Effects of sorption on the biodegradation of 2-methylpyridine in aqueous suspensions of reference clay minerals

The effects of sorption on the bioavailability of 2-methylpyridine (2-MP) w ere investigated by determining the biodegradation of 2-MP by an Arthrobact er sp. in aqueous suspensions of reference clay minerals and a synthetic ca tion exchange resin. Adsorption of 2-MP on kaolinite, illite, hectorite, mo ntmorillonite, and Dowex(R) was determined by the batch equilibrium method. In general, adsorption of 2-MP was positively correlated with the cation e xchange capacity of the sorbent, suggesting that sorption of 2-MP on clay m inerals occurs through a cation exchange reaction via the 2-methylpyridiniu m ion. The biodegradation of 2-MP was most rapid in the kaolinite suspensio ns, followed by no clay > illite much greater than Dowex > hectorite/montmo rillonite. With the exception of kaolinite, adsorption of 2-MP on clay mine rals and Dowex reduced the rate of biodegradation. The degree of attenuatio n was positively correlated with the fraction of 2-MP sorbed, suggesting th at sorbed 2-MP was not directly available for degradation. Desorption was n ot rate limiting in suspensions containing hectorite, montmorillonite, or D owex; however, desorption may have become limiting in the kaolinite and ill ite suspensions. The results of this study clearly indicate that adsorption can directly affect the degradation of 2-MP in complex mineral systems.