Surface and Charge Characteristics of the Oxide/Solution Interface Towards Chromium(VI) Sorption

Abstract

The interfacial properties of zirconium oxide, titanium oxide and bismuth oxide have been studied under various experimental conditions. The oxides were characterized by means of their pH titration curves, intrinsic dissociation constants [pKai*(intr.), i = 1, 2) and point of zero charge (pHpzc) in varying concentrations of KNO3 and Na2CrO4 solutions. The pHpzc values of all the oxide samples tended to shift to higher pH values in the presence of Na2CrO4 solution and remain the same in the presence of KNO3 solution. A mechanism for the sorption process is proposed proceeding through an exchange with surface OH– or H2O groups and is interpreted as a case of specific adsorption.

p-Block Metal Oxide Noninnocence in the Oxygen Evolution Reaction in Acid: The Case of Bismuth Oxide

“… , Integration of the peaks suggests near-equal amounts of the two oxygen environments in the BiO x film samples. The significant amount of hydroxyl oxygens in the BiO x films after immersion in solutions at pH ∼ 2 is consistent with the reported point of zero charge of ∼6–9 for bismuth oxides in water. − …”

“…Alternatively, the intramolecular disproportionation step may be accompanied by a dehydration step to give precatalyst 3 with a Bi V oxo moiety rather than Bi V hydroxo. Although such an oxo species may be formed transiently during OER, the prominence of hydroxyl oxygens in O 1s XPS data and the point of zero charge of 6–9 of bismuth oxides in water − strongly suggests that the edge sites in the BiO x lattice are more likely to be protonated at pH 1.0–2.25. Additionally, instead of 4 , an OER pathway featuring a symmetric Bi V species with a bridging peroxo may also be considered.…”

A Comparison of Chemisorption Kinetic Models Applied to Pollutant Removal on Various Sorbents

“…Other data from the literature were also tested by plotting t/q t against t for the sorption of lead(II) and copper(II) onto bottom ash according to equation (6) 22 . The agreement of experimental data and the pseudo-second order equation is much better than those for the other two equations.…”

“…An early application of the pseudo-® rst order rate equation of Lagergren was the sorption of cellulose triacetate from chloroform onto calcium silicate by Trivedi et al 2 . Numerous studies report ® rst order Lagergren kinetics for the sorption of metals such as the sorption of As(III) from aqueous solutions by haematite 3 , the sorption of nickel(II) from aqueous solutions by Woolastonite and china clay 4,5 , the sorption of chromium(VI) by bismuth trioxide 6 , the sorption of cadmium(II) onto hydrous ceric oxide 7 , the sorption of chromium(III) by natural moss and chromium(VI) by copper-coated moss 8 , the sorption of mercury(II) onto hydrous zirconium oxide 9 , the sorption of lead(II) onto kaolinitic clay 10 , the sorption of arsenite(III) and arsenate(V) using basic yttrium carbonate 11 and the sorption of arsenic(V) on haematite and feldspar 12 ; of dyes such as the sorption of Omega Chrome Red ME (OCRME) using a 1:1 ratio of¯y ash and coal 13 , the sorption of Methylene Blue on water hyacinth roots 14 , the sorption of Orlamar Red BG (ORBG) by Fomitopsis carnea 15 , the sorption of Congo Red, Procin Orange and Rhodamine-B by waste orange peel 16 , the sorption of Congo Red on red mud 17 and the sorption of Acid Blue 29 and Reactive Blue 3 on chrome sludge 18 . Others studies utilizing the pseudo-® rst order model include the sorption of Acid Violet dye onto waste banana pith 19 and the sorption of¯uoride, phosphate and arsenate(V) using lanthanum-impregnated silica gel 20 .…”