A PROCESS FOR THE DETECTION AND ADSORPTION OF ARSENIC

Abstract

The present invention relates to a process for the detection and adsorption of arsenic from ground water and industrial waste water using lanthanide doped nanoparticles. More particularly, the present invention provides a process for the detection and adsorption arsenic in ppm level using Eu.sub.0.05Y.sub.0.95PO.sub.4 nanoparticles.

Claims

1. A process for the detection of arsenic in water comprising the steps of: a. Adding lanthanide doped nanoparticles to arsenic solution at a pH in the range of 1 to 6; b. Analyzing the arsenic adsorbed on nanoparticles of the solution of step (a) to obtain photoluminescence effect; wherein said lanthanide doped nanoparticle is Eu.sub.0.05Y.sub.0.95PO.sub.4.

2. The process as claimed in claim 1, wherein size of lanthanide doped nanoparticle is 1-2 μm in length and about 20 nm in width.

3. The process as claimed in claim 1, wherein arsenic containing water is selected from hard or soft ground water, effluent, domestic or potable water.

4. The process as claimed in claim 1, wherein said process detects arsenic at a concentration greater than 9 ppm, producing visual change in luminescence.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1: XRD patterns of Eu.sup.3+:YPO.sub.4 (as prepared, water treated, arsenic adsorbed at pH=1.5 and 3.5) along with JCPDS No. 42-0082 and 11-0254.

[0017] FIG. 2: PL spectra of arsenic YPO.sub.4:Eu.sup.3+ after arsenic adsorption at pH=1.5 and 3.5 along with variation of asymmetric ratio.

[0018] FIG. 3: PL spectra of Chlorine effect.

[0019] FIG. 4: Life time measurements of arsenic and chloride adsorbed samples.

[0020] FIG. 5: XPS spectra of the arsenic adsorbed sample.

[0021] FIG. 6: TEM images of Eu.sup.3+:YPO.sub.4 nanomaterials treated with As solution, SAED pattern and the lattice fringe.

[0022] FIG. 7: SEM images and EDAX spectra of arsenic adsorbed Eu.sup.3+:YPO.sub.4 nanoparticles.

[0023] FIG. 8: Raman spectra of Eu.sup.3+:YPO.sub.4 at different concentrations of As solution (a) 0, (b) 80 and (c) 100 ppm.

[0024] FIG. 9: Schematic diagram for the interaction of As ion with the nanomaterials.

DETAILED DESCRIPTION OF THE INVENTION

[0025] The invention will now be described in detail in connection with certain preferred and optional embodiments, so that various aspects thereof may be more fully understood and appreciated.

[0026] As used herein, “adsorption” refers to the adherence of atoms, ions, molecules, polyatomic ions, or other substances of a gas or liquid to the surface of another substance, called the adsorbent. The attractive force for adsorption can be, for example, ionic forces such as covalent, or electrostatic forces, such as van der Waals and/or London's forces.

[0027] Accordingly, the inventors disclose arsenic detection in ppm level using Eu.sub.0.05Y.sub.0.95PO.sub.4 nanoparticles.

[0028] In view of above, the present invention provides a process for flourimetric or Raman spectroscopy detection of Arsenic in water comprising lanthanide doped nanoparticles is disclosed herein, wherein the limit of detection of Arsenic is 10 ppm.

[0029] In an embodiment, the present invention provides a process for flourimetric or Raman spectroscopy detection of arsenic in water comprising: [0030] a. Adding lanthanide doped nanomaterials to arsenic solution with >9 ppm at a pH in the range of 1 to 6; [0031] b. Analyzing the arsenic adsorbed on nanoparticles of the solution of step (a) to obtain photoluminescence effect.

[0032] In preferred embodiment, the lanthanide doped nanoparticle comprises europium and ytterbium.

[0033] In another preferred embodiment, the lanthanide doped nanoparticle is Eu.sub.0.05Y.sub.0.95PO.sub.4.

[0034] In another preferred embodiment, the size of lanthanide doped nanoparticle is 1-2 μm in length and 20 nm in width.

[0035] The arsenic containing water is selected from hard or soft ground water, effluent, domestic or potable water.

[0036] The process of the present invention can detects arsenic at a concentration greater than 9 ppm.

[0037] In one embodiment, the present invention provides Eu.sup.3+ (5%) doped hexagonal YPO.sub.4 nanoparticles prepared by co-precipitation method and are used for arsenic detection.

[0038] In another preferred embodiment the present invention provides Eu.sup.3+ (5%) doped hexagonal YPO.sub.4 nanoparticles which are stable in acidic medium.

[0039] Adsorption of arsenic on the surface of lanthanide doped nanoparticles reduces the luminescence intensity of the doped lanthanide ions. This change in luminescence property may be used to detect arsenic in ground water and the lanthanide doped nanomaterials are also a good adsorbent. In the emission spectra of Eu.sup.3+, intensity ratio of magnetic transition (591 nm) and the electrical transition (617 nm) is influenced by the environment around the lanthanide ion.

[0040] In yet another preferred embodiment, the invention provides a process of detection of Arsenic wherein the process detects arsenic at a concentration greater than 9 ppm.

[0041] In another aspect, the present invention provides using the luminescence enhancement and quenching properties of the nanoparticles for the detection of both arsenic and arsenous acid in the industrial waste.

[0042] In still another aspect, the lanthanide doped Eu.sub.0.05Y.sub.0.95PO.sub.4 nanoparticles may be synthesized by methods known in the art.

[0043] In an embodiment of the invention, the present invention provides a process, which detects arsenic at a concentration greater than 9 ppm, producing visual change in luminescence.

[0044] In a preferred embodiment, the nanoparticles are synthesized by co-precipitation method.

[0045] Amount of arsenic adsorbed by the nanoparticles are measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). (Table 2)

[0046] The following examples, which include preferred embodiments, will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purpose of illustrative discussion of preferred embodiments of the invention.

EXAMPLES

Reagents and Materials:

[0047] Yttrium(III) nitrate hexahydrate, Y(NO.sub.3).sub.3, 6H.sub.2O (99.9%), ammonium dihydrogen phosphate, (NH.sub.4)H.sub.2PO.sub.4 (99.999%), polyethylene glycol (PEG) from Sigma-Aldrich. Arsenic(III) oxide, As.sub.2O.sub.3 sodium hydroxide, hydrochloric acid, Glycerol from Merck was used without further purification. Deionized water was used throughout the experiment.

Example 1

Synthesis of YPO.SUB.4.:Eu.SUP.3+ Nanorods

[0048] Eu.sub.0.05Y.sub.0.95PO.sub.4 nanoparticles were synthesised by co-precipitation method. Stoichoimetric amounts of Y(NO.sub.3).sub.3.6H.sub.2O (1.582 g), Eu(NO.sub.3).sub.3.5H.sub.2O (0.093 g), and 3 g of PEG were dissolved in a mixture of 40 ml of water and 60 ml of ethylene glycol (EG). The mixture was stirred at 80° C. for half an hour. Then a solution of 0.5 g of (NH.sub.4)H.sub.2PO.sub.4 in 10 ml of deionised water was added slowly to the reaction mixture and refluxed at 140° C. for three hour in a 250 ml round bottom flask fitted with a condenser under water circulation. The resulting white precipitate was collected by centrifuging at 10,000 rpm after washing with water and methanol. The precipitate was dried in an oven at 100° C. temperature and used as sensing material for arsenic. (FIG. 1)

Example 2

Preparation of 100 ppm Arsenic (III) Solution: (FIG. 2, 3)

[0049] At pH=1.5

[0050] 132 mg of As.sub.2O.sub.3 was dissolved in 10 ml 1(N) NaOH solution. 2 ml conc. HCl was added and diluted with deionised water to 100 ml. This solution was further diluted with 2% (V/V) HCl solution to 1000 ml to get an arsenic solution of 100 ppm strength. pH of this arsenic solution is 1.5. [0051] At pH=3.5

[0052] 132 mg of As.sub.2O.sub.3 was dissolved in 10 ml 1(N) NaOH solution. 1 ml conc. HCl was added and diluted with deionised water to 100 ml. This solution was further diluted with 1% (V/V) HCl solution to 1000 ml to get an arsenic solution of 100 ppm strength. pH of this arsenic solution is 3.5. These standard arsenic solutions were further diluted with 2% and 1% of HCl solutions respectively to get solutions of different concentrations. Only freshly prepared arsenic solutions were used for surface adsorption reactions to prevent arial oxidation of arsenic.

Example 3

Adsorption of Arsenic on YPO.SUB.4.:Eu.SUP.3+ Surface

[0053] To each 50 ml solution of arsenic of different conc. (100 ppm, 80 ppm, 60 ppm, 40 ppm, 20 ppm, 10 ppm), 0.15 g of Eu.sub.0.05Y.sub.0.95PO.sub.4 nanoparticles were added and stirred at room temperature for three hours. Then the arsenic adsorbed nanoparticles were collected by centrifuging at 10000 rpm and washing with methanol. These collected nanoparticles were dried at 150° C. temperature and their corresponding analyses were performed. (FIG. 4-9)

Example 4

Photoluminescence Study

[0054] Photoluminescence study of pure nanoparticles and arsenic adsorbed nanoparticles were performed. On excitation at 375 nm and 395 nm Eu.sup.3+ showed its characteristic red light emission. The experimental study indicates that on arsenic adsorption, luminescence intensity is much reduced. This decrease in luminescence intensity due to adsorption (surface complex formation and non-radiative thermal quenching) may be used to detect arsenic conc. in ground water. (Table 1)

[0055] At pH=1.5 the electronic predominates over magnetic transition with increase in the arsenic concentration which we observed in the increasing asymmetric ratio (I.sub.AS). At pH=3.5 electronic transition and magnetic transitions are almost equal or magnetic transition predominating.

[0056] To determine the amount of arsenic adsorbed by the nanoparticles inductively coupled plasma mass spectroscopy was performed with mother and the filtrate arsenic solutions. The ICP-AES analysis shows that some definite quantity of the arsenic species is adsorbed by the nanoparticles. Amount of adsorption is higher at higher concentration of arsenic and it is low at lower concentration. This analysis support the interaction of arsenic with the nanoparticles and the enhancement trend observed in the luminescence spectra. (Table 2)

TABLE-US-00001 TABLE 1 Relation between arsenic concentration and asymmetric ratio (I). Area of peak Electric Magnetic Arsenic transitions transitions Asymmetric Sl. Concentration (.sup.5D.sub.0.fwdarw..sup.7F.sub.2) (.sup.5D.sub.0.fwdarw..sup.7F.sub.1) ratio No. (ppm) (A.sub.e) (A.sub.m) (I = A.sub.e/A.sub.m) 1 pH = 1.5 0 112374.21938 119382.59727 0.94 2 10 143034.95019 143748.94145 0.99 3 20 144614.91105 141406.28489 1.02 4 60 178697.97057 173600.00968 1.03 5 100 191237.05734 165359.29374 1.15 6 pH = 3.5 0 216934.30064 229095.76553 0.94 7 10 119028.93677 209459.68526 0.56 8 40 111569.8393 185278.86541 0.60 9 60 99067.39673 174811.64582 0.56 10 80 83159.20339 91497.84235 0.90 11 100 70293.04284 74149.92192 0.94

TABLE-US-00002 TABLE 2 ICP-AES data showing percentage change in As concentration. Mother Filtrate Change in Sl. solution solution concentration % no. (ppm) (ppm) (ppm) change 1 67.022 61.265 5.757 8.58 2 53.655 50.05 3.605 6.72 3 39.45 38.205 1.245 3.15 4 26.165 24.89 1.275 4.87 5 12.265 12.055 0.21 1.71 6 6.405 6.355 0.05 0.78

Results

[0057] The photoluminescence study of pure nanoparticles and arsenic adsorbed nanoparticles are performed. On excitation at 375 nm and 395 nm Eu.sup.3+ showed its characteristic red light emission. The experimental study indicates that on arsenic adsorption, luminescence intensity is much reduced. This decrease in luminescence intensity due to adsorption (surface complex formation and non-radiative thermal quenching) may be used to detect arsenic conc. in ground water. (Table 1) At pH=1.5 the electronic predominates over magnetic transition with increase in the arsenic concentration which is observed in the increasing asymmetric ratio (I.sub.AS). At pH=3.5 electronic transition and magnetic transitions are almost equal or magnetic transition predominating. To determine the amount of arsenic adsorbed by the nanoparticles inductively coupled plasma mass spectroscopy are performed with mother and the filtrate arsenic solutions. The ICP-AES analysis shows that some definite quantity of the arsenic species is adsorbed by the nanoparticles. Amount of adsorption is higher at higher concentration of arsenic and it is low at lower concentration. This analysis support the interaction of arsenic with the nanoparticles and the enhancement trend observed in the luminescence spectra. (Table 2).

Advantages of Invention:

[0058] Detects very low concentration of As

[0059] Avoids expensive analytical instruments

[0060] Portable kits may be made, making detection on site easy

[0061] Works for analyte that may be hard or soft ground water, effluent, domestic or potable.