Size reduction has a definite effect on leaching
In batch leaching, an end over end tumbler or roller table is the preferred agitation device as other types of agitation devices lead to too much size reduction (wrist shaker) of the test material or incomplete exposure (shaker table) to leachant.
Performing a percolation test with alkaline flue gas treatment waste and similar materials with self-cementing properties may lead to disruption of the column apparatus when a peristaltic pump is applied for controlled leachate flow. As the material start to cement the net flow through the column decreases and pressure builds up. A solution to the problem is to pre-wet the material, thus allowing the cementation reaction to complete , then crush the materials and place in a column for percolation.
When in the leaching tests with long contact times (percolation and monolith leaching) eluates are exposed to the surrounding atmosphere there is a substantial chance that the pH in resulting alkaline eluates is affected by uptake of CO2 from the laboratory atmosphere. This effect can be very large when carbonation experiments or other CO2 producing activities in the laboratory environment take place. The collection bottles should be closed off as much as possible and verification of the magnitude of the effect can be tested by placing a similar collection vessel filled with solution adjusted to pH 11 for the same period of the eluate collection cycles and measuring pH at regular intervals.
