacting at 140° C. for 10 h, and washing the product three times with ethanol and deionized water, and vacuum drying in a drying oven at 60° C. for 12 hours to obtain the product Fe.sub.2O.sub.3@PNH.

(22) 2 mg Fe.sub.2O.sub.3@PNH (prepared in Example 3) is dispersed in 30 ml of a 50 ppm aqueous solution of tetracycline, 10 mM of H.sub.2O.sub.2 is added, and the suspension is stirred in the dark for 2 hours to achieve adsorption-desorption equilibrium. A xenon lamp source (filter>420 nm) irradiates on the suspension, and 2 mL of the supernatant is collected by filtration through a 0.45 um filter, and analyzed by a UV-vis spectrometer at X, =354 nm to analyze the tetracycline concentration.

(23) FIG. 6 is the ultraviolet absorption diagram of tetracycline; FIG. 7 is the effect of Fe.sub.2O.sub.3@PNH catalytic degradation of tetracycline; FIG. 6 and FIG. 7 show that the catalytic reaction is carried out after adsorption-desorption for two hours, and the results show that Fe.sub.2O.sub.3@PNH 90% of tetracycline can be degraded within 4 hours, while the polymer exhibits only weak adsorption properties under light conditions. The weak degradation may be caused by decomposition of hydrogen peroxide. The pure Fe.sub.2O.sub.3 shows a certain degree of degradation after the balance of adsorbed-desorbed reached, but only 35%, the degradation effect is much lower than the Fe.sub.2O.sub.3@PNH composite.

(24) The Fe.sub.2O.sub.3@PNH of the invention has good chemical stability in an aqueous medium, low synthesis cost, abundant raw materials and no toxicity, and can be one of the most promising materials for photocatalytic degradation and water decomposition application.