Combination of electroreduction with biosorption for enhancement for removal of hexavalent chromium

Abstract

a b s t r a c tHexavalent chromium is one of the most toxic heavy metals in aqueous solutions. It has been well documented that the brown seaweed can be used as a promising biosorbent for the sequestration of this heavy metal from wastewater. However, the uptake of Cr(VI) is reportedly a rather slower process; the sorption equilibrium can only be established after a few days, much slower than a few hours for the trivalent chromium ion. In this study, we developed a novel technology of electrochemically assisted biosorption (ECAB) system for the enhancement of the treatment efficiency. It was found through our study that the removal efficiencies of Cr(VI) and total chromium were greatly enhanced by 48.1% and 51.3%, respectively, with the application of À1.0 V in the ECAB system. The conversion of Cr(III) due to the electroreduction of Cr(VI) and the higher pH due to the cathodic H 2 evolution created a favorable condition for the uptake of chromium onto the modified seaweed (MSW). The reduction and adsorption of Cr(VI) by MSW was proved to play a minor role in the removal. Both direct electroreduction and indirect electroreduction by atomic H Ã contributed to the reduction of Cr(VI).

Preparation of Amidoxime Adsorbent by Radiation Induced Grafting of Acrylonitrile on Polyethylene Film and Its Application in Cr(VI) Removal

“…15 For this purpose, many types of adsorbents have been investigated for the removal of chromium including activated carbon, biomaterials and nanomaterials. [15][16][17][18][19][20][21][22][23][24] Recently, many researchers have focused attention on grafted polymers as alternative heavy metal adsorbent. [25][26][27][28][29][30][31][32][33][34][35] "Grafting" is a method in which functional monomers are covalently bonded onto the backbone polymer chain.…”

Preparation and Characterization of Chitosan Thin Films on Mixed-Matrix Membranes for Complete Removal of Chromium

“…As soon as the Cr VI solution comes into contact with the CS layer, the reduction starts, which can be confirmed from Figure . The reduced Cr III is present in Cr +3 , Cr(OH) 2 + , and Cr(OH) +2 forms, which are adsorbed onto the CS surface by complexation; this is supported by the change in membrane color from yellow to pale green, which is typical for Cr III complexes . The presence of Cr +3 can also be substantiated by the peak observed at λ max =580 nm in the UV/Vis spectra of the used membrane (Figure ).…”

“…In this study the mediumw as maintained at pH 4b yt he addition of formic acid to facilitate the formation of HCrO 4 À and Cr 2 O 7 2À ions and reduction by the electron-donor groups present in the CS layer.A ss oon as the Cr VI solution comes into contact with the CS layer,t he reduction starts, which can be confirmed from Figure 8. Ther educed Cr III is presenti nC r + 3 , Cr(OH) 2 + ,a nd Cr(OH) + 2 forms, [39] which are adsorbed onto the CS surface by complexation;t his is supported by the change in membrane color from yellow to pale green,w hich is typical for Cr III complexes. [40] The presence of Cr + 3 can also be substantiated by the peak observed at l max = 580 nm [41] in the UV/ Vis spectra of the used membrane ( Figure 9).…”

A comparative study on the efficiency of various cathodes in reducing hexavalent chromium at low voltage

“…The efficiency of Cr (VI) ions removal using the electrochemical method with biosorbents added to the cathode section electrolyte is studied by Hou et al. (2012). Electrochemical reduction of hexavalent chromium ions forms a sludge as the reduced Cr (III) forms a complex with dissociated ions from anode like Fe (II) and precipitates out even at low initial Cr (VI) concentration in the treating water, continuous dissociation of such anode materials creates iron pollution in the treated water (Mouedhen et al., 2009).…”