Adsorption mechanisms of thallium(I) and thallium(III) by titanate nanotubes: Ion-exchange and co-precipitation

Abstract

Hydrothermally-synthesized titanate nanotubes (TNTs) are found to be excellent at adsorption of highly toxic thallium ions. Uptake of both thallium ions is very fast in the first 10 min. The adsorption isotherm of Tl(I) follows the Langmuir model with maximum adsorption capacity of 709.2 mg g(-1). Ion-exchange between Tl(+) and Na(+) in the interlayers of TNTs is the primary mechanism for Tl(I) adsorption. Excess Tl(+) undergoes further exchange with H(+). The adsorption mechanism is different for Tl(III), and involves either ion-exchange with Na(+) at low Tl(III) concentration or co-precipitation in the form of Tl(OH)3 with TNTs at high Tl(III) concentration. XPS analysis indicates that the ion-exchange process does not change the basic skeleton [TiO6] of TNTs, whereas Tl(OH)3 precipitation increases the percentage composition of O within the surface hydroxyl groups. XRD analysis also confirms the formation of Tl(OH)3 on TNTs at high initial concentration of Tl(III). Coexisting Na(+) and Ca(2+) hardly inhibit adsorption, indicating good selectivity for thallium by TNTs. Furthermore, TNTs can be reused efficiently after HNO3 desorption and NaOH regeneration, making TNTs a promising material to remove thallium from wastewaters. This study also confirms that co-precipitation is another important adsorption mechanism for easily hydrolytic metals by TNTs.

Selective and irreversible adsorption of mercury(ii) from aqueous solution by a flower-like titanate nanomaterial

“…It was because TNFs were positively charged in these pH ranges, thus capture of Hg(II) cations was inhibited due to electrostatic repulsion. 45 When pH was increased to 4, the adsorption capacity sharply increased to 224.6 mg g À1 because the surface charge of TNFs turned negative (Fig.…”

“…Aer hydrothermal treatment for synthesis of TNFs, all the anatase transformed into titanate. 12,45 Furthermore, no crystalline Hg(II) or relegated compounds formed aer adsorption, indicating that ion-exchange just processed in the interlayers. 31-1329).…”

Synergistic effect of Cu adsorption on the enhanced photocatalytic degradation of bisphenol A by TiO2/titanate nanotubes composites

“…Pore diameter (nm) phase [17,25]. The temperature for phase transformation is dependent on the morphology of TNTs, addition of additives and synthesis temperature and duration of TNTs [25,32].…”

“…Doong). removal of heavy metal ions, radioactive elements and rare earth elements such as Cs(I), Cd(II), Pb(II), Cu(II), Tl(II), and Eu(III) [17][18][19]. A previous study has reported that the adsorption capacity of metal ions onto hydrothermally as-prepared TNTs followed the sequence Pb(II) Cd(II) > Cu(II) > Cr(III), and the adsorption capacity was up to 2.64 mmol/g for Pb(II) and 1.92 mmol/g for Cu(II) [20].…”

Removal of Tl(I) Ions From Aqueous Solution Using Fe@Fe2O3 Core‐Shell Nanowires

“…Tl exists as Tl(I) and Tl(III) in the environment, and the former form has relatively high solubility and forms only weak complexes so that Tl(I) is readily transported through aqueous routes into the environment. Industrial wastewater, solid waste from coal combustion, and metal smelting are the main anthropogenic sources of Tl . The fascinating chemistry and high toxicity potential make Tl and its compounds of particular scientific interest and environmental concern.…”