Abstract

The effects of sorption on the bioavailability of 2‐methylpyridine (2‐MP) were investigated by determining the biodegradation of 2‐MP by an Arthrobacter sp. in aqueous suspensions of reference clay minerals and a synthetic cation exchange resin. Adsorption of 2‐MP on kaolinite, illite, hectorite, montmorillonite, and Dowex® was determined by the batch equilibrium method. In general, adsorption of 2‐MP was positively correlated with the cation exchange capacity of the sorbent, suggesting that sorption of 2‐MP on clay minerals occurs through a cation exchange reaction via the 2‐methylpyridinium ion. The biodegradation of 2‐MP was most rapid in the kaolinite suspensions, followed by no clay > illite ≫ Dowex > hectorite/montmorillonite. With the exception of kaolinite, adsorption of 2‐MP on clay minerals and Dowex reduced the rate of biodegradation. The degree of attenuation was positively correlated with the fraction of 2‐MP sorbed, suggesting that sorbed 2‐MP was not directly available for degradation. Desorption was not rate limiting in suspensions containing hectorite, montmorillonite, or Dowex; however, desorption may have become limiting in the kaolinite and illite suspensions. The results of this study clearly indicate that adsorption can directly affect the degradation of 2‐MP in complex mineral systems.

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