The disclosure generally relates to a water purification medium for obtaining potable water and a water purification cartridge comprising the said water purification medium.. More particularly, the disclosure relates to a water purification medium comprising rice husk ash and quartz sand.

BACKGROUND

Potable water is a basic human requirement. However, a large portion of the world's population, especially those living in the developing countries, does not have access to clean potable water.

Growing population, lack of sanitary conditions, poverty, poor planning, industrial pollution, over-exploitation of natural water and national disasters are the main reasons of contamination of water. Bacterial contamination transmitted through water is the cause of many diseases such as diarrhoea, dysentery, fever, abdominal pain, and constipation. Water sources in most countries contain levels of synthetic chemicals, heavy metals, parasites and/or chlorination by-products that pose significant health risks.

Many water purification devices like in-line (electricity operated) devices, terminal end devices including counter top and faucet mounted filtration and self-contained batch system including gravity fed systems have been introduced into the market. However, many communities of the developing countries do not have access to piped water or reliable electricity connection to make use of inline or electrically driven purification units. They also do not have access to central water purification units installed near the water bodies from where they source their water. Moreover, the people in these communities cannot afford the point-of-use water purifies currently available in the market. The maintenance requirements and the high cost of consumables of these purifiers pose further hurdles for the adoption of these devices.

Water filters containing various purification media have been developed to filter contaminants from water to provide clean potable water. Rice husk ash is considered as an economical purification medium.

However, the use of rice husk ash as a medium for purification has some limitations, and the results obtained are not consistent over time. The filter devices required for adequate filtration using such purification media tend to be bulky. Rice husk ash when used as purification medium for water filtration has a tendency to leak into the water. Further, rice husk ash, when used as a purification medium, is unable to remove all microorganisms that may be present in the water. Moreover, when used over a period of time, the purification medium is prone to bacterial growth.

Bacterial growth on the purification medium may be prevented by coating the purification medium with an antibacterial agent. Copper or silver may act as antibacterial agents that can impart antibacterial properties to a purification medium. However, a substantial use of copper or silver in a purification composition significantly increases the cost of the medium.

Thus there is a need for a water purification composition that is inexpensive, easy to use and effective in removing bacterial contamination from potable water.

SUMMARY

The present invention relates to a water purification medium comprising a layer of rice husk ash and a layer of quartz sand adjacent to it with a bactericidal agent coated on to either the rice husk ash or the quartz sand or both, such that the layer of quartz sand is positioned after the layer of rice husk ash in the direction of flow of water through the water purification medium.

The present invention also relates to a water purification cartridge comprising a water purification medium, a water inlet for the purification medium and an outlet for purified water from the purification medium. The said water purification medium comprises a layer of rice husk ash and a layer of quartz sand adjacent to it with a bactericidal agent coated on to either the rice husk ash or the quartz sand or both, such that the layer of quartz sand is positioned after the layer of rice husk ash and proximate the outlet in the direction of flow of water through the water purification medium.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic, partial view of an exemplary embodiment of a water purification cartridge comprising water purification medium.

DETAILED DESCRIPTION:

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment described and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the process, and such further applications of the principles of the invention therein being contemplated as would normally occur to one skilled in the art to which the invention relates. The following description discusses certain specific compounds such as stabilizing agents, reducing agents and antioxidizing agent to explain the principles of the process. The process however is not restricted to such compounds as equivalent chemical compounds may be utilized to achieve the desired end result as taught by the disclosure.

Rice husk is a perennially renewable agro-waste available at virtually no cost wherever rice paddy is grown. On combustion, the rice husk ash residue contains 75-95% silica, 4-12% carbon and the rest comprising various metal oxides such as alkali, alkali earth metal and ion oxides. On account of its crypto-crystalline or amorphous and highly porous structure, the BET (Brunauer Emmett Teller) surface area of rice husk ash can be as high as 80-100 square meters per gram, depending on the conditions employed for the combustion of rice husk. Its high surface area and porosity make rice husk ash an effective filtration medium that removes particulate matter as well as color and odor from water. Rice husk ash is a highly adsorbent material and is capable of removing bacteria as well as suspended particles from the water.

Rice husk ash is thus a suitable water purifier material as it contains an activated surface with abundant pores, has a large surface area, is easily available and is cheap.

The rice husk ash used for the composition of treatment of water may be any rice husk ash that is produced by burning rice husk. The rice husk ash may be produced by burning rice husk in heaps, in a step grate furnace, fluidized bed furnace or tube-in-basket (TiB) burner. The rice husk ash may also be obtained from boilers and brick kiln, provided it is free of unburned husk and wood tar, grit, stone, and fused lumps of silica. The particle size of rice husk ash may be in the range of 38 to 850 microns and preferably the particle size is less than 425 microns. Quartz is a rock formed from cooling magma. Quartz sand is a kind of hard and wearable silicic acid mineral with stable chemical properties. The main component is Si02. The quartz sands are ivory or without colour and translucent. It is brittle and without cleavage. It has the textural anisotropy in chemical, thermal and mechanical properties. Due to their specific chemical and physical properties it can be used as purifying medium.

A water purification medium is described. More particularly, a water purification medium for treatment of water to remove bacterial contaminants is described. The water purification medium for treatment of water comprises a layer of rice husk ash and a layer of quartz sand adjacent to it with a bactericidal agent coated on to either the rice husk ash or the quartz sand or both, such that the layer of quartz sand is positioned after the layer of rice husk ash in the direction of flow of water through the water purification medium. Herein, positioning the layer of quartz sand after the layer of rice husk ash in the direction of flow of water prevents leakage of rice husk ash with water when water is passed through the water purification medium.

In accordance with an aspect the water purification medium comprises of a plurality of layers of rice husk ash or a plurality of layers of quartz sand or a plurality of layers of both, each layer abutting another layer, with a bactericidal agent coated on to one or more layers of either the rice husk ash or the quartz sand or both.

In accordance with an embodiment, the water purification medium comprises of alternate layers of the rice husk ash and the quartz sand.

In accordance with another embodiment, the water purification medium comprises of a layer of rice husk ash between a top and a bottom layer of quartz sand.

The bactericidal agent coated on the rice husk ash and quartz sand may be any compound with bactericidal property. The bactericidal agent can be one or more of silver, copper or their compounds and preferably the bactericidal agent is silver nanoparticles or copper nanoparticles or both.

In accordance with an aspect, a plurality of bactericidal agents is coated on one or more layers of rice husk ash or quartz sand or both. More than one bactericidal agent, or a mixture of one or more bactericidal agents, may be bonded to either the rice husk ash or quartz sand or both.

The bonding of a bactericidal agent to the rice husk ash and quartz sand includes a chemical bonding, adsorption or trapping of bactericidal particles in the pores of the rice husk ash.

In accordance with an aspect, one or more layers are compacted before providing the next layer. The compaction of each layer results in a firmer purification bed with increased efficiency. The compacted layers also assist in achieving the desired flow rate of water through the medium.

The purification media may have rice husk ash and quartz in any suitable proportion. By way of a specific example the water purification medium comprises of a first layer of 60 grams quartz sand, second layer of 25 grams rice husk ash, a third layer of 25 grams rice husk ash, a fourth layer of 25 grams rice husk ash, a fifth layer of 25 grams rice husk ash and a sixth layer of 60 grams quartz sand. The layers are compacted.

In accordance with an embodiment, at least 60% of rice husk ash bonded with nanoparticles is used.

A method of preparing rice husk ash bonded with bactericidal agent is disclosed. A method of preparing quartz bonded with bactericidal agent is also disclosed. More particularly, a method of preparing rice husk ash and quartz sand bonded with nanoparticles is disclosed. Any known method of treating a substrate may be used to apply the bactericidal agent to the rice husk ash. Such method for example may include mixing in a container the rice husk ash with a bactericidal agent till the bactericidal agent is coated on or adsorbed on or bonded with the rice husk ash.

By way of specific example, a process for binding silver nanoparticles to rice husk ash is described. The process effectively binds silver nanoparticles to rice husk ash such that minimum leaching of silver occurs when water is passed through the rice husk ash. The rice husk ash with bonded silver nanoparticles is a useful composition for water purification and the bactericidal qualities of rice husk ash and silver work together in making the composition very effective.

The process involves preparing silver nanoparticles in the presence of a stabilising agent and adding to the rice husk ash the silver nanoparticles to obtain rice husk ash with bonded silver nanoparticles. The stabilizing agent prevents the aggregation of nanoparticles during their formation by capping the silver nanoparticles that are formed. The stabilizing agent also facilitates in binding of silver nanoparticles to rice husk ash due to associated charge. The silver nanoparticles formed are then added to rice husk ash to obtain rice husk ash with bonded silver nanoparticles. In accordance with an aspect the silver nanoparticles are prepared in an aqueous medium.

In accordance with an aspect the silver nanoparticles are prepared in the presence of a stabilizing agent and stored to avoid aggregation of the prepared nanoparticles. The rice husk ash is added to the solution of capped silver nanoparticles to obtain rice husk ash with bonded nanoparticles.

A process for binding the bactericidal agent to quartz sand is disclosed. By way of specific example, a process for binding copper nanoparticles comprises of first binding a copper precursor to the quartz sand in the presence of a stabilizing agent to obtain quartz sand bonded with copper precursor and reducing the copper precursor coated on the quartz sand to obtain quartz sand bonded with copper nanoparticles.

The process for coating copper nanoparticles to quartz sand comprises of preparing an aqueous solution of a copper precursor. To the aqueous solution of copper precursor a stabilizing agent is added to obtain a copper precursor - stabilizing agent mixture.

In accordance with an aspect, the copper precursor - stabilizing agent mixture is heated to predetermined temperature to dissolve the stabilizing agent in the aqueous copper precursor solution. In accordance with an embodiment the precursor - stabilizing agent mixture is heated to a temperature in the range of 50 °C to 100 °C and preferably the precursor - stabilizing agent mixture is heated to a temperature of 80 °C.

To the copper precursor - stabilizing agent mixture quartz sand is added to obtain a mixture of quartz sand coated with copper precursor in presence of a stabilizing agent. The quartz sand is washed with water and dried prior to its addition in the copper precursor - stabilizing agent mixture. In accordance with an aspect, after the addition of the quartz sand to the copper precursor - stabilizing agent mixture is stirred for a predetermined period of time to allow for binding of the copper precursor to the quartz sand.

The copper precursor coated on the quartz sand is reduced by adding to the mixture of quartz sand coated with copper precursor a reducing agent to obtain quartz sand coated with copper nanoparticles.

The invention also relates to a water purification cartridge comprising a water purification medium, a water inlet for the purification medium and an outlet for purified water from the purification medium. The said water purification medium comprises a layer of rice husk ash and a layer of quartz sand adjacent to it with a bactericidal agent coated on to either the rice husk ash or the quartz sand or both, such that the layer of quartz sand is positioned after the layer of rice husk ash and proximate to the outlet in the direction of flow of water through the water purification medium.

In accordance with an aspect the water purification cartridge includes the water purification medium comprising a plurality of layers of rice husk ash or a plurality of layers of quartz sand or a plurality of layers of both, each layer abutting another layer, with a bactericidal agent coated on to one or more layers of either the rice husk ash or the quartz sand of both.

In accordance with an aspect, the layer of quartz sand may be placed in the water purification cartridge, such that it surrounds the layer of rice husk ash so as to keep the rice husk ash in place and to prevent leakage of the rice husk ash into the water.

In accordance with an embodiment, the layer of quartz sand bonded with nanoparticles may be positioned immediately before the outlet of the water purification cartridge.

In accordance with another embodiment, the layer of quartz sand bonded with nanoparticles may be placed either at the top or bottom of the water purification cartridge, or in both locations, such that it secures the layer of rice husk ash bonded with nanoparticles.

In accordance with an embodiment, the layer of quartz sand bonded with nanoparticles may be placed as an intermediate layer in addition to being placed at the top, bottom or both locations in the water purification cartridge.

By way of an example, figure 1 illustrates one such embodiment and provides a schematic partial view of the water purification cartridge (10) comprising the water purification media as described earlier. In figure 1 , the water to be purified enters through the inlet (11) which comprises of a netted material. The water then proceeds into the water purification medium as described above. The water first flows through a primary layer of quartz sand bonded with nanoparticles. It then proceeds through a series of layers of rice husk ash bonded with nanoparticles, before encountering a final layer of quartz sand bonded with nanoparticles,past a mesh plate. Before passing through outlet (12) of the purification medium, water then flows into a hollow cavity placed within the water purification cartridge (10) , as illustrated in the figure, towards the bottom of the water purification cartridge (10). The water exits the water purification cartridge (10) through the cartridge outlet (13) as shown in the figure.

SPECIFIC EMBODIMENTS ARE DESCRIBED BELOW

A water purification medium comprising a layer of rice husk ash and a layer of quartz sand adjacent to it with a bactericidal agent coated on to either the rice husk ash or the quartz sand or both, such that the layer of quartz sand is positioned after the layer of rice husk ash in the direction of flow of water through the water purification medium.

' Such a water purification medium comprising a plurality of layers of rice husk ash or a plurality of layers of quartz sand or a plurality of layers of both, each layer abutting another layer, with a bactericidal agent coated on to one or more layers of either the rice husk ash or the quartz sand or both.

Such a water purification medium comprising alternate layers of rice husk ash and the quartz sand.

Such a water purification medium comprising a layer of rice husk ash between a top and a bottom layer of quartz sand. Such a water purification medium comprising a plurality of layers of rice husk ash between a top and a bottom layer of quartz sand.

Such a water purification medium wherein one or more layers are compacted.

Such a water purification medium wherein a plurality of bactericidal agents are coated on one or more layers of rice husk ash or quartz sand or both.

Such a purification medium wherein the bactericidal agent is one or more of silver, copper or their compounds.

Such a purification medium wherein the bactericidal agent is silver nanoparticles or copper nanoparticles or both.

A water purification cartridge comprising a water purification medium,a water inlet for the purification medium and an outlet for purified water from the purification medium, the water purification medium comprising a layer of rice husk ash and a layer of quartz sand adjacent to it with a bactericidal agent coated on to either the rice husk ash or the quartz sand or both, such that the layer of quartz sand is positioned after the layer of rice husk ash and proximate the outlet in the direction of flow of water through the water purification medium.

Such a water purification cartridge wherein the water purification medium comprises a plurality of layers of rice husk ash or a plurality of layers of quartz sand or a plurality of layers of both, each layer abutting another layer, with a bactericidal agent coated on to one or more layers of either the rice husk ash or the quartz sand or both.

Such a water purification cartridge comprising a layer of quartz positioned proximate the water inlet. INDUSTRIAL APPLICABILITY

The water purification medium as described above is a simple composition that is inexpensive, easy to use and effective in removing bacterial contamination from potable water. A water purification cartridge comprising the said water purification medium in one or more preferred arrangements as described above provides an effective means to obtain potable water for a sustained duration.