Zirconium doped terbium nano oxides for wastewater remediation

Abstract

Zirconium doped terbium nano oxides (ZrTb.sub.2O.sub.3). The nano oxides can have an average diameter ranging from about 17 nm to about 22 nm. The nano oxides can be used as a photocatalyst for photodegradation of organic dyes. In an embodiment, the organic dyes include textile wastewater dyes. In an embodiment, the textile wastewater dyes include methylene blue (MB) and/or Congo Red (CR). In an embodiment, the zirconium doped terbium nano oxides (ZrTb.sub.2O.sub.3) can be prepared by a dual co-precipitation and calcination method.

Claims

1. A method for photodegradation of an organic dye, comprising: dispersing zirconium doped terbium nano oxides (ZrTb2O3) in an aqueous solution including the organic dye to provide a suspension; and subjecting the suspension to light irradiation; wherein the zirconium doped terbium nano oxides are prepared according to a method comprising: dissolving terbium nitrate (Tb(NO.sub.3).sub.3.Math.6H.sub.2O) and zirconium nitrate hydrate (Zr(NO.sub.3).sub.3.Math.xH.sub.2O) in water to obtain a solution; adjusting pH of the solution to about 7.5 by dropwise addition of a solution of NaHCO.sub.3; stirring to obtain a homogenous solution containing zirconium (Zr(CO.sub.3).sub.2.Math.xH.sub.2O) and terbium (Tb.sub.2(CO.sub.3).sub.3.Math.xH.sub.2O) carbonate precipitates; centrifuging and drying the homogenous solution to obtain Zr(CO.sub.3).sub.2 and Tb.sub.2(CO.sub.3).sub.3 metal carbonates; calcinating the Zr(CO.sub.3).sub.2 and Tb.sub.2(CO.sub.3).sub.3 metal carbonates at a temperature of about 825? C. to about 875? C.; and obtaining the zirconium doped terbium nano oxides (ZrTb.sub.2O.sub.3); and wherein the nano oxides are nanoparticles having an average diameter ranging from about 17 nm to about 22 nm.

2. The method of claim 1, wherein a concentration of the organic dye in the aqueous solution is about 10 mg/L.

3. The method of claim 1, wherein the light irradiation is selected from the group consisting of ultraviolet radiation and visible light radiation.

4. The method of claim 3, wherein the light irradiation comprises ultraviolet irradiation.

5. The method of claim 1, further comprising stirring the suspension in dark conditions prior to light irradiation.

6. The method of claim 5, wherein the stirring comprises magnetic stirring for a period of time of about one hour.

7. The method of claim 1, wherein the organic dye is methylene blue, Congo red, or a combination thereof.

8. The method of claim 1, wherein about 98% of the methylene blue or about 99.5% of the Congo red is degraded.

9. The method of claim 1, wherein about 20 mg of the zirconium doped terbium nano oxides (ZrTb.sub.2O.sub.3) are dispersed in the aqueous solution.

10. A method for photodegradation of an organic dye, comprising: dispersing ZrTb.sub.2O nano oxides in an aqueous solution including the organic dye to provide a suspension, the ZrTb.sub.2O.sub.3 nano oxides having an average diameter ranging from about 17 nm to about 22 nm; and subjecting the suspension to light irradiation.

11. The method of claim 10, wherein a concentration of the organic dye in the aqueous solution is about 10 mg/L.

12. The method of claim 10, wherein the light irradiation is selected from the group consisting of ultraviolet radiation and visible light radiation.

13. The method of claim 12, wherein the light irradiation comprises ultraviolet irradiation.

14. The method of claim 10, wherein the organic dye is methylene blue, Congo red, or a combination thereof.

15. The method of claim 1, wherein a solution of NaHCO.sub.3 is added dropwise to the solution until the solution reaches a pH of about 7.5 before the homogenous solution containing the zirconium (Zr(CO.sub.3).sub.2.Math.xH.sub.2O) and terbium (Tb.sub.2(CO.sub.3).sub.3.Math.xH.sub.2O) carbonate precipitates is obtained.

16. The method of claim 1 wherein the calcinating occurs for at least about 2 hours at a temperature of about 850? C.

17. The method of claim 1, wherein the drying occurs at about 120? C. for at least about 2 hours.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a reaction scheme for preparing the zirconium doped terbium nano oxides (ZrTb.sub.2O.sub.3).

(2) FIG. 2A is a Scanning Electron Microscopy image (SEM) of ZrO.sub.2 nanoparticles.

(3) FIG. 2B is a Scanning Electron Microscopy image (SEM) of the zirconium doped terbium nano oxides (ZrTb.sub.2O.sub.3) nanoparticles.

(4) FIG. 3 is a Transmission Electron Microscopy image (TEM) of the zirconium doped terbium nano oxides (ZrTb.sub.2O.sub.3) nanoparticles.

DETAILED DESCRIPTION

(5) The following definitions are provided for the purpose of understanding the present subject matter and for construing the appended patent claims.

(6) Throughout the application, where compositions are described as having, including, or comprising specific components, or where processes are described as having, including, or comprising specific process steps, it is contemplated that compositions of the present teachings can also consist essentially of, or consist of, the recited components, and that the processes of the present teachings can also consist essentially of, or consist of, the recited process steps.

(7) It is noted that, as used in this specification and the appended claims, the singular forms a, an, and the include plural references unless the context clearly dictates otherwise.

(8) In the application, where an element or component is said to be included in and/or selected from a list of recited elements or components, it should be understood that the element or component can be any one of the recited elements or components, or the element or component can be selected from a group consisting of two or more of the recited elements or components. Further, it should be understood that elements and/or features of a composition or a method described herein can be combined in a variety of ways without departing from the spirit and scope of the present teachings, whether explicit or implicit herein.

(9) The use of the terms include, includes, including, have, has, or having should be generally understood as open-ended and non-limiting unless specifically stated otherwise.

(10) The use of the singular herein includes the plural (and vice versa) unless specifically stated otherwise. In addition, where the use of the term about is before a quantitative value, the present teachings also include the specific quantitative value itself, unless specifically stated otherwise. As used herein, the term about refers to a ?10% variation from the nominal value unless otherwise indicated or inferred.

(11) The term optional or optionally means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances in which it does not.

(12) Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the presently described subject matter pertains.

(13) Where a range of values is provided, for example, concentration ranges, percentage ranges, or ratio ranges, it is understood that each intervening value, to the tenth of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the described subject matter. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and such embodiments are also encompassed within the described subject matter, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the described subject matter.

(14) Throughout the application, descriptions of various embodiments use comprising language. However, it will be understood by one of skill in the art, that in some specific instances, an embodiment can alternatively be described using the language consisting essentially of or consisting of.

(15) For purposes of better understanding the present teachings and in no way limiting the scope of the teachings, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term about. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

(16) The present subject matter relates to zirconium doped terbium nano oxides and/or terbium doped zirconium nano oxides prepared by a dual co-precipitation and calcination method.

(17) In an embodiment, the present subject matter relates to a method for making zirconium doped terbium nano oxides, the method comprising: dissolving terbium nitrate (Tb(NO.sub.3).sub.3.Math.6H.sub.2O) and zirconium nitrate hydrate (Zr(NO.sub.3).sub.3.Math.xH.sub.2O) in water to obtain a solution; adjusting pH of the solution to about 7.5 by dropwise addition of a solution of NaHCO.sub.3; stirring to obtain a homogenous solution containing zirconium (Zr(CO.sub.3).sub.2.Math.xH.sub.2O) and terbium (Tb.sub.2(CO.sub.3).sub.3.Math.xH.sub.2O) carbonate precipitates; centrifuging and drying the homogenous solution to obtain Zr(CO.sub.3).sub.2 and Tb.sub.2(CO.sub.3).sub.3 metal carbonates; calcinating the Zr(CO.sub.3).sub.2 and Tb.sub.2(CO.sub.3).sub.3 metal carbonates at a temperature of about 825? C. to about 875? C.; and obtaining the zirconium doped terbium nano oxides (ZrTb.sub.2O.sub.3).

(18) In an embodiment in this regard, a solution of NaHCO.sub.3 can be added dropwise to the solution until the solution reaches a pH of about 7.5 before the homogenous solution containing the zirconium (Zr(CO.sub.3).sub.2.Math.xH.sub.2O) and terbium (Tb.sub.2(CO.sub.3).sub.3.Math.xH.sub.2O) carbonate precipitates is obtained. Similarly, the calcinating can occur for at least about 2 hours at a temperature of about 850? C. Likewise, the drying can occur at about 120? C. for at least about 2 hours.

(19) For example, the zirconium doped terbium nano oxides (ZrTb.sub.2O.sub.3) can be prepared by dissolving terbium nitrate (Tb(NO.sub.3).sub.3.Math.6H.sub.2O) and zirconium nitrate hydrate (Zr(NO.sub.3).sub.3.Math.xH.sub.2O) in water to provide a mixture. A solution of NaHCO.sub.3 can be added to the mixture dropwise until a pH of the mixture is about pH 7.5. The mixture can be centrifuged and dried to obtain Zr(CO.sub.3).sub.2 and Tb.sub.2(CO.sub.3).sub.3 metal carbonates. The obtained metal carbonates can then calcinated. In an embodiment, the powders can be calcinated at a temperature ranging from about 825? C. to about 875? C., or at a temperature of about 850? C., for about 1 hour to about 3 hours, or for about 2 hours.

(20) The present subject matter relates to zirconium doped terbium nano oxides, also referred to herein as nanoparticles (NPs), also referred to herein as zirconium doped terbium nano oxides (ZrTb.sub.2O.sub.3), as made according to the present methods. In an embodiment, the zirconium doped terbium nano oxides can have an average diameter ranging from about 17 nm to about 22 nm. The nano oxides can be used as a photocatalyst for photodegradation of organic dyes. In an embodiment, the organic dyes include textile wastewater dyes. In an embodiment, the textile wastewater dyes include methylene blue (MB) and/or Congo red (CR). The present nano oxides can provide a more efficient photodegradation of the organic dyes than zirconium oxide, or terbium oxide, alone, or than any other oxides mixed with zirconium oxide. In this regard, the present nano oxides can provide an about 98% photodegradation, or degradation, of the methylene blue and/or an about 99.5% photodegradation, or degradation, of the Congo red. This increased photodegradation may, in part, be a result of increased surface area of the zirconium doped terbium nano oxides (ZrTb.sub.2O.sub.3) nanoparticles compared with, for example, ZrO.sub.2 nanoparticles.

(21) The nanocomposite can include ZrO.sub.2 which has a high melting point and phase stability and low thermal expansion. ZrO.sub.2 is also known to have a wide band gap of 4.97-5.90 eV. ZrO.sub.2 possesses a unique set of characteristics like considerable mechanical strength, hardness, and thermal conductivity. ZrO.sub.2 can be easily doped with ions of rare earth elements.

(22) According to an embodiment, a method for photodegradation of organic dyes can include dispersing zirconium doped terbium nano oxides (ZrTb.sub.2O.sub.3) in an aqueous solution including the organic dyes to provide a suspension and irradiating the suspension with light. In an embodiment, a concentration of the organic dye in the solution is about 10 mg/L. Other concentrations of the organic dye in the solution are further contemplated herein including, by way of non-limiting example, about 5 to about 15 mg/L, about 5 mg/L, about 10 mg/L, or about 15 mg/L. In an embodiment, about 15 mg to about 25 mg of the zirconium doped terbium nano oxides (ZrTb.sub.2O.sub.3), about 15 mg, about 16 mg, about 17 mg, about 18 mg, about 19 mg, about 20 mg, about 21 mg, about 22 mg, about 23 mg, about 24 mg, about 25 mg, or about 20 mg of the nano oxides can be dissolved in about 70 ml to about 80 mL of the solution, or in about 75 mL of the solution.

(23) In an embodiment, the mixture can be subjected to light irradiation selected from ultraviolet (UV) radiation and visible light (Vis) radiation. In an embodiment, the emission wavelength of the light irradiation can be about 254 nm. In an embodiment, the mixture is stirred to achieve an adsorption-desorption equilibrium prior to irradiating the mixture. In an embodiment, the mixture can be magnetically stirred prior to irradiation. In an embodiment, the mixture can be magnetically stirred for a period of time ranging from about one hour. In a further embodiment, the mixture can be stirred under dark conditions. The present teachings are illustrated by the following examples.

EXAMPLES

Synthetic Examples

Example 1

Synthesis of Zirconium-Doped Terbium Nano Oxides

(24) Zirconium doped Terbium nano oxides were prepared via a combination of co-precipitation and calcination methods according to the reaction scheme shown in FIG. 1.

(25) Zirconium doped Terbium nano oxides were prepared by dissolving stoichiometric molar amounts of Terbium nitrate Tb(NO.sub.3).sub.3.Math.6H.sub.2O (for Tb.sub.1-Tb.sub.3 (0.05-0.15 mmole) and zirconium nitrate hydrate Zr(NO.sub.3).sub.3.Math.xH.sub.2O in 20 mL of deionized water. The mixture was stirred magnetically until the starting material metal salts were completely dissolved in deionized water. After that, the pH of the solution was adopted to 7.5 by adding a solution of NaHCO.sub.3 (2 M) drop-by-drop. After 0.5 h under continuous stirring, a homogeneous solution containing carbonate precipitates of the metal salts was obtained. The obtained products were centrifuged, washed several times with de-ionized water, acetone, and absolute ethanol, and then dried at 120? C. for 2 h. The obtained solid was subjected to calcination at 850? C. for 2 h to obtain the desired products.

Example 2

Characterization of the Prepared Zirconium Doped Terbium Nano Oxides Using SEM

(26) The surface morphology of pure ZrO.sub.2 nanoparticles and zirconium-doped terbium nano oxides were examined by scanning electron microscopy (SEM) as illustrated in FIGS. 2A-2B. SEM analysis verified the pure ZrO.sub.2 nanoparticle sample had a spherical shape with good separation of particles. TEM analysis shows that the prepared zirconium doped terbium nano oxides lie within the range of 17-22 nm as shown in FIG. 3.

Example 3

Photocatalytic Activity Test

(27) The photocatalytic activities of the as-synthesized samples were investigated by the photo-degradation of Congo red (CR) or methylene blue (MB) dyes as a pollutant model under ultraviolet (UV) irradiation (30 Watt, 280 nm-100 nm UV-C Germicidal lamp with main emission wavelength 254 nm). The degradation efficiency depends on illumination time and was evaluated by using a double-beam UV-VIS-NIR spectrophotometer. In a typical experiment, 20 mg of the photocatalyst was dispersed in 75 ml MB aqueous solution at a concentration of 10 mg/L to produce a suspension for the degradation reaction. Prior to illumination, the obtained solution was magnetically stirred in the dark for 60 min to attain adsorption-desorption equilibrium. All experiments were performed under the same experimental conditions (at room temperature, constant magnetic stirring, and natural pH). During the UV irradiation and at regular intervals, about 4 ml of suspension was sampled by syringe and subsequently centrifuged at a rate of 4000 rpm to remove the photocatalyst powder from the MB solution. In order to follow the degradation of the MB, the absorption spectra and then the concentration of MB in the UV-Vis region was monitored by Jasco, V-570 UV-Vis-NIR Spectrophotometer.

(28) The degradation efficiency for ZrTb.sub.2O.sub.3 nanoparticles (NPs) compared with ZrO.sub.2 NPs show enhancement in the activity from 85% in the case of ZrO.sub.2 to 99.5% and 98% in the case of ZrTb.sub.2O.sub.3 NPs for Congo red and methylene blue dyes, respectively. This could be ascribed to the increase of the surface area of ZrTb.sub.2O.sub.3 NPs compared with ZrO.sub.2 NPs.

(29) It is to be understood that the ZrTb.sub.2O.sub.3 nanoparticles are not limited to the specific embodiments described above, but encompasses any and all embodiments within the scope of the generic language of the following claims enabled by the embodiments described herein, or otherwise shown in the drawings or described above in terms sufficient to enable one of ordinary skill in the art to make and use the claimed subject matter.