NATURAL FLOCCULANTS BASED ON BIOPOLYMERS AND METHODS FOR PREPARING THEM

Abstract

This invention consists of the development of a new method to stabilize natural biopolymers, especially chitosan, for use as a flocculant by adding metallic sulfates in a certain proportion, thereby improving shelf life at least 10 times and improving turbidity removal performance by up to 50% compared to the biopolymer alone or other chemical flocculants-coagulants, without significantly increasing production costs, thus offering a competitive and environmentally compatible advantage for users of these products.

Description

NATURAL FLOCCULANTS BASED ON BIOPOLYMERS AND METHODS FOR PREPARING THEM FIELD OF INVENTION The present invention relates to the preparation of flocculant agents, more precisely to the biopolymer chitosan stabilized with the addition of certain metallic compounds to improve its functionality in water treatment. BACKGROUND OF THE INVENTION Water is a vital natural resource for industrial activity. While its local use has decreased over time, it remains essential. It is estimated that by 2025, water consumption in this sector will reach 1.2 x 10¹² m³ / year, compared to 0.75 x 10¹² m³ / year in 1995. The productive sector is not only the biggest spender, but also the biggest polluter, since more than 80% of the world's hazardous waste is produced in industrialized countries, while in developing nations this figure reaches 70%, originating from processes that discharge their water without any treatment, thus contaminating available water resources. (Fernández-Alba, 2006). 59% of total water consumption in the countries Ref. 309318 Developed water is allocated to industrial use, 30% to agricultural consumption, and 11% to domestic use, according to the first United Nations report on the development of the world's water resources. (Fernández-Alba, 2006). Conventional water treatment for drinking water purification and clarification basically comprises the stages of coagulation-flocculation, sedimentation, filtration, and disinfection. A similar process is followed for wastewater treatment, although with important differences due to the type and concentration of substances present, such as suspended and dissolved solids of biological or chemical origin. To carry out these clarification processes, cationic and / or anionic chemicals are often added during the coagulation-flocculation process, in conjunction with polymers, to accelerate this process. Among the most commonly used products are: aluminum sulfate, sodium aluminate, aluminum chloride, ferric chloride, ferric sulfate, ferrous sulfate, and polyelectrolytes, among others, some of which are documented and some patented: US 3,338,828, US 3,446,731, US 4,332,693, US 4,415,467, and US 5,415,808. However, the presence of aluminum in these compounds has been associated with health problems, such as the correct mineralization of calcium in bones, anemia, glucose intolerance, heart problems or neurological problems such as Parkinson's disease, amyotrophic sclerosis or Alzheimer's disease among others, because aluminum replaces common metal ions in proteins and enzymes, causing a decrease in cell metabolism (Labarces Campo, 2007). It is estimated that the average person in the United States consumes between 20 and 40 mg of aluminum per day, with 1% coming from drinking water and approximately 90% from food. For this reason, in developed countries and regions such as Japan, the United States, and Europe, chemical flocculants are being replaced by natural alternatives. These are water-soluble substances derived from plant or animal materials that act similarly to chemical flocculants by clumping together suspended particles in raw water, facilitating sedimentation and reducing initial turbidity. Furthermore, some of these flocculants possess antimicrobial properties, thus helping to reduce the use of disinfectants in water. The most studied natural coagulant and flocculant species currently include Moringa oleifera, cassava, starch, cactus (Latifaria and Prosopis juliflora), tamarind, seaweed, white bean, cactus, prickly pear (Opuntia cochinellifera), and chitosan, among others, which are present in the following patents: US 5,433,865, US 5,543,056 and in application WO 2012 / 018249. All the references mentioned above are related to obtaining other flocculants of natural origin, and those in which chitosan is mentioned are for its use as an antimicrobial and in no way refer to procedures similar to those proposed in the invention. Some of the advantages of flocculants of natural origin are that, unlike chemical flocculants that produce sludge rich in hydrated aluminum oxides, which are toxic and easily resuspended, biological alternatives form sludges of greater size and density, making them more stable, but at the same time biodegradable by the microbial flora present in the water. Chitosan (poly-β-(1,4)-D-glucosamine-N-acetyl-D-glucosamine) is one of the few naturally occurring cationic polysaccharides that exhibits remarkably interesting physicochemical characteristics; it can have a molecular weight ranging from 30,000 to several hundred thousand g / mol. It is derived from chitin by deacetylation under highly alkaline conditions and at high temperatures. It is a biodegradable, non-toxic, biocompatible, semipermeable, and versatile polymer. Furthermore, it has the ability to bind lipids and metals such as copper, zinc, lead, vanadium, and iron. That is why the market for The main use of chitosan products is as a flocculant in water treatment. Coagulation and flocculation mechanisms are proposed for water contaminated with organic waste. This positively charged polymer has the ability to combine with negatively charged molecules. The efficiency of this process depends primarily on the pH. By 2006, the chitosan market was over eight thousand tons, of which 49% was used for water treatment. Japan was the main consumer with almost 3,000 tons, followed by the United States and Europe with almost 500,000 and 400,000 tons respectively. (Global Industry Analyst Inc., 2008). The state of the art describes flocculants comprising chitosan along with organic acids and metallic sulfates, for example in documents CN 106830251, CN 102977227, CN 108996643, CN 103043764 and US 2004 / 0026657 Al. However, chitosan, being a polymer of biological origin, progressively hydrolyzes once it is solubilized under acidic conditions, causing it to lose its effectiveness as a flocculant over time. Therefore, there is a need for chitosan-based flocculants that minimize aluminum content while maintaining their functionality in water treatment and having an extended shelf life. ML / a / ZUZU / UUO ML / a / ZUZU / UUO OBJECT OF THE INVENTION Considering the disadvantages of currently available flocculants, it is an object of the present invention to provide biopolymer-based flocculants, especially chitosan, conditioned to extend their shelf life and functionality as a flocculant-coagulant in water treatment. Another object of the present invention is to provide a flocculant whose aluminum levels are less than 0.2 ppm. An additional object of the present invention is to provide a method for preparing a stabilized chitosan-based flocculant so that it can maintain its flocculant-coagulant activity for at least 60 days in high and low turbidity waters. BRIEF DESCRIPTION OF THE INVENTION In a first aspect of the present invention, a polymeric flocculant comprising chitosan and metallic salts is described. In another aspect of the present invention, a kit comprising granulated chitosan and an activating solution comprising metallic salts is also described. Another aspect of the present invention relates to a method for preparing stabilized biopolymers, particularly chitosan, which, once solubilized in an acidic medium, can maintain its activity as a flocculant-coagulant for at least 60 days in high and low turbidity waters. BRIEF DESCRIPTION OF THE FIGURES The novel aspects considered characteristic of the present invention will be set forth in detail in the appended claims. However, some embodiments, features, and some of its objects and advantages will be better understood in the detailed description when read in conjunction with the appended figures described below: Figure 1 represents the viscosity drop of 1% w / v chitosan with open and closed container solubilized in acidic medium (1% glacial acetic acid v / v) as a function of time (up to 28 days after preparation). Figure 2 reflects the effectiveness of mature and new chitosan as a flocculant for water with a solids concentration between 176 and 965 mg / L. Figure 3 reflects the effectiveness of chitosan as a flocculant for water with a solids concentration between 176 and 965 mg / L compared to chemical flocculants and aluminum sulfate dosed at 20 mg / L respectively. Figure 4 reflects the effectiveness of chitosan older than 60 days conditioned with CUSO4 and Fe2(804)3 for the removal of dissolved and / or suspended solids in a range between 88 and 1053 mg / L. ML / a / ZUZU / UUO ML / a / ZUZU / UUO Figure 5 is a graph that represents the percentage decrease in turbidity of raw water with 42mg / L of dissolved solids treated with different copper sulfate-chitosan ratios. Figure 6 represents a graph of the turbidity reduction effectiveness of different flocculants evaluated over a period of 96 h. Figure 7 represents a graph of the results of the evolution of turbidity in the inlet water, overflow and after the filter system of the J&F Field water treatment plant during a period of 96 hours. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flocculant based on one or more biopolymers and one or more metallic salts and one or more acids. In accordance with this aspect of the invention, the natural biopolymers that can be used as a flocculant are: starch, cellulose, beta-glucans, dextrins, pechins, chitin, chitosan, among others, independently or in combination. In a particular embodiment of the invention, the biopolymer is chitosan. In accordance with this aspect of the invention, chitosan refers to granulated chitosan, non-granulated chitosan, high molecular weight chitosan, low molecular weight chitosan, wherein the chitosan can have a dry basis purity of approximately 40%, approximately 50%, approximately 60%, approximately 70%, approximately 80%, approximately 90% or up to approximately 95%. In a preferred embodiment of the present invention, chitosan has a degree of deacetylation of approximately 65%, approximately 75%, approximately 85%, and up to approximately 95%. In a preferred embodiment of the present invention, the chitosan is low molecular weight chitosan (10,000 to 190,000 g / mol). In a preferred embodiment of the present invention, the chitosan is medium molecular weight chitosan (190,000 g / mol to 310,000 g / mol). In a preferred embodiment of the present invention, the chitosan is high molecular weight chitosan (310,000 g / mol to 375,000 g / mol). In a preferred embodiment, the particle size of the chitosan should be in the order of 0.1 mm to 5 mm in diameter. In a preferred embodiment of the present invention, the chitosan is chitosan purified from crustacean biomass. In one embodiment of the invention, the metallic salts are selected from sulfates, nitrates, chlorides, iodides, phosphates, carbonates, and acetates of metals such as aluminum, cobalt, manganese, chromium, nickel, iron, copper, silver, gold, ML / a / ZUZU / UUO ML / a / ZUZU / UUO zinc, among others independently or in combination. In one embodiment of the invention, the acids are organic acids, inorganic acids, and mixtures thereof. In a preferred embodiment of the invention, the organic acids are selected from the group comprising formic, acetic, propionic, butyric, citric, lactic, carbonic acid and their associated salts and / or combinations thereof. In a preferred embodiment of the invention, the inorganic acids are selected from the group comprising hydrochloric, nitric, phosphoric, sulfuric, hydrofluoric acid and their associated salts and / or combinations thereof. In a second aspect of the present invention, a kit comprising i) a granulated biopolymer product A and ii) an activating solution B is also described. In a preferred embodiment of this second aspect of the invention, the biopolymer granule product A is a granule product of starch, cellulose, beta-glucans, dextrins, pechins, chitin, chitosan, among others, either independently or in combination. Preferably, the biopolymer granule product A of the kit is chitosan. Even more preferably, the chitosan granule product A comprises up to 30% pure chitosan. In a preferred embodiment of this second aspect of the invention, the activating solution B comprises selected metal salts of sulfates, nitrates, chlorides, iodides, phosphates, carbonates and acetates of metals such as aluminum, cobalt, manganese, chromium, nickel, iron, copper, silver, gold, zinc, among others, independently or in combination, dissolved in acids. Preferably, the activator solution B of the kit is a solution of copper(II) sulfate and ferric sulfate dissolved in hydrochloric acid, acetic acid and water. In a third aspect of the present invention, a process for stabilizing natural coagulant flocculants based on biopolymers is also described, with the addition of metallic sulfates, prepared under laminar flow mixing conditions in an acidic medium and at a temperature less than or equal to 333 Kelvin (60°C). It is known that biopolymer-based flocculants suffer degradation due to acid hydrolysis of the medium in which they are solubilized, or by the action of enzymes of microbial or plant origin, which reduce the length and weight of their chains, thus decreasing their effectiveness in removing dissolved and / or suspended solids in water. This process is well documented by Reza et al. (2013), who analyzed samples of the biopolymer chitosan at 1% w / v, with initial molecular weights that decreased more than 25 times over a period of 36 hours, at a temperature of 338.15 Kelvin (65°C), in a medium ML / a / ZUZU / UUO ML / a / ZUZU / UUO containing hydrochloric acid with a concentration of 5M, confirming that as the temperature or concentration of the acid increases, the size of the biopolymer will decrease exponentially. These results were corroborated in the Biotechnology laboratory of Industrias VEPINSA SA de CV, in which a drop in the viscosity of a 1% w / v chitosan solution was observed as shown in figure 1, in which the effect of this drop was studied as a function of time and possible microbial contamination. During the study, chitosan solubilized in 1% acetic acid was separated into two containers, one was kept open, exposed to microbial contamination, while the other was kept hermetically sealed at a temperature of 25°C + / - 5°C for 30 days. With these results, it was confirmed that the drop in viscosity was mainly due to the effect of the acidic medium in which the chitosan had been solubilized, and not to possible microbial contamination since, being a natural biopolymer, it is susceptible to being hydrolyzed by microorganisms that are capable of producing chitosanases such as Bacillus subtilis, a microorganism commonly present in the soil. In this aspect of the invention, a chitosan solution after at least 96 hours have elapsed since its solubilization in an acidic medium has been referred to as mature chitosan. Mature chitosan solution is used as a natural flocculant to remove different concentrations of dissolved and / or suspended solids using a jar test. In this test, the effectiveness of mature chitosan solution was compared to that of fresh chitosan solution, prepared and used immediately. Figure 2 shows the results of the percentage of remaining dissolved solids present in the water, with respect to the initial concentration of these in a range between 176 and 965 mg / L, and it was observed that the mature chitosan solution had an effectiveness up to 50% less than the new chitosan solution, in cases where the concentration of dissolved and / or suspended solids in the water was below 180 mg / L. Due to the change in the molecular weight of chitosan in the mature chitosan solution, its loss of effectiveness as a flocculant can be explained mainly in waters with low turbidity, since, in these cases, as the molecular weight is greater and / or the chains are longer, the agglomeration of suspended and dissolved solids is facilitated, since in waters with low turbidity the scarce formation of flocs prevents a higher percentage of removal of these contaminants. This difference in activity is even more evident when comparing the mature chitosan solution with chemical flocculants dosed at a ratio of 20:20 mg / L, as shown in Figure 3. Thus, the process for preparing natural stabilized flocculants based on biopolymers in accordance with the present invention was developed to solve this problem. For this purpose, metallic sulfates, mainly copper and iron, were added to the chitosan biopolymer at a specific concentration, which stabilize the chains of these biopolymers. This not only allowed an increase in their shelf life to at least 60 days, but also enhanced their capacity to remove dissolved and / or suspended solids in waters with low and high dissolved solids content (between 10-100 mg / L and more than 100 mg / L, respectively), as shown in Figure 4. In a preferred embodiment of the process, copper(II) sulfate pentahydrate or cupric sulfate pentahydrate is used. Its chemical formula is CuSO4·5H2O. Copper(II) sulfate pentahydrate is commonly used as an algaecide in water treatment, as it eliminates both suspended and surface algae in swimming pools. Its bactericidal action allows for a chlorine dose to be reduced by half. It acts immediately and with a prolonged effect, giving the water a bluish and crystal-clear color. (Martínez Camacho, 2009). ML / a / ZUZU / UUO ML / a / ZUZU / UUO Copper sulfate is a strong irritant to the skin and mucous membranes, including the nose, throat, and eyes. Ingestion of 250 mg of copper sulfate resulted in toxicity (Region of Murcia, 2008). However, the amount of copper sulfate added to chitosan as a flocculant is at least 10 times lower than the maximum limit established by Mexican Official Standard NOM-127 SSA1-1994, ENVIRONMENTAL HEALTH, WATER FOR HUMAN USE AND CONSUMPTION - PERMISSIBLE QUALITY LIMITS AND TREATMENT TO WHICH WATER MUST BE SUBJECTED FOR ITS POTABILIZATION, which is 2 mg / L, thus representing a significant advantage for the present invention. In a preferred embodiment of the process, ferric sulfate nonahydrate is used. Its chemical formula is Fe2(SO4)3·9H2O. In another modality of the process for preparing natural stabilized flocculants based on biopolymers in accordance with the present invention, the use of copper sulfate and other metals relative to the concentration of the biopolymer was tested to verify its range of effectiveness within the limits established by NOM-127SSA1-1994, the results of which are shown in Figure 5. In these results it was found that the dosage of copper(II) sulfate pentahydrate and / or other metallic salts should be below 50% relative to the weight of the biopolymer, which is environmentally and economically convenient. The applicant surprisingly discovered that the ML / a / ZUZU / UUO conditioning with sulfates of different metals allows the re-polymerization of the chains of biopolymers such as chitosan, thereby reversing the effect of acid or enzymatic hydrolysis, resulting in the functionality of the flocculant-coagulant being recovered to levels comparable with a freshly prepared solution, which allows the removal of more than 90% of the turbidity present in cases with more than 100 mg / L and up to 70% of the turbidity of waters with less than 100 mg / L of suspended and / or dissolved solids. In a preferred embodiment, the process for preparing a biopolymer-based stabilized flocculant according to the present invention comprises the following steps: i) prepare an aqueous solution with one or more biopolymer(s) at a concentration of approximately 0.5-5% w / v; ii) adding an activating solution comprising metallic salts; and iii) adding water to the solution obtained in step ii) so as to obtain a stabilized biopolymer-based flocculant with a final biopolymer concentration equivalent to 1% w / v. In a preferred embodiment of the process, the activating solution comprising metallic salts is obtained by the following steps: i) prepare an aqueous solution of copper sulfate and subsequently add hydrochloric acid (HCl); ii) add ferric sulfate; and iii) add acetic acid. Preferably, the preparation process results in a stabilized flocculant with the following proportions: MA / a / ζυζυ / υυυ / ου Per Kg of biopolymer (e.g., chitosan) moles From To Inorganic acid (e.g., HCl) 150 500 Organic acid (e.g., acetic acid) 100 400 Metallic salts (e.g., copper sulfate, iron, alone or in combination) 5 50 For the purpose of improving the understanding of the present invention, the following examples are listed: EXAMPLE 1. Step 1: Weigh 1000 g of 30% granulated chitosan and add 28 L of water to obtain an aqueous chitosan solution. Step 2: In another container, copper sulfate is dissolved in an aqueous solution, to which hydrochloric acid is subsequently added to form an acidic copper sulfate solution with a final concentration of approximately xx. ML / a / ZUZU / UUO A solution of ferric sulfate is added to the acidic copper sulfate solution, and then acetic acid is added to obtain a solution that activates metallic salts. Step 3: Mix the aqueous chitosan solution from step 1 with 816.25 g of the activator solution from step 2 and fill to volume with water until a final volume of 30 L is obtained, which is equivalent to 1% chitosan. EXAMPLE 2. A 20L sample of raw water was taken from Lateral Canal 18 coming from the Miguel Hidalgo Dam (El Fuerte, Sinaloa Mexico) in the Industrial Zone of Los Mochis-Sinaloa, Mexico during the month of November 2015, with a solids concentration of 20 mg / L equivalent to a turbidity of 24.52 NTU (Nephelometric Units) and an initial pH of 7.3. Two 800 mL samples of this water were taken and the 1% chitosan-based bioflocculant prepared 144 hours before use was added, conditioned with copper sulfate to reach a concentration of 3.0 and 0.5 PPM respectively; In parallel, two other 800 mL water samples were taken, one as a negative control to which no flocculant was added, and the other as a positive control to which the chemical flocculants Catfloc© and Aluminum Sulfate (Supplier CLARVI) were added to reach a concentration of 10 and 20 PPM, respectively, and a jar test was started. ML / a / ZUZU / UUO (Phipps & Bird, Six Paddle Stirrer - Jar Tester Model 7790300, Virginia, USA.) with the following times and cycles: 1 minute at 100 RPM, 14 minutes at 40 RPM and 15 minutes of rest. At the end of the settling period, a 15 mL sample was taken from each treatment, 2 cm below the surface of the treated water in the flasks. The turbidity of each sample was analyzed using a turbidimeter (LTLutron-Turbidity Meter, Model TU-2016, Taiwan) with a 10 mL glass cell, using triple-distilled water (HYCEL, Jalisco, Mexico) as a blank. The pH of the samples was also analyzed using a potentiometer (HANNA-Potentiometer-210, Port Louis, Mauritius). Water treated with the chitosan-based flocculant conditioned with 3.0 PPM copper sulfate showed a turbidity of 1.70 NTU and pH= 7.05, while that treated with the chemical flocculants had a turbidity of 12 NTU and pH of 6.97; additionally, it was observed that the size of the flocs formed in the water treated with the chitosan-based flocculant was at least 4 times larger. EXAMPLE 3. A 200L barrel was prepared with the chitosan-based bioflocculant at 0.5% dissolved in glacial acetic acid (Sigma-Aldrich 98%) at 0.5% with pH= 4.3, density of 1.05 g / mL which was left to stand for 30 days, after the time period the bioflocculant was conditioned with sulfate Copper ML / a / ZUZU / UUO (Sigma-Aldrich) at 0.1% (referred to as Mature Chitosan-CuSO₄). The conditioned bioflocculant was dosed in the water treatment plant of the J&F Production Field located in Los Mochis, Sinaloa, Mexico, with a capacity of 80 m³ / day, a flow rate of 1.8 m³, and a residence time of 0.54 hours. Dosing was carried out with a pair of peristaltic pumps, one for the flocculant at a rate of 3 PPM and another for sodium hypochlorite at a rate of 4 PPM. Water quality was analyzed at the inlet and outlet of the water treatment system every 24 hours for a period of up to 120 hours without removal of the formed sludge (precipitates). Similar to what was described above, another 200 L barrel was prepared with the 0.5% chitosan-based bioflocculant dissolved in 0.5% acetic acid, but prepared at the beginning of a week, which was also dosed in the same J&F Production Field water treatment plant for a period of 120 h, analyzed every 24 h. As a positive control, the water quality was analyzed in the same drinking water system, but using the chemical flocculants CatFloc© and Aluminum Sulfate at a rate of 10 and 20 PPM respectively and as in the previous cases, the water quality was analyzed before and after treatment every 24 hours until completing 96 hours. The results were analyzed using a turbidimeter (LTLutron Turbidity Meter, Model TU-2016, Taiwan), and the percentage decrease in turbidity over time was calculated. The results are shown in Figure 6. This figure shows that both bioflocculants (new and mature with CuSCu) reduced water turbidity by up to 60% between time 0 and the first 72 hours, and then decreased to 30% because the sludge formed was not purged, and the reduced sedimentation space also decreased the residence time. In contrast, using chemical flocculants required at least 24 hours of operation to reduce turbidity by almost 50%. EXAMPLE 4. A 200 L barrel was prepared with a 0.5% chitosan-based bioflocculant dissolved in 0.5% glacial acetic acid (Sigma-Aldrich 98%) with a pH of 4.3 and a density of 1.05 g / mL. This mixture was left to stand for 40 days. After this period, it was conditioned with 0.1% copper sulfate (Sigma-Aldrich) (referred to as Chitosan-MaduroCUSO4). The conditioned bioflocculant was dosed into the J&F Production Field water treatment plant located in Los Mochis, Sinaloa, Mexico, which has a capacity of 80 m³ / day, a flow rate of 1.8 m³, and a residence time of 0.54 hours. The dosing was carried out with a pair of peristaltic pumps, one for the flocculant at a rate of 3 PPM and another to dose sodium hypochlorite at a rate of 4 PPM and the water quality was analyzed at the inlet and outlet of the water treatment system, as well as after the silica gel filter system every 24 hours for up to 120 hours, with the removal of the formed sludge, precipitated every 24 hours to prevent the residence time of the flocs from decreasing. The samples were analyzed using a turbidimeter (LTLutron Turbidity Meter, Model TU-2016, Taiwan) with triple-distilled water as a blank. These results can be seen in Figure 7. These data show that the inlet turbidity value remained consistently close to 107 NTU throughout the 96-hour monitoring period. Similarly, the turbidity decreased consistently to 5.3 NTU. Once the water passed through the silica filter system, the turbidity exceeded 19.2 NTU in all cases, representing an 82% improvement over the inlet turbidity. This confirms that the accumulation of sludge in the precipitation unit was responsible for the reduced residence time and, consequently, the decreased effectiveness of the bioflocculant. In turn, it was again verified that the use of the bioflocculant, despite being more than 40 days old, maintained its effectiveness despite being a product of biological origin and that, being a polymer, under acidic conditions its molecular weight is reduced as time passes or when exposed to temperatures higher than 40°C. MA / a / zyzy / yyy / ou EXAMPLE 5. A 20 L sample of raw water was taken from Lateral Canal 18 coming from the Miguel Hidalgo Dam (El Fuerte, Sinaloa Mexico) in the Industrial Zone of Los Mochis-Sinaloa, Mexico during the month of December 2015, with a solids concentration of 11.5 mg / L equivalent to a turbidity of 10.7 NTU and an initial pH of 7.29. In triplicate, 800 mL of this water were taken and the 1% chitosan-based bioflocculant prepared 150 days before use was added, so that they reached a concentration of 3.0 PPM; In parallel, another 800 mL water sample (triple) was taken, to which the 1% chitosan-based bioflocculant prepared 150 days before the test was also added, conditioned with copper sulfate at a concentration equivalent to 0.4% copper sulfate in the product and dosed to achieve a concentration of 3PPM of bioflocculant in the water.The removal of turbidity from both treatments was analyzed through the jar test with the following times and cycles: 1 minute at 100 RPM, 14 minutes at 40 RPM and 15 minutes of rest. At the end of the resting time, at a depth of 2 cm from the surface of the flasks with the treated water, a 5 mL sample was taken from each treatment and the turbidity of each was analyzed using a turbidimeter (LTLutron- Turbidity Meter, Model TU-2016, Taiwan), with a 10 mL glass cell using triple-distilled water as a blank. ML / a / ZUZU / UUO The pH of these was also analyzed with a potentiometer (HANNAPotentiometer-210, Fort Louis, Mauritius). Water treated with the chitosan-based flocculant without copper sulfate showed a final average turbidity of 5.9, equivalent to a solids concentration of 6.6 mg / L and a pH of 7.07. Meanwhile, the treatment with the bioflocculant that was also treated with copper sulfate showed a final average turbidity of 4.4 (equivalent to 4.8 mg / L of solids) and a pH of 7.07. This indicates that although both bioflocculants were prepared more than 150 days prior, they are sufficiently effective to remove more than 40% of the turbidity present in slightly turbid water. However, the results obtained with the bioflocculant that was also treated with copper sulfate were 34% higher than its counterpart without this sulfate. EXAMPLE 6. A 40L sample of raw water was taken from Lateral Canal 18 coming from the Miguel Hidalgo Dam (El Fuerte, Sinaloa Mexico) in the Industrial Zone of Los Mochis-Sinaloa, Mexico during the month of December 2015, with a solids concentration of 48 mg / L equivalent to a turbidity of 46.2 NTU and an initial pH of 7.35. In triplicate, 800 mL of this water were taken, which was analyzed by the jar test at a temperature of 25°C and with the following times and cycles: 1 minute at 100 RPM, 14 minutes at 40 RPM and 15 minutes of rest. The flocculants used and their dosage are shown in Table 1. Table 1. Raw canal water treatments with different flocculants supplemented with sulfates of different metals and their effect on reducing turbidity in the jar test. ML / a / zuzu / uuo se» Sample Type Flocculant Type Dosage (ppm) Sulfate Type Initial Turbidity (NTU) Turbidity after Jar Test (NTU) % Turbidity Reduction after Jar Test Natural Flocculant Chitosan 3 Cupric 46.2 1.7 96% Cupric+Ferric 47.2 2.1 96% Cupric+Zinc 47.2 2.7 94% Zinc 46.2 3.7 92% Sulfate-Free 47.2 4.4 91% Aluminum 46.2 4.4 90% Ferric 46.2 5.1 89% Positive Control Aluminum Sulfate; Synthetic Cationic Polymer 20, 10 Aluminum 47.2 12.2 74% Negative Control - - - 47.2 44.2 6% At the end of the resting time, at a depth of 2 cm from the surface of the flasks with the treated water, a 15 mL sample was taken from each treatment and the turbidity of each was analyzed using a turbidimeter with a 10 mL glass cell using triple-distilled water as a blank. Table 1 shows the initial and final turbidity results, as well as the normalized percentage improvement. These results indicate that the treatment with the least turbidity reduction was the one in which chemical flocculants were added. This is because, in cases of low turbidity, the artificial polymer must act as a seed for floc formation and is directly influenced by its molecular weight. In contrast, all chitosan-based treatments had initial turbidity results above 30.7 NTU, and the maximum turbidity improvement values ​​were in those treatments based on this biopolymer complemented with copper sulfate alone or in combination, with results above 13.2 NTU. This confirms that the combination of these allows for a more effective removal of dissolved and / or suspended solids because chitosan, being a biopolymer with a molecular weight greater than 50,000 g / mol and composed of chains of hundreds to thousands of glucosamine monomers, can complex more efficiently with the negatively charged particles present in surface waters. This leads to the generation of larger and denser flocs that allow for the faster removal of dissolved and / or suspended solids, which could reduce the settling time required for these particles to precipitate and therefore increase the handling capacity of ML / a / ZUZU / UUO ML / a / ZUZU / UUO water from the drinking water systems. It should be clarified that for the addition of all sulfates, it was considered that their concentration in the water would never exceed the limits established by NOM-127-SSA11994, to guarantee their safe use for human consumption systems. It is hereby stated that, as of this date, the best method known to the applicant for putting the aforementioned invention into practice is the one that is clear from the present description of the invention.

Claims

CLAIMS Having described the invention as above, the following claims are claimed as property:

1. A flocculant characterized in that it comprises: one or more biopolymers selected from starch, cellulose, beta-glucans, dextrins, pectins, chitin, chitosan or combinations thereof; one or more metal salts selected from sulfates, nitrates, chlorides, iodides, phosphates, carbonates and acetates of metals selected from the group of aluminum, cobalt, manganese, chromium, nickel, iron, copper, silver, gold, zinc, among others, independently or in combination; one or more acids selected from formic, acetic, propionic, butyric, citric, lactic, carbonic, hydrochloric, nitric, phosphoric, sulfuric, hydrofluoric acids and their associated salts and / or combinations thereof.

2. The flocculant according to claim 1, characterized in that the biopolymer is chitosan.

3. The flocculant according to claim 2, characterized in that the chitosan is granulated chitosan.

4. The flocculant according to claim 1, characterized in that the metallic salts are sulfates.

5. The flocculant according to claims 3 and 4, characterized in that the sulfates are selected from copper sulfate and iron sulfate.

6. The flocculant according to the preceding claims, characterized in that the chitosan has a degree of deacetylation of at least 65%.

7. The flocculant according to the preceding claims, characterized in that the chitosan is of high molecular weight.

8. The flocculant according to the preceding claims, characterized in that the chitosan has a dry basis purity of at least 50%.

9. The flocculant according to the preceding claims, characterized in that the chitosan has a particle size of between 0.1 mm and 5 mm.

10. The flocculant according to the preceding claims, characterized in that one or more acids are hydrochloric acid and acetic acid.

11. A flocculant kit characterized in that it comprises a granulated product A and an activating solution B.

12. The kit according to claim 11, characterized in that the granulated product A is granulated chitosan and wherein the activating solution B comprises a solution of copper(II) sulfate and ferric sulfate dissolved in hydrochloric acid, acetic acid and water.

13. Method for the preparation of a biopolymer-based stabilized flocculant, characterized in that ML / a / ZUZU / UUO ML / a / ZUZU / UUO comprises: i) preparing an aqueous solution with one or more biopolymer(s) at a concentration of approximately 0.5-5% w / v; ii) adding an activating solution comprising metal salts; and iii) adding water to the solution obtained in step ii) to obtain a biopolymer-based stabilized flocculant with a final biopolymer concentration equivalent to 1% w / v.

14. The method according to claim 13, characterized in that the activating solution is prepared by the following steps: i) preparing an aqueous solution of copper sulfate and subsequently adding inorganic acid; ii) adding ferric sulfate; and iii) adding an organic acid.

15. The method according to claim 14, characterized in that the copper sulfate and / or ferric sulfate have a ratio of between 5 and 50 moles per kg of biopolymer.

16. The method according to claim 14, characterized in that the inorganic acid has a ratio of between 150 and 500 moles per kg of biopolymer.

17. The method according to claim 14, characterized in that the organic acid has a ratio of between 100 and 400 moles per kg of biopolymer.

18. The method according to claim 14, characterized in that the inorganic acid is selected from hydrochloric acid and nitric acid.

19. The method according to claim 14, characterized in that the organic acid is selected from acetic, citric, and lactic acids.