RO135381A2 - Composition and process for making micro spheres based on alginate and titanium oxide (tio2) nanoparticles, with application in environment protection - Google Patents

Abstract

The invention relates to a process for preparing micro spheres based on sodium alginate, polyphenols and TiO2 nanoparticles with antioxidant and antifungal activity and with capacity of retaining heavy metals from waste water. According to the invention, the process consists, in a first stage, in preparing the polyphenol extract from rose petals, preparing a sodium alginate 2% solution by dissolving the polysaccharide in the polyphenol extract, by stirring mechanically, preparing TiO2 nanoparticles of titanium tetraisopropoxide, concentrated acetic acid and solution of polyvinylpyrrolidone dissolved in ethyl alcohol, by electrospinning, followed by calcination, adding the nanoparticles in the alginate solution, extruding the solution in a vessel containing calcium chloride solution as reticulation agent, resulting in micro spheres which exhibit antifungal properties against Aspergillus niger, as well as the property of retaining Cu2+ from contaminated water.

Description

STATE OFFICE FOR INVENTIONS AND TRADEMARKS Patent application

No.

Deposit date.....Z.9...Q5j.2Q20L

COMPOSITION AND PROCEDURE FOR MAKING MICROSPHERES BASED ON » »

OF ALGINATE AND TITANIUM OXIDE (TiO ₂ ) NANOPARTICLES WITH APPLICATIONS IN

ENVIRONMENT PROTECTION

DESCRIPTION OF THE INVENTION

Drinking water sources are subject to contamination and require appropriate treatment to remove disease-causing contaminants. Contamination of the drinking water supply can occur in both the source water and the distribution system after water treatment has already taken place. There are many sources of water contamination, including natural chemicals and minerals (eg, heavy metals, bacteria), local land use practices (fertilizers, pesticides, concentrate feed operations), manufacturing processes, and sewer overflows or spills of waste water. Fungi are potentially important contaminants because they produce certain toxic metabolites that can cause severe health hazards to humans and animals [l, 2].

The use of biopolymer systems for the retention of heavy metals from contaminated waters has gained increased attention due to the abundance of natural resources, relatively low cost price, low carbon emissions and low environmental impact [3, 4],

Sodium alginate is a water-soluble salt of alginic acid, a non-toxic natural polysaccharide extracted from marine brown algae that is used in the removal of pollutants from water, food, pharmaceutical and medicine industries [5-8].

Studies show that sodium alginate is preferred as a bioadsorbent compared to other materials due to various advantages: biodegradability, biocompatibility, hydrophilic properties due to carboxyl groups and abundance. The carboxyl groups of sodium alginate (-COO) induce the ability to form biodegradable gels (insoluble calcium alginate) in the presence of polyvalent cations (Ba ²⁺ , Ca ²⁺ , Zn ²⁺ , Cu ²⁺ or Fe ³⁺ ) through interactions ionic. The presence of divalent cations, especially Ca ²⁺ , leads to important conformational changes of sodium alginate, the well-known "egg box" model, due to the complexation of the carboxylic groups of the guluronate monomer [9],

For the removal of pollutants from water, compositions of sodium alginate in the form of microspheres, with polyvinyl alcohol [IO], starch [l l], cellulose [12], starch and clays [13], activated carbon [14], etc. . The formulations presented above refer only to the removal of pollutants in the form of heavy metals or organic compounds from contaminated waters, without considering obtaining an adsorbent based on sodium alginate that exhibits both the ability to remove heavy metals by photocatalysis and and antifungal activity.

Titanium dioxide (TiO2) exhibits excellent chemical-physical properties, which allows its use in environmental applications, photocatalysis, gas sensors, solar cells and lithium-based batteries [15]. The small surface area and wide band gap represent the main disadvantages of TiO ₂ . Titanium dioxide can be prepared in the form of nanoparticles, nanotubes [16] by the hydrothermal method, the sol-gel method [17], The disadvantage of the presented methods for obtaining T1O2 nanoparticles is the long synthesis time.

The electrospinning process is a new, easy-to-apply process for the production of nanowires from different polymers, due to its ease of handling and low costs. Through this process, wires with different diameters (from 10 pm to 10 nm) and a high surface/volume ratio are obtained, which is suitable for various industrial applications, such as: solar cells, biosensors, and medical. This process was patented in 1934. in the electrospinning process, a drop of polymer solution is placed at the end of a syringe needle by a pump. By applying a voltage to the polymer solution, such that the surface tension is overcome, the solvent is allowed to evaporate and obtain interconnected nanowires that are collected on a support. Increasing the electric field strength changes the hemispherical surface of the fluid at the tip of the needle into a conical shape, a shape known as the Taylor cone. At a certain intensity of the electric field, the repulsive electrostatic force dominates the surface tension and the solvent evaporates and a jet of the polymer solution is ejected from the tip of the Taylor cone. It is known to obtain TiO ₂ nanowires by electrospinning [18].

Patent application ROI25151 [19] describes the preparation of titanium dioxide photocatalysts in the form of nanostructured thin films used in the photocatalytic depollution of water polluted with various chlorinated organic pollutants. The advantages of using T1O2 nanoparticles as an adsorbent are due to their large surface area, high adsorption capacity, stability, lack of toxicity, biological and chemical inertness, and high affinity for organic and inorganic pollutants [20-22], Also, sa reported the use of dopants to improve the photocatalytic activity of TiO ₂ [23]. patent application RO133146 [24] presents the use of titanium dioxide (TiO ₂ ) doped with Fe and nitrogen / reduced graphene oxide, in the form of nanometric powder, for the photocatalytic degradation of chemical pollutants in the environment, active in the ultraviolet and visible ranges .

It is known to incorporate TiO ₂ in sodium alginate, in order to obtain antimicrobial food films [25] capable of destroying bacteria when irradiated with ultraviolet light. Both TiO ₂ and sodium alginate are approved by the US Food and Drug Administration as food additives. Under the action of the fluorescent lamp, for 5 h, the photocatalytic activity of the alginate/TiO ₂ nanocomposite led to the inhibition of the proliferation of Escherichia coli and Staphylococcus aureus bacteria, while no effect was registered by exposing the nanocomposite to light in the visible region [ 25].

The use of TiO ₂ nanoparticles in the form of a suspension for the adsorption of metal ions presents the following drawbacks: particle aggregation, loss of adsorption activity and difficulty in recovery after use. in order to reuse TiO 2 nanoparticles, spheres based on sodium alginate, TiO ₂ nanoparticles and magnetic particles [26, 27] or aerogels obtained from sodium alginate and TiO ₂ nanoparticles have been reported [ ₂₈ ],

Loosli and co-authors [29] suggest that calcium alginate induces a partial but significant deagglomeration of TiO ₂ nanoparticle agglomerates,

The compositions based on TiO ₂ presented above show either capacity for photocatalytic degradation of water pollutants, adsorption of pollutants in the ultraviolet-visible range, or antimicrobial activity.

The present invention removes the disadvantages of using TiO ₂ nanoparticle suspension by using TiO ₂ nanoparticles in the form of nanowires, obtained by electrospinning, and immobilizing them in a hydrophobic calcium alginate matrix.

In recent years, researchers have been increasingly concerned with studying phenolic compounds (from fruits, vegetables, grains, herbs and spices) due to their beneficial effects on human health. It is known from patent application RO133170 [30] the biochemical extraction of polyphenols from all parts of the Vitis vinifera plant, especially the red, black or blue species.

In addition to antioxidant activity, several studies have shown that phenolic compounds also have antimicrobial properties [31],

RO 135381 Α2 53

Natural polyphenols have been studied in water treatment, as flocculants and as bioadsorbents for heavy metals and dyes [32], due to their hydroxyl and carboxyl groups able to bind metal ions that have strong positive charges, such as iron ions ( ³⁺ ) and copper ( ²⁺ )· Polyphenols can act in different ways: by molecular complexation with pro-oxidant proteins, by chelation of potentially pro-oxidant metal ions (Fe ³⁺ , AI ³⁺ , Cu ²⁺ ) or by direct capture of reactive oxygen species (ROS) [33],

The main disadvantage of polyphenols is their lack of long-term stability, making these natural compounds very sensitive to light and heat. encapsulation of polyphenols is a method of their stabilization.

The technical problem that the invention solves, consists in making microspheres based on sodium alginate, polyphenol extract and titanium oxide nanoparticles, with antioxidant, antifungal activity and capacity to retain heavy metals from waste water. The microspheres, according to the invention, are made of a solution of sodium alginate dissolved in polyphenols extract and titanium dioxide nanoparticles obtained by electrospinning and calcination.

The process for obtaining the microspheres consists in a first stage of the preparation of the polyphenol extract from rose petals, the preparation of the sodium alginate solution 2% sodium alginate (g/vol.) by dissolving the polysaccharide in the polyphenol extract, by magnetic stirring, obtaining TiO2 nanoparticles starting from titanium tetraisopropoxide, concentrated acetic acid and polyvinyl _pyrrolidone solution dissolved in ethyl alcohol, by electrospinning and then calcination, and in the last step TiO2 nanoparticles are added to the sodium alginate solution and the solution is extruded with the help of a pump equipped with a needle and syringe, in a vessel containing a solution of calcium chloride as a cross-linking agent, from which microspheres are obtained with both antifungal properties against the Aspergillus niger fungus and copper retention (Cu ^{2 +} ) from contaminated waters, through photocatalysis.

The present invention presents the following advantages:

The obtained compound simultaneously exhibits antifungal activity and capacity to retain heavy metals from waste water, through photocatalysis;

- To obtain polyphenols, pomace waste and rose petals are used, thus contributing to reducing the impact on the environment;

TiO ₂ nanoparticles are used, which present photocatalytic activity, to the detriment of UV absorbers of organic origin, which present toxicity;

The instability of polysaccharide (sodium alginate) and polyphenols is removed by making water-insoluble microspheres.

Raw materials:

- Sodium alginate, powder, (C6H ₇ O ₆ Na) _n supplied by BioChemica, characterized by: molecular mass in the range 10000-600000 g/mol, purity 90.8%, heavy metals (Pb) max. 0.002%, loss on drying max. 15%, pH (1% water) 5.5-8.0, sulphated ash 18-27%.

- Polyphenol extract from rose petals, characterized by a total polyphenol content of 53 mg/g GAE and DPPH radical quenching activity of 52.6% (under the conditions of testing a concentration of 2 g polyphenol extract /100 mL methanol)

- Titanium tetraisopropoxide

- Concentrated acetic acid

- Polyvinylpyrrolidone

- Ethyl alcohol 98% concentration

- 2% CaCU solution in distilled water

The method of making the invention is presented below:

(a) Preparation of polyphenol extract from rose petals. 20 g of red rose petals, fresh, native, freshly washed, are placed in an Erlenmeyer vessel with 100 mL of distilled water, with the help of a magnetic stirrer, where they are boiled at a temperature of 80 °C, for 30 minutes and 200 rpm. After 30 minutes, the extract is filtered through a filter paper and stored in the dark until use.

(b) Preparation of the sodium alginate solution 2% sodium alginate (g/vol.) by dissolving the polysaccharide in the polyphenol extract, by magnetic stirring at a temperature of 90+1 °C, for 4 h, 200 rpm.

(c) Obtaining TiO2 nanoparticles by electrospinning a solution consisting of 1.5 mL of titanium tetraisopropoxide dissolved in 3 mL of concentrated acetic acid, over which was added with stirring for 30 minutes, a solution consisting of 0.45 g of polyvinylpyrrolidone dissolved in 10 mL ethyl alcohol of concentration 98%. Electrospinning took place in an electrospinning equipment equipped with a peristaltic pump into which the electrospinning solution and a circular collector were introduced, under voltage conditions of +16.22 kV, a solution flow rate of 1.5 mL/h and a distance between needle and collector of 14 cm. The obtained nanofibers were calcined at a temperature of 550 °C, speed of 2 °C/min, for 3 h. As shown in Figure 1 (a), T1O2 nanoparticles with a size between 24-188 nm were obtained .

(d) Addition of 0.1% (g/vOl) T1O2 nanoparticles into the sodium alginate solution and further mixing at 90±1 °C for 30 minutes, 200 rpm (e) Extrusion of the obtained solution in a peristaltic pump equipped with a needle and syringe, at a flow rate of 180 mL/h, at room temperature, in a vessel containing 2% calcium chloride solution, crosslinking agent, for 24 h.

(f) Filtering through a Whatman #1 filter paper, washing with distilled water and drying the formed microspheres at 60±1 °C for 8 hours.

in parallel, microspheres were obtained without T1O2 nanoparticles (control sample), under the same conditions.

For the microspheres based on sodium alginate, polyphenols and T1O2 nanoparticles obtained, the following properties were determined:

- morphology, diameter and size of nanowires and elemental analysis by scanning electron microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDS) using a high-resolution scanning electron microscope QUANTA 450 FEG (FEI, Eindhoven, The Netherlands) , high vacuum working mode, after deposition on the C strip.

- retention of the copper ion (Cu ² ) from synthetic waters using an Atomic Absorption Spectrometer with graphite furnace, Model Avanta ULTRA Z 933 PLUS (GBC Scientific Equipment PTY.Ltd.-Australia). 0.5 g of adsorbent is introduced into 50 mL of Cu ( ²⁺ ) 3 mg/L solution in a Berzelius glass which is then placed under a UV lamp for 60 minutes. Every 10 minutes, 3 mL of sample is extracted from the Berzelius beaker, filtered using a syringe with a filter membrane having a pore diameter of 0.45 µm and analyzed for the detection of Cu ( ²⁺ ) ion.

- the antifungal activity on the fungus Aspergillus niger, which is also found in waste water, for this purpose, the fungus Aspergillus niger was grown on Potato Dextrose Agar (PDA) culture medium in Petri plates with a diameter of 90 mm, for 7-9 days at a temperature of 25 °C. The spore suspension was obtained under aseptic conditions; the number of spores being determined by reading in the Thoma camera. The spore concentration used was 10 ⁶ spores/mL. The culture medium was prepared in reagent bottles according to package instructions and autoclaved at 121 °C for 20 minutes. After sterilization and cooling, approximately 0.7 g of powdered sample was incorporated into 20 mL of culture medium under aseptic conditions and then

V) this was poured into petri dishes. After solidification, the culture medium was inoculated with 2 µL of spore suspension in the center of the plate. All determinations were performed in duplicate. Blank samples were made using the same working method, but without the sample.

Petri dishes were then insulated with parafilm and incubated at 25 °C for 7 days. Colony growth was determined by measuring their diameters on the 7th day of incubation.

Scanning electron microscopy images for electrospinning TiO2 nanoparticles, calcium alginate and polyphenol extract microspheres, and microspheres containing TiO2 nanoparticles are shown in Figure 1 (a–d). in agreement with the surface images obtained by SEM analysis, the obtained microspheres (Fig. 1 (b, c)) presented a rough surface, with a diameter between 0.903-1.069 mm and nanoparticles of T1O2 had a size between 50.13 -101.1 nm (Fig, 1 (a, d)). The presence of TiO2 nanoparticles in the calcium alginate matrix is also evidenced by elemental analysis (Table 1).

Table 1. Elemental analysis of T1O2 nanoparticles and calcium alginate microspheres/TiOi nanoparticles compared to calcium alginate microspheres.

Chemical element Calcium alginate microspheres/TiO ₂ nanoparticles TiO2 nanoparticles Percentage by weight, % Atomic percentages, % Percentage by weight, % Atomic percentages, % C K 41.77 51.36 K 50.17 46.31 75.67 90.30 They have M 1.92 0.14 CaK 4.82 1.78 You K 1.32 0.41 24.33 9.70

The obtained adsorbent has an efficiency of 84.3% for the retention of the Cu ( ²⁺ ) ion in a concentration of 3 mg/L, with the maximum efficiency being reached at 60 minutes (88.14%), under conditions of magnetic stirring with speed of 400 rpm and UV lamp exposure.

It was observed that the degree of inhibition on the development of the fungus Aspergillus niger was 16.4% for the calcium alginate sample and 18.6% for the calcium alginate/TiO ₂ nanoparticle sample. The antifungal activity can be explained both due to TiO ₂ nanoparticles by the migration of the electron from the valence band to the conduction band, generating hydroxyl radicals on the surface, as well as to the polyphenols in the structure of the microspheres.

Claims (2)

demand 1. Composition of microspheres based on sodium alginate, polyphenols and TiO2 nanoparticles, characterized in that 2 g of sodium alginate powder dissolved in 100 mL of polyphenol extract and 0,1 g were used to obtain them. TiO ₂ nanoparticles obtained by electrofilament with a size of 50,13-101,1 nm, having a diameter of 0,903-1,069 mm, a Cu ( ²⁺ ) retention efficiency of 88.14%, at 60 minutes of exposure to UV lamp and antifungal activity against Aspergillus niger for 7 days of exposure, used to prevent the growth and development of toxic fungi and to retain heavy metal ions from wastewater. 2. Process for the production of microspheres based on sodium alginate, polyphenols and TiO ₂ nanoparticles, characterized in that they are obtained in a peristaltic pump at a flow rate of 180 mL / h at room temperature by drip into a vessel containing 300 mL of 2% calcium chloride solution.