WO2018078641A1

WO2018078641A1 - Novel method for the removal of mercury ions from water using organic probe tethered diatoms

Info

Publication number: WO2018078641A1
Application number: PCT/IN2017/050321
Authority: WO
Inventors: Pravin Patil; Dr.madhuprasad KIGGA; Dr.mahaveer KURKURI
Original assignee: Centre For Nano And Material Sciences, Jain University
Priority date: 2016-10-24
Filing date: 2017-08-03
Publication date: 2018-05-03

Abstract

The present invention is a method for the removal of mercury ions from water using organic probe tethered diatoms. The UV-vis and fluorescence titration studies showed that 1:1(P2:Hg²⁺) stoichiometric complex is forming. Further, the organic probe P2 has been immobilized on diatoms and synthetic silica surface separately for the efficient removal of Hg²⁺ ions from water. These molecules were characterized by XPS, TGA, FTIR, and SEM. As a practical application, the P2 immobilized diatoms and synthetic silica were used for the removal of Hg²⁺ ions. Results revealed that, P2 functionalized diatoms can remove upto 1 ppb of 10 mercury ions which can be visualized by the colour change whereas efficiency of synthetic silica was comparatively less. The P2 functionalized diatoms and/or synthetic silica particles can be used in remote areas where a level of mercury is high.

Description

NOVEL METHOD FOR THE REMOVAL OF MERCURY IONS FROM WATER USING ORGANIC PROBE TETHERED

DIATOMS

The present invention relates to a novel method for the removal of mercury ions from water using organic probe tethered diatoms/synthetic silica particles.

BACKGROUND OF THE INVENTION

In recent years, the research on detection and removal of heavy metal ions is rapidly expanding. The metal ions cause severe threats to human beings when the concentration exceeds the permissible limit. The main causes of heavy metal contamination in the environment are fast growing industries, urbanization, metal mining, the volcanic eruption in past decades and combustion of fossil fuels, etc. High concentration of heavy metal ions causes deadly diseases related to the brain, kidney, nervous system, liver, etc. Thus, the need for low-cost, reliable devices to detect and remove these metal ions have to develop on urgent basis. During the past decades, researchers are trying to develop new materials and methods to detect and remove heavy metal ions from water. The materials such as graphene, magnetic nanoparticles, polymers and biological materials show very high sensitivity and selectivity to detect and remove these metal ions. The use of conventional methods for the quantitative detection and analysis of these metal ions involves electrochemical sensing, atomic absorption spectroscopy, high- performance liquid chromatography, laser induced fluorescence spectroscopy, etc. Though these methods are significantly selective and sensitive, their cost and bulky instrumentation systems hinder the field studies. To overcome the above disadvantages, researchers are trying to develop simple, equally selective and sensitive probes for the colorimetric detection and removal of metal ions.

Among several other heavy metal ions, mercury (Hg²⁺) is one such ion which is highly toxic when it is present in either in organic or inorganic form. Mercury methylation is an organic form of mercury which can directly interact with lipids to cause cancer-related diseases. Above a permissible limit (2 ppb/mL), the mercury can cause several diseases such as Mina-Mata and many other waterborne diseases related to kidney, liver, and bones, etc. Owing to this, detection and removal of traces of mercury from the water become essential. There are several reports on synthesis of organic probes for the colorimetric detection of Hg²⁺ ions. However, these probes work efficiently either in organic solvents or mixed organic solvents. Further, few reports suggest that rhodamine- based probes can detect Hg²⁺ ions which are present in water with high sensitivity. Therefore, the rhodamine-based probes have attracted many researchers by virtue of their excellent photophysical properties, such as long wavelength absorption and emission, high fluorescence quantum yield, large extinction coefficient and high stability against light. The detection is based on the fluorescence switching of rhodamine moiety between spirocyclic and ring opening forms before and after the addition of Hg²⁺ ions.

On the other hand, research on grafting of these probes on solid substrates such as silica, carbon-based materials, nanoparticles and polymers for the removal of Hg²⁺ ions is growing fast. Alternatively, use of naturally available materials to graft these molecules to remove Hg²⁺ ions is still pending. Therefore, naturally available diatom particles could be used to graft these probes for the removal of Hg²⁺ ions. Diatoms are the class of algae, and their cell wall is made of silica which has high surface area compared to conventional silica. The use of diatom particles in various applications from chemistry to medicine has been explored to date. However, these diatoms frustules which have similar properties of silica can replace conventional silica particles in several applications such as water purification, filtration of beer and wine, optical sensing, drug delivery due to the inherent properties such as high porosity, surface area, biocompatibility, chemical inertness, surface tenability and low-cost. Thus, the main focus of this invention is to report the novel process and product invention for the removal of Hg²⁺ ions from water by using diatoms which can remove up to 1 ppb of Hg²⁺ ions from water and can be visualized by color change. FIELD OF THE INVENTION

The present invention relates to the field of organic chemistry, and metal ion detection and removal from water. Specifically, relates to the synthesis of organic probes for colorimetric detection of mercury ions in water and further functionalize on diatoms for removal of the same.

DISCUSSION OF PRIOR ART

All the patents cited within this specification are hereby incorporated by reference.

US 2016/0060133 Altitled "Removal of metals and cations thereof from water based fluids " discloses the methods for the removal of metal cations from water- based fluids. The filter media is made up of diatoms and can remove only one cation present in water fluid. The metal cations within the filter media may react with diatoms to form a precipitate, which may be separated from the water-based fluid. US 2016/0002054 Altitled "Diatomaceous energy storage devices" discloses the area of energy storage devices. The device consists of a first electrode, a second electrode, and separator electrode. Anyone of the electrode is made up of diatom frustules. The shape, dimension, size and porosity are the main parameters to control the efficiency of storage devices. The invention suggests that modifying diatom frustules with various nanomaterials will increase the energy storage efficiency.

US 2015/0175457 Altitled "Treatment of waste water "discloses the use of diatoms for the biological treatment of wastewater. It has been suggested that introducing the algal component into the wastewater can extract at least one nutrient from wastewater to remediate the same. The algal component of diatoms is comprised of a derivative of chlorella which will interact with any one of the wastewater components and removes from the wastewater. By changing the class of diatoms, removal of several other components also can be achieved. US 2015/0241412 Al titled "Self-assembled nanostructured sensors and methods thereof" discloses the area of sensors using diatoms. The diatoms and sensor materials will self-assemble to form a nanostructured diatoms composition which can be able to detect the gas, bacteria, explosive degradation materials and neurotoxins.

Disadvantages of reported patents and brief description of the present invention

The discovery and development of the above-mentioned novel diatoms-based energy storage and water purification devices have a huge impact in the scientific community because of the potential properties of the diatoms. Thus, diatoms can be used in every field of science and technology. However, efficient colorimetric removal of mercury ions from water using diatoms is lacking. Therefore, the process for the grafting of an organic probe on diatoms surface which can remove the mercury ions from water. The development of low-cost devices using the abundant diatoms for the spot monitoring as well as removal of mercury ions from water which can be visualized by a color change of diatoms will impact the society.

Advantages and brief description of the invention

Naturally available diatom particles are the class of algae, and their cell wall is made up of silica which has intrinsic properties such as high porosity, surface area, biocompatibility, chemical inertness, surface tenability and low-cost compared to conventional silica. The use of diatom particles in various applications from chemistry to medicine has been explored to date. However, these diatoms frustules which have similar properties of silica can replace conventional silica particles in several applications such as water purification, filtration of beer and wine, optical sensing, drug delivery, etc. The conventional silica particles are produced by chemical processes, the byproducts may be harmful to the environment. Whereas, diatoms are naturally available in various form. Presently, researchers used synthetic silica as a solid platform to functionalize the organic probes. However, these solid platforms showed good sensitivity, using the natural resources for the environmental remediation is highly desirable. Owing to this, diatoms can give tremendous ways to use as solid platforms for the immobilization of organic probes which can be used to remove mercury ions from water. SUMMARY OF THE INVENTION

The main objective of this invention is to provide a novel process for the removal of trace level mercury ions from water using rhodamine derivative functionalized diatoms. The present invention is based on the discovery that would increasingly impact the removal processes which are reported presently. This process can be used for other molecules functionalization, and same can be used for the removal of several other metal ions from water. Other objects and advantages will be apparent from the description which is elaborated in the coming sections.

A novel method for the removal of mercury ions from water using organic probe tethered diatoms/synthetic silica particles mentioned here. In first step, synthesis of rhodamine-terephthaldehyde Schiff base, herein referred as P2, comprising the steps of, dissolving rhodamine-6G in minimum amount of ethanol, adding of 3 equivalence of hydrazine hydrate, dropwise to the said solution, sonicating of above-prepared mixture for 5 minutes to get a Schiff base product, filtering out of the Schiff base (imine) solid product using a vacuum pump, and washing residue thoroughly with the ethanol and drying at room temperature to obtain 2-amino- 3',6'-bis(ethylamino)-2',7'-dimethylspiro[isoindoline-l,9'-xanthen]-3-one, herein referred as PMl. Dissolving the PMl and Terephthalaldehyde in the ethanol and adding a drop of glacial acetic acid, obtaining the P2 as a yellow precipitate, after refluxing at 80°C for overnight, filtering of the said yellow precipitate and washing with ethanol for several times to remove unreacted reactants and drying at room temperature overnight..

Further, immobilizing of the P2 onto diatoms and/or synthetic silica particles through a condensation reaction as follows. Dispersing of required quantity of diatoms and/or synthetic silica particleslin required quantity of ethanol 4and stirring to form a suspension. The dissolving of required quantity of the P2 in required quantity of ethanol and adding slowly under vigorous stirring at room temperature for overnight. Washing of the resulting solid material with the ethanol for several times to remove unreacted P2 to get P2 functionalized diatoms and/or synthetic silica particles. Finally, adding Hg²⁺ solution to supernatant solution, if the solution changes its colour, then it is confirmed that still P2 is present in the solvent.

In the present invention, the concentration of rhodamine-6G and hydrazine hydrate is about2.0876 mM and 6.2628 mM respectively, and the concentration of PM1 and Terephthalaldehyde is about0.500 g, 1.1668 mM and 0.157 g, 1.1668 mM respectively. The functionalization of diatoms and/or synthetic silica particles particles comprising the steps of, adding required amount of toluene to required amount of diatoms in a three-neck round bottom flask, followed by constant stirring and refluxing at 60°C for an hour under a nitrogen atmosphere, adding required amount of water dropwise using a syringe and stirring for another 2 hours, adding required amount of 3-aminopropyl-triethoxy silane (APTES) gradually to the said solution and stirred for 6 hours at the same temperature, obtaining of APTES treated diatoms and/or synthetic silica particleslO, after the reaction by repeated centrifugation, washing with isopropanol and toluene for several times and vacuum dried for 6 hours at room temperature. Further, APTES treated diatoms and/or synthetic silica particles were treated with P2 in ethanol solvent to yield P2 functionalized diatoms and/or synthetic silica particlesl2 which were used to remove Hg²⁺ ions from water.

The concentration of diatoms and toluene are 5.0 g and 50 mL respectively, and the concentration of water and 3-aminopropyl-triethoxy silane (APTES) is 500 μΐ_^ and lmL respectively, the three-neck round bottom flask is of 100 mL size. For the condensation reaction the concentration of diatoms and ethanol is about lg and 8ml respectively. Also the concentration of P2 isabout0.2g which is dissolved in about 2mL of ethanol. Cartridges for water purifying systems, both domestic and industrial applications, made using organic probe tethered diatoms. Application of organic probe tethered diatoms in making colorimetric probes to detect Hg²⁺ ions, a fixed bed in syringes of various sizes for medical and laboratory purposes, and straws for instant removal of Hg²⁺ ions. Further, the same invention was repeated by replacing diatoms with synthetic silica particles which resulted in similar changes. However, the efficiency was slightly lower than that of the P2 functionalized diatom particles.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the general schematic representation for the immobilization of probe on diatoms.

Figure 2 shows a schematic route for the synthesis of compound P2. Figure 3 shows the synthesis of P2 immobilised silica and diatoms surface. Figure 4 shows the 1H NMR spectra for the compound PM1. Figure 5 shows 1H NMR spectra for the compound P2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The advanced developments in the synthesis of novel organic probe functionalized solid platforms for the removal of metal ions have led to the dawn of a new age in the sensor field. The organic probes can be immobilized in highly porous diatoms to meet this requirement and thus improve the removal efficiency.

Figure 1 illustrates the general schematic for the immobilization of organic probe on diatoms. The present invention is directed to synthesize organic probe immobilized diatoms for the removal of trace mercury from water which results in visual color change. Using the concept of "imine formation", the organic probe will be successfully attached to diatoms 1 for the first time. An imine is a functional group or chemical compound that includes a carbon-nitrogen double bond. Nitrogen atom can be attached to a hydrogen (H) or an organic group. If this group is not a hydrogen atom, then the compound can sometimes be referred to as a Schiff base. The carbon atom has two additional single bonds. Imines are typically prepared by the condensation of primary amines and aldehydes and less commonly ketones:

RNH₂ + R'C(0)R→ RN=C(R ')(R) + H₂0

In terms of mechanism, such reactions proceed via the nucleophilic addition giving a hemiaminal -C(OH)(NHR)- intermediate, followed by an elimination of water to yield the imine. The equilibrium in this reaction usually favors the carbonyl compound and amine, so that a zeotropic distillation or use of a dehydrating agent, such as molecular sieves or magnesium sulfate, is required to push the reaction to aid the imine formation.

The resulting solid substrate was found to remove ppb mercury ions from water and can be seen with naked eyes. These results will provide new hope in the field of sensors referred in the prior art i.e. the probe which can selectively detect bacteria. The present invention will now be described more specifically concerning the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for the purpose of illustration and description only and not intended to be exhaustive or to be limited to the precise form disclosed. The following example is illustrative of the best mode now contemplated for carrying out the invention.

I. Materials:

Analytical grade reagents and solvents have been used as received without any further purification throughout the experiments. Rhodamine-6G2, Terephthalaldehyde and 3-aminopropyl-triethoxy silane (APTES) 6were purchased from Sigma- Aldrich (India) Pvt. Ltd. Glacial acetic acid 5was obtained from Fischer Scientific (India) Pvt. Ltd. All metal ions were purchased from NICE Chemicals (India) Pvt. Ltd. Silica gel (60- 120 mesh) was purchased from CDH Chemicals (India) Pvt. Ltd. Diatom silica microparticles were prepared by purification of raw diatomaceous earth (DE) materials supplied from Mount Sylvia (Australia) Pty. Ltd. Synthetic silica was procured from Spectrochem (India) Pvt. Ltd. Deionized water has been used for this work, and all metal nitrate solutions were prepared in DI water.

II. Synthesis of organic probe (rhodamine-terephthaldehyde Schiff base);

• Synthesis of PM1

Figure 2 depicts the synthetic route to obtain the desired product. Briefly, rhodamine-6G 2(2.0876 mM) was dissolved in minimum amount of ethanol4, 3 equivalence (6.2628 mM) of hydrazine hydrate 3 was then dropwise added to the solution. The mixture was then sonicated for 5 minutes to get the Schiff base product. The Schiff base (imine) solid product was filtered out using a vacuum pump. The residue was thoroughly washed with ethanol 4and dried at room temperature to obtain PM19.1H NMR (500 MHz, OMSO-d6, d/ppm): 7.75 (m, J= 5 Hz, ArH), 7.46 (m, J=5 Hz, ArH), 6.93 (m, J=5Hz, ArH), 6.26(s, ArH), 6.10 (s, ArH), 5.00 (s, 1H), 4.22 (s, 1H), 3.13 (m, J= 5 Hz, 2H), 1.86 (s, 3H), 1.21 (t, J=10Hz, 3H).

• Synthesis of P2

PM1 9(0.500 g, 1.1668 mM) and Terephthalaldehyde 6(0.157 g, 1.1668 mM) were dissolved in 20 mL of ethanol 4and a drop of glacial acetic acid 5was added to the solution. After refluxing at 80°C for overnight, the yellow precipitate (P2)8whose chemical name is (E)-4-(((3',6'-bis(ethylamino)-2',7'-dimethyl-3- oxospiro[isoindoline-l,9'-xanthen]-2-yl)imino)methyl)benzaldehyde,were obtained which was filtered, washed with ethanol for several times to remove the non-reacted reactants and kept for drying at room temperature overnight. 1H NMR (500 MHz, DMSO-iM, d/ppm): 9.96 (s, 1H), 8.489 (s, 1H), 8.125 (s, ArH), 7.897 (m, J=7.5Hz, ArH), 7.609 (m, J=7.5Hz, ArH), 7.33 (s, ArH), 7.029 (m, J=7.5Hz, ArH), 6.320 (m, J=8Hz, ArH), 6.140 (m, J=19Hz, ArH), 5.042 (t, J=5Hz, 1H), 3.120 (m, J=6.5Hz, 2H), 1.809 (s, 3H), 1.193 (t, J=6.5Hz, 3H) • Synthesis of P2 functionalized diatom particles and/or synthetic silica

Functionalization of naturally available diatoms and/or synthetic silica was carried out using reported literature. Briefly, the 5.0 g of diatoms lwere taken in 100 mL three-neck round bottom flask, 50 mL toluene was then added and kept for constant stirring and refluxed at 60°C for an hour, under a nitrogen atmosphere. 500 μΐ_^ of water was added dropwise using a syringe and allowed to stir for another 2 hours. Further, lmL Terephthalaldehyde and 3-aminopropyl-triethoxy silane (APTES) 6 was added slowly to the solution and stirred for 6 hours at the same temperature. After the reaction, the APTES treated diatoms 10 were obtained by repeated centrifugation (3000 rpm), washed with isopropanol and toluene for several times and vacuum dried for 6 hours at room temperature. Furthermore, similar procedure was adopted to functionalize APTES on synthetic silica particles.

In next step, P2 12which is used to functionalize on diatoms to remove Hg²⁺ ions from water. Said P2was immobilized onto diatom through the condensation reaction as in Figure 3. 1 g of diatoms ldispersed in 8 ml of ethanol 4and stirred to form a suspension. 0.2 g of P2 8dissolved in 2mL of ethanol 4and added slowly with vigorous stirring at room temperature stirred for overnightll. The resulting solid material was washed with ethanol 4for several times to remove the unreacted P28. Further, by adding Hg²⁺ solution to supernatant solution, if the solution changes its colour then it is confirmed that still P2 8is present in the solvent. Thus, obtained material was used to study the performance of mercury removal from water which is confirmed by UV-vis spectroscopy. Furthermore, similar procedure was adopted to functionalize P2 on APTES treated synthetic silica particles.

III. Characterization:

In all embodiments, all the synthesized compounds will go through a series of characterization to determine the desired product. The procedures that will be used for characterization are, spectroscopic (1H NMR and FTIR), microscopic (SEM) techniques, and elemental analysis using XPS, TGA. In some embodiments, the mercury detection using P2 8in solution form was carried out through UV-vis and fluorescence spectroscopic techniques. Further, UV-vis and fluorescence titrations were carried out to find binding stoichiometry of complex (P2:Hg²⁺). Further, the removal studies were carried out using, UV-vis spectroscopic technique. The removal of mercury is also can be visualized through observing the color change from colorless to pink after addition of mercury.

The1H NMR spectra for the compound PM1 is given below and indicated in Figure 4:

1H NMR (500 MHz, DMSO-iM, <5/ppm): 7.75 (1H, 7 = 5 Hz, d), 7.46 (2H, 7= 5 Hz, d), 6.93 (1H, 7=5 Hz, d), 6.26(2H, s), 6.10 (2H, s), 5.00 (3H, J =5 Hz, t), 4.22 (1H, s), 3.13 (2H, 7 = 5 Hz, m), 1.86 (3H, s), 1.21 (3H, 7 = 10 Hz, t)

The1H NMR spectra for the compound P2 is given below and indicated in Figure 5:

1H NMR (500 MHz, DMSO-iM, <5/ppm): 9.9 (1H, s), 8.4 (1H, s), 7.9 (2H, J = 7.5 Hz, m), 7.6 (3H, J = 7.5 Hz, m), 7.3 (2H, s), 7.0 (1H, J = 5 Hz, d), 6.3 (2H, s), 6.1 (2H, s), 5.0 (2H, J = 5Hz, t), 3.1 (4H, J = 6.5 Hz, m), 1.8 (6H, s), 1.1 (6H, J = 6.5 Hz, m)

The modified diatomaceous earth (DE) can be used for making various types of devices, for example and not limited to, such as cartridges for water purifying systems domestic and industrial scale, to make colorimetric probes to detect Hg²⁺ ions, to make a fixed bed in syringes of various sizes for medical and laboratory applications, and to make straws for instant removal of Hg²⁺ ions.

Claims

A novel method for the removal of mercury ions from water using organic probe tethered diatoms and/or synthetic silica particles in which, synthesis of rhodamine-terephthaldehyde Schiff base, herein referred as P2 8, comprising the steps of:

(i) Dissolving rhodamine-6G 5in minimum amount of ethanol 4;

(ii) Adding of 3 equivalence of hydrazine hydrate 3, dropwise to the said solution;

(iii) Sonicating of above-prepared mixture for 5 minutes to get a Schiff base product;

(iv) Filtering out of the Schiff base (imine) solid product using a vacuum pump, and washing residue thoroughly with the ethanol 4 and drying at room temperature to obtain 2-amino-3',6'-bis(ethylamino)-2',7'- dimethylspiro[isoindoline-l,9'-xanthen]-3-one, herein referred as PM1 9;

(v) Dissolving the PM1 9and Terephthalaldehyde 6in the ethanol4 and adding a drop of glacial acetic acid 5;

(vi) Obtaining the P2 8 as a yellow precipitate, after refluxing at 80°C for overnight;

(vii) Filtering of the said yellow precipitate and washing with ethanol 4 for several times to remove unreacted reactants and drying at room temperature overnight;

(viii) Functionalizing of naturally available diatoms and/or synthetic silica particles using known methods; and

(ix) Immobilizing of the P2 12 onto diatoms and/or synthetic silica particles through a condensation reaction comprising the steps of:

(a) Dispersing of required quantity of diatoms and/or synthetic silicalin required quantity of ethanol 4 and stirring to form a suspension; (b) Dissolving of required quantity of the P2 8 in required quantity of ethanol 4 and adding slowly to the diatoms and/or synthetic silica dispersion under vigorous stirring at room temperature stirring for overnight 11;

(c) Washing of the resulting solid material with the ethanol 4for several times to remove unreacted P 28; and

(d) Adding Hg²⁺ solution to supernatant solution, if the solution changes its colour then it is confirmed that still P2 8is present in the solvent.

The novel method for the removal of mercury ions from the water of Claim 1, wherein the concentration of rhodamine-6G 2 and hydrazine hydrate 3is about2.0876 mM and 6.2628 mM respectively, and the concentration of PM1 9 and Terephthalaldehyde 6 is about0.500 g, 1.1668 mM and 0.157 g, 1.1668 mM respectively.

The novel method for the removal of mercury ions from the water of Claim 1, wherein functionalization of diatoms and/or synthetic silica particles comprising the steps of:

(i) Adding required amount of toluene to required amount of diatoms and/or synthetic silica in a three-neck round bottom flask, followed by constant stirring and refluxing at 60°C for an hour under a nitrogen atmosphere;

(ii) Adding required amount of water dropwise using a syringe and stirring for another 2 hours;

(iii) Adding required amount of 3-aminopropyl-triethoxy silane (APTES) 6 gradually to the said solution and stirred for 6 hours at the same temperature;

(iv) Obtaining of APTES treated diatoms and/or synthetic silica particleslO, after the reaction by repeated centrifugation; (v) Washing with isopropanol and toluene for several times and vacuum dried for 6 hours at room temperature; and

(vi) Getting P2 functionalized diatoms and/or synthetic silica 12 by subjecting the APTES treated diatoms and/or synthetic silica to react with P2 8, said P2 functionalized diatoms and/or synthetic silica 12 is used further for the removal of Hg²⁺ ions.

4. The novel method for the removal of mercury ions from the water of Claim 3, wherein the concentration of diatoms and/or synthetic silica and toluene are 5.0 g and 50 mL respectively, and the concentration of water and 3-aminopropyl-triethoxy silane (APTES)6is 500 μΐ_^ and lmL respectively, the three-neck round bottom flask is of 100 mL size.

5. The novel method for the removal of mercury ions from the water of Claim 1, wherein for the condensation reaction the concentration of diatoms and/or synthetic silical and ethanol 4is about lg and 8mL respectively, also the concentration of P2 8 isabout0.2g which is dissolved in about 2mL of ethanol 4.

6. Cartridges for water purifying systems, both domestic and industrial applications, made using organic probe tethered diatoms.

7. Application of organic probe tethered diatoms in making colorimetric probes to detect Hg²⁺ ions, a fixed bed in syringes of various sizes for medical and laboratory purposes, and straws for instant removal of Hg²⁺ ions.