Cation exchange in clays and mudrocks by methylene blue

Abstract

The nature of methylene blue (hydrochloride) adsorption is reviewed because the dye has recently been adopted for determining the presence of clay in quarry aggregates. Although it is demonstrated that methylene blue is not an ideal exchange reagent, details are given for overcoming most of the shortcomings, with particular reference to the aggregates test. It is demonstrated that methylene blue commonly underestimates the cation exchange capacity (CEC) of untreated expandable smectites. In contrast, it provides a fair reflection of the change in ratio of 7 Å/10 Å clay minerals in British mudrocks and overconsolidated clays. Plasticity indices of the latter show a high level of positive correlation with measured CEC.

Two-step kinetic study on the adsorption and desorption of reactive dyes at cationic polymer/bentonite

“…The cation exchange capacity (CEC) of the clay, measured by the methylene blue method [23], was 700 mmol/kg. The cationic polyelectrolyte polyepicholorohydrin-dimethylamine (EPI-DMA) was produced by Bin Zhou Chemical Co. (Shandong, China), which has a viscosity of 400 mPa/s, and a cationic degree of 3.6 mmol/g.…”

Adsorption of Acid Blue 193 from aqueous solutions onto DEDMA-sepiolite

“…It was crushed, ground, sieved through a 63 m sieve, and dried at 110 • C in an oven for 2 h prior to use. The cation exchange capacity (CEC) and surface area determined by the methylene blue method [22] were 299.4 mmol kg −1 and 234.3 m 2 g −1 , respectively. …”

Adsorption of Acid Red 57 from aqueous solutions onto surfactant-modified sepiolite

“…It was crushed, ground by a miller and sieved through a 63 m sieve and dried at 110 • C in oven for 2 h before use. Sepiolite was characterized with respect to cation exchange capacity (CEC) and the surface area by methylene blue method [21,22]. The CEC and surface area of sepiolite were 544.3 mmol kg −1 and 426.0 m 2 g −1 , respectively.…”