Sulfur-doped carbonaceous porous materials

Abstract

The present invention relates to novel sulfur-doped carbonaceous porous materials. The present invention also relates to processes for the preparation of these materials and to the use of these materials in applications such as gas adsorption, mercury and gold capture, gas storage and as catalysts or catalyst supports.

Claims

1. A process for the preparation of a sulfur-doped carbonaceous porous material, the process comprising the steps of: i) preparing a sulfur-based polymer by reacting elemental sulfur with one or more organic crosslinking agents, wherein the organic crosslinking agent(s) comprises two or more carbon-carbon double bonds; ii) carbonising the sulfur-based polymer of step (i) in the presence of at least one porosity enhancement agent selected from one or more of potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), rubidium hydroxide (RbOH), caesium hydroxide (CsOH), magnesium hydroxide (Mg(OH).sub.2), calcium hydroxide (Ca(OH).sub.2), potassium carbonate (K.sub.2CO.sub.3), sodium carbonate (Na.sub.2CO.sub.3), aluminium hydroxide (Al(OH).sub.3), zinc hydroxide (Zn(OH).sub.2), barium hydroxide (Ba(OH).sub.2), phosphoric acid, sodium chloride, calcium chloride, magnesium chloride or zinc chloride; wherein the mass ratio of sulfur-based polymer to porosity enhancement agent in step (ii) of the process is between 3:1 and 1:3; wherein the carbonisation of step (ii) is carried out under an inert atmosphere; and wherein the sulfur-doped carbonaceous porous material comprises greater than or equal to 12 wt % sulfur and comprises micropores and mesopores.

2. The process according to claim 1, wherein the porosity enhancement agent is an inorganic base, an inorganic acid or an inorganic salt.

3. The process according to claim 1, wherein the carbonisation of step (ii) is conducted at a temperature of between 500° C. and 1000° C.

4. A process according to claim 1, wherein the mass ratio of sulfur-based polymer to porosity enhancement agent in step (ii) of the process is between 2:1 and 1:2.

5. The process according to claim 1, wherein the sulfur-based polymer is carbonised for a duration of between 30 minutes and 5 hours.

6. The process according to claim 1, wherein the mass ratio of elemental sulfur to organic crosslinking agent in step (i) of the process is between 20:80 and 95:5.

7. The process according to claim 1, wherein the one or more organic crosslinking agents of step (i) of the process comprises two double bonds.

8. The process according to claim 1, wherein the sulfur-based polymer of step (i) is formed by reacting elemental sulfur with one organic crosslinking agent.

9. The process according to claim 1, wherein the sulfur-based polymer of step (i) is formed by reacting elemental sulfur with one or more organic crosslinking agents at a temperature of greater than or equal to 120° C.

10. The process according to claim 1, wherein the sulfur-based polymer of step (i) is a solid.

Description

EXAMPLES

Description of Drawings

(1) Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 shows the synthesis of the hypercrosslinked polymers and the subsequent carbonization method.

(3) FIG. 2 shows the nitrogen adsorption-desorption isotherms of KOH activated S-DCPD carbons at 77.3 K (the adsorption and desorption branches are labelled with filled and empty symbols, respectively).

(4) FIG. 3 shows the FE-SEM images of a) S-DCPD-850 and c) 1K-S-DCPD-750. TEM images of b) S-DCPD-850 and d) 1K-S-DCPD-750. Higher e) FE-SEM and f) TEM magnification of 1K-S-DCPD-750.

(5) FIG. 4 shows a) CO.sub.2 sorption isotherms at 298 K over pressure range 0-1 bar. b) CH.sub.4 sorption isotherms at 298 K over pressure range 0-1 bar. c) H2 sorption isotherms at 77 K over pressure range 0-1 bar. d) CO.sub.2 and CH.sub.4 sorption isotherms at 298 K and H2 sorption isotherms at 77 K of 1K-S-DCPD-750 over pressure range 0 10 bar.

(6) FIG. 5 shows the adsorption isotherm of mercury (as aqueous HgCl.sub.2) into samples of carbonized sulfur polymer (orange circles) and conventional activated carbon (black squares), with Langmuir isotherm fitting shown as dashed red and black lines.

(7) FIG. 6 shows photographs of a) directly carbonized S-DCPD resulting in a large grey metallic monolith and b) KOH activated S-DCPD carbon black powder.

(8) FIG. 7 shows the nitrogen adsorption-desorption isotherms of directly carbonized S-DCPD at 77.3 K (the adsorption and desorption branches are labelled with filled and empty symbols, respectively).

(9) FIG. 8 shows the pore size distributions of carbonised S-DCPD calculated by non-local density functional theory (NL-DFT).

(10) FIG. 9 shows the HR-TEM images of a) S-DCPD-850 and b) 1K-S-DCPD-750 with higher resolution images of 1K S-DCPD-750 at c) 20 nm and d) 10 nm scale.

(11) FIG. 10 shows the PXRD patterns of carbonized S-DCPD samples. Samples 1K-S-DCPD-750 and 4K-S-DCPD-750 contain additional alumina peaks associated from the ceramic boat and/or use of pestle and mortar.

(12) FIG. 11 shows the CO.sub.2 and CH.sub.4 sorption isotherms at 298 K and H2 sorption isotherms at 77 K of S-DCPD-850 over a pressure range of 0-10 bar.

(13) FIG. 12 shows the uptake of various metal ions from deionised water using 1K-S-DCPD-750 and activated charcoal.

(14) FIG. 13 shows the capture of gold from deionised water using 1K-S-DCPD-750 and activated charcoal.

SULFUR-DOPED CARBONACEOUS POROUS MATERIAL NOMENCLATURE

(15) In the illustrative examples hereinbelow, the following nomenclature is used to denote each of the sulfur-doped carbonaceous porous materials prepared:
nB-S-[Crosslinker]-Δ
wherein: n is the mass ratio of porosity enhancement agent (e.g. inorganic base) to sulfur-based polymer; B is the porosity enhancement agent (e.g. potassium hydroxide); S is sulfur; [Crosslinker] is the crosslinker used (e.g. [DCPD]=dicyclopentadiene) Δ is the temperature at which carbonisation is conducted.

(16) For example, using the above labelling system, the carbonisation of a sulfur-based polymer (formed from the reaction between elemental sulfur and dicyclopentadiene) with a 1:1 mass ratio of KOH at 750° C. would be given the following label—1K-S-DCPD-750.

(17) Materials

(18) Dicyclopentadiene (DCPD) was purchased from Tokyo Chemicals Industry. Sulfur and potassium hydroxide were purchased from Sigma Aldrich. High purity nitrogen was purchased from BOC. All chemicals were used as received without any further purification. Distilled water was used in purifications.

(19) Synthesis of S-DCPD

(20) Polymerisations were carried out in open glass samples vials (12 or 40 mL volume) in aluminium heating blocks, with heating and stirring provided by electronic hotplates and magnetic stirrer bars. All reactions were begun by allowing the sulfur to fully melt, at 160° C., before adding the organic crosslinking agent directly. Sulfur:organic crosslinking agent mass ratios were varied, but total mass was typically between 5 and 20 g.

(21) Using DCPD as the crosslinker, heating was maintained at 160° C. for 2 hours (the reaction vitrifies after typically ˜20 minutes). The colour became increasingly dark during the polymerisation, resulting in a black solid product. Moulded objects were prepared by polymerising the crosslinker (DCPD) and sulfur together as normal in a stirred glass vial, to ensure homogeneous mixing, before transferring them into a silicone mould and curing in an oven at 140° C. for 12 hours. The point to transfer the reaction mixture from the stirred vial to the mould was taken as the point at which an aliquot of the reaction mixture, when removed on a spatula and allowed to cool to room temperature, would no longer visibly separate to clear organic monomer, and precipitated yellow sulfur powder, but instead remain as a homogeneous brown viscous liquid.

(22) Synthesis of Directly Carbonised Materials (Comparative Examples)

(23) In a typical procedure, S-DCPD (300 mg) was homogeneously ground using a pestle and mortar. The polymer was placed in a ceramic boat and inserted within a tube furnace. The furnace was purged with N.sub.2 at room temperature for 30 min, heated to the specified temperature at a rate of 5° C. min.sup.−1, held at the set temperature for the associated time, and finally cooled to room temperature. The material was used without further purification.

(24) Synthesis of KOH Activated Carbonised Materials

(25) In a typical procedure, S-DCPD (1.0 g) and the associated amount of KOH was homogeneously ground using a pestle and mortar. The mixture was placed in a ceramic boat and inserted within a tube furnace. The furnace was purged with N.sub.2 at room temperature for 30 min, heated to the specified temperature at a rate of 5° C. min.sup.−1, held at the set temperature for 2 h, and finally cooled to room temperature. The residue was washed thoroughly with DI water and 1 M HCl until the filtrate attained pH 7. The resultant carbons were dried under vacuum for 1 d at 70° C.

(26) Mercury Uptake Studies

(27) A stock solution of mercury was made by dissolving HgCl.sub.2 (338 mg) in deionised water (250 mL) to produce a concentration of 1000 ppm, this was then used to prepare the test solutions of 20, 100, 500 and 750 ppm by serial dilutions. Activated charcoal (Sigma Aldrich, measured at 594 m.sup.2 g.sup.−1) and 1K-S-DCPD were coarsely ground and screened through a 45 mesh sieve to ensure particles no larger than 350 microns. 12 mL of each solution was decanted in to a series of glass vials along with either 15, 30 or 60 mg of 1K-S-DCPD or activated charcoal, the vials were then capped and placed on a roller for 1 hour at room temperature. After 1 hour, the vials were removed and the test solutions filtered into clean sample vials using a 0.22 μm filter and a polypropylene syringe. Samples were analysed by ICP-OES, conducted using an Agilent 5110. The data were fitted to a Langmuir isotherm, q.sub.A=(K.C.sub.e.Q.sub.sat)/(1+K.C.sub.e), where qA=mg adsorbate per g adsorbent (mg g.sup.−1), K=adsorption parameter (L mg.sup.−1), Ce=equilibrium concentration (mg L.sup.−1) and Q.sub.sat=maximum capacity (mg g.sup.−1)

(28) Gas Sorption

(29) The porous properties of the networks were investigated by nitrogen adsorption and desorption at 77.3 K using an ASAP2420 volumetric adsorption analyser (Micrometrics Instrument Corporation). 1 bar CO.sub.2 and CH.sub.4 isotherms at 298 K and H.sub.2 isotherms at 77.3 K were collected on a Micromeritics ASAP2020 and ASAP2050. 10 bar CO.sub.2 and CH.sub.4 isotherms at 298 K and H.sub.2 isotherms at 77.3 K were collected using a Micromeritics ASAP2050. All samples were degassed at 100° C. for 15 h under vacuum (10.sup.−5 bar) before analysis.

(30) Pore Structure Analysis

(31) Pore structure properties of the samples were determined via nitrogen adsorption and desorption at 77.3 K using a volumetric technique on an ASAP2420 adsorption analyser (Micromeritics Instrument Corporation). Before analysis, the samples were degassed at 100° C. for 15 h under vacuum (10.sup.−5 bar).

(32) Brunauer-Emmett-Teller (BET) surface area was obtained in the relative pressure (P/P.sub.0) range of 0.05-0.20, and total pore volume (V.sub.t) was determined from the amount of nitrogen adsorbed at P/P.sub.0=ca. 0.99.

(33) FE-SEM

(34) High resolution imaging of the polymer morphology was achieved using a Hitachi S-4800 cold field emission scanning electron microscope (FE-SEM).

(35) HR-TEM

(36) High-resolution transmission electron microscopy (HR-TEM) was performed using a JEOL 2100FCS microscope, equipped with a Schottky field emission gun, operating at 200 kV. Bright field images were recorded in conventional TEM illumination mode. Chemical analyses were performed by energy dispersive x-ray spectroscopy using a windowless EDAX spectrometer.

(37) TEM specimens were produced by ultrasonically dispersing powder in analytical grade methanol, the suspension was then dropped onto copper mesh grids with holey carbon support films and allowed to dry.

(38) Elemental Analysis

(39) CHN elemental analysis was conducted on a Thermo FlashEA 1112.

(40) PXRD

(41) Powder X-ray diffraction (PXRD) data were collected in transmission mode on loose powder samples held on thin Mylar film in Stainless steel well plates on a Panalytical X'Pert PRO MPD equipped with an high throughput screening (HTS) XYZ stage, X-ray focusing mirror, ½ degree divergence slit, 0.04 degree soller slits, 4 mm beam mask and PIXcel detector, using Cu Kα radiation. Data were measured over the range 5-50° 2θ in 0.013° steps over 60 minutes.

(42) Design and Porosity of S-Doped Carbons

(43) S-DCPD was initially carbonised under a flow of nitrogen at 750° C. for 1 h as a direct comparison with the previously reported carbonised inverse vulcansed polymer,.sup.19 and the product was denoted as S-DCPD-750-1. This material became microporous with a SA.sub.BET of 403 m.sup.2 g.sup.−1. A yellow powder appeared in the tube furnace exhaust due to the leeching of elemental sulfur, and the resultant material was a shiny grey/black monolith (FIG. 6).

(44) With the aim of increasing the surface areas, S-DCPD was further carbonised for an extended time of 2 h and another sample was carbonised at a higher temperature, 850° C., for 2 h (S-DCPD-750-2 and S-DCPD-850, respectively). The nitrogen sorption isotherms for S-DCPD-750-1 and S-DCPD-750-2 were very similar (FIG. 7); both exhibited Type Ia behaviour where most of the nitrogen uptake occurs at P/P.sub.0<0.02, indicating narrow micropores (FIG. 8), resulting in a SA.sub.BET of 415 m.sup.2 g.sup.−1 for S-DCPD-750-2.

(45) S-DCPD-850 also showed a Type Ia isotherm, but the somewhat larger gas uptake at the microporous region resulted in a higher SA.sub.BET of 511 m.sup.2 g.sup.−1. These surface areas are comparable to previously reported carbonised inverse vulcansed polymers..sup.19

(46) We next moved to a different carbonisation approach with the aid of KOH as a chemical activating agent to target higher surface area S-doped carbons. S-DCPD was synthesised and thoroughly mixed with varying amounts of KOH before being carbonised under a nitrogen flow for 2 h (FIG. 1). The carbons are referred to as nK-S-DCPD-Δ where n is the mass ratio of KOH to S-DCPD and Δ signifies the carbonisation temperature. The nitrogen sorption isotherms of the KOH-activated carbonised S-DCPD showed high levels of microporosity in all samples (FIG. 2). The physical properties of these carbons and their precursors are summarized in Table 1.

(47) 0.5K-S-DCPD-750 showed a Type Ib isotherm indicating high levels of microporosity with pore size distributions over a broader range compared with the directly carbonised samples (FIG. 8). As the KOH to S-DCPD ratio was increased to 1:1 in 1K-S-DCPD-750, the nitrogen sorption increases, especially in the P/P.sub.0<0.02 microporous region, resulting in a higher micropore volume (0.80 versus 0.51 cm.sup.3 g.sup.−1) and an increase in SA.sub.BET (2216 m.sup.2 g.sup.−1 versus 1792 m.sup.2 g.sup.−1). Further increases in the KOH quantity in 2K-S-DCPD-750 and 4K-S-DCPD-750 resulted in some Type IVa character, where a hysteresis loop gradually appeared at P/P.sub.0=0.5 indicative of the development of mesopores. The SA.sub.BET values for these hierarchically-porous materials were 2197 and 1520 m.sup.2 g.sup.−1, respectively. The micropore percentage fell from 73% in 1K-S-DCPD-750 to 56% in 2K-S-DCPD-750 and 28% in 4K-S-DCPD-750, perhaps because of an oversaturation of the KOH activating agent causing micropore collapse. Since S-DCPD contains 50 wt % sulfur, smaller quantities of KOH activating agent are required compared with conventional carbonisations, where the precursor contains a much higher carbon content..sup.23

(48) Higher carbonisation temperatures (850° C.) were also tested with 1K-S-DCPD-850 since it is known that higher surface areas can be achieved with temperature optimisation,.sup.1 but the resulting carbon yielded a Type Ib isotherm with a SA.sub.BET of 1599 m.sup.2 g.sup.−1. The carbonised S-DCPD materials retain a significant amount of their parent sulfur heteroatom in their structure—up to 18.16 wt %—showing that incorporation of sulfur into the porous carbon is possible when using inverse vulcansed polymers as a carbonisation precursor (Table 2). The SA.sub.BET of 2216 m.sup.2 g.sup.−1 for 1K-S-DCPD-750 outperforms other microporous S-doped carbons,.sup.24 including carbonisation precursors that were inherently porous and more costly..sup.25

(49) TABLE-US-00001 TABLE 1 Physical properties, H.sub.2, CO.sub.2, and CH.sub.4 uptake of KOH activated S-DCPD carbons. Surface area Pore volume.sup.a (m.sup.2 g.sup.−1) (cm.sup.3 g.sup.−1) Gas uptake BET Langmuir Micro- Total CO.sub.2.sup.c CH.sub.4.sup.d H.sub.2.sup.e Sample method method pore pore.sup.b (mmol g.sup.−1) (mmol g.sup.−1) (wt %) 0.5KS-DCPD-750 1792 2379 0.51 1.00 2.01 1.07 1.99 1KS-DCPD-750 2216 2976 0.80 1.09 2.20 1.03 2.09 2KS-DCPD-750 2197 3015 0.68 1.21 1.79 0.58 1.88 4KS-DCPD-750 1520 1995 0.26 0.92 1.29 0.50 1.40 1KS-DCPD-850 1599 2226 0.48 0.84 1.31 0.57 1.41 .sup.aCalculated by single point pore volume. .sup.bTotal pore volume at P/P.sub.0 = 0.99. .sup.cCO.sub.2 uptake at 298K and 1 bar. .sup.dCH.sub.4 uptake at 298K and 1 bar. .sup.eH.sub.2 uptake at 77K and 1 bar.

(50) TABLE-US-00002 TABLE 2 Carbonisation yields and CHNS elemental analysis of S-doped porous carbon products. Sample Yield (%) C H S S-DCPD-750-1 36 75.85 0.66 18.16 S-DCPD-750-2 35 77.25 0.63 17.67 S-DCPD-850 32 81.86 0.50 11.89 0.5K-S-DCPD-750 23 74.91 0.35 13.54 1K-S-DCPD-750 34 74.14 0.55 13.27 2K-S-DCPD-750 14 78.37 0.95 12.77 4K-S-DCPD-750 16 77.98 0.55 12.73 1K-S-DCPD-850 34 69.40 0.87 9.55
Characterisation of Carbons

(51) Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) was used to study the morphology of carbonised S-DCPD products (FIG. 3). The shiny, monolithic structure from directly carbonising S-DCPD in S-DCPD-850 is shown in FIG. 3a. The observed structure was smooth with few signs of pores on the surface. TEM of the sample also backed up this observation since the white spots that are typically indicative of pores were not apparent (FIG. 3b).

(52) The KOH-activated carbonised product, 1K-S-DCPD-750, was a black powder (FIG. 6b) and its rough, particulate surface was apparent under FE-SEM (FIG. 3c & e). TEM of the porous carbon indicated high porosity, and a lower density was structure observed (FIG. 3d & f).

(53) High-resolution transmission electron microscopy (HR-TEM) was also used to examine both types of products and was found that the KOH-activated sample resulted in a more fibrous network due to its greater porosity (FIG. 9).

(54) The morphology of the KOH-activated sample was also observed to be more homogeneous when scanning across the material compared to the directly carbonised sample, which can be advantageous.

(55) Powder X-ray diffraction patterns of the carbonised products showed two broad characteristic peaks located at 25 and 43° (FIG. 10), corresponding to the (002) and (100) planes of hexagonal graphite, respectively, revealing the presence of an amorphous structure and a low degree of graphitisation..sup.26

(56) CO.sub.2, CH.sub.4 and H.sub.2 Storage

(57) The affinities of the S-DCPD carbons towards small gas sorption (CO.sub.2, CH.sub.4, and H.sub.2) were studied (FIG. 4).

(58) The CO.sub.2 uptakes for the KOH-activated materials were tested at room temperature (ca. 298 K) with the full isotherms shown in FIG. 4a. Table 1 summarizes the amount of CO.sub.2 absorbed by each material at a pressure of 1 bar. The CO.sub.2 uptake was roughly proportional to the surface area of each material, with a CO.sub.2 uptake of up to 2.20 mmol g.sup.−1 for 1K-S-DCPD-750, outperforming recent reports of sulfur-containing microporous polymers,.sup.20 previous carbonised inverse-vulcansed polymers,.sup.19 sulfur-containing hypercrosslinked microporous polymers,.sup.27 and microporous networks COF-6,.sup.28 CMP-1,.sup.29 and highly porous PAF-1..sup.30

(59) The CH.sub.4 sorption behaviour was also tested at 298 K and 1 bar with an uptake of up to 1.07 mmol g.sup.−1 for 0.5KS-DCPD-750 (FIG. 4b).

(60) H.sub.2 uptakes tested at 77 K and 1 bar were high with all KOH-activated samples, with an uptake of 2.09 wt % observed from 1K-S-DCPD-750 (FIG. 4c). The large uptakes are due to H.sub.2 being purely attracted to a large surface via physisorption as a result of weak van der Waals interactions.

(61) The H.sub.2 uptake is more than three times larger than the previously reported carbonised inverse vulcansed polymers; this a dramatic improvement for this cheap synthetic method,.sup.19 although more striking results were found at higher gas pressures, as discussed below.

(62) The absorption of small gases were also evaluated at pressures of up to 10 bar for the optimised sample, 1K-S-DCPD-750 (FIG. 4d). This material adsorbed up to 10.1 mmol g.sup.−1 of CO.sub.2 at 298 K with no sign of saturation, matching and outperforming more costly materials such as carbonised polyacrylonitrile AC-3000,.sup.31 mesoporous silica templated carbon IBN-9,.sup.32 and directly carbonised MOF-74 and MIL-53..sup.33

(63) 1K-S-DCPD-750 adsorbs 2.74 wt % H2 at 77 K and 10 bar, outperforming industrial BPL activated carbon,.sup.28 and exceeding porous carbons 12ACA-800 made from carbon aerogel via subcritical drying,.sup.34 AC-C4 (activated at very high temperatures with further activation using CO.sub.2 gas),.sup.35 and even porous carbons measured at high pressures of over 60 bar..sup.36

(64) Mercury Capture Studies

(65) The sulfur-doping in the structure of these microporous carbons may have further benefits, such as providing anchor sites for metal catalysts. The combination of high surfaces areas, hierarchical porosity, and high sulfur loading is also very attractive for the removal of trace heavy metals from water. Mercury pollution from industrial wastewater is a significant global health concern because of its relatively high solubility in water and tendency to bioaccumulate and cause severe toxic effects..sup.37

(66) Sulfur is known to have a high affinity for mercury, and therefore 1K-S-DCPD-750 was tested for the capture of HgCl.sub.2 from water (FIG. 5). 1K-S-DCPD-750 showed a greatly enhanced uptake of mercury in comparison to activated carbon, especially at low mercury concentrations. Activated carbons are frequently used for the adsorption of mercury from wastewater, and they generally show maximum Hg uptakes in the ˜10-500 mg g.sup.−1 range..sup.38

(67) At an equilibrium Hg concentration of ˜10 ppm, 1K-S-DCPD-750 absorbed over 15 times more Hg than the activated carbon control (151 mg g.sup.−1 versus 7.8 mg g.sup.−1). Fitting these data to a Langmuir isotherm also indicated a higher saturation capacity for the sulfur loaded material (850 mg g.sup.−1 vs. 498 mg g.sup.−1) and adsorption parameters that were over 20 times higher (0.058 L mg.sup.−1 vs. 0.0028 L mg.sup.−1). Absorption of mercury at low concentrations (<1 mg g.sup.−1) has particular practical relevance. For example, the Environmental Protection Agency has set a maximum contaminant level goal for mercury of 0.002 mg/L, or 1×10.sup.−6 mg/g..sup.39

(68) Capture of Other Metals

(69) 100 ppm solutions (50 ml) of chromium, cobalt, copper, manganese, iron, nickel and mercury were made up from stock solutions respective metal salts (either chloride or nitrate forms) and de-ionised water. Activated charcoal and 1K-S-DCPD-750 were coarsely ground and screened through a 45 Mesh sieve to ensure that all tests would contain particles no larger than 350 microns. 15 ml plastic vials were loaded with 30 mg of either 1K-S-DCPD-750 or activated charcoal and 12 ml of the chosen metal solution, the tubes were then capped and placed on a roller for 1 hour at room temperature. Multiple metals were tested at a time by conducting tests in parallel. After 1 hour, the vials were removed and stood in a rack to allow the particulates to settle, whilst a 1 ml aliquot was removed for analysis. The samples were diluted by a factor of 10 by adding the 1 ml aliquots each to a vial containing 9 ml of de-ionised water. Samples were analysed along with a water blank and 100 ppm control samples of each metal using the same calibration method on the ICP-OES, with the data being corrected post collection. ICP-OES analysis was conducted using an Agilent 5110.

(70) Results from the application of the above described method are depicted in FIG. 12.

(71) Capture of Gold

(72) A 1,000 ppm gold solution (250 ml) was made up from a stock solution of Chloroauric acid (HAuCl.sub.4) and deionised water, with the pH adjusted to 3-4 with the addition of Hydrochloric acid. Activated charcoal and 1K-S-DCPD-750 were coarsely ground and screened through a 45 Mesh sieve to ensure that all tests would contain particles no larger than 350 microns. 15 ml plastic vials were loaded with 5, 10, 20, 40 and 80 mg of either 1K-S-DCPD-750 or activated charcoal and 12 ml of the gold solution, the tubes were then capped and placed on a roller for 1 hour at room temperature. After 1 hour, the vials were removed and stood in a rack to allow the particulates to settle, whilst a 1 ml aliquot was removed for analysis. The samples were diluted by a factor of 10 by adding the 1 ml aliquots each to a vial containing 9 ml of de-ionised water. Samples were analysed along with a water blank and a 1,000 ppm control sample using the same calibration method on the ICP-OES, with the data being corrected post collection. ICP-OES analysis was conducted using an Agilent 5110.

(73) Results from the application of the above described method are depicted in FIG. 13.

(74) While specific embodiments of the invention have been described herein for the purpose of reference and illustration, various modifications will be apparent to a person skilled in the art without departing from the scope of the invention as defined by the appended claims.

REFERENCES

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