Additive-incorporated building materials

Abstract

Bismuth oxyhalide-added building materials are disclosed. The building material is a binder-containing building material, which sets and harden when mixed with water, such as gypsum and cement-based building material. Methods for applying bismuth oxyhalidecomprising coatings onto surfaces of building materials, to protect them against pollutants, are described.

Claims

1. Bismuth oxyhalide-added gypsum, wherein the bismuth oxyhalide is selected from the group consisting of BiOCl.sub.yBr.sub.1-y [0.6y0.95]; Bi.sup.(0) doped-BiOCl; Bi.sup.(0) doped-BiOBr; and Bi.sup.(0) doped-BiOCl.sub.yBr.sub.1-y [0.6y0.95].

2. Bismuth oxyhalide-added gypsum according to claim 1, which is bismuth oxyhalide-coated gypsum, wherein the bismuth oxyhalide-coated gypsum has bismuth oxyhalide particles that are located in a bismuth oxyhalide-containing surface layer deposited on a gypsum-made base, with said gypsum-made base being essentially free of bismuth oxyhalide particles.

3. Bismuth oxyhalide-added gypsum according to claim 2, wherein the thickness of the bismuth oxyhalide-containing surface layer is from 4 to 100 m.

4. Bismuth oxyhalide-added gypsum according to claim 1, wherein the bismuth oxyhalide is selected from the group consisting of BiOCl.sub.yBr.sub.1-y [0.6y0.95] and Bi.sup.(0) doped-BiOCl.sub.yBr.sub.1-y [0.6y0.95].

5. Bismuth oxyhalide-added gypsum according to claim 4, wherein the bismuth oxyhalide is BiOCl.sub.yBr.sub.1-y [0.6y0.95].

6. Bismuth oxyhalide-added gypsum according to claim 5, wherein the bismuth oxyhalide is BiOCl.sub.yBr.sub.1-y [0.75y0.90].

7. Bismuth oxyhalide-added gypsum according to claim 6, wherein the BiOCl.sub.yBr.sub.1-y is BiOCl.sub.0.8Br.sub.0.2 (0.010.05).

8. A method for preparing bismuth oxyhalide-coated gypsum, comprising mixing plaster of Paris powder (CaSO.sub.4.0.5H.sub.2O) and water, allowing a so-formed mass to set and harden partially, applying onto the surface of the mass an aqueous suspension of bismuth oxyhalide microspheres selected from the group consisting of BiOCl.sub.yBr.sub.1-y [0.6y0.95]; Bi.sup.(0) doped-BiOCl; Bi.sup.(0) doped-BiOBr; and Bi.sup.(0) doped-BiOCl.sub.yBr.sub.1-y [0.6y0.95], and allowing the mass to dry and solidify.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows X-ray powder diffraction patterns of the BiOCl.sub.0.8Br.sub.0.2 photocatalyst (a), the BiOCl.sub.0.8Br.sub.0.2-coated gypsum (b) and pure gypsum (c).

(2) FIGS. 2a and 2b are images produced with a scanning electron microscope showing the surface morphology of BiOCl.sub.0.8Br.sub.0.2. FIG. 2c shows the topography of a BiOCl.sub.0.8Br.sub.0.2-coated gypsum sample with the corresponding EDS spectrum (FIG. 2d).

(3) FIG. 3A is an image produced with a scanning electron microscope showing a cross section of BiOCl.sub.0.8Br.sub.0.2-coated gypsum sample and FIG. 3B shows EDS spectra corresponding to two distinct regions in the sample.

(4) FIGS. 4a-4i are photos showing the gradual decomposition over time of a dye stain applied onto BiOCl.sub.0.8Br.sub.0.2-coated gypsum on exposure to Xe visible light lamp.

(5) FIGS. 5a-5f are photos showing the gradual decomposition over time of a dye stain applied onto BiOCl.sub.0.8Br.sub.0.2-coated gypsum on exposure to natural sunlight.

(6) FIG. 6 is a graph showing the results of Total Organic Carbon (TOC) measurements.

(7) FIG. 7 is a SEM image of a BiOCl.sub.0.8Br.sub.0.2-coated mortar sample.

EXAMPLES

(8) Methods

(9) X-ray powder diffraction measurements were performed on the D8 Advance diffractometer (Bruker AXS, Karlsruhe, Germany) with a goniometer radius 217.5 mm, secondary graphite monochromator, 2 Sollers slits and 0.2 mm receiving slit. XRD patterns within the range 5 to 70 2 were recorded at room temperature using CuK radiation (=1.5418 ) with the following measurement conditions: tube voltage of 40 kV, tube current of 40 mA, step-scan mode with a step size of 0.02 2 and counting time of 1 s/step. Gypsum plasters coated by BiOCl.sub.yBr.sub.1-y were placed on sample stage that is regulated along the vertical axis, and allows obtaining XRD patterns from as-manufactured samples with various sizes. Uncoated material of plaster was grinded in agate mortar to powder and placed into low-back ground quartz sample holders.

(10) Morphological observations and chemical analysis were performed with environmental scanning electron microscope (ESEM) Quanta 200 (FEI Company, Netherlands) equipped with EDS detector (EDAX-TSL, USA) and with the Extra High Resolution Scanning Electron Microscopy (XHR SEM) Magellan 400 L (FEICompany, Netherland) equipped with large area EDS silicon drift detector Oxford X-Max (Oxford Instruments, UK).

(11) Total Organic Carbon (TOC) measurements were conducted using SKALAR PRIMACSSLC Solid TOC ANALYZER, Model no. 2C522901.

Example 1

BiOCl0.8Br0.2-Coated Gypsum

(12) Synthesis of BiOCl.sub.0.8Br.sub.0.2

(13) Deionized water (75 ml), glacial acetic acid (35 ml) and bismuth nitrate (9.18 g) are added to a flask and mixed at room temperature for fifteen minutes until a clear, transparent solution is formed. Cetyltrimethylammonium bromide (1.378 g dissolved in 10 ml of water) and Cetyltrimethylammonium chloride (4.85 g in the form of 25 wt % aqueous solution) are added to the solution, for additional 30 minutes of mixing at room temperature. The white precipitate thus formed is separated from the liquid phase by filtration, washed five times with ethanol (20 ml) and five times with water (50 ml), in order to remove the non-reactive organic species. The solid is then dried (in air). The weight of the solid collected is 7 g (yield=91%).

(14) Preparation of BiOCl.sub.0.8Br.sub.0.2-Coated Gypsum

(15) Samples were prepared according to the following procedure. A commercially available plaster powder (50 g; from Tambur, Israel) was mixed with distilled water (20 ml). The so-formed mixture was poured into a petri dish and allowed to set for about five minutes. A suspension consisting of the BiOCl.sub.0.8Br.sub.0.2 photocatalyst in water (5-10 ml) was then sprayed onto the surface of the mass while the mass is still in the process of hardening (the amount of BiOCl.sub.0.8Br.sub.0.2 photocatalyst in the suspension was adjusted to obtain either 1% by weight, 2% by weight and 4% by weight photocatalyst in the dry gypsum sample). The gypsum plaster was then allowed to complete its hardening.

(16) Characterization of BiOCl.sub.0.8Br.sub.0.2-Coated Gypsum

(17) The X-ray powder diffraction patterns of the as-synthesized BiOCl.sub.0.8Br.sub.0.2, the BiOCl.sub.0.8Br.sub.0.2-coated gypsum and pure gypsum are shown in FIG. 1 (indicated a, b and c, respectively). The diffraction pattern of the BiOCl.sub.0.8Br.sub.0.2-coated gypsum (1b) exhibits peaks assigned either to the BiOCl.sub.0.8Br.sub.0.2 photocatalyst or pure gypsum. In particular, one or more characteristic peaks (relatively broad) which could be used to detect the presence of the photocatalyst in the gypsum are at positions 11.5, 26, 32.5, 41, 46.8, 54.3 and 58.92 (0.1 2).

(18) SEM images of the as-synthesized BiOCl.sub.0.8Br.sub.0.2 are shown in FIGS. 2a and 2b. The photocatalyst particles have a shape of microspheres exhibiting flower-like surface morphology with a size about 3 m, which are built of thin plates having lateral dimensions of hundreds of nanometers. Although the lateral dimensions of the plates were about hundreds of nanometers, their thickness is about 10 nm only. The SEM image of the BiOCl.sub.0.8Br.sub.0.2-added gypsum (FIG. 2c) illustrates the formation of a BiOCl.sub.0.8Br.sub.0.2 coating, indicating the presence of the BiOCl.sub.0.8Br.sub.0.2 microspheres on the surface of the gypsum; the elongated gypsum crystals are also perfectly visible. The adduced EDS spectrum (FIG. 2d) confirms the chemical composition of the BiOCl.sub.0.8Br.sub.0.2-coated gypsum.

(19) To determine the distribution and location of the BiOCl.sub.0.8Br.sub.0.2 particles across the sample, SEM images of the cross section of the sample were generated. It was found that the BiOCl.sub.0.8Br.sub.0.2 is absent from the bulk of the gyspum while it is present in the superficial layer. The SEM image obtained from cross-sectional sample is shown in FIG. 3A. As is clearly seen from FIG. 3A, BiOCl.sub.0.8Br.sub.0.2 photocatalyst consists of micron size particles exhibiting very strong contrast at back scattered electron (BSE) imaging. The thickness of coating layer is about 50-80 m. There are two distinct regions which are marked by dashed squares in FIG. 3A: the upper square indicates the coating region whereas the lower square corresponds to the bulk of the sample; the two regions were subjected to elemental analysis and the EDS spectra acquired from the marked areas are shown in FIG. 3B (the brown and red lines correspond to the coating and bulk regions, respectively; the brown line is the line which includes the Bi-assigned peaks). The EDS analysis shows that the plaster material beneath the coating layer is gypsum. A weak calcium peak appears in the EDS spectra acquired at coated regions (brown line), indicating the presence of gypsum in the coating layer, but the gypsum content is much less in the coating than in the gypsum body.

Example 2

Decomposition of Rhodamine B Applied onto the Surface of BiOCl0.8Br0.2-Coated Gypsum

(20) RhB dye (30 ppm) was sprayed on a sample of BiOCl.sub.0.8Br.sub.0.2-coated gypsum prepared as described in Example 1 (with 2% by weight photocatalyst concentration). The sample was exposed to various irradiation sources, at different day times, including natural sunlight and 300 W Xe arc lamp (Max-302, Asahi spectra). Power consumption of Max-302 is 500 VA. For visible light experiments a 422 nm cut-off filter was used. The light intensity was fixed at 70 mW/cm.sup.2 and the samples were placed 10 cm away from the light's source mirror.

(21) FIG. 4 demonstrates the gradual photocatalytic decomposition of a RhB stain over BiOCl.sub.0.8Br.sub.0.2-coated gypsum under Xe lamp visible light irradiation (=422-740 nm). Nine photos were taken for recording the photo-degradation processes with time interval of 0.5 min between one photo to the next one. The clear-cut disappearance of the dye stain is easily visible and can be monitored by naked eye. As it is clearly shown, the complete and swift destruction of the RhB dye could be successfully achieved within only 4 minutes of irradiation.

(22) FIG. 5 illustrates that RhB dye stain applied onto a sample of BiOCl.sub.0.80Br.sub.0.20-coated gypsum undergoes swift photo-oxidation following exposure of the sample to natural afternoon solar light. Six photos were taken for recording the decomposition of the dye, at time interval of 0.5 min between one photo to another. Complete self-cleaning is achieved after 2.5 minutes of illumination.

(23) Running the same experiments with BiOCl.sub.0.8Br.sub.0.2-coated gypsum having 4% by weight photocatalyst concentration gave essentially the same results, indicating that the mixed bismuth oxyhalide of the formula BiOCl.sub.yBr.sub.1-y [0.6y0.95] demonstrates high efficacy when incorporated into construction materials at a low loading (e.g., >0.5% by weight, preferably >1% by weight).

(24) The ultimate visible light driven photo-decomposition of RhB contamination presented above was tested in numerous number of cycles without any loss in activity. Additionally, the prepared surfaces maintained their superb photocatalytic efficiency even after seven months after fabrication. Lastly, further experiments, conducted under the same conditions, using simple 11 W table lamp and even 6 W LED lamps demonstrated rapid photo-destruction of RhB which was accomplished within less than 60 minutes of illumination.

Example 3

Decomposition of Naphthalene Applied onto the Surface of BiOCl0.8Br0.2-Coated Gypsum

(25) Very thin gypsum plates (1 mm thick) were prepared and coated with BiOCl.sub.0.8Br.sub.0.2 using the molding and coating procedure set forth in Example 1; an aqueous suspension of the photocatalyst was sprayed onto the surface of the progressively hardening mass in a petri dish, to achieve 2% by weight photocatalyst in the dry gypsum sample.

(26) Two BiOCl.sub.0.8Br.sub.0.2-coated gypsum plates were prepared. Each plate was then contaminated with naphthalene (50 mg naphthalene dissolved in ethanol; the ethanol solution was applied onto the upper face of the gypsum plate, and the ethanol was allowed to evaporate). One plate was kept in the dark whereas the other plate was illuminated with visible light (Xe, 422-740 nm; the same conditions set forth in Example 2) for 20 minutes. Both plates were then subjected to solid TOC analysis.

(27) The results of the solid Total Organic Carbon measurements are shown graphically in FIG. 6. The left peak indicates the total content of organic carbon in the reference sample, that is, this result corresponds to the total content of organic carbon in a contaminated gypsum plate before treatment (prior to illumination with visible light). The right peak shows the total content of organic carbon measured for the sample that was subjected to light-irradiation. It is seen that more than 90% decrease in the TOC value was achieved, indicating almost complete destruction of the organic pollutant.

Example 4

BiOCl0.8Br0.2-Coated Mortar

(28) A mixture consisting of cement, sand and water (1:3:0.5 weight ratio) was prepared and introduced into a 9-cm diameter petri dish, to form a 1.5 cm thick mortar-made cylinder. After 30 minutes, a suspension consisting of BiOCl.sub.0.8Br.sub.0.2 particles in water (1.5 g in 20 ml of water) was applied onto the fresh mortar face, to form a uniform coating thereon (approximately 15-18 ml of the suspension were used).

(29) The SEM image of the BiOCl.sub.0.8Br.sub.0.2-coated mortar is represented in FIG. 7. The presence of a spherical BiOCl.sub.0.8Br.sub.0.2 particle, with its unique flower-like surface morphology, is easily observed in the center of the image, indicating the generation of a photocatalytically-active coating onto the mortar substrate.

Example 5

Decomposition of Rhodamine B Applied onto the Surface of BiOCl0.8Br0.2-Coated Mortar

(30) The self-cleaning function of BiOCl.sub.0.8Br.sub.0.2-coated mortar prepared as described in Example 4 was assessed in the decomposition test of RhB dye. An aqueous solution of the dye was sprayed onto the surface of a BiOCl.sub.0.8Br.sub.0.2-coated mortar to form a central pink stain (of 4.5 cm diameter). Then, Xe lamp (422-740 nm) was used to illuminate the sample. The light intensity was fixed at 70 mW/cm.sup.2 and the samples were placed cm away from the light's source mirror. The sample was visually inspected after two minutes of light-irradiation: the pink color ascribed to Rhb has vanished, with only colorless water spots remaining on the face of BiOCl.sub.0.8Br.sub.0.2-coated mortar.

Example 6

Testing the Adhesion Strength of a BiOCl0.8Br0.2-Containing Coating Applied onto a Mortar Substrate

(31) The adhesion strength of a BiOCl.sub.0.8Br.sub.0.2-containing coating applied onto a mortar substrate was evaluated with the aid of the Cross-Cut test. To this end, a mortar plate [lengthwidththickness=12 cm13 cm3 cm] was coated as follows. First, mortar formulation was prepared by thoroughly mixing cement, sand and water (1:3:0.5 weight ratio). This formulation was spread over one face of the plate. An aqueous suspension of the BiOCl.sub.0.8Br.sub.0.2 particles was applied onto the fresh mortar layer to form a coating thereon (2 g in 30 ml of water was used).

(32) Fourteen days following the fabrication of the coated plate, the adhesion strength of the coating was assessed with the standard Cross-Cut test. The test consists of (i) forming a lattice pattern in the coating with the aid of a suitable tool, penetrating into the substrate, (ii) applying a brush pen and Permacel tape over the cut and (iii) inspecting the grid area with the aid of an illuminated magnifier. Approximately 10% loss in the grid area was assessed (ISO Class 2 (ASTM Class 3B), indicating a fairly strong adhesion of the photocatalytically active coating on the mortar.

Preparation 1

Preparation of Bi(0) Doped-Mixed Halide BiOCl0.875Br0.125

(33) Deionized water (50 ml), glacial acetic acid (40 ml) and bismuth nitrate (14.69 g) are added to a flask and are mixed at room temperature for fifteen minutes until a clear, transparent solution is formed. The so-formed solution is added to a previously prepared solution consisting of CTAC (33.92 g of 25 wt % aqueous solution) and CTAB (1.38 g). Finally, sodium borohydride (11.456 mg) and ethanol (20 ml) are added to the reaction mixture, which is then stirred for additional 60 minutes at about 25-30 C.

(34) The precipitate thus formed is separated from the liquid phase by filtration, washed five with ethanol (550 ml) and then five times with water (5200 ml). The off-white solid is then dried (3 hours in air). The weight of the solid collected is 9 grams.

Preparation 2

Preparation of Bi(0) Doped-BiOBr

(35) Deionized water (50 ml), glacial acetic acid (40 ml) and bismuth nitrate (9.7 g) are added to a flask and are mixed at room temperature for fifteen minutes until a clear, transparent solution is formed. The so-formed solution is added to a previously prepared aqueous ethanolic solution of CTAB (1.38 g CTAB dissolved in a mixture consisting of 30 ml ethanol and 10 ml deionised water). Finally, sodium borohydride (7.56 mg) is added to the reaction mixture, which is then stirred for additional 60 minutes at about 25-30 C.

(36) The precipitate thus formed is separated from the liquid phase by filtration, washed five with ethanol (550 ml) and then five times with water (5200 ml). The off-white solid is then dried (3 hours in air). The weight of the solid collected is 7 grams.