TECHNICAL FIELD

[001] The present subject matter generally relates to a nanoparticle system. More specifically the subject matter relates to a cationic nanoparticle system coated. Even more specifically the subject matter relates to a cationic nanoparticle system for desalination and method of desalination.

BACKGROUND

[002] Despite of the fact that the earth has abundance of water only small percentage of the water is in the form usable for humans. In many parts of the world local demand of the water exceeds capacity of conventional resources of water. Therefore, efforts are not only required to ensure that water is used judiciously but also to convert waste water into usable water. More economical use of water, reducing distribution losses and increased use of recycled water can help in addressing the demand supply imbalance.

[003] One of the water recycling challenge is desalination. Conventional desalination processes generally exploit one or many of thermal, mechanical, electrical, and chemical properties for desalination. For example, evaporation and crystallization exploit primarily thermal properties, whereas filtration, reverse osmosis, forward osmosis exploit primarily mechanical properties. Similarly, electro-dialysis and ionic exchange may deploy combination of electrical and chemical properties. Most of these techniques have limitations, e.g. cost and complexity, scalability efficiency, economic viability etc.

[004] The present subject matter addresses these issues and provides a solution that may not only be used for recycling industrial refuse but also generating fresh water from seawater, brackish water etc. SUM MARY

[005] The present subject matter provides solution to the above and other problems. The present subject matter provides a cationic nanoparticle system for desalination and a method of desalination thereof. [006] Some of the problems faced by nanoparticle based desalination systems are: low efficiency; poor quality of desalination; high time and iteration requirements. One of the reasons for such limitations is the charge carrying capacity of the nanoparticles and problems associated with the process required for enhancing charge carrying capacity. Generally, the process of increasing charge carrying capacity inherently requires addition of impurities to the nanoparticle system, which turns out to be counterproductive for desalination process. The present subject matter provides a solution to at least these limitations by controllably enhancing the charge carrying capacity of the nanoparticles while ensuring that the resulting nanoparticle system, also significantly improves the desalination process. The present subject matter not only enables desalination but also provides easy recyclability of the nanoparticle system thereby providing a solution that is efficient, cost effective and of interest in industrial application.

[007] According to one aspect, the present subject matter provides a nanoparticle system for desalination comprising: a nanoparticle system having a core and a positively charged species coated on the core, wherein the positively charged species has an ionizable group and wherein the pH value of the

nanoparticle system is more than the pKa value of the ionizable group and the nanoparticle system is configured to cause desalination of negatively charged ions from an effluent. In one embodiment, the core includes any one or more of:

transition elements, second group elements, third group elements, fourth group element and fifth group elements. In a second embodiment, the core is a metallic core including metal oxide core, an iron core and iron oxide core, in a third embodiment, the positively charged species is selected from poly amines, alkonium salts, poly ethylam ine, cataionic polymers, poly amines, poly peptides, quaternary ammon ium salts. In a fourth embodiment,the positively charged species is any one or more of Benzalkonium chloride (BKC), cetyl

trimethylammonium bromide (CTAB), peptides. In a fifth embodiment, the size of the nanoparticle system is below 100 microns. In a sixth embodiment, the size of the nanoparticle system is between 20 nm to 10 microns, in a seventh

embodiment, the nanoparticle system is in the form of any one of: solution, slurry, paste, solid and powder. In a eighth embodiment, the pH value of the nanoparticle system is above 7 and is higher than the highest pKa value of ionizable group of the positively charged species. In a ninth embodiment, the core is coated with a stabilizing agent. In a tenth embodiment, wherein the stabilizing agent is any one of polymer, surfactant, and reducing agent, chelating agent. In a eleventh embodiment, the stabilizing agent is dextron or PVP.

[008] According to another aspect the present subject matter provides a desalination method comprising: supplying a nanoparticle system having a core and a positively charged species coated on the core, wherein the positively cha rged species has an ionizable group and wherein the pH value of the nanoparticle system is more than the pKa value of the ionizable group and causing desalination by binding the nanoparticles system and anions present in the effluent. In one embodiment, the core includes any one or more of: transition elements, second group elements, third group elements, fourth group element and fifth group elements. In a second embod iment, the method includes extracting the nanoparticles system from the effluent. In a third embodiment, the core of the nanoparticle system is a n iron based core and includes magnetic extraction. In a fourth, the extracting includes one or more of filtration, centrifugation,

sedimentation, magnetic separation. In a fifth embodiment, the method includes purifying the nanoparticle system for reuse in the desalination. In a sixth embodiment, the purifying includes basifying the nanoparticles system and removing desalinated salts from the nanoparticles. In a seventh embodiment, the positively charged species is selected from poly amines, alkonium salts, poly ethylamine, cataionic polymers, poly amines, poly peptides, quaternary ammonium salts, the positively charged species is any one or more of

Benzalkonium chloride (BKC), cetyl trimethylammonium bromide (CTAB), peptides.

DETAILED DESCRIPTION

[009] It shall become clear to a person, after reading this specification, that the following discussion is intended only for illustration purpose and that the subject matter may be practiced without departing from the spirit of the present subject matter in other embodiments different than the embodiments discussed herein. Before the present subject matter is further described in more details, it is to be understood that the subject matter is not limited to the particular embodiments described, and may vary as such. The present subject matter is being described, for the purpose of explanation only, however it shall become abundantly clear to a person in the art, after reading this specification, that the subject matter may be practiced in other applications where altering nanoparticles charge carrying capacity is required or desalination/purification of natural or industrial refuge is required It is also to be understood that the terminology used throughout the preceding and forthcoming discussion is for the purpose of describing particular embodiments only, and is not intended to be limiting. It must be noted that as used herein, the singular forms "a", "an", and "the" include plural references unless the context clearly expressly dictates otherwise.

[0010] Use of nanotechnologies in water recycling and purification presents a theoretically and potentially promising solution that may help in preventing future water shortages. However a practical solution that may be implemented on industrial scale and meet harsh commercial requirements still waits to see light of the day. Some challenges may be posed by the chemical characteristics of the dissolved solids of an effluent for implementing nanoparticle based solution for desalination. It is desirable that nanoparticle systems achieve desalination of most, if not all, salts without regards to the chemical characteristics. In some cases, lower valance salts present challenges during desalination. This is because charge carrying capacity of nanoparticle systems plays an important role in desalination and to desalinate lower valance salts require that nanoparticle system must have a higher charge carrying capacity. Obtaining a nanoparticle system that has high charge carrying capacity is challenging in itself, because the process of obtaining high charge carrying capacity nanoparticle systems inherently require addition of impurities to the system. Therefore, there is a need of a process to obtain a high charge carrying nanoparticles system that reduces above challenges.

[0011] Further nanoparticle systems are expensive. Therefore it is required that most is achieved priorto trashing such nanoparticle systems. Hence recyclability of the nanoparticle systems is desirable. In fact, most desirable is a nanoparticle system that may be substantially perpetually used. However, desalination process poisons the nanoparticle system quickly and effective recyclability may not be achieved. The present subject matter provides not only recyclability but also provides possibility of multiple rounds to charging of nanoparticle system to enhance its charge carrying capacity after its use. Thereby achieving most from the nanoparticle system.

[0012] The present subject matter addresses the above and other problems and offer many advantages, including but not limited to, simplifying desalination process, reduced energy consumption, enablement desalination process for industrial application, recyclability of nanoparticle systems, effective desalination substantially independent of valances of the salts, enablement of the system for application in: industrial refuse, sea water, salty water, brackish water, removal of hardness and toxic heavy metal ions etc.

[0013] The present subject matter provides nanoparticle system having a core. The core includes any one or more of: transition elements, second group elements, third group elements, fourth group element and fifth group elements. In one example, the core is a metallic core including metal oxide core, an iron core and iron oxide core. Having an iron core offers additional advantage, which is to say, that magnetic filtration of the nanoparticle system becomes possible. The core is coated with a positively charged species. The positively charged species may be selected from poly amines, polyalkonium salts, poly ethylamine, cationic polymers, poly amines, poly peptides, quaternary ammonium salts, the positively charged species is any one or more of Benzalkonium chloride (BKC), cetyl trimethylammonium bromide (CTAB), peptides. [0014] According to one feature of the subject matter, the pH value of nanoparticle system is controlled by controlling pH depending on the pKa value of the positively charged species. It should become clearto a person in the art, the positively charged species may have multiple ionizable groups and each of the inonizable group may have a pKa value. The pKa value of one ionizable group may be different than the pKa value of other ionizable groups in the positively charged species. In some examples, the pH value of the nanoparticle system is kept above the highest pKa value in the positively charged species. In some examples, the pH value of the nanoparticle system is kept above the lowest pKa value in the positively charged species. This ensures that charge carrying capacity of the core or the nanoparticle system is at optimal levels, which in turn assist in improved binding of the oppositely charged ions.

[0015] Size of the nanoparticle system is in the range from 20 nanometers to 100 micrometer. Nanoparticle systems size in the above referred range has shown relatively better desalination results. In one embodiment, for practicing the subject matter, the nanoparticles system having size below 50 micron may be prepared, in some examples, the nanoparticle system may be in the form of solution, slurry, paste, solid or powder. [0016] In some examples, the core may also be coated with a stabilizing agent. The stabilizing agent may be coated prior to coating of the positively charged sp.ecies. In some examples, the stabilizing agent may be a polymer, a surfactant, a reducing agent or a chelating agent. In some example, the stabilizing agent may be dextran or PVP. The stabilizing agent assists in ensuring that the core remains stable during the coating and desalination process.

[0017] The nanoparticle system so prepared has capability to capture the oppositely charged ions of an effluent, when it is mixed with the effluent. It shall become clear to a person in the art, after reading this specification, that the effluent may have a number of dissolved solids and have high Total Dissolved Solids (TDS) concentration. The effluent may be an industrial effluent or any solution that needs to be subjected to desalination, removal of hardness and toxic heavy metal ions etc. Such solution may include, but not limited to industrial refuse, sea water, salty water, brackish water. The nanoparticle system when mixed with the effluent, binds with the oppositely charged ions of the TDS. The nanoparticle system bound with the ions can then be separated through filtration, sedimentation, magnetically, centrifugation, osmosis or any other means leaving behind the water with significantly reduced TDS. The present subject matter has demonstrated up to 90% of targeted TDS desalination from the effluent of industrial grade, that is to say an effluent having TDS upto 100,000 ppm or more.

[0018] Among many other advantages, the present subject matter provides a desalination process that requires minimal external energy and also the process is substantially independent of ion type and its valances. The subject matter provides improved removal of ions such chloride, bromide, fluoride, sulphate, sulphite, carbonate, nitrate, other halogen ions, nitrite, phosphates and other ions having affinity towards cations..

[0019] In some examples, the nanoparticle system has demonstrated effective treatment of an effluent having variety of ions. The variety of ions include but not limited, to transition metal ions, first group ions, second group ions, third group ions, fourth group ions and fifth group ions, effectively and substantially covering entire range of ions of the period table.

[0020] Among other advantages of the present subject matter also offers advantages of chemistry based desalination, minimal energy requirement, targeted ion desalination, small equipment size, repeatability and reusability of the nanoparticle systems, magnetic and easy separation processes, process independent of effluent type and usable for variety of effluents, improved sedimentation of TDS, effective binding of the TDS and nanoparticle systems, and manufacturing and scalability ease.

[0021] The present subject matter has been developed and tested for variety of parameters and characteristics; some of them are: Spectroscopy; zeta potential measurement; chromatography; particle size and shape measurement; dispersibility and stability; binding efficiency to different ions; and scalability.

[0022] The present subject matter further provides a desalination method using the nanoparticle system of the present subject matter. At a step of the method the nanoparticle system is supplied to an effluent. The nanoparticle system is prepared as taught herein. The effluent generally has both the cations and the anions that are needed to be desalinated. In some examples, the effluent has alkaline pH. However, a person skilled in art shall understand, after reading this specification, that the present subject matter may be practiced for effluents of any pH value. The nanoparticle system being positively charged binds with the anions of the effluent. The nanoparticle system having bound anions may be then separated from the effluent. In one example, where core of the nanoparticle system has iron or its derivatives, magnetic separation may be employed for separating nanoparticle system from the effluent. However, it shall become clear to a person skilled in the art, after reading this specification, that other separation methods such as filtration, centrifugation, sedimentation etc. may also be employed for separation. It shall also become clear to a person, after reading this specification that multiple iterations of separations methods may be employed. Further it shall also become clear to a person, after reading this specification, that one or more of different methods substantially simultaneously or in succession may be employed for separation. Once the nanoparticle system bound with anions of the effluent is separated from the effluent, the nanoparticle system may be cleaned and filtered for redeployment in further desalination process.

[0023] Some of the examples of practicing the present subject matter and some results of the test and characteristics are is as follows:

Example - 1: An Example for Development of Core and Coating thereof:

[0024] A standard solution of ferric chloride (FeCI ₃ ) and ferrous sulphate (FeS0 _4. 7H ₂ 0) may be prepared while ensuring that the solution is stirred constantly. At a next step, a positively charged species such as, BKC, CTAB, etc may be added to the solution and stirred. At a further step, concentrated NaOH solution may be added to the above solution under constant stirring and temperature of range about 30°C to 6o°C. The rate of addition of NaOH may be kept slow enough to increase the pH of the solution to around 9-11 and the color of the solution turns into coke black. Sequential heating of the above mixture may be carried out at different temperatures over a period of time. For example, the solution may be heated to 6o-7o°C for 15-30 minutes and then at 75-85°C for 15-30 minutes and final heating up to 90 - ioo°C for 30-60 minutes. In an optional step, a known concentration of polymer such as Dextran or PVP may be added to the solution under constant stirring. The solution is then cooled to room temperature and cleaned with demineralized water. Cleaning may be performed 2-3 times or as many times as required to obtained the core. The core obtained, in an optional step, may be characterized for the size distribution. The nanoparticle system obtained may be subject to TDS correction using any one or more of filtration, magnetic extraction, centrifugation techniques etc. Example - 2: Example of Measurement of Core Size:

[0025] In one example, the nanoparticle system size characteristics may be determined using Malvern Zetasizer Nano ZS. In the present example data obtained in show in the below appended Ta ble 1. Table-i

Example - 3: Example of TDS reduction from Effluent:

[0026] In one example, an effluents having NaCI and different TDS values were treated for desalination using the method of the present subject matter. Following Table 2 shows results of treatment according to the present subject matter.

Table 2

[0027] While the subject matter may be susceptible to various

modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described herein. Alternate embodiments or modifications may be practiced without departing from the spirit of the subject matter. The drawings shown are schematic drawings and may not be to the scale. While the drawings show some features of the subject matter, some features may be omitted. In some other cases, some features may be emphasized while others are not. Further, the methods disclosed herein may be performed in manner and/or order in which the methods are explained. Alternatively, the methods may be performed in manner or order different than what is explained without departing from the spirit of the present subject matter. It should be understood that the subject matter is not intended to be limited to the particular forms disclosed. Rather, the subject matter is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as described above.

[0028] In the above description, while describing the present subject matter, some of the proprietary terms as well as some proprietary terms of expression including trademarks or other copyrighted subject matter may have been used, the applicant has taken best care in acknowledge the ownership of the proprietary subject matter. However, if the applicant has inadvertently omitted any such acknowledgement, the applicant states that any such omission is unintentional and without any malicious intention and the applicant states that should any such inadvertent omission is brought to the attention of the applicant, the applicant is willing take actions that the applicant believes are fit to

acknowledge such proprietary ownership.