Oxidation of Sodium Thiocyanate (NaSCN) in Stretford Aqueous

Feb 18, 2016 - ... for suppressing formation of sodium thiosulphate and for reducing the consumption of sodium anthraquinone 2,7-disulphonate (Na2[ADA...
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Oxidation of Sodium Thiocyanate (NaSCN) in Stretford Aqueous Liquor using Air and Commercial Hydrogen Peroxide (H2O2) R. H. Matjie,*,† R. Singh,‡,§ and C. A. Strydom§ †

Unit for Energy and Technology Systems, School of Chemical and Minerals Engineering, and §Chemical Resource Beneficiation, North-West University, Potchefstroom, 2520, Republic of South Africa ‡ Business Development Department, Sasol Secunda Chemical Operations, Secunda, 2302, Republic of South Africa ABSTRACT: Stretford processes are most widely utilized for the absorption of H2S from gaseous streams from the coal gasification process and converting the absorbed H2S into elemental sulfur. Hydrogen cyanide in the gaseous streams is efficiently absorbed and quickly ionised in the Stretford liquor during the absorption of H2S. The free cyanide ions react with polysulphide and suspended elemental sulfur to form thiocyanate ions. Sodium thiocyanate (NaSCN), which is a very expensive reagent, is used for bacterial control; for suppressing formation of sodium thiosulphate and for reducing the consumption of sodium anthraquinone 2,7-disulphonate (Na2[ADA]) in Stretford liquors. The objective of this paper is to report on the degree of oxidation of NaSCN in Stretford liquors using air and hydrogen peroxide (H2O2). The X-ray fluorescence and X-ray diffraction results indicated that NaSCN in the Stretford liquors oxidized to form sticky sodium and ammonium based salts (Na2SO4, Na6(CO3)(SO4)2, NaHSO4, and (NH4)2SO4) when using air and H2O2. The NaSCN oxidation led to high concentrations of Na2SO4 that enhanced crystallization and precipitation that resulted in severe blockages of plant equipment and contamination of the element sulfur. The results also indicated clearly that the concentration of NaSCN in the Stretford liquors steadily decreased, while the concentration of Na2SO4 increased during the oxidation of Stretford liquors using air and H2O2. Therefore, it is critical to ensure that NaSCN does not oxidize to form sodium based salts under operating conditions as a result of increased concentrations of dissolved oxygen from the oxidizing plant equipment and from hydrogen peroxide formed from catalysts. The oxidation of NaSCN in the Stretford liquors with H2O2 and air to sulfate salts also revealed that hydrogen cyanide and carbon dioxide gases were evolved. The results obtained from the NaSCN oxidation experiments can be used in conjunction with process changes to optimize plant parameters and critical chemical concentrations.

1. INTRODUCTION The Stretford process oxidizes the absorbed hydrogen sulphide gas to form elemental sulfur.1−4 This process employs an aqueous solution containing dissolved V5+ salts and dissolved sodium anthraquinone disulfonate (Na2[ADA]) to facilitate the absorption of H2S into an alkaline solution. V5+ salts and Na2[ADA] act as catalysts and facilitate an oxidation reaction with HS− ions to elemental sulfur. The absorbed hydrogen sulphide in the resulting reduced solution is passed into the oxidizing tanks where it reacts with oxygen from the air to form hydrophobic elemental sulfur particles.1−4 The sulfur particles are concentrated in the froth layer on the top of the Stretford aqueous liquors. The reduced solution contains V4+ and Na3[HADA] which are reoxidized in the presence of air to V5+ and Na2[ADA]3 respectively. The regenerated solution is recycled back to the absorption stage, where it is ready for further contact with H2S. The hydrogen cyanide gas in the offgas feed dissolves and ionises in the Stretford aqueous liquor.5 The cyanide ions subsequently react with polysulphides and elemental sulfur present in the Stretford liquor to form sodium thiocyanate.5 The SCN− anion has bacteriostatic properties1 and is therefore added into the Stretford aqueous liquor to control the growth of sulfur oxidizing bacteria (SOB’s) in the Stretford aqueous liquors.1 NaSCN at a concentration of 0.62 mol·dm−3 has been reported as being sufficient for the control of sulfur oxidizing bacteria.1 © XXXX American Chemical Society

It has also been reported that the addition of NaSCN to the Stretford process may facilitate the solubilization of vanadium compounds and reduces sulfur byproduct formation.6 The formation of thiosulphate in the simultaneous scrubbing and oxidation of H2S is suppressed by the addition of thiocyanates. These can be added in the form of sodium, potassium or ammonium thiocyanate. The addition of sodium thiocyanate in the concentration range of 0.06−0.5 mol·dm−3 was shown to be advantageous; however 0.3−0.4 mol·dm−3 is preferred.6 The oxidation of NaSCN in alkaline solutions has been studied many times due to its physiological importance;8−11 however, the oxidation of NaSCN in Stretford aqueous liquor has not been investigated in detail. SCN− ions in the aqueous solution were oxidized by hydrogen peroxide to form NaHSO4 and NH4HCO3 using the following reactions sequence.8−11 NaSCN(aq) + H 2O2(aq) → NaOSCN(aq) + H 2O(aq)

(1)

NaOSCN(aq) + 3H 2O2(aq) → NaHSO4(aq) + NH4HCO3(aq) (2)

It will be important to minimize the oxidation of NaSCN to form sodium based salts under operating conditions as a result of increased concentrations of dissolved oxygen from the Received: November 12, 2015 Revised: January 24, 2016

A

DOI: 10.1021/acs.energyfuels.5b02665 Energy Fuels XXXX, XXX, XXX−XXX

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Energy & Fuels

2.2. Analytical Methods. In this paper various analytical techniques were followed to determine the concentrations of inorganic elements, sodium compounds, ions, and crystalline phases present in the liquid and solid samples produced from the experiments. 2.2.1. Ion Chromatography (IC). An anion chromatographic technique was used to determine the concentrations of sulphates, thiosulphates, and thiocyanates in the Stretford aqueous liquor samples. The ions were separated on an anion exchange resin using conductivity detection on a Metrohm 882 Compact IC Plus connected to an 858 Professional sample processor.12 An A-Supp 5 column was used with a guard column. The eluent comprises of Na2CO3 and NaHCO3. 2.2.2. Automated Titrations for the Total Alkalinity Determination. An aliquot of known volume of alkaline Stretford aqueous liquor was titrated in a beaker using a standardized hydrochloric acid solution. A pH electrode connected to a pH meter was used to monitor the pH values during the titration. The total alkalinity was analyzed by titrating the Stretford aqueous liquor with HCl using a Metrohm autotitrator 809 Titrando with 800 Dosino and 772 pump connected to an 814 USB sample processor.12 2.2.3. Na2[ADA] Analysis by Visible Spectrophotometry. The absorbance of the red-colored Stretford liquor samples was measured spectrophotometrically and the concentration of Na2[ADA] in this sample was calculated by means of an external calibration prepared using standards of known Na2[ADA] concentrations.12 A sample of the Stretford aqueous liquor was heated to 40 °C and filtered through a Whatman 42 filter paper. The Na2[ADA] was reduced using sodium dithionate in a strongly alkaline solution obtained by the addition of sodium hydroxide (NaOH) to the Stretford aqueous liquor. The resulting solution was a red-colored solution and its absorbance was determined at 448 nm using a 10 mm glass cuvette.12 2.2.4. Vanadium Analysis (Total Vanadium Concentration Determination). Ultraviolet (UV) visible spectroscopy was used to determine the concentration of total vanadium in Stretford aqueous liquor samples.13 The gallic acid method (approved standard method 3500-V B)13 was employed to determine the concentration of total vanadium in the Stretford process aqueous liquor. The concentration of total vanadium was determined by measuring the catalytic effect it exerts on the rate of oxidation of gallic acid by persulphate in an acid solution. The extent of oxidation of gallic acid is proportional to the concentration of total vanadium. Total vanadium concentration was then determined by measuring the absorbance of the resulting blue colored complex at 415 nm and compared with standard solutions treated in the same way.14,15 2.2.5. pH Value Measurement. The pH values in the Stretford aqueous liquor samples were measured potentiometrically using a pH meter, Mettler Toledo, seven multi with pH cartridge and expert pro electrode Microsep.12 A standard hydrogen electrode or glass electrode with a reference electrode was used and the combination electrode was also used. Certified buffer solutions were used for the calibration. The potential of the solution was measured in millivolts and converted to pH units. Before measuring the pH values in the liquid samples, the pH meter was calibrated using buffer solutions of pH 4.01, 7.00. and 9.21, respectively. The samples were analyzed at a temperature of 40 °C to ensure that there

oxidizing plant equipment and from hydrogen peroxide that will be formed from the reduction−oxidation reactions in the presence of catalysts. In order to better understand the oxidation of NaSCN in Stretford process aqueous liquor, laboratory experiments using Stretford process aqueous liquor containing the V5+ and Na2[ADA] salts were used. The oxidation of NaSCN in Stretford aqueous solutions at a pH of approximately 8.3 using hydrogen peroxide and air was monitored. After the oxidation of NaSCN using hydrogen peroxide and air, the solutions were submitted for the analyses of NaSCN, Na2SO4, Na2S2O3, total alkalinity, total vanadium and Na2[ADA], and pH measurements. After the chemical analyses of the solutions were completed, the resulting solutions were evaporated in order to produce solid samples for analyses using X-ray diffraction (XRD) and X-ray fluorescence (XRF). The XRD and XRF data for the solid samples that will produce during the evaporation of the treated and untreated solutions will confirm the presence of possible sticky sodium based salts19 (sodium sulfate (Na2SO4), sodium bisulphate (NaHSO4), sodium thiosulphate (Na2S2O3), burkeite (Na6(CO3)(SO4)2), and sodium cyanate (NaOCN)) that will be formed during the oxidation of NaSCN in the Stretford process aqueous solutions. The sticky sodium based salts crystals that will be formed in the Stretford process during the oxidation of NaSCN can result in severe blockages of the plant equipment, and subsequently will contaminate the final elemental sulfur product. Gases evolved during the oxidation of NaSCN using hydrogen peroxide and air will be identified by gas chromatography−mass spectrometry (GC-MS).

2. EXPERIMENTAL DETAILS 2.1. Chemicals. Stretford aqueous liquors containing sodium sulfate, sodium thiocyanate, sodium carbonate, sodium hydrogen carbonate, vanadium, and Na2[ADA] species were taken from two South African commercial sulfur recovery plants and used in this research study. The process liquors that were taken from these commercial sulfur recovery plants contained different concentrations of NaSCN and total dissolved salts (TDS) contents. The chemicals that were used in the experimental investigation and chemical analyses are listed in Table 1 below. Also, the chemical purities and suppliers are also given in Table 1. Table 1. Chemical Names, Chemical Purities, and Suppliers of Chemical Species That Were Used in This Study chemical names analytical reagent (AR) NaSCN technical grade, Na2[ADA] powder vanadium pentoxide sodium ammonium vanadate analytical reagent Na2SO4 Na2CO3 anhydrous platinum linea (AR) H2O2 gold lineb (CP) analytical reagent NaOH

purities (%)

suppliers

98.5

Merck

90.0

London Chemicals and Resources LTD Merck Vanchem Vanadium Products (PTY) LTD Sigma Aldrich Ace Chemicals

>99.0 68−75 ≥99.0 ≥99.5 50% V/V ≥99.0

Ace Chemicals Sigma Aldrich

Platinum line: analytically pure qualitysupplied with “warranty certificate”. bGold line: Chemically pure qualitysupplied with “typical analysis”.

a

B

DOI: 10.1021/acs.energyfuels.5b02665 Energy Fuels XXXX, XXX, XXX−XXX

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Figure 1. Stretford aqueous liquor A sample (1) and Stretford aqueous liquor A samples (2−5) with increasing [H2O2]. (a) Solution sample 1: Stretford aqueous liquor A + 0 mol·dm−3 H2O2. (b) Solution sample 2: Stretford aqueous liquor A + 0.83 mol·dm−3 H2O2. (c) Solution sample 3: Stretford aqueous liquor A + 1.66 mol·dm−3 H2O2. (d) Solution sample 4: Stretford aqueous liquor A + 3.32 mol·dm−3 H2O2. (e) Solution sample 5: Stretford aqueous liquor A + 4.98 mol·dm−3 H2O2.

Figure 2. Stretford aqueous liquor B sample (6) and Stretford aqueous liquor B samples (7−10 with increasing [H2O2]. (f) Solution sample 6: Stretford aqueous liquor B + 0 mol·dm−3 H2O2. (g) Solution sample 7: Stretford aqueous liquor B + 0.83 mol·dm−3 H2O2. (h) Solution sample 8: Stretford aqueous liquor B + 1.66 mol·dm−3 H2O2. (i) Solution sample 9: Stretford aqueous liquor B + 3.32 mol·dm−3 H2O2. (j) Solution sample 10: Stretford aqueous liquor B + 4.98 mol·dm−3 H2O2.

fused into a borosilicate disk18) and analyzed by ARL 9800XP Thermo-Scientific XRF spectrometry techniques. 2.2.8. Gas Chromatography−Mass Spectrometry (GC-MS). Gas samples that were taken from the addition of H2O2 to Stretford process liquors experiments were analyzed on an Agilent 7890A gas chromatograph coupled with a 5975C MSD. 2.3. Experimental Procedures. 2.3.1. Safety Precautions in the Laboratory Procedures. The following important safety considerations when adding H2O2 to Stretford liquors were used in this study:

was no crystallization of sodium based salts at low pH values when taking the pH measurements. 2.2.6. X-ray Diffraction (XRD) Analysis of the Solid Samples. Solid samples that were produced from the evaporation experiments without oxidizing sodium thiocyanate (Figures 1 and 2.) were subjected to mineralogical analysis using PANalytical Inc. XRD, with the Rietveld-based X’Pert HighScore Plus Software.16,17 2.2.7. X-ray Fluorescence (XRF) Analysis of the Solid Samples. Liquids were evaporated from the samples without oxidizing NaSCN (Figures 1 and 2) to produce solid samples for the XRF analysis using the fusion method (the solids were

• Suitable personal protective equipment (PPE) was always worn when using H2O2 to oxidize NaSCN to form sulfate salts and poisonous HCN. C

DOI: 10.1021/acs.energyfuels.5b02665 Energy Fuels XXXX, XXX, XXX−XXX

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Table 2. Concentrations of Total Alkalinity, Sodium Sulfate, Sodium Thiocyanate, Total Vanadium, and Na2[ADA] in the Two Working Stretford Aqueous Liquors (i.e., A and B). sodium based salts, total vanadium, and Na2[ADA]

Stretford aqueous liquor A concentration (mol·dm−3)

Stretford aqueous liquor B concentration (mol·dm−3)

total alkalinity Na2SO4 NaSCN total vanadium Na2[ADA]

0.28 0.86 0.93 0.024 0.00078

0.33 0.61 1.90 0.028 0.0012

• H2O2 is a powerful oxidizing agent resulting in highly exothermic reactions. • When hydrogen peroxide is added to aqueous solutions or Stretford aqueous solutions, vigorous, exothermic reactions occur. The experiments must be done in the fume-cupboard. • The reaction takes approximately 1−2 min to proceed after the initial addition of hydrogen peroxide to the respective solutions. • Therefore the addition of hydrogen peroxide to the solutions was done carefully and slowly to avoid possible spillage of the sample during the reactions. • The addition of hydrogen peroxide to the aqueous solutions or to the Stretford aqueous solutions was done in an ice bath as the temperature of the solution increases significantly during these reactions. 2.3.2. Oxidation of NaSCN in Stretford Aqueous Liquor Samples at a pH of 8.3 Using Hydrogen Peroxide. The pH of the Stretford process aqueous solution was approximately 8.3. The experiment was performed in two individual Stretford aqueous solutions with varying concentrations of NaSCN. The oxidation of NaSCN in Stretford aqueous solutions which contained Na2CO3 + NaHCO3 (total alkalinity), Na2SO4, Na2S2O3, NaSCN, vanadium species, and Na2[ADA] was monitored using H2O2 as an oxidizing agent. Table 2 shows the concentrations of the sodium based salts and total vanadium present in the two Stretford aqueous liquors (i.e., A and B) used. The pH values of Stretford aqueous liquors A and B were 8.29 and 8.26, respectively. Approximately 200 mL each of Stretford aqueous liquor A was measured and decanted into each of 5 separate bottles. The same procedure was followed for Stretford aqueous liquor B. Table 3 shows the volumes and concentrations of 50% v/v hydrogen peroxide added to Stretford aqueous liquors A and B. The resulting solutions from Table 3 were placed in an oven at a temperature of 50 °C for an hour to prevent salt crystallization/precipitation prior to NaSCN, Na 2 SO 4 , Na2S2O3, total alkalinity, total vanadium and Na2[ADA] analyses, and pH measurements. 2.3.3. Evaporation of the Aqueous Solutions to Form Solid Samples. The series of aqueous solutions (shown in Table 3) was evaporated in an oven at 105 °C to obtain solids. All resulting solids were prepared and submitted for XRD and XRF analyses. The XRD analysis was done to determine the crystalline phases of sodium based salts present in the solids formed after evaporation of the solutions produced from the oxidation study. The XRF analysis was used to determine the concentrations of the inorganic elements in the solids. 2.3.4. Air Oxidation of NaSCN in Stretford Aqueous Liquor Samples at a pH of 8.3. The oxidation of NaSCN in Stretford aqueous solutions that contain total alkalinity, Na2SO4, NaSCN, Na2S2O3, total vanadium, and Na2[ADA] were monitored using air as an oxidizing agent. The pH of the

Table 3. Volumes and Concentrations of Hydrogen Peroxide That Were Added to the Respective Stretford Aqueous Solutions Containing Different Concentrations of NaSCN

solution IDa

volume (mL) Stretford aqueous solution

A A A A A B B B B B

200 200 200 200 200 200 200 200 200 200

a

[NaSCN] (mol·dm−3) in the Stretford aqueous solution

volume (mL) of H2O2 added to the Stretford aqueous solution

[H2O2] (mol·dm−3) in the Stretford aqueous solution

0.93 0.93 0.93 0.93 0.93 1.90 1.90 1.90 1.90 1.90

0 10 20 40 60 0 10 20 40 60

0 0.83 1.66 3.32 4.98 0 0.83 1.66 3.32 4.98

A = Stretford aqueous liquor A. B = Stretford aqueous liquor B.

solution was approximately 8.3. The experiment was performed in two individual Stretford aqueous solutions with varying concentrations of NaSCN and total dissolved salts. Table 4 shows the concentrations of the various compounds present in the two Stretford aqueous liquors C and D used. The pH values of Stretford aqueous liquors C and D were 8.29 and 8.26 respectively. Approximately 2000 mL of Stretford aqueous liquor C was measured and decanted into each of four separate 5000 mL beakers. The same procedure was followed for Stretford aqueous liquor D. Bubbling of air through the Stretford aqueous liquors C and D was performed for 0, 2, 6, 12, and 24 h. The solutions were bubbled while keeping the temperature between 40 and 50 °C on a hotplate. The samples were taken from the hotplate after the stipulated durations of oxidation with air and were subsequently submitted for the NaSCN, Na2SO4, Na2S2O3, total alkalinity, total vanadium and Na2[ADA] analyses, and pH measurement. 2.3.5. Evolution of Gases during the Oxidation of NaSCN in the Stretford Aqueous Samples Using Hydrogen Peroxide. Gases were evolved during the oxidation of NaSCN in Stretford aqueous solutions using hydrogen peroxide. The gases evolved were subsequently collected using a syringe while adding 3.32 mol·dm−3 H2O2 (40 mL) to a 200 mL Stretford aqueous solution containing total alkalinity, Na2SO4, NaSCN, Na2S2O3, total vanadium, and Na2[ADA]. In order to identify these gases qualitatively, the volatilized gases were subsequently injected onto a GC-MS. A 28 vol. % CO2 standard was also injected into the GC-MS to confirm that carbon dioxide was liberated during the oxidation of NaSCN in Stretford aqueous solutions using hydrogen peroxide. Due to no HCN standard being readily available, the Dräger tube technique was employed to confirm the presence of HCN in the liberated gases from the NaSCN oxidation reaction. The Dräger short-term tubes have proven to D

DOI: 10.1021/acs.energyfuels.5b02665 Energy Fuels XXXX, XXX, XXX−XXX

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Table 4. Concentrations of Total Alkalinity, Na2SO4, NaSCN, Total Vanadium, and Na2[ADA] in the Two Stretford Aqueous Liquors (i.e., C and D). sodium based salts and total vanadium

Stretford aqueous liquor C concentration (mol·dm−3)

Stretford aqueous liquor D concentration (mol·dm−3)

total alkalinity Na2SO4 NaSCN total vanadium Na2[ADA] pH

0.31 0.88 0.99 0.029 0.0012 8.29

0.33 0.57 1.74 0.029 0.00097 8.26

the initial concentration of 0.86 mol·dm−3 Na2SO4 was increased to 1.08 mol·dm−3 after the addition of 0.83 mol· dm−3 H2O2 to Stretford aqueous liquor A. As the concentration of H2O2 in Stretford aqueous liquor A was increased to 4.98 mol·dm−3, the initial concentration of 0.93 mol·dm−3 NaSCN was decreased to 0.00 mol·dm−3 and the initial concentration of 0.86 mol·dm−3 Na2SO4 was subsequently increased to 1.49 mol·dm−3. Other sodium sulfate and sulfate ions that were formed during the addition of H2O2 to the Stretford liquor can react with sodium carbonate and ammonium ions to form burkeite (Na6(CO3)(SO4)2) and mascagnite ((NH4)2SO4 respectively (Tables 6 and 8). At a concentration of 3.32 mol·dm−3 H2O2 complete oxidation of NaSCN to Na2SO4 and other salts (burkeite and magscagnite) was observed in Stretford aqueous liquor A. The percentage oxidation at a concentration of 4.98 mol·dm−3 H2O2 was 100%. This could be attributed to the fact that H2O2 present in excess concentrations facilitates the formation of Na2SO4 at faster reaction rates.19 Due to a noticeable decrease in the pH from approximately 8 to 6, it can be deduced that H2O2 is present in excess concentrations in solutions 4 (Stretford aqueous liquor A + 3.32 mol·dm−3 H2O2) and 5 (Stretford aqueous liquor A + 4.98 mol·dm−3 H2O2) (Figure 3) hence confirming the complete oxidation of NaSCN to Na2SO4 and other sodium based salts (NH4)2SO4, NaHSO4 and Na6(CO3)(SO4)2). In addition, the XRF and XRD results (Tables 5 and 6) for the solid samples that were produced from the solutions of the

be a very reliable and cost-effective method for the measurement of gases.

3. RESULTS AND DISCUSSION 3.1. Oxidation of NaSCN in Stretford Aqueous Liquor Samples at a pH of 8.3 Using Hydrogen Peroxide. 3.1.1. Chemical Analyses of the Stretford Aqueous Liquor A Solutions. The chemical analyses results for the various sodium based salts and pH for Stretford aqueous liquor A are shown in Figure 3. The results indicate that as the concentration of H2O2

Figure 3. Concentrations of sodium based salts and pH values in Stretford aqueous liquor A before and after the addition of H2O2.

in the Stretford aqueous liquor A increased, there was an impact on the total alkalinity concentration, pH values, and the concentration of Na2SO4. The total alkalinity decreased from 0.28 mol·dm−3 in solution 1 (Stretford aqueous liquor A + 0 mol·dm−3 H2O2) to 0.04 mol·dm−3 in solution 5 (Stretford aqueous liquor A + 4.98 mol·dm−3 H2O2) (Figure 3). Hydrogen peroxide reacted with sodium carbonate salts (Na2CO3 and NaHCO3) in solutions 1 and 5 to evolve carbon dioxide gas. As expected, the decrease in total alkalinity concentration in the Stretford aqueous liquor sample impacted the pH values directly, and hence a reduction in pH was observed as the concentration of H2O2 that was added to Stretford aqueous liquor A was increased. As the concentration of H2O2 was increased in the Stretford aqueous liquor solutions, the concentration of NaSCN was subsequently decreased while the concentration of Na2SO4 was increased. This implies that NaSCN in the Stretford aqueous liquor sample was oxidized to form Na2SO4 upon addition of H2O2. The oxidation of thiocyanate by hydrogen peroxide proceeds through an intermediate hypothiocyanite ion.19,20 Depending on the pH values of the solution, this intermediate ion undergoes a series of reactions and is further oxidized to sulfate, ammonia and bicarbonate (HCO3−).19 The initial concentration of 0.93 mol·dm−3 NaSCN in the Stretford aqueous liquor A was decreased to 0.73 mol·dm−3 and

Table 5. XRF Analyses Results for the Solid Samples That Were Formed after Evaporation of the Stretford Aqueous Liquor A Samples sample identificationa mass %

1

2

3

4

5

Fe2O3 MnO Cr2O3 V2O5 TiO2 CaO K2O P2O5 SiO2 Al2O3 MgO Na2O Cl SO3

0.01