Irreversibility of sorption of cobalt to goethite (α-FeOOH) and disparities in dissolution of aged synthetic Co-goethite

Investigation of magnetite–Co interactions: from environmentally relevant trace Co levels to core–shell Fe3O4@Co(OH)2 nanoparticles with magnetic applications

“…Therefore, to achieve a cation surface loading of 7 atom per nm 2 , not only magnetite-bound Co-monomers but also small oligomers might form. 63–65…”

Sorption of Heavy Metals on Clay Minerals and Oxides: A Review

“…Mononuclear V(V) complexes are present at 25 ppm whereas both mononuclear and polynuclear V(V) complexes exist at 25 mg//solution species form [94]. In another study, at concentration < 10 mg/L and pH 7, cobalt sorbs on goethite at pH 7 to form bidentate edge and corner complexes but form surface precipitates, bidentate edge and corner complexes from 10 to 58 mg/L and pH 7.5 [37]. With ageing, Co sorption on goethite is irreversible depending on the initial concentration [37].…”

“…In another study, at concentration < 10 mg/L and pH 7, cobalt sorbs on goethite at pH 7 to form bidentate edge and corner complexes but form surface precipitates, bidentate edge and corner complexes from 10 to 58 mg/L and pH 7.5 [37]. With ageing, Co sorption on goethite is irreversible depending on the initial concentration [37]. In addition, sorption of Pb, Hg, Cd, Zn, Cu, Ni, Co, Mn, Cr and Al on goethite from solution 10 À6 M was achieved in 2 h and 20°C, but different pH [94].…”

“…Determination of partitioning of heavy metals among the solid phase and accurately predicting their mobility in natural environment requires adequate knowledge of the chemical process such as ion exchange, adsorption, surface precipitation, coprecipitation and mineralisation, that govern sorption mechanism [36]. For example, cobalt sorbs to goethite through surface complexation, surface precipitate and structural incorporation depending on the concentration and sorption duration [37].…”

“…Better understanding of sorption mechanism is done using technologies and spectroscopy studies such as Attenuated Total Reflection Infrared [37,54], Fourier Transform Infrared (FTIR) spectroscopy, extend X-ray absorption fine structure spectroscopy (EXAFS) [55][56][57], powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Electron paramagnetic resonance (EPR) [58]. Spectroscopic studies show that copper, nickel, zinc and cobalt bind to Mn(IV) vacancy sites in birnessite to form inner-sphere surface complexes via interlayer triple-corner-sharing or enter the vacancy site to become part of the structure [56].…”