Phase inversion pore-forming agent and pore-forming method for fly ash-based ceramic flat membrane support

Abstract

The present disclosure provides a phase inversion pore-forming agent and a pore-forming method for a fly ash-based ceramic flat membrane support. The phase inversion pore-forming agent includes poly(oxyphenylene sulfone) and N-methylpyrrolidone (NMP), and is used in a preparation process of the fly ash-based ceramic flat membrane support. Pores can be formed through phase inversion, forming straight-through pores with gradient distribution inside the ceramic flat membrane support, thus avoiding a low porosity, a poor water flux, and uneven pore formation of the existing fly ash-based ceramic flat membrane support.

Claims

1. A pore-forming method for a fly ash-based ceramic flat membrane support, comprising: mixing fly ash with a phase inversion pore-forming agent and an oil additive, and then conducting aging and extrusion molding to obtain a green body; and subjecting the green body to static curing in a constant-temperature and constant-humidity environment, placing in water to allow phase inversion, and then conducting drying and sintering; wherein the phase inversion pore-forming agent comprises poly(oxyphenylene sulfone) and N-methylpyrrolidone (NMP) at a mass ratio of 1:(3.5-5); the oil additive comprises glycerol, oleic acid, and tung oil at a mass ratio of (1.2-2):1:(1.5-2.5); and the phase inversion pore-forming agent and the fly ash are at a mass ratio of (1-2):4.

2. The pore-forming method for a fly ash-based ceramic flat membrane support according to claim 1, wherein the oil additive and the fly ash are at a mass ratio of (0.8-1.5):10.

3. The pore-forming method for a fly ash-based ceramic flat membrane support according to claim 2, wherein the static curing is conducted with a humidity of 90% to 95% relative humidity (rh) at 35? C.?3? C. for 4 h to 6 h.

4. The pore-forming method for a fly ash-based ceramic flat membrane support according to claim 3, wherein the phase inversion is conducted at 25? C. to 35? C. for 5 h to 8 h.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a microphotograph of a pore structure obtained when starch is used as a pore-forming agent in Comparative Example 2; and

(2) FIG. 2 shows a microphotograph of a pore structure obtained using the phase inversion pore-forming agent in Example 1; where as shown in the comparison between FIG. 1 and FIG. 2, the support prepared by the phase inversion pore-forming agent has a higher porosity than that of the starch pore-forming agent; moreover, after phase inversion to form pores, pore channels are straight and there is low material transmission resistance.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) The following examples are intended to further illustrate the protection content of the present disclosure and are not intended to limit the protection scope of the present disclosure.

(4) All chemical reagents relate in the following examples are commercially available products, unless otherwise specified.

Example 1

(5) 1. 260 g of poly(oxyphenylene sulfone) (with a molecular weight of 4,200) and 1,040 g of NMP were stirred at 50? C. for 6 h until completely dissolved to form a mixed solution.

(6) 2. 150 g of tung oil, 150 g of glycerol, and 100 g of oleic acid were stirred at a room temperature for 10 min.

(7) 3. 4 kg of fly ash and the mixed solution were mixed through a mixer for 10 min, then added with an oil mixture obtained in step 2 and stirred for 5 min.

(8) 4. An obtained ceramic mud was further mixed with a pugging machine to achieve a certain plasticity; after the pugging was completed, the ceramic mud was aged in a aging room at 25? C. for 24 h.

(9) 5. An obtained aged ceramic mud was subjected to extrusion molding through an extruder, and then a resulting extruded green body was allowed to stand in an environment of 95% rh at 35? C. for 4 h; the green body was placed in pure water to allow phase inversion with water for 5 h at a room temperature, such that the NMP in the green body was dissolved into the water through capillary action, forming pores with a gradient in the green body.

(10) 6. The green body obtained in step 5 was subjected to conventional drying and sintering to form a fly ash-based ceramic flat membrane support with a gradient pore structure.

Example 2

(11) 1. 200 g of poly(oxyphenylene sulfone) (with a molecular weight of 4,200) and 1,000 g of NMP were stirred at 50? C. for 6 h until completely dissolved to form a mixed solution.

(12) 2. 250 g of tung oil, 200 g of glycerol, and 100 g of oleic acid were stirred at a room temperature for 10 min.

(13) 3. 4 kg of fly ash and the mixed solution were mixed through a mixer for 10 min, then added with an oil mixture obtained in step 2 and stirred for 5 min.

(14) 4. An obtained ceramic mud was further mixed with a pugging machine to achieve a certain plasticity; after the pugging was completed, the ceramic mud was aged in a aging room at 25? C. for 24 h.

(15) 5. An obtained aged ceramic mud was subjected to extrusion molding through an extruder, and then a resulting extruded green body was allowed to stand in an environment of 95% rh at 35? C. for 4 h; the green body was placed in pure water to allow phase inversion with water for 5 h at a room temperature, such that the NMP in the green body was dissolved into the water through capillary action, forming pores with a gradient in the green body.

(16) 6. The green body obtained in step 5 was subjected to conventional drying and sintering to form a fly ash-based ceramic flat membrane support with a gradient pore structure.

Example 3

(17) 1. 200 g of poly(oxyphenylene sulfone) (with a molecular weight of 4,600) and 900 g of NMP were stirred at 50? C. for 6 h until completely dissolved to form a mixed solution.

(18) 2. 150 g of tung oil, 120 g of glycerol, and 100 g of oleic acid were stirred at a room temperature for 10 min.

(19) 3. 4 kg of fly ash and the mixed solution were mixed through a mixer for 10 min, then added with an oil mixture obtained in step 2 and stirred for 5 min.

(20) 4. An obtained ceramic mud was further mixed with a pugging machine to achieve a certain plasticity; after the pugging was completed, the ceramic mud was aged in a aging room at 25? C. for 24 h.

(21) 5. An obtained aged ceramic mud was subjected to extrusion molding through an extruder, and then a resulting extruded green body was allowed to stand in an environment of 95% rh at 35? C. for 4 h; the green body was placed in pure water to allow phase inversion with water for 5 h at a room temperature, such that the NMP in the green body was dissolved into the water through capillary action, forming pores with a gradient in the green body.

(22) 6. The green body obtained in step 5 was subjected to conventional drying and sintering to form a fly ash-based ceramic flat membrane support with a gradient pore structure.

Comparative Example 1

(23) 1. 150 g of tung oil, 150 g of glycerol, and 100 g of oleic acid were stirred at a room temperature for 10 min.

(24) 2. 4 kg of fly ash was stirred through a mixer for 10 min, then added with an oil mixture obtained in step 1 and stirred for 5 min.

(25) 3. An obtained ceramic mud was further mixed with a pugging machine to achieve a certain plasticity; after the pugging was completed, the ceramic mud was aged in a aging room at 25? C. for 24 h.

(26) 4. An obtained aged ceramic mud was subjected to extrusion molding through an extruder, and then a resulting extruded green body was allowed to stand in an environment of 95% rh at 35? C. for 4 h.

(27) 5. The green body obtained in step 4 was subjected to conventional drying and sintering to form a fly ash-based ceramic flat membrane support.

Comparative Example 2

(28) The operating steps were the same as those in Example 1, except that an equal amount of starch was used to replace the poly(oxyphenylene sulfone)-NMP mixed solution, as shown in FIG. 1.

(29) TABLE-US-00001 TABLE 1 Comparison of properties of ceramic flat membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 2 Support Strength Water flux Pore Name (MPa) (m.sup.3/m.sup.2 .Math. h) size .Math. (?m) Example 1 26 4.8 6.53 Example 2 24 4.4 5.64 Example 3 20 4.3 5.70 Comparative Example 1 36 0.8 1.05 Comparative Example 2 30 1.7 2.67