Specific surface area testing

Specific surface area testing was measured by the methylene blue dye drop procedure outlined in Santamarina et al. (2002). The methylene blue solution was prepared by mixing 1.0 g of dry powder with 200 mL of deionized water. The ash suspension was prepared by mixing 10 g of oven-dry ash with 30 mL of deionized water. The methylene blue solution as added to the ash suspension in 0.5 mL increments, and for each addition of MB, the ash suspension was mixed for 1 min. Then, a small drop was taken from the suspension and placed on filter paper P5. If the unabsorbed methylene blue formed a permanent light blue halo around the ash aggregate spot, the “end point” has been reached (i.e., the MB has replaced cations in the double layer and coated all the mineral surfaces). The processes was repeated until the "end point" was reached, and the specific surface area was determined.