SI24144A - Nanocomposite ultrafiltration membrane production procedure with integrated mineral clay particles for sewage water cleaning - Google Patents

Abstract

The invention relates to a process for the production of a nanocomposite ultrafiltration membrane with incorporated minerals of clay minerals having a large active surface and an excellent ability to adsorize the various pollutants from the waste water. The proposed process comprises pretreating the PP membrane in acetone and wetting the wet membrane with a monomer solution with dispersed O-MMT particles (organically modified montmorillonite) by treatment in ultrasound. The in-situ polymerization of the nanocomposite hydrogel in the pore PP of the membrane is followed by UVA light. According to the procedure described, the entire surface of the membrane is covered with a hydrogel or The hydrogel also polymerizes in the interior of the PP membrane. The mechanism of removing pollutants from waste water is in this case a combination of filtration and adsorption, which makes the cleaning effect greater than in the case of commercial ultrafiltration membranes, where the pollutants on the membrane are retained only mechanically.

Description

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PROCESS OF PRODUCTION OF NANOCOMPOSITE ULTRAFILTRATION MEMBRANE WITH INCLUDED CLINICAL MINERAL PARTICLES FOR CLEANING

WASTE WATER

FIELD OF THE INVENTION

The present invention relates to the field of environmental protection and materials, and relates to a process for the production of nanocomposite ultrafiltration membranes, the active part of which is a natural, environmentally friendly clay mineral particles having a large active surface and an excellent ability to adsorb dyes, heavy metals, herbicides, pesticides, etc. for wastewater treatment.

TECHNICAL FIELD

A technical improvement of this invention is the use of clay minerals in the ultrafiltration membrane, which, by increasing the number of active sites in the membrane, improves the ability to remove various pollutants from wastewater compared to conventional ultrafiltration membranes. The mechanism of removal of pollutants from wastewater in this case is a combination of filtration and adsorption, which makes the cleaning effect greater than in the case of commercial ultrafiltration membranes, where the pollutants on the membrane are retained only mechanically.

The wastewater of many industries generates large amounts of colored wastewater. Even the small presence of colored releases has an environmental impact, as it inhibits photosynthesis in the aquatic ecosystem. Colored effluents also have a detrimental effect on humans, as they can be mutagenic and / or carcinogenic. They can cause damage to the reproductive system, liver, brain and lead to kidney failure.

Clay minerals are naturally occurring, environmentally friendly materials with a high active surface area, which are often used lately for the purpose of adsorption and removal of organic impurities from water. Organic modification enhances their sorption capacity for non-flammable organic compounds (phenols, naphthalenes, benzenes, anthracenes, etc.), dyes and heavy metal ions. Their advantage over charcoal is its affordability, its high chemical and mechanical stability and its ecological integrity. The most commonly used clay minerals for dye adsorption in textile waste water are sepiolite, zeolite, montmorillonite, smectite and bentonite. However, the practical utility of dispersed particles as adsorbents is limited. The problem is primarily the separation of solids from the liquid after the cleaning process. It is therefore an object of the invention to develop such an ultrafiltration membrane that will have clay mineral particles incorporated into the membrane membrane system so that the adsorption capacity (active surface) of the particles to remove pollutants from wastewater is maintained. For membrane systems with diffused adsorbents, solid-liquid separation is not required, and their advantage is the possibility of upgrading by simply combining larger membranes or using a membrane with a larger active surface.

Known state of the art

In many studies, the authors have studied the influence of different modifications of clay minerals (in the form of dispersed adsorbents) on the adsorption of different dyes. Ceyhan et al., Turk. J. Chem. 25 (2001) 193-200, synthesized hexadecyltrimethylammonium bentonite (HDTAbentonite) and was the first to conduct an adsorption study of some textile dyes such as Everdirect Supra Yellow PG, Everdirects Supra Orange 26 CG, Everdirect Supra Rubine BL, Everdirect Supra Blue 4BL and Everdirect Supra Red BWS on Na-bentonite and HDTMA-bentonite. He found that although Na-bentonite had no affinity for these dyes, HDTMA-bentonite showed a significant ability to adsorb dyes from solution. Baskaralingam et al., Journal of Hazardous Materials 128 (2006) 138-144, in their study examined the possibility of removing Acid Red 151 acidic dye from aqueous solution using cetyldimethylbenzylammonium bentonite and cetylpyridine bentonite and found that modified bentonite exhibits acid dye adsorption capacity . A similar survey was also conducted for hectorites. Yang et al., Textile Research Journal 75 (2005) 622-626, used nano-montmorillonite and some modified clay nanominerals to study the adsorption of non-ionic, anionic and cationic dyes. He monitored the influence of the dependence between different dyes and different structures (both chemical structures and morphologies) of the clays on the adsorption rate. He found that clay nano-minerals have an adsorption capacity of 600 mg and more of adsorbate per gram of adsorbent at a liquid / solid ratio of 100: 1. At the same time, he also found that clay nano-minerals can adsorb 90% of the dye at an initial dye concentration of 6 g / L or 60% based on the weight of the adsorbent, indicating a high affinity of the adsorbent for the dye. This study showed that with certain modifications of nano-clays, e.g. montmorillonite, we can very easily get excellent adsorbents for anionic, cationic and non-ionic dyes.

Clay minerals are incorporated into polymer hydrogels mainly to improve mechanical and thermal properties, stability and swelling of the hydrogel. Xia et al., Polymer 44 (2003) 33893393, designed a hydrogel with Na ⁺ - montmorillonite particles incorporated as a reinforcing part of the hydrogel matrix in order to improve the mechanical properties or swelling ability of the hydrogel. Such hydrogels have attracted a great deal of attention especially in the fields of medicine, sensors and separation processes. Liang et al., Advances in Colloid andInterface Science 134-135 (2007) 151-166, used organically modified montmorillonite for hydrogel preparation and found that the swelling rate was increased and that the thermal properties of nanocomposite hydrogel were improved compared to conventional N- isopropylacrylamide (NIPAM) hydrogel. Haraguchi et al., Current Opinion in Solid State and Materials Science 11 (2007) 47-54; Advanced Materials 14 (2002) 1120-1124; Macromolecules 35 (2002) 10162-10171, synthesized a hydrogel with incorporated laponite particles without the presence of a crosslinker. The layered laponite particles acted as a multifunctional crosslinker that anchors the polymer chains to the particles, forming a hydrogel network.

The process of hydrogel synthesis in membrane pores was performed by Ronald F. Childs et al., Journal of Membrane Science 108 (1995) 37-56, which used mainly polyelectrolyte hydrogels with numerous ion-exchange capable side groups. Poly (4-vinyl pyridine) was used as the cation-exchange hydrogel, while poly (styrene sulfonic) acid was used for the anion-exchange hydrogel. The filling of the pores of the carrier material was performed by in situ polymerization or by crosslinking of polyelectrolyte hydrogel in the pores of the substrate by UV light. As a carrier material, it used a PP microporous substrate, which limits the swelling of the hydrogel and gives the whole system mechanical strength. Since then, his team of researchers has produced numerous filled pore membranes with different polyelectrolyte hydrogels that have improved and more uniform properties compared to membranes having pore walls coated with an ion exchange substance, United States Patent, Patent no: US 6,258,276 BI ; Journal of Membrane Science 135 (1997) 81-92; Desalination 140 (2001) 265-275; Journal of Membrane Science 152 (1999) 129-140; Journal of Membrane Science 136 (1997) 221-232; Journal of Membrane Science 153 (1999) 45-56; Desalination 121 (1999) 149-158; Separation and Purification Technology 22-23 (2001) 507-517; Journal of Membrane Science 254 (2005) 89-99.

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After reviewing the state of the research, we have found that the manufacture of nanocomposite membranes, the pores of which are filled with hydrogel with incorporated particles of organically modified montmorillonite layered in a hydrogel matrix, is a novelty in the field of nanocomposite membranes. Another novelty is the use of such a membrane to remove dyes from textile wastewater.

DESCRIPTION OF THE INVENTION

The present invention describes a process for manufacturing an ultrafiltration membrane by in-situ polymerization of nanocomposite hydrogel in pores of a PP membrane, in which the active part is a natural, environmentally friendly clay mineral particles having a large active surface and an excellent ability to adsorb dyes, heavy metals, herbicides, pesticides, etc. for wastewater treatment.

To prepare the nanocomposite membrane, we used a polypropylene (PP) film membrane manufactured by Wathman Internacional Ltd. (England) with a pore size of 0.2 pm. 90 mm circular PP membrane membranes were used.

In the manufacture of the composite hydrogel, the monomer (N-isopropyl acrylamide NIPAM), crosslinker (Ν, Ν-methylenebisacrylamide - BIS) and photoinitiator (Irgacure 2959) were dissolved in an aqueous dispersion of O-MMT particles (organically modified montmorillonite, type Nalcafil Chem, manufactured by Nalcafil Chem. Germany) dispersed in a solution of 1 g / L surfactant Inutec SPI (Orafti Bio Based Chemicals). The crosslinker content was 1 wt% and the O-MMT particle weight was 0.25; 0.5; 0.75 and 1 wt%, based on the weight of monomers included in the composite hydrogel.

Due to the hydrophobicity and incompatibility of the membrane with the hydrogel, the membrane was pretreated according to various procedures before polymerization of the hydrogel. We used Tanaterge INF (Tanatex), which was dissolved once in water, second in acetone, and acetone as a wetting agent. The wetting agents were used to achieve greater deposition of composite hydrogel in the pores of PP membranes. The nanocomposite hydrogels were polymerized in the pores of the membrane after two procedures. In the first method, the dry PP membrane was immersed in a monomer solution with dispersed O-MMT particles, and in the second method, a wetted PP membrane was immersed in a monomer solution with dispersed O-MMT particles. Prior to the polymerization process, the monomer solutions in which the submerged PP membrane was immersed were purged with N2.

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The composite hydrogel was polymerized in the pores of the PP membrane in such a way that the wetted and monomial solution with the included O-MMT particles was embedded in the dipped PP membrane between two PET films, so that the layers were gently compressed, thereby removing excess solution and squeezing air bubbles. . The sample thus prepared was inserted into a UV chamber and irradiated for 2 hours with UVA light with a wavelength of 350 nm. After polymerization was complete, the films were removed and the PP membrane was washed in 500 mL of distilled water to remove unreacted monomer and crosslinker. We rinsed for 4 days, replacing water several times a day.

A nanocomposite membrane with particles of clay minerals included in the hydrogel was used to discolor the wastewater by adsorbing the dye molecules to a large specific particle surface.

The effect of various PP membrane pretreatment processes on the uptake ability of the nanocomposite hydrogel, which is the subject of the invention, is explained by the increase in membrane mass after in situ UV polymerization of the nanocomposite hydrogel. The results are summarized in Table 1.

The labels of the various pre-treated PP membranes in the tables and figures are as follows:

T - PP membrane treated with wetting agent dissolved in water TA - PP membrane treated with wetting agent dissolved in acetone A - PP membrane treated with acetone as wetting agent S - PP membrane pre-treated and dry submerged M - PP membrane pre-treated and wet submerged U-PP diaphragm solution, pre-treated and submerged in ultrasound monomial solution

Table 1: Increase in PP membrane mass after in situ UV polymerization of nanocomposite hydrogel depending on the wetting mode

Table 1 shows that, for samples pretreated with Tanaterge INF dissolved in water, the PP membrane mass increases from 1.6 to 2.3% depending on the condition of the pre-treated PP membrane (dry or wet). The ultrasonic treatment of the PP membrane achieves an additional increase in mass: in the dry PP membrane immersed in the monomial solution and treated in the ultrasound, the mass increases by 3.4%, while in the PP membrane which is wet immersed in the monomial solution and treated in ultrasound by 3%.

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The ultrasonic treatment of the PP membrane allows better penetration of a larger amount of the monomeme solution into the pores of the PP membrane. In the case of PP membranes pretreated with Tanaterge INF dissolved in acetone and dry immersed in the monomial solution, the mass increase is 2.3%, whereas for the PP membranes dry immersed in the monomial solution and treated in ultrasound, the mass increases by 1.1%. The increase in PP membrane mass is greatest for PP membranes that have been immersed in a wet monomer solution, with a PP membrane pre-treated with Tanaterge INF dissolved in acetone and wet immersed in a monomial solution, and a 5.5% increase in mass PP membranes pretreated with Tanategre INF wetting agent dissolved in acetone and wet immersed in a monomial solution and sonicated 14.9%. Even in this case, ultrasound treatment further increases the mass of the PP membrane.

In acetone-wetted PP membranes, dried and immersed in a monomial solution, the mass did not increase. The acetone with which the PP membrane was pretreated evaporates during drying and thus does not help to improve the passage of the monomeme solution into the pompous membrane system. However, a significant increase in mass was detected in the PP membrane, which was pretreated in acetone and immersed in a monomial solution wet, since the increase in mass was 28%, respectively. in the case of PP membranes pretreated in acetone and wet immersed in a monomial solution and ultrasound treated as much as 50%.

The morphology of the in situ polymerized nanocomposite ultrafiltration membrane, which was pretreated in acetone and wet immersed in the monomial solution and treated in the ultrasound of the invention, is explained by the electron microscope (SEM) images in Figure 1.

Figure 1: SEM images of the nanocomposite ultrafiltration PP membrane after UV polymerization of the nanocomposite hydrogel in the membrane; a - the surface of the membrane, which has been pretreated in acetone and wet immersed in a monomemic solution with O-MMT particles; b - the surface of the membrane, which has been pretreated in acetone and wet immersed in a monomemic solution with O-MMT particles and treated in ultrasound; c - cross-section of a membrane that has been pretreated in acetone and wet immersed in a monomemic solution with O-MMT particles and treated in ultrasound

The SEM images of the PP membrane surfaces (Figs. 1a and 1b) clearly show the polymerization of the hydrogel in the pores of the membrane. Membrane appearance and amount of nanocomposite application

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hydrogels depend on the type of pretreatment. In the acetone pretreated membrane, which was immersed wet in a monomial solution with O-MMT particles and treated with ultrasound, the entire surface was covered with hydrogel, compared to the ultrasound treated membrane, where the surface was only partially covered with hydrogel. It is clear from the SEM cross-sectional view (Fig. 1c) that the hydrogel polymerized also inside the PP membrane or. that the pores of PP membranes are filled with nanocomposite hydrogel.

The change in the hydrophilic / hydrophobic character of the PP membrane due to the polymerization of the hydrogel with the included clay mineral particles in the pores of the membrane is explained by the results of contact angle measurements (Table 2).

Table 2: Contact angles of untreated PP membranes and membranes with nanocomposite hydrogel incorporated

Table 2 shows that the contact angle of untreated PP membranes is 139.42 °, meaning that the membrane surface is completely hydrophobic. After polymerization of the hydrogel in the PP membrane, the contact, as in the case of the PP membrane sample pretreated with acetone and wet immersed in the monomial solution, decreased slightly (137.98 °). Nevertheless, the PP membrane is still hydrophobic (most of the PP membrane remained uncovered by nanocomposite hydrogel - Figure 1a). While the contact angle of the PP membrane specimen pretreated in acetone and wet immersed in the monomial solution and treated in ultrasound is reduced to 44.55 °; the surface is completely covered with nanocomposite hydrogel (Fig. 1b) and therefore hydrophilic. Therefore, this treatment process represents the most optimal way of fabricating a nanocomposite ultrafiltration PP membrane with O-MMT particles involved.

The effect of the removal of dyes from wastewater by means of a developed nanocomposite ultrafiltration membrane containing clay mineral particles, which is the subject of the invention, is explained by the results presented in Table 3.

An aqueous solution of 0.1 g / L Acid Orange 33 (commercial protein fiber dye) was prepared for the discoloration test. The pH of the dye solution was adjusted to pH 3 with a 0.1 mol HCl solution. The untreated PP membrane and the PP membrane with the highest hydrogel content (PP A / M / U) were placed in an ultrafiltration cell through which the dye solution was discharged at various pressures (100, 200 and 300 kPa). Discoloration with :: ····

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were determined spectrophotometrically by measuring the absorbance of the dye solution before and after ultrafiltration.

Table 3: Degree of removal of dye from solution and time of passage of solution through untreated PP membrane (PP) and hydrogel treated membrane (PP A / M / U) as a function of pressure in the ultrafiltration cell

Table 3 shows that the degree of discoloration using the untreated PP membrane at a pressure of 100 kPa is 21.94%. As the pressure in the ultrafiltration cell increases, the time of solution flow through the membrane decreases. At higher pressure, the pushing force that causes the solution to flow through the pores of the membrane is higher, which causes the decolourisation rate to decrease by 15.98% at a pressure of 200 kPa and 9.75% at a pressure of 300 kPa.

The treated PP membrane requires different filtration conditions than the untreated one, since the polymerized nanocomposite hydrogel fills the pores and thus reduces them (which is also observed in SEM images - Fig. 1b and 1c), so that at 100 kPa the dye solution does not pass through the membrane. At a pressure of 200 kPa, the time of passage of the solution through the membrane was extended to 60 minutes, and the removal rate of the dye (adsorption of the dye molecules to the active sites of O-MMT particles in the nanocomposite) was 80.33%. While at a pressure of 300 kPa, the passage time of the solution is 45 minutes and the degree of discoloration is 67.30%.

Claims (7)

PATENT APPLICATIONS A process for manufacturing a nanocomposite ultrafiltration membrane with clay mineral particles incorporated, characterized in that a commercial PP membrane is used as the carrier material. A manufacturing process according to claim 1, characterized in that the commercial PP membrane is wetted in acetone. A manufacturing process according to the preceding claims, characterized in that a nanocomposite hydrogel is used for filling the pores of the support material into which the dipped membrane is dipped according to claim 2 and ultrasound treated. A manufacturing process according to the preceding claims, characterized in that the nanocomposite hydrogel is polymerized in situ with membrane UVA light (at 350 nm) for at least 2 hours. A manufacturing process according to the preceding claims, characterized in that the entire surface of the PP membrane is covered with a nanocomposite hydrogel. Manufacturing process according to the preceding claims, characterized in that for the production of the nanocomposite hydrogel, the monomer (N-isopropyl acrylamide NIPAM), the crosslinker (Ν, Ν-methylenebisacrylamide - BIS) and the photoinitiator (Irgacure 2959) are dissolved in aqueous dispersion of particulate minerals. A manufacturing process according to the preceding claims, characterized in that the weight fraction of the clay mineral particles is at least 1% by weight. 1/2 Table 1 The pattern Weight gain (%) PP_T / S 1.6 PPT / M 2.3 PP_T / S / U 3.4 PP T / M / U 3 PPTA / S 2.3 PPTA / M 5.5 PP_TA / S / U 1.1 PPTA / M / U 14.9 PPA / S 0 PP_A / M 28.1 PP_A / S / U 0 PP A / M / U 50.3 Table 2 The pattern Contact angle (°) Standard error (°) PP 139.42 1,73 PP A / M 137.98 3.23 PP A / M / U 44.55 2.75 Table 3 The pattern Pressure (kPa) Pass time (min) The rate discolored a (%) PP 100 11 21,94 PP 200 4 15.98 PP 300 1 9.75 PP A / M / U 200 60 80.33 PP A / M / U 300 45 67.30 2/2