Introduction: Cyanidation is a hydrometallurgical process used to extract gold and silver from low grade ores by converting them to water soluble metal cyanide complexes for recovery by precipitation on zinc dust, activated carbon, or ion exchange resins. Measurement and control of cyanide concentration has a major impact on process efficiency and operating cost. Accurately measuring cyanide available for leaching ores containing copper and metallic sulfides is problematic. Titration methods commonly used for process control in gold leaching poorly estimate the amount of cyanide when copper is present. Other reaction products including thiocyanate, nitrate, nitrite, ammonia, and sulfur (IV) oxides interfere with most cyanide analysis methods.
Summary: The CNSolution 9310 On-line Cyanide Analyzer is designed to measure and control cyanide used in hydrometallurgical leaching of gold and silver from ores. Most gold occurs at very low concentrations in ores: less than 10 grams/ton (0.001%). Hydrometallurgical extraction is the only economically viable method of extracting gold from such ore. Leaching solutions typically contain cyanide in concentrations ranging from 50 ppm to 2,000 ppm.
Introduction: A new total cyanide method, ASTM D 7284-08, determines cyanide using traditional scaled down distillations and replaces pyridine barbituric acid colorimetry with gas-diffusion amperometry as the determinative step. The use of flow injection with gas diffusion and amperometric detection is also an optional determinative step utilized in ASTM D 2036-06 Test Method A. EPA already recognizes gas diffusion amperometry in two methods (OIA 1677 and ASTM D6888-04) for the analysis of available cyanide in CWA reporting and “free” cyanide under the SDWA. The method utilizes the same distillation currently performed in EPA 335.4 and/or LACHAT 10-204-00-1-X.
On March 12, 2007 (72 FR 11200) (1), the U.S. Environmental Protection Agency (EPA) amended the analytical regulations of 40 CFR Part 136 for wastewater. A significant change was the addition of required cyanide preservation and sample pretreatment procedures to the footnotes of Table II, Required Containers, Preservation Techniques, and Holding Times. The preservation procedures included a consolidation of procedures that were present in existing EPA–approved cyanide methods and were based on knowledge available at the time. The EPA has received many comments concerning these cyanide footnotes. The commentary has centered on difficulties associated with collecting samples in the field, and cyanide formation as a result of high pH sample preservation procedures.
In this third edition of the Cyanide Analysis Guide, OI Analytical provides updated information on collecting and preserving samples, analytical interferences, and new ASTM and USEPA analytical methods.
The acute toxicity and wide spread industrial usage of cyanide makes environmental testing critically important. Intentional contamination of drinking water or food products with cyanide is also a potential Homeland Security threat.
Cyanide Analysis – Reducing Laboratory Operating Costs without Compromising Data Quality or Regulatory Compliance
The first generation of U.S. EPA cyanide analysis methods for Cyanides Amenable to Chlorination ([CATC] 335.1) and Total Cyanide (335.2) date back to the 1970s. The acid distillation step and colorimetric chemistries employed in these methods are susceptible to matrix interferences and are known to cause either negative or positive analytical biases. In fact, the U.S. EPA Solutions to Analytical Chemistry Problems with Clean Water Act Methods (“Pumpkin Guide”) states; “Next to oil and grease, cyanide is the pollutant for which the most matrix interferences have been reported to EPA.” The preliminary distillation step in these methods is also labor-intensive, increases the cost per analysis, and has a significantly lower sample throughput rate than nondistillation methods.
Cyanide Analysis of Wastewater Samples from FCC and Hydrocracking Operations
Fluid catalytic cracking (FCC) is a major unit operation in refineries around the world. FCC is used to convert lowvalue, high molecular weight feedstocks such as shale oil, tar sands oil, and coker gas oils into lighter, high-value products by “cracking” C-C bonds. These feedstocks may contain high levels of organic nitrogen compounds such as indole, carbozole, pyridine, and quinoline (Figure 1), which form ammonia and cyanide in the reactor of FCC units. The nitrogen content of crude petroleums is generally in the range of 0.1 – 0.9%, however, some crude may contain up to 2% nitrogen. The more asphaltic the oil the higher the nitrogen content.
Hydrocracking is a thermal process (>350 °C) in which hydrogenation is performed concurrently with catalytic cracking Hydrocracking converts high-boiling feedstocks to lower boiling products by cracking the hydrocarbons and hydrogenating the resulting unsaturated reaction products. Polycyclic aromatics are partially hydrogenated before the aromatic nucleus is cracked. Sulfur and nitrogen atoms are converted into hydrogen sulfide, ammonia,
Hydrocracking reactions are catalyzed by dual-function catalysts. Cracking is performed by silica-alumina (or zeolite) catalysts, and hydrogenation by platinum or nickel catalysts.
From the Environmental Technology May-June Volume 23: New On-line Cyanide Analyser to Help Gold Milling Operations
Xylem’s 01 Analytical (USA) announce the launch of a new on-line cyanide analyser for gold milling applications. The new CNSolution 9310, when incorporated into the gold milling process, can facilitate significant cost savings for mill operators.
Most gold occurs at very low concentrations in ores; less than 1Ograms/ton (0.001 %). Hydrometallurgical extraction using cyanide is the only economically viable method of recovering gold from such low-grade ore. Leaching solutions typically contain cyanide in concentrations from 50 to 2,000ppm, and purchasing, transporting, handling and detoxifying cyanide is a major operating expense for gold mills.
Accurately measuring cyanide available for leaching gold from ores containing copper and metallic sulphides is problematic, since copper complexes with cyanide and reduces the amount of cyanide available for leaching.To complicate the process further, titration methods commonly used for process control do a poor job of measuring available cyanide when copper is present. An excessive amount of cyanide must be added to the leaching solution to compensate for this measurement inaccuracy and to ensure a sufficient concentration is present for efficient extraction of gold.
Guidelines Establishing Test Procedures for the Analysis of Pollutants; Available Cyanide in Water
SUMMARY: This final rule amends the “Guidelines Establishing Test Procedures for the Analysis of Pollutants” under section 304(h) of the Clean Water Act by adding Method OIA–1677: Available Cyanide by Flow Injection, Ligand Exchange, and Amperometry (hereafter Method OIA– 1677).
The U.S. EPA has issued a comprehensive set of cyanide analysis methods based on gas-diffusion amperometry for Safe Water Drinking Act and Clean Water Act compliance testing and reporting. These employ ligand exchange or UV-digestion under acidic conditions to dissociate metal-cyanide complexes and form hydrogen cyanide gas which diffuses across a membrane into a base receptor solution where it converts back to CN- and is measured amperometrically.
The situation is not so clear cut for cyanide analysis of soil and sediment samples. There are currently no U.S. EPA approved total cyanide analysis methods written specifically for soil. SW-846 9013A Extraction Procedure for Solids and Oils (Appendix to Method 9010) is the closest to a total cyanide procedure for solid and soil samples.
Flow injection analysis (FIA) with gas diffusion separation and amperometric detection has been demonstrated to be the most effective way for automating the chemical analysis of cyanide. In 1999, the USEPA approved Method OIA-1677 for NPDES monitoring of available cyanide using ligand displacement and fl ow injection analysis with amperometric detection as an alternative to the problematic cyanide-amenableto- chlorination (CATC) procedure. Using similar technology, ASTM Committee D19 on Water developed ASTM Standard Test Method D6888. ASTM Committee D19 has also developed a new method to measure aquatic free cyanide and is currently working on amperometric methods for determination of total cyanide using UV digestion or manual distillation to dissociate the cyanide metal complexes. ASTM Committee D22 on Air Quality is currently reviewing new methodology for determination of hydrogen cyanide in air and combustion products.
This poster highlights methods using current technology and summarizes improvements in fl ow injection analysis with amperometric detection using the CNSolution FS 3100 from OI Analytical. The results for sample evaluation are reviewed. The advantages of using new methods employing fl ow injection analysis with amperometric detection for cyanide analysis are also discussed.
Hydrogen cyanide (HCN) is commonly present in refinery gases. Because of its low volatility and, to some extent, its acidity, it travels through amine and sour water systems in an unusual and, heretofore, poorly understood way. To shine some light on this subject and perhaps develop a worthy solution, a simulation study has been performed with HCN removal being treated on a mass transfer rate basis. This will help develop an understanding of how HCN distributes in the sour water system and where it might form an internal recycle within a tower.
Method comparison studies of two different methods for the analysis of weak acid dissociable (WAD) cyanide revealed analytical flaws and/or matrix interference problems with both procedures. EPA “draft” method 1677 using a Perstorp 3202CNanalyzer was compared to Standard Method 4500 CN I. It was discovered that the Perstorp analyzer produced more precise and more accurate results once appropriate and necessary procedural steps from the EPA draft method were modified. Comparison of these two methods, was based on “real world” samples collected from a mine-tailing solution. The mine-tailing solution contained high concentrations of cyanide and metals. Inconsistencies in method procedures were traced to sulfide interferences and high concentrations of WAD metals. Conclusions were based upon a large sample base collected from a mine site over a 90-day period.
Distillation-based methods for determination of operationally defined cyanide have very limited application because of the serious interferences from the species likely to be found in most of the cyanide containing effluents. To the best of our knowledge, there are no reliable spot tests for detecting the presence of some of these interfering species. Hence, distillation-based methods should only be used for cyanide determination of samples that have well defined and constant matrix that do not contain interfering species. For example, distillationbased methods should not be used for cyanide determination of samples originating from precious metals cyanidation effluents, water treatment plants, petroleum refineries, coke producing plants, elemental phosphorous producing facilities, etc. In addition, these methods should not be used to monitor cyanide detoxification processes because cyanide and oxidant(s) (sulfite, thiosulfate, peroxide, etc.) can coexist in solution. The high temperature during distillation shifts the equilibrium towards the formation of the oxidation products (OCNand/ or SCN-, etc.), which can result in serious underestimation of cyanide levels that are actually present in the original sample.
On July 7, 1998, the U.S. Environmental Protection Agency (USEPA) proposed amending the Guidelines Establishing Test Procedures for the Analysis of Pollutants under Section 304(h) of the Clean Water Act by adding Method OIA-1677: Available Cyanide by Flow Injection, Ligand Exchange, and Amperometry. This method employs flow injection analysis (FIA) and was developed and validated by ALPKEM™ (purchased by OI Analytical in 1996) in cooperation with the University of Nevada – Reno Mackay School of Mines. According to the Federal Register notice, the USEPA considers Method OIA-1677 to be “a significant addition to the suite of analytical testing procedures for available cyanide because it has greater specificity for cyanide in matrices where interferences have been encountered using currently approved methods, has improved precision and accuracy compared to currently approved CATC cyanide methods, measures available cyanide at lower concentrations, offers improved analyst safety, shortens sample analysis time, and reduces laboratory waste.”
OI Analytical has released an improved reference electrode for use in CNSolution™ amperometric detectors. This new electrode (P/N 325348) is a one-piece design with the Ag/AgCl junction inside a sealed housing filled with 3M-KCl gel. Interaction with working and auxiliary electrodes occurs through a low-flow frit.
This one-piece reference electrode is compatible with the flow cells of CNSolution 3100 and 3000 amperometric detectors. It is available as a convenient direct replacement to the previous design that required filling with a reference solution and reassembly with an o-ring to seal the amperometric membrane inside the cell.
Cyanide analysis methods attempt to measure groups of compounds with similar chemical characteristics and report them as a single value. Various techniques are employed to separate specific types of cyanide complexes from each other and potential matrix interferences to achieve accurate quantitation.
The regulated community is presented with an array of conflicting definitions of cyanide species, which leads to misunderstandings about what the various techniques and methods actually measure. In fact, the U.S. EPA Solutions to Analytical Chemistry Problems with Clean Water Act Methods (1), or “Pumpkin Guide”, states; “Next to oil and grease, cyanide is the pollutant for which the most matrix interferences have been reported to EPA.”
This study presents an overview and assessment of the most commonly used cyanide analysis methods including cyanide species measured, analytical techniques employed, potential matrix interferences, and final determinative steps.
Introduction: Before the introduction of the visible spectrophotometer in 1933, automation in most laboratories consisted of a vacuum filtration apparatus, buret dispensers, wooden racks of test tubes, and a visual colorimeter. Analysis methods emphasized volumetric and gravimetric techniques that did not require instrumentation. The advent of the visible spectrometer made certain chemical determinations easier and faster, but sample preparation prior to color measurement was laborintensive and time-consuming. Despite its drawbacks, manual colorimetric analysis is still used today and has value for laboratories performing a few determinations per day or a large variety of determinations on a few samples.
This document includes information on:
Manual Colorimetric Analysis
Segmented Flow Analysis
Flow Injection Analysis
Comparing SFA and FIA
Limitations of Automated Wet Chemical Methods
Grouping of Test Parameters by Matrix and Holding Time for Maximum Efficiency
Method Detection Limits and Maximum Contaminant Levels
Accurate Measurement of Cyanide in Leaching Solutions
Accurately measuring cyanide available for leaching precious metal ores containing copper and metallic sulfides is problematic. Copper complexes with cyanide reducing the cyanide available for leaching. Titration methods commonly used for process control in gold leaching poorly estimate the amount of cyanide available when copper is present. Other reaction products, including thiocyanate, nitrate, nitrite, ammonia, and sulfur (IV) oxides interfere with most cyanide analysis methods.
The OI Analytical CNSolution™ 9310 On-line Cyanide Analyzer is designed to measure available cyanide in precious metal leaching solutions by U.S. EPA Method OIA-1677 and ASTM D 6888-09. The gas diffusion amperometry technique in these methods has been demonstrated to be free of interferences from copper and metallic sulfides in precious metal leaching solutions.
On-line monitoring with the CNSolution 9310 enables gold and silver mills to reduce cyanide consumption and operating costs associated with the cyanidation process.
The CNSolution 9310 supports measurement and control of cyanide in multiple cyanidation unit operations including:
OI Analytical has been a leader in cyanide analysis instrumentation since 1990. Research supported by OI has made significant contributions to the science of cyanide analysis and the reliability of cyanide testing methods.
OI Analytical CNSolution Cyanide Analyzers are configurable to support virtually all applications and regulatory methods. Four different CNSolution system configurations are described in this article. These configurations are based upon the analysis technique and detection method each is equipped to perform.
A compact, modular design allows CNSolution Cyanide Analyzers to be configured for virtually all applications and regulatory methods. The modular design also provides users flexibility to add an additional analysis channel to any of the single channel CNSolution analyzer configurations listed below:
CNSolution – Available Cyanide Analyzer
CNSolution – Total Cyanide Analyzer
CNSolution – A/P Dual Channel Cyanide Analyzer
CNSolution – Post-Distillation Total Cyanide Analyzer
Introduction: OI Analytical introduced the CNSolution FS 3100 flow injection analysis system (Figure 1) at Pittcon 2005. Following the conference, the FS 3100 system was installed for testing in an environmental analytical laboratory at Bayer MaterialScience LLC, Pittsburgh, PA. This application note presents the test report, which shows the exceptional quality of typical data that can be acquired on this improved FS 3100 flow injection analysis system for USEPA Method OIA-1677, ASTM D6888-04, and the new FIA / amperometry methods that are currently being standardized at the ASTM.
This document includes:
OI Analytical CNSolution™ FS3100 Beta Test Report
Methods Evaluated: Available Cyanide, Aquatic Free Cyanide, Total Cyanide and Hydrogen Cyanide Present or Generated During Fires
Cyanide Concentration Changes in Environmental Water Samples as a Function of Sample Preservation, and Holding Time
Most cyanide analysis sampling protocols specify preservation of samples at a pH of 12 or higher. Sample preservation is intended to minimize changes in analyte concentration to allow sample storage for up to 14 days prior to analysis. The source of a water sample, sample pretreatment, and the presence of possible matrix interferences must also be considered in determining the appropriate sampling and preservation procedure to avoid inadvertent formation or destruction of cyanide species.
Oxidation of cyanide by ozone in basic aqueous solution was studied in the absence and presence of copper and iron. Free cyanide was oxidized via a fast reaction under mass-transfer-limited conditions. Copper catalyzed the oxidation of cyanide further by entering into an oxidation-reduction reaction. Oxidation of cyanide consumed equal moles of ozone and produced equal moles of cyanate. Upon prolonged ozonation, cyanate was converted to carbon dioxide. Complexation of cyanide with iron hindered the oxidation reaction. Under the experimental conditions, oxidation of each mole of iron-complexed cyanide to carbon dioxide required the consumption of more than 30 mol of ozone. Cyanate was not detected during ozonation of iron-cyanide complex.
Most standard and other analytical procedures tor the determination for cyanide suffer from sulfide interferences. As sulfide and cyanide co-exist in many ‘real world’ samples, this presents a significant problem. The standard procedure for removal of sulfide is its precipitation with a lead salt. However, lower cyanide recoveries are often obtained if this procedure is performed improperly. In this paper, the chemistry of the sulfide interferences in cyanide determination methods is explained and procedures are suggested tor alleviating the problem.
Problems Associated with Using Current EPA Approved Total Cyanide Analytical Methods for Determining Municipal Wastewater Treatment Plant NPDES Permit Compliance by Ben D. Giudice, M.S., Brant Jorgenson, Michael Bryan, Ph.D.
Many municipal wastewater discharges currently exceed total cyanide (CN) effluent limitations when based on analytical results from standard EPA methods. The approved EPA methods used to measure CN in wastewater effluent are prone to numerous interferences that are unpredictable and difficult to mitigate. Substantial evidence indicates that these analytical problems are causing many current CN compliance issues, rather than actual high CN concentrations in the treated effluent. The preservative NaOH is required to be added to all samples that cannot be analyzed in less than 15 minutes, and NaOH is itself a proven interference for which there is no specific mitigation technique. Substantial evidence suggests NaOH addition may be unnecessary to maintain sample integrity over typical hold-times prior to analysis. Based on this information, CN measurements made under the current paradigm are likely inaccurate and produce unreliable information for determining NPDES permit compliance.
It is obvious that the proposed method has significant advantages over the standard approved methods available for determining the free cyanides levels. Some characteristics and/or advantages of the FIILE method are summarized below:
(1) Complete cyanide recoveries from all metal cyano complexes that produce free cyanides.
(2)Cyanide recoveries are not concentration dependent throughout dynamic range of the method (1 ug/L-5 ug/mL).
The first generation of U.S. EPA cyanide analysis methods from the 1970s employ an acid distillation sample pretreatment step to dissociate cyanide from metal-cyanide complexes and separate cyanide from the matrix. Acid distillation is known to cause either negative or positive analytical biases depending upon the composition of the sample matrix being tested. In fact, the U. S. EPA Solutions to Analytical Chemistry Problems with Clean Water and Methods(1) (“Pumpkin Guide”) notes; “Next to oil and grease, cyanide is the pollutant for which the most matrix interferences have been reported.”
ASTM D 7511-09e2 uses narrow-band, low- watt UV irradiation to decompose metal cyanide complexes in samples at ambient temperature in a continuously flowing acidic stream. Reducing and complexing reagents, combined with ambient temperature UV digestion minimize the formation of matrix interferences. Elimination of the sample distillation step enables measurement of cyanide at lower concentrations with improved precision.
ASTM D 7511-09e2 defines design and performance characteristics a flow injection analysis (FIA) instrument should possess to perform the method. Among the design features needed for this in-line UV digestion, gasdiffusion amperometry method are a UV digestion module with a 312-nm lamp, a gas diffusion manifold with a hydrophobic membrane, an amperometric detector equipped with a silver working electrode, an AgCl reference electrode, and a Pt or stainless steel counter electrode.
The CNSolution™ Cyanide Analyzer is a compact, modular system for performing flow injection cyanide analysis on drinking water samples and wastewater samples from mining, metal plating, and other industrial operations. The CNSolution consists of a 90 position random access X-Y-Z autosampler, a multi-channel precision pump, an electrically actuated sample injection valve, a VersaChem reaction manifold, and an amperometric detector.
Introduction: Total Kjeldahl Nitrogen (TKN) is the U.S. EPA approved parameter used to measure organic nitrogen and
ammonia. The TKN content of influent municipal wastewater is typically between 35 and 60 mg/L. Organic nitrogen compounds in wastewater undergo microbial conversion to NH3 and ammonium ion NH+4. Ammonium ion is the first inorganic nitrogen species produced during biological wastewater treatment.(1) Nitrification is a two step biological process used to remove ammonium in wastewater. The bacterium Nitrosomonas converts ammonium to nitrite (NO-2). The bacterium Nitrobacter converts nitrite to nitrate (NO-3).
A denitrification process is used to reduce the nitrate generated in the preceding steps to nitrogen gas. The
NPDES effluent limit for ammonium-nitrogen (NH+4 – N) can range from 0.1 to 1.0 mg/L and the limit for nitratenitrogen (NO-3 – N) from 3-10 mg/L.
Description: The Flow Solution® FS 3100 Automated Chemistry Analyzer is a modular system for performing continuous fl ow analysis methods on water samples, soil, or plant extracts and digests using FIA or SFA techniques. The FS 3100 consists of an X-Y-Z autosampler (90 or 360 position), multi-channel precision pump, electrically-actuated
sample injection valve, VersaChem Multi-Test Manifold™, and Expanded Range™ photometric or amperometric detector.
The FS 3100 supports two channels for FIA methods and three channels for SFA methods, minimizing the time involved in changing chemistries for different analytes.
Introduction: Along with carbon, nitrogen and phosphorus containing (N/P) compounds are the most important nutrients found in fresh and natural waters, directly influencing algal and bacterial growths. Indirectly, the eutrophic effects of compounds containing these analytes can profoundly impact organisms within the ecosystems in which they are found. Complete and accurate measurements of N/P–compounds as collectives are an increasingly important component of nutrient monitoring and management programs.
Introduction: Recent increases in demand for soil testing and plant analyses are driving nutrient management regulations and associated requirements for environmental monitoring. The benefits of regular environmental
examination are easily recognizable to the agricultural industry. A program of soil and plant analyses at defined intervals can eliminate unnecessary expenditures on fertilizers by preventing excessive plant nutrient loss to surface and groundwater runoffs.
Introduction: A high proportion of the workload in environmental laboratories involves analysis of total phosphorous (TP) and total nitrogen (TN) in water samples for Clean Water Act compliance reporting. At the present time, these analyses must be performed using manual or semi-automated methods as there are no U.S. EPA-approved automated methods.
Continuous Flow Analysis of ppb-Level Total Phosphorus in Natural Waters Following Manual Persulfate Digests as an Alternative to Kjeldahl Methodologies
Introduction: The influx of nutrient pollutants from agriculture and other human activities is one of the major factors causing impairment of surface waters within the U.S. Excess levels of phosphorus can cause algal blooms and eutrophication of natural water ecosystems. U.S. Environmental Protection Agency (USEPA) regulations call for states to develop nutrient water quality standards for lakes, rivers, wetlands, estuaries, and coastal waters.
Determination of Total Recoverable Phenolics in Waters at sub-ppb Levels by In-Line Distillation and Injection Segmented Flow Analysis (iSFA)
Introduction: Phenolic compounds are naturally occurring and man-made chemicals found in natural waters, domestic and industrial wastewater effluents, and drinking water. Phenols are high toxicity persistent pollutants, many of which have low taste and odor thresholds. Chlorination of water for disinfection purposes is known to produce chlorophenols as byproducts of the process.
This document contains a list of maintenance items to perform at least as often as recommended for each item. Good Laboratory Practices (GLPs) suggest all instrument maintenance be recorded in an instrument maintenance log book.