Chromium removal on chitosan-based sorbents – An EXAFS/XANES investigation of mechanism

A comparative study with biologically and chemically synthesized nZVI: applications in Cr (VI) removal and ecotoxicity assessment using indigenous microorganisms from chromium-contaminated site

“…The absorption peak at 796 cm −1 confirms the presence of chromium on the CS-nZVI immobilized alginate beads surface (Vieira et al 2014;Paul et al 2014). The characterization results discussed above reveal clearly that the surface functional groups on the sorbent plays a major role in the adsorption process.…”

“…Moreover, new absorption peak corresponding to Cr-O vibrations at 810 cm −1 was observed, which confirms the presence of chromium on the BS-nZVI immobilized alginate bead surface (Paul et al 2014). The new peak at 1031 cm −1 represents C-O stretching vibrations due to the complexation of chromium ions (Vieira et al 2014;Tytłak et al 2015). In the case of CS-nZVI immobilized alginate beads after interaction with Cr (VI), the intensity of peaks at 2178, 1621, and 1438 cm −1 was decreased.…”

“…A number of adsorbents were used for Cr (VI) removal including biopolymers, activated carbon, metal oxides, microorganisms, bio-waste products, sewage sludge, and nanomaterialimmobilized beads (Lv et al 2013;Vieira et al 2014;Idris et al 2010;Paul et al 2014;Janaki et al 2014;Liu et al 2010) Nano zero valent iron (nZVI) was found to be the most effective adsorbent for Cr (VI) removal from the aqueous solutions compared to the other adsorbents. In the last 20 years, nZVI has been identified to have a significant potential for environmental applications due to its small particle size, large surface area, and greater density of reactive and adsorptive sites (Mueller et al 2012;Singh et al 2011;Savasaria et al 2015;Esfahani et al 2014).…”

Efficient simultaneous removal of Cu(II) and Cr2O72− from aqueous solution by a renewable amphoteric functionalized mesoporous silica

“…Furthermore, the peak at 578.95 eV was stronger than that at 587.95 eV, suggesting that most of Cr(VI) was reduced to Cr(III) by AG-SBA-15 [9]. The electrons for the reduction of Cr(VI) to Cr(III) were probably from the abundant amine group of AG-SBA-15 [2,43,51,53]. It is well known that the metal cations adsorbed at the liquid is generally considered to be the result of electrostatic interaction between adsorbent and adsorbate [41,47].…”

“…15d. The Cr 2p1/2 and Cr 2p3/2 photoelectron peaks were located at 587.95 and 578.95 eV, respectively [9,51,52] which were assigned to the characteristic peaks of Cr(VI) (K 2 Cr 2 O 7 ) and Cr(III) (Cr 2 O 3 ), respectively [51]. The results indicated that both Cr(VI) and Cr(III) were present on surface of AG-SBA-15 during adsorption process [2].…”