MX2011005678A - Apatite and magnetite fluidized bed for removing heavy metals from water. - Google Patents

Abstract

One of the major causes for water pollution is due to the presence of heavy metals. Water- soluble salts of heavy metals such as lead, cadmium and arsenic are very toxic, which in turn are a source of pollution in the food chain when ingested by any of its constituent links. When consumed by humans through food and water contaminated by arsenic, lead or cadmium, said pollutants will cause blindness, amnesia, rickets and myasthenia among other ailments or even death. Therefore, the process of the present invention comprises using apatite from animal bones and magnetite for removal of heavy metals (Pb, Cd and As) from water, which is based on the fluidized bed principle, as well as the removal of mesophilic and coliform bacteria that are found in domestic water. The results obtained with the fluidized bed showed a removal of metals such as lead, cadmium and arsenic in an amount of up to 99% at concentrations of up to 1 ppm (parts per million) from water, and a removal of mesophilic and coliform bacteria in an amount of up to 90%.

Description

FLUIDIZED BED OF APATITE AND MAGNETITE FOR REMOVAL OF HEAVY METALS OF WATER DESCRIPTION OBJECT OF THE INVENTION The object of the present invention is to present a fluidized bed capable of removing heavy metals, such as lead, cadmium and arsenic, as well as mesophilic and coliform bacteria from domestic water. This fluidized bed is based on the use of apatite impregnated with magnetite in order to make the water suitable for its consumption, as well as to develop technology with a low cost and in harmony with the environment.

BACKGROUND It is said that the water supplied by the public network of the country is potable water. It is common to hear this term especially when it comes to hygiene and food in the home, however in most cases it is completely unknown if in fact the water that reaches our homes is potable water, so first of all it is necessary understand what defines the potability or purity of water. In a generalized way, it can be said that drinking water is one that is free of substances and microorganisms that can affect health (impurities not soluble in water). Specifically, the potability requirements of the water, which can vary depending on multiple factors, are the following: • That has less than 10 intestinal bacteria per liter.

• That does not contain chemical impurities.

• That it does not present objectionable taste, smell or color or turbidity.

• That it does not come from springs subject to contamination by sewage.

However, much of the water that comes to our home, is contaminated on the way or inside homes, for example, many tanks have leaks, cracks and cavities that allow the entry of insects and animals carrying bacteria. At the same time, a large number of water tanks are badly covered and remain exposed to the elements. We know that cisterns and water tanks should be washed regularly, but in very few houses is it done. Thus, although the water that reaches the intake of our houses is potable, when it comes out of the tap it is not always suitable for drinking.

Due to this, in many cases an important part of the family expenditure is destined to the purchase of bottled purified water, which has a better taste and is considered advisable to drink. Unfortunately, there are clandestine water trading companies that do not meet the minimum requirements to purify it or even simply fill the jugs with tap water and place labels and warranty seals.

Against this background, it is advisable, and even necessary, to learn to purify water at home. Some of the methods or procedures to purify water at home are the following: DISINFECTION WITH IONIC SILVER In the market there are some products to disinfect water and vegetables that use ionic or colloidal silver compounds. Although manufacturers recommend waiting approximately ten minutes after adding them to the water, it is preferable to wait for twice the suggested time.

CERAMIC FILTERS These filters separate solid matter from the liquid because they have a very fine pore, that is, they retain very small particles. A drawback of these filters is that colonies of microorganisms can develop on them. Therefore, when buying a filter of this type, it will be important to verify that it is free or impregnated with ionic silver, since this substance has a germicidal effect. The simplest filter is formed by a ceramic bar covered by a metal cylinder that adapts to the water tap. A ceramic filter with ionic silver provides about 60 liters of water per day. If it is given an adequate maintenance, this implement can last for at least 5 years.

ACTIVATED CARBON FILTER In this system the water passes through an activated carbon filter, which contains millions of microscopic holes that capture and break down the molecules of the contaminants. This method is very efficient to eliminate chlorine, bad odor, unpleasant flavors and heavy solids in water. It also retains some organic pollutants, such as insecticides, pesticides and herbicides.

The risk posed by these filters is that they can become saturated and contaminated with microorganisms, therefore, it is necessary to change them every five months, otherwise, if there is no disinfection system placed after the filter (such as UV light or ionic silver) , the water is no longer safe to drink. The activated carbon filtration equipment includes a fiberglass tank, a control valve and the filter; It can last up to 6 years.

PURIFICATION BY REVERSE OSMOSIS The reverse osmosis process uses a semipermeable membrane that separates and removes solid water, organic substances, viruses and bacteria dissolved in the water. It can eliminate around 95% of total dissolved solids (TDS) and 99% of all bacteria. The membranes only allow water molecules to pass through, trapping even the dissolved salts. For every liter that enters a reverse osmosis system, 500 ml of water of the highest quality are obtained, however, the other 500 ml containing SDT must be discarded. During the operation, the same water is responsible for cleaning the membrane, reducing costs. An osmosis filtration equipment includes a sedimentation filter, an activated carbon filter, a membrane, a UV lamp and two post filters. Its daily performance is 200 liters of water and, with proper maintenance, can be used for up to 10 years. This method is not recommended when it comes to hard water, that is, water that contains a high percentage of calcium and magnesium salts.

ELECTRODESIONIZA TION Electrodeionization is an electrically activated purification process and includes a combination of ion exchange resins and ion selective membranes. Electrodeionization, which is normally combined with reverse osmosis, offers a useful alternative to other purification methods. It offers laboratory reactive water at high volumes without the need for deionization cartridges. This approach avoids the decrease in the quality of the produced water that is associated with the cartridges as they are spent, and reduces the costs involved in replacing the cartridges.

OPERATION OF ELECTRODESIONISATION Electrodeionization has evolved from electrodialysis. The principle of electrodialysis is the purification of water in a cuvette containing two types of ion-selective membranes (permeable to cations and anions) and located between a pair of electrodes. When a direct electric potential is applied through the cuvette, the water cations are sent to the positively charged cathode. The cations can pass through the membrane permeable to the cations, but not through the permeable to the anions. Similarly, anions can pass through the membrane permeable to anions, but not permeable to cations. The net result is the movement of ions between the chambers, and the water in one section can be deionized while in the other section the water is more concentrated. In practice, electrodialysis can only be used profitably to produce water of relatively high conductivity (200 pS / cm or more) due to the prohibitively high electrical voltages that are necessary to drive the ions through one water at a time of greater purity.

ABSORPTION MEANS TO PURIFY WATER MICROPOROSE FILTRATION The microporous filtration membranes offer a physical barrier to the passage of particles and microorganisms, and have absolute values of up to 0.1 microns. Some systems also include "ultra micro filters" with a value of 0.05 microns. Most untreated waters contain colloids, which have a small negative charge (measured by the Zeta potential). The performance of the filter can be improved by using microfilters that include a modified surface that will attract and retain these naturally occurring colloids, which are generally much smaller than the pore sizes in the membrane. Microfilters with an absolute pore size of 0, 2 microns are widely used in water treatment systems. They trap contaminants, including carbon disintegrates from organic adsorption cartridges, resin particles from ion exchange cartridges and bacteria. The submicron filter can be attached to the spout, so that the last filter through which the water passes before it is used is the submicrometer filter. An alternative approach is to include the submicron filter in the recirculation circuit to continuously remove the bacteria from the purified water. Submicron filters should also be placed at critical points of use to offer absolute protection and to avoid recontamination of the system by bacteria that access this path. Microporous membranes are generally considered indispensable in a water purification system, unless they are replaced by an ultrafilter.

IONIC EXCHANGE Ion exchange is used extensively in laboratories to provide purified water on demand. Laboratory deionizers incorporate mixed bed cartridges of ion exchange resins that either pass to a regeneration station for recharging when they are depleted or disposed of. The anions and cations of the feed water are removed by ion exchange resins, and replaced by hydrogen and hydroxyl ions from the resin. The hydrogen and hydroxyl ions combine to form water molecules.

OPERATION OF IONIC EXCHANGE The ion exchange acts by exchanging the hydrogen ions of the cationic contaminants and the hydroxyl ions of the ammonia contaminants in the feed water. The beds of the ion exchange resins are composed of small spherical beads through which the feed water passes. After a period of time, the cations and anions will have replaced most of the active hydrogen and hydroxyl points in the resins, and it will be necessary to replace or regenerate the cartridges.

In addition to analyzing the impact of water pollution and the elimination of metallic toxic substances, useful information was also researched and reviewed for the creation of our heavy metal removal system in the water, topics about the fluidized bed were discussed, as well as their solid components such as magnetite and apatite contained in animal bone. This allowed us to evaluate the qualities of magnetite based on its magnetic properties, how heavy metals act as substitutes in the place of calcium, and to appreciate the porous surface of the apatite contained in the bone by means of micrographs emitted by an Electronic Scanning Microscope (SEM). And to know that said qualities favor that the solid components of the fluidized bed act as retention agents of the heavy metals included in the water, purifying it to be acceptable for human consumption.

We have also based on the theory that not all bones are equal in size and consistency, but on average have the same composition and internal structural organization, this allows us to assume that they behave in the same way before the accumulation of heavy metals, not It matters if it is a bone that comes from human or animal origin.

BRIEF DESCRIPTION OF THE FIGURES Figure No. 1 shows a perspective view of the fluidized bed of apatite and magnetite for the removal of heavy metals from water, where their internal composition and the interaction between each of the parts are shown.

DETAILED DESCRIPTION OF THE INVENTION The fluidized bed of apatite and magnetite removes metals from water such as lead, cadmium and arsenic because today the water destined for human consumption and its activities has been contaminated naturally, when the water passes through mineralized soils, or in the case of being extracted from the subsoil where there is a high concentration of minerals or by contamination of industries such as steel processes, metal finishes, textiles, etc. Reason for which both the ecosystem, the animals and in turn people get sick due to the intake of food that was irrigated with water of high concentration of heavy metals or by drinking directly contaminated water. However, companies that are dedicated to water purification, both private and governmental, are not aware of this problem until it becomes very evident in society as it has been happening all over the world today. That is why the need to generate a technology like the one described here, accessible to all the public, easy to install, with the possibility of adapting to the needs of the users as well as complying with the elimination of bacteria so that it is not necessary to have different systems to make the water suitable for the consumption and human activities in a sustainable way with respect to the environment.

The present invention operates according to the fluidized-bed principle, that is to say when a liquid passes through a solid surface, the contaminating elements of the liquid are removed, remaining lodged in the solid due to the physico-chemical properties thereof. Applying this principle to us, the solid components used are preferably Apatite Ca5 (P04) 3 (F, Cl, OH) and Magnetite (Fe304) in a proportion that goes in the case of apatite from 75% to 85% and in the case of magnetite from 15% to 25%; the apatite being in the form of ground bone (grain size> 3 mm and <1/16 mm in diameter) impregnated with magnetite, contained in a preferably acrylic cavity through which a liter of water was flowed contaminated with lppm concentrations of lead (Pb), cadmium (Cd) and arsenic (As).

Through the electrostatic forces of magnetite, an affinity of the metals is generated by the sites of molecular action of calcium, and together with the (porous) surface of the apatite contained in the ground bone, the heavy metals included are retained in water to give it a quality fit for human consumption.

In the case of the presented innovation, the solid components are the apatite of the animal bone that when coming into contact with the heavy metals is carried out two phenomena known as absorption and adsorption. The first case is chemical, that is to say, an ion exchange is carried out between the heavy metals and the apatite of the bone present as hydroxyapatite or fiuorapatite. In the second case it is a physical process in which the heavy metals stay lodged in the porous micro structure of the bone.

The fluidized bed of apatite and magnetite for the removal of heavy metals from the water is constituted in its upper part by an inlet valve (1), where water will be constantly circulating, to be dislodged later by an outlet valve (7), when the water is already clean and ready to be consumed. After the water has entered, it passes through the fluidized bed of apatite and magnetite (5), which is constituted by Apatite Ca5 (P04) 3 (F, Cl, OH) and Magnetite (Fe304) in a proportion that goes the case of apatite from 75% to 85% and in the case of magnetite from 15% to 25%. After the inlet valve (1) there are two double-threaded covers, one upper (2) and one lower (6). After the upper cover (2) there is a packing (3), which will prevent leaks and the fluidized bed of apatite and magnetite (5) is well compacted and perform its function correctly. Between the fluidized milk of apatite and magnetite (5) and the package (3) there is a mesh (8), preferably made of cloth, which will prevent larger particles from entering the fluidized bed.

Claims (3)

CLAIMS Having sufficiently described my invention, I consider it a novelty and therefore claim as my exclusive property, what is contained in the following clauses:

1. Fluid bed of apatite and magnetite for removal of heavy metals from water, characterized in that it is constituted by Apatite Ca5 (P04) 3 (F, Cl, OH) and Magnetite (Fe304) in a proportion, preferably that it goes in the case of apatite from 75% to 85% and in the case of magnetite from 15% to 25%.

2. Fluid bed of apatite and magnetite for removal of heavy metals from water, according to claim 1, characterized in that the apatite is preferably in the form of ground bone in grain size between 3 mm. and 1/16 mm. diameter.

3. Fluidized bed of apatite and magnetite for removal of heavy metals from water, according to claim 1, characterized in that said fluidized bed removes heavy metals from water, preferably lead (Pb), cadmium (Cd) and arsenic (As) with concentrations of up to 1 ppm and up to 90% elimination of mesophilic bacteria and fecal coliforms.