Uptake of trivalent chromium from aqueous solutions by xanthate pine bark: Characterization, batch and column studies

In this study, the performance of chemically modified pine bark for removal of Cr(III) from solutions was investigated. Initially, several chemicals were tested (NaOH, C5H9NO4, H3PO2 and CS2). The xanthate pine bark (XPB) obtained with CS2, was screened as the best adsorbent and thus, it was characterized in respect to morphological and textural properties. Sulfur groups after xanthation reaction were identified on XPB by FTIR and EDS spectroscopies. Equilibrium isotherm and kinetics were determined. The equilibrium data were well described by the Langmuir isotherm allowing to calculate the maximum adsorption capacity (56.5 mg/g). The kinetics is fast and follows a pseudo-second order model. Furthermore, an ion-exchange sorption mechanism between Cr(III) and Na+ was proposed. Among the desorbing agents tested, the best results were achieved with 2.0 M H2SO4. Moreover, in the column tests, a reduction on the breakthrough time and the stoichiometric time from 36.5 and 22.8%, respectively, was observed, when the feed concentration increased from 230 to 500 mg/L. The breakthrough curves were well modeled by Bohard-Adams, Thomas or Yoon-Nelson equations. Globally, XPB revealed to be a promising adsorbent for uptake Cr(III). The scale-up design and the economic assessment indicated potential applicability for the treatment of real effluents.