WO2018104957A1

WO2018104957A1 - Anionic nanoparticle system for desalination and method thereof

Info

Publication number: WO2018104957A1
Application number: PCT/IN2017/050509
Authority: WO
Inventors: Ajay Kumar Gupta; Dinesh Kumar Jagroopsingh YADAV; Mihir Kanjibhai RATHOD
Original assignee: Arvind Envisol Ltd.
Priority date: 2016-12-09
Filing date: 2017-11-04
Publication date: 2018-06-14
Also published as: CN110049816A

Abstract

The present subject matter provides a nanoparticle based desalination system and a method of desalination thereof. The subject matter provides a nanoparticle system having a core and a negatively charged species coated on the core. The pH value of the nanoparticle system is less than the pKa values of the negatively charged species. The nanoparticle system is configured to cause desalination of positively charged ions from an effluent.

Description

ANIONIC NANOPARTICLE SYSTEM FOR DESALINATION AND METHOD THEREOF

TECH NICAL FIELD

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

BACKGROUN D

[002] Despite of the fact that 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 water exceeds the 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 their own 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 refuge but also generating fresh water from seawater, brackish water etc. SUMMARY

[005] The present subject matter provides solution to the above and other problems. The present subject matter provides an anionic nanoparticle system for desalination and a method of desalination thereof. 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 control lably 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.

[006] According to one aspect, the present subject matter provides a nanoparticle based desalination system comprising: a nanoparticle system having a core and a negatively charged species coated on the core, wherein the pH value of the nanoparticle system is less than at least one pKa value of the negatively charged species and the nanoparticle system is configured to cause desalination of positively charged ions from an effluent. According to 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. According to a second embodiment, the core is a metallic core including metal oxide core, an iron core and iron oxide core. According to a third embodiment, the negatively charged species is selected from poly carboxylic acid, poly sulphonic acid. According to a fourth embodiment, the negatively charged species is any one or more of humic acid, Ethylenediaminetetraaceticacid (EDTA), Diethylenetriaminepentaacetic (DTPA), citric acid. According to a fourth embodiment, the size of the nanoparticle system is below 100 microns. According to a fifth embodiment, the size of the nanoparticle system is between 20 nm to 10 microns. According to a six embodiment, the nanoparticle system is in the form of any one of: solution, slurry, paste, solid and powder. According to a seventh embodiment, the pH value of the nanoparticle system is below7 and is lowerthan the lowest pKa value of the negatively charged species. According to an eighth embodiment, the core is coated with a stabilizing agent. According to a ninth embodiment, the stabilizing agent is any one of polymer, surfactant, reducing agent, and chelating agent. According to a tenth embodiment, the stabilizing agent is dextran or

polyvinylpyrrolidone (PVP). According to an eleventh embodiment, the effluent has positively charged ions. According to a twelfth embodiment, the negatively charged nanoparticles bind to positively charged ions present in the effluent causing desalination.

[007] According to another aspect the present subject matter provides, a desalination method. The desalination method comprising: supplying a nanoparticle system to an effluent, wherein the nanoparticle system having a core and a negatively charged species coated on the core, wherein the pH value of the nanoparticle system is lessthan at least one pKa value of the negatively charged species causing desalination by binding the nanoparticles system and cations 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 embodiment the method includes extracting the nanoparticles system from the effluent. In a third embodiment, the core of the nanoparticle system is an iron based core and includes magnetic extraction. In a fourth embodiment, the extracting includes one or more of filtration, centrifugation, sedimentation, magnetic separation. In a fifth embodiment, method includes purifying the nanoparticle system for reuse in the desalination. In a sixth embodiment, the purifying includes acidifying the nanoparticles system and removing desalinated salts from the nanoparticles. In a seventh embodiment, the negatively charged species is selected from poly carboxylic acid, poly sulphonic acid.

DETAILED DESCRIPTION

[008] 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 particuiar embodiments oniy, 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.

[009] 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.

[0010] Further nanoparticle systems are expensive. Therefore it is required that most is achieved prior to 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 enhancing its charge carrying capacity after its use.

Thereby achieving most from the nanoparticle system.

[0011] 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.

[0012] The present subject matter provides nanoparticle system having a core. The core includes any one or more of, transition elements, second group elements, th ird group elements, fourth group element and fifth group elements. In one example, the core is a meta ll ic core includ ing metal oxide core, an iron core and iron oxide core. Having an iron core offers add itional advantage, wh ich is to say, that magnetic fi ltration becomes easier. The core is coated with a negatively charged species. The negatively charged species may be selected from poly carboxyl ic acid, poly sulphon ic acid etc. Some other examples of the negatively charged species may include hum ic acid, E DTA, DTPA, citric acid etc.

[0013] Accord ing to one feature of the subject matter, the pH va lue of nanoparticle system is controlled and is kept less than at least one pKa value of the ioniza ble groups present in negatively charged species. It should become clear to a person in the art, the negatively charged species may have mu ltiple ionizable groups and each of the ion izable group may have a pKa value. The pKa value of one ion izable group may be d ifferent than the pKa value of other ion izable groups in the negatively charged species. In some examples, the pH value of the nanoparticle system is kept below the lowest pKa value in the negatively charged species. In some example the pH va lue of the nano particle system is kept below the hig hest pKa value in the negatively charged species. Th is ensures that charge carrying capacity of the core or the nanoparticle system is at optima l levels, wh ich in turn assist in improved bind ing of the oppositely charged ions.

[0014] Size of the nanoparticle system is in the range from 20 nanometer to 100 micrometer. Nanoparticle systems size in the above referred range has shown relatively better desalination results. I n one em bod iment, for practicing the subject matter, the nanoparticles system having size below 50 m icron may be prepared . In some examples, the nanoparticle system may be in the form of solution, slurry, paste, sol id or powder.

[0015] In some examples, the core may also be coated with a sta bi l izing agent. The stabi l izing agent may be coated prior to coating of the negatively charged species. I n some examples, the sta bi lizing 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.

[0016] 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 clearto 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 solution. 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. In some example, the present subject matter has demonstrated up to 90% of targeted TDS desalination from the effluent of industrial grade, that isto say an effluent having TDS upto 100,000 ppm or more.

[0017] 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 has demonstrated improved removal of ions such as sodium, potassium, calcium, aluminum, magnesium, arsenic, lead etc.

[0018] Among many 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.

[0019] 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.

[0020] 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. The nanoparticle system being negatively charged binds with the cations of the effluent. The nanoparticle system along with the cations may be then filtered 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.

[0021] Once the nanoparticle system bound with cations of the effluent is separated from the effluent, the nanoparticle system may be cleaned and filtered for redeployment in further desalination process. [0022] 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 of a Nanoparticle System:

[0023] A standard solution of 0.1 M ferric chloride (FeCI₃) and 0.1 M ferrous sulphate (FeS0₄) may be prepared while ensuring that the solution is stirred constantly. 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 alkaline around 8-11 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-70°C for 15-30 minutes and then at 75-85^ 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 (ranging 2 to 20 grams) may be added before addition of NaOH solution 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. Example - 2: An Example of Coating of A Charged Species on the Core:

[0024] In one example, the core obtained in the Example 1 may be further coated with a negatively charged species. As may become clear to a person skilled in the art, after reading this specification that the negatively charged species may be poly carboxylic acid, poly sulphonic acid or alike. More specifically, the negatively charged species may be humic acid, EDTA, DTPA, citric acid or alike. In the present example, a humic acid is coated on the core. While coating the negatively charged species it is ensured that the pH value of the nanoparticle system is less than the pKa values of the negatively charged species. This is achieved by acidifying the nanoparticle system. In some examples, acid such HCI, sulphuric acid, nitric acid, etc may be used for controlling pH value.

[0025] The pH value of the nanoparticle system may be adjusted to keep the value within acidic range. The pH value may be adjusted by incubating the nanoparticle system for about 2 hours. The nanoparticle system may be purified with DM water. While adjusting the pH value of the nanoparticle system it is ensured that the total dissolved solids in the nanoparticle system remain may below 1000 ppm. In some other embodiments, dissolved solids in the nanoparticle system may remain below 200.

[0026] For coating humic acid on the core, humic acid and core are mixed and stirred for about 2-4 hours at the temperature between 30-50 °C. From the mixture excess salts are removed to obtain the nanoparticle system. The present subject matter also provides recycling of nanoparticles system. According to this aspect the present subject matter provides extracting used nanoparticles system from the refuge and cleaning the nanoparticle system. The nanoparticles system may then be further coated with the negatively charged species, as in this case humic acid by mixing and stirring in a temperature controlled environment as taught above. In an optional step, the nanoparticle system may be tested for efficiency for cation removal.

Example - 3: Example of Measurement of Core Size:

[0027] 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 Table 1.

Table-i

S. No. Dextran quantity Reaction Temperature Size

(Gram) (°C) (nm)

Example - : Example of TDS reduction from Effluent:

[0028] In one example, an effluent having NaCI and TDS around 980 ppm and alkaline pH in nature where treated for desalination using the method of the present subject matter. Following Table 2 shows results of sequential treatment according to the present subject matter. In the below example pH of the nanoparticle system is kept around 3.0 (i.e. below the pKa values of all ionizable groups in the humic acid).

Table 2

[0029] Table 3 further shows results of TDS reduction in effluent containing

NaCI in varying concentration between 1000 - 100,000 ppm and the effluent having alkaline pH.

Table ¾

solution (ppm) solution (Lit) particles added

1120 2-5 1 23 5ΟΟ 1 2 22.2

10000 1 2 22

50800 1 6 31

78000 1 6 26

88000 1 6 20.5 looooo 4 20 23 looooo 4 18 21.6 looooo 1 ¹5 46

100000 3 ¹5 22

Example - 6: Another Example of TDS reduction from Effluent, wherein the Multiple Salts are Present in the Effluent:

[0030] In one example, the present subject matter provides cation reduction up to 84%. In that, the effluent has TDS upto 1000 ppm and has salts such Calcium chloride, magnesium chloride, sodium chloride, aluminium sulphate etc. The effluent has pH in alkaline range. In some examples, the nanoparticle system has demonstrated effective treatment of an effluent having variety of ions, first group ions, second group ions, third group ions, fourth group ions, fifth group ions, effectively and substantially covering entire range of ions of the periodic table.

[0031] Example - 7 Another Example of TDS reduction experiments with different coating ligands -

[0032] In one example, the present subject matter provides nanoparticle system having coating of a negatively charged species. In this example a coating of any one or more of citric acid, EDTA or DTPA (i.e. polycarboxylic acids) is provided. In an example of effluent having about 1000 ppm of NaCI salts and pH of in alkaline range desalination of cations upto 60-80% is achieved. In another example, higher the carboxylic acid moieties in the coating materials result in better binding of nanoparticle systems and salt and therefore results in better desalination.

[0033] 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.

[0034] 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 hastaken 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.

IS

Claims

Claims :

1. A nanoparticle based desal ination system comprising : a nanoparticle system having a core and a negatively charged species coated on the core, wherein the negatively charged species has an ion izable group and wherein the pH value of the nanoparticle system is less than at least one pKa va lue of the ionizable group of the negatively charged species and the nanoparticle system is configured to cause desa lination of positively charged ions from an effluent.

2. The nanoparticle based desal ination system of claim ι, wherein the core includes any one or more of, transition elements, second group elements, th ird group elements, fourth group element and fifth group elements.

3. The nanoparticle system of claim 1, wherein the core is a metal lic core includ ing metal oxide core, an iron core and iron oxide core. . The nanoparticle system for desal ination system of cla im 1, wherein the negatively charged species selected from poly carboxyl ic acid, poly su lphon ic acid . 5. The nanoparticle system for desal ination system of claim 1, wherein the negatively charged species is any one or more of humic acid, E DTA, DTPA, citric acid .

6. The nanoparticle based desal ination system of claim 1, wherein the size of the nanoparticle system is below 100 m icrons. 7. The nanoparticle based desal ination system of claim 1, wherein the size of the nanoparticle system is between 20 nm to 10 m icrons.

8. The nanoparticle system for desal ination of claim 1, wherein the

nanoparticle system is in the form of any one of: solution, slurry, paste, sol id and powder.

9. The nanoparticles based desa lination system of claim 1, wherein the pH va lue of the nanoparticle system is below 7 and is lower than the lowest pKa va lue correspond ing to the negatively charged species.

10. The nanoparticles based desa lination system of claim 1, wherein the core is coated with a stabi l izing agent.

11. The nanoparticles system for desa lination system of claim 10, wherein the stabi l izing agent is any one of polymer, surfactant, reducing agent, and chelating agent.

12. The nanoparticles based desa lination system of claim 10, wherein the stabi l izing agent is dextran or PVP .

13. A desal ination method comprising : supplying a nanoparticle system having a core and a negatively charged species coated on the core, wherein the negatively charged species has an ionizable group and wherein the pH value of the

nanoparticle system is less than at least one pKa value of the ion iza ble group of the negatively charged species and causing desal ination by bind ing the nanoparticles system and cations present in the effluent.

14. The desal ination method of claim 13, wherein the core includes any one or more of, transition elements, second group elements, th ird group elements, fourth group element and fifth group elements. 15. The desal ination method of claim 13, wherein the method includes extracting the nanoparticles system from the effluent.

16. The desal ination method of claim 15, wherein the core of the nanoparticle system is an iron based core and includes magnetic extraction .

17. The desal ination method of claim 15, wherein the extracting includes one or more of filtration, centrifugation, sedimentation, magnetic separation.

18. The desalination method of claim 15, wherein the method includes purifying the nanoparticle system for reuse in the desal ination.

19. The desal ination method of claim 15, wherein the purifying includes acid ifying the nanoparticles system and removing desa linated sa lts from the nanoparticles.

20. The desal ination method of claim 13, wherein the negatively charged species is selected from poly carboxylic acid, poly su lphon ic acid.