Chromate ion-exchange process at alkaline pH

Removal of Cr(VI) from alkaline aqueous solutions using chemically modified magnetic chitosan resins

“…The observed higher uptake value of R2 than that of R1 at all pH values may be attributed to the presence of trimethylammonium chloride moiety (which works in acid/neutral/basic media) in addition to amine moiety. It has been reported that HCrO 4− , CrO 4 2− and Cr 2 O 7 2− are the predominant species at pH < 6.5 while CrO 4 2− is the dominant species at pH > 7.5 [18,19]. It is seen that R1 works efficiently towards the removal of chromate in acidic medium, whilst R2 works efficiently in all pH ranges (acidic/neutral/basic).…”

Synthesis of a quaternary amine anion exchange resin and study its adsorption behaviour for chromate oxyanions

“…The slightly lower value of concentration of quaternary amine sites of RQA compared to the amine active sites of RPA may be Scheme 1. attributed to that not all amine sites are amenable to react with GTA since such interaction requires presence of replaceable Hatom on RPA. is the dominant species at pH > 7.5 [20][21][22]. The uptake of chromate by resin is considered as competition between different chromate species.…”

“…clays and activated carbons [8], organo-clays [9][10][11][12], biomass [13][14][15], biopolymers [16][17][18], agriculture products [19]. Ion exchange resins have been also widely used in recovery and pre-concentration of metal ions [20][21][22]. Kabay et al [1] used impregnated resins to remove Cr(VI) and obtained a maximum uptake of 10.32 mg/g resin.…”

Cr(VI)‐containing wastewater treatment by means of ion exchange on weak‐ and strong‐base anion exchangers

“…10,11,15 The strong-base anion exchangers with a macroporous structure are most frequently used but they present drawbacks regarding to the regeneration and washing operations. 2,9 Ion exchange is a stoichiometric process and an equilibrium is attained when an ion exchanger is placed in an electrolyte solution containing a different counterion.…”

“…[2][3][4][5][6] The efficiency of the Cr(VI)-containing wastewater treatment by means of ion exchange depends on the type and the characteristics of the anion exchanger, its ionic form, and the solution pH value. [7][8][9][10][11][12][13][14] For the strong-base anion exchangers, the presence of other anions influences their ion-exchange affinity in the following order: Cr 2 O 7 2Ϫ Ͼ CrO 4 2Ϫ Ͼ PO 4…”