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Leaching Methods

Unsure about what leaching methods are available to you or which are most appropriate to your requirements? Let us help.

What Leaching Methods are available to me?
There are four main types of leaching carried out at Chemex, each having their own particular characteristics and applications. The methods available are DIN leaching, TCLP leaching, EA/NRA leaching and the leaching methods applicable to the Environment Agencies Waste Acceptance Criteria.

DIN Leaching
This is derived from the Deutsches Institut Für Normung e.V  (DIN), German Standard Method for the Examination of Water, Wastewater and Sludge, DIN 38414 part 4, Oct 1994. The method is intended to represent materials coming into contact with fresh rain water or ground water. The leaching procedure is carried out by adding to the required sample weight, a volume of deionised water to give a 10:1 ratio of water to dry soil. This is then tumbled at a rate of ~0.5 revolutions per minute at room temperature for 24 hours. The resultant leachant can then be analysed for any parameters desired.

TCLP Leaching
Derived from the USEPA Method 1311 TCLP (Toxicity Characteristic Leaching Procedure) is actually a leaching procedure accompanied by a specific analytical suite. Many clients, however, prefer to combine the TCLP leaching with their own specific list of analytical parameters. The leaching procedure uses an acidic buffer, with the pH of this buffer dependent on the initial pH of the sample. The sample is leached at a liquid to solid ratio of 20:1 and tumbled for 18hours.

The TCLP leaching procedure is principally designed to determine the mobility of both organic and inorganic analytes present in liquid, solid and multiphasic wastes. The leaching procedure is intended to simulate the conditions present in landfill.

EA Leaching
This is also commonly referred to as NRA leaching and is derived from the EA Recommended Test (R&D note 301). The leaching fluid used in this method is intended to represent materials coming into contact with acid rain. Leaching is carried out by adding to the required sample weight, a volume of water left overnight to attain carbonate equilibrium (pH ~ 5.6) to give a 10:1 ratio of water to soil. The bottle is tumbled at a rate of ~0.5 revolutions per minute at room temperature for 24 hours. The resultant leachant can then be analysed for any parameters desired.

BS EN 12457
These leaching methods are actually a set of related methods that are generally linked to the Environment Agencies Waste Acceptance Criteria for Landfill Disposal, but can, as many clients desire, be performed and tested for any analytical parameters of interest. For a full description of the leaching procedures and associated analytical suites see the WAC Testing section.

Zero Headspace Extraction
Zero headspace extraction can be performed when volatile determinants are required. This facility can be applied to any of the aforementioned leaching procedures with the appropriate ratio of sample to leachate and tumbling times, although it was originally associated with the TCLP leaching procedure.

Which method?
The particular leaching method that you choose will depend upon a number of factors. These are likely to include specific regulatory requirements associated for disposal of waste, for example the Environment Agencies Waste Acceptance Criteria. The conditions that you are trying to simulate will also affect your decision of leaching method. We can help you to make a decision on the most appropriate methods to provide you with the results you need for your personal needs.

Author: Julian Froment

If you need to determine the leachability of particular parameters from your samples for whatever purpose and are unsure as to what method is most appropriate, let us aid you in making an informed decision.

Chemex have been involved in a number of long term projects designed to classify and categorise the leachability of individual clients products, designing bespoke leaching programmes to suit particular needs.

Chemex also work closely with a number of waste contractors and landfill operators to ensure that correct disposal of hazardous wastes occurs.