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NAG Static Net Acid Generation Procedure

SGS laboratories are staffed by professionals with extensive experience in the minerals sector. We understand why you need to mitigate Acid Rock Drainage (ARD) and can provide you with extensive analytical testing options including the Static Net Acid Generation (NAG) Procedure.

Net acid generation (NAG) testing determines the balance between the acid producing and acid consuming components of tailings/waste rock samples. NAG results provide the acid rock drainage characteristics based on the complete oxidation of the sample’s sulphide content (as well as ferrous iron from siderite dissolution). Acid that is produced by oxidation is consumed by carbonates and/or other acid consuming components of the material. The pH of the solution is measured (NAG pH). The acid remaining after the reaction is titrated with standardised NaOH to determine the net acid generated.

Samples that have high sulphide contents may need more than a single aliquot of hydrogen peroxide to ensure complete oxidation of all the sulphides present. At the end of each stage, the sample is filtered to separate the solids from the NAG solution. The NAG solution is then assayed for pH and acidity, while the solids are recovered for repeat oxidation using another aliquot of hydrogen peroxide. The total NAG capacity of the sample is determined by summing the individual acid capacities from each stage.

SGS provides you with the systematic characterisation of the acid producing potential of your ores. Partner with us to get confidence in your ARD programme and prevent long-term environmental liabilities.

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