How to study Cr(VI) biosorption: Use of fermentation waste for detoxifying Cr(VI) in aqueous solution

For the last fewdecades,many researchers have tested various biomaterials as biosorbent for Cr(VI) removal from aqueous solution. Unfortunately, however, they have misunderstood the Cr(VI) biosorption by biomaterials; they have used common kinetic and/or equilibrium models based on ‘anionic adsorption’ mechanism in order to evaluate the Cr(VI) removal from aqueous solution. In this study, a new efficient biomass, the fermentation waste of Corynebacterium glutamicum, capable of detoxifying Cr(VI) was used as a model biomass to study the Cr(VI) biosorption by biomaterials. To analyze both Cr(VI) and total Cr in aqueous solution, colorimetric method combined with excess potassium permanganate was used. X-ray photoelectron spectroscope was also used to ascertain the oxidation state of chromium bound on the biomass. These analytical methods showed that the removal mechanism of Cr(VI) by the fermentation waste was a reduction reaction of Cr(VI) to Cr(III). Thus, kinetic and equilibrium models based on the ‘reduction’ mechanism were used to describe Cr(VI) and total Cr behaviors in aqueous solution.