Hexavalent chromium interaction with chitosan

Abstract

SynopsisChitosan prepared from fresh water crab shells was used for hexavalent chromium removal. Kinetic studies indicated a rapid removal of chromium from aqueous solutions. The first-order rate constant for chromium removal was calculated to be 1.92 h-I. Sorption isothermal data could be interpreted by the Langmuir relationship. Drastic decrease in chromium removal was observed with the increase in pH. Sorption was almost 90% at pH 3 at an initial chromium concentration of 5 mg/L and reduced to 10% at pH 7 and above. Presence of electrolytes and chloride significantly affected the chromium removal, indicating the electrostatic attraction as the main removal mechanism. Regeneration of the sorbent with alkali was not very effective as only 60-65% of sorbed chromium could be recovered.

Adsorption of Cu(II) and Cr(VI) ions by chitosan: kinetics and equilibrium studies

“…From the pK a value, it can be calculated that the extent of protonation is 9, 50, 91, and 99 % at a pH of 7. , and HCr 2 O 7 -; the fraction of any particular species is dependent upon the chromium concentration and pH (Udaybhaskar et al, 1990). Below the pK a value of chitosan, the sorbent is positively charged, while the sorbate is negatively charged.…”

“…Current treatment for the removal of Cr (VI) involves acid catalysed chemical reduction to Cr 3+ . The Cr 3+ is then precipitated as hydroxide at alkaline conditions using either caustic or lime (Udaybhaskar et al, 1990). The presence of Cu (II) in wastewater is also a problem.…”

Arsenic Sorption Using Mixtures of Ion Exchange Resins Containing N-Methyl-D-Glucamine and Quaternary Ammonium Groups

“…A number of these studies have developed sorption processes including adsorption and ion-exchange mechanisms, precipitation, solvent extraction, conjunction of membranes and polymers using simple materials such as activated carbon or more sophisticated materials such as especially tailored polymers as well as biosorbents, such as fungal or bacterial biomass, and materials of biological origin, including alginate and chitosan [2][3][4][5][6][7][8][9][10][11][12][13][14] .…”

“…The adsorption process, which can reduce the arsenic concentration to the minimum level, appears to be the most promising approach amongst the available methods and has been widely used for arsenic removal because of its low cost and high efficiency 25,26 . Strong base anionexchange resins that contain quaternary ammonium groups attached to a polymeric matrix have been extensively studied for their ability to remove arsenic and have been found to exhibit a higher affinity for divalent species (HAsO 4 2-) 24 . Therefore, for these resins, the optimum pH for sorption is between 7 and 9, where the concentration of HAsO 4 2-species is high 27 .…”

Adsorption of nuclease p1 on chitosan nano-particles

“…Muzzarelli (Muzzarelli, 1986) pointed out that chitosan combines with metal ions in three forms: ion exchange, sorption and chelation. Chitosan has been broadly used for the sorption of heavy metal ions (Coughlin and Deshaies et al, 1990;Udaybhaskar and Iyengar et al, 1990;Jansson and Guibal et al, 1996). Further physical and chemical modifications of chitosan have been made to improve the selectivity and the capacity for metals ions (Kumar and Majeti, 2000;Guibal and Jansson et al, 1995;Piron and Accominoti et al, 1997;Choong and Wolfgang, 2003).…”