Co-adsorption of phosphate and zinc(II) on the surface of ferrihydrite

Abstract

h i g h l i g h t s• Phosphate and Zn(II) exhibited a synergistic adsorption on Ferrihydrite.• The effects of pH on the adsorption of the two contaminants were investigated.• XPS and ATR-FTIR demonstrated ternary complexes were formed on Ferrihydrite.• A phosphate-bridged ternary complexes model was proposed. a r t i c l e i n f o b s t r a c tFerrihydrite (Fh) is of great importance in affecting the migration and transformation of heavy-metal cations and oxyanions. To advance the understanding of co-adsorption reactions on Fh surface, the coadsorption of phosphate and Zn(II) from aqueous solution to a synthesized Fh was determined. The batch experiments demonstrated a synergistic adsorption of phosphate and Zn(II) on Fh. In the pH range of 3.5-6, the adsorption of the two contaminants showed strong pH dependence in the single solute adsorption systems, but the dependence alleviated in the simultaneous adsorption system. X-ray photoelectron spectroscopy (XPS) revealed that the chemical shifts of Zn 2p 1/2 and Zn 2p 3/2 binding energies were more significant than that of P 2p in the single and simultaneous adsorption systems. On the other side, in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) observed increased formation of outer-and inner-sphere complexes of phosphate in the simultaneous system. Thus, the synergistic adsorption of the two contaminants could be attributed to the formation of ternary complexes as well as electrostatic interactions, while surface precipitation could not be completely ruled out. On the basis of the results from both the batch adsorption experiments and structural characterization, these two contaminants were likely to form phosphate-bridged ternary complexes (≡Fe-P-Zn) in the simultaneous adsorption system.

Enhanced removal of heavy metal ions from aqueous solution using manganese dioxide-loaded biochar: Behavior and mechanism

“…S4c) appear in the XPS spectra of BC@ MnO 2 -26.6 after Cd(II) and Zn(II) adsorption, respectively, demonstrating the successful adsorption of Cd(II) and Zn(II) by the adsorbent. The peaks of Cd 3d and Zn 2p can be ascribed to CdO and ZnO, respectively, because of the consistency between the measured value and reported value 43,44 . This explains the mechanism of Cd(II) and Zn(II) removal by BC@MnO 2 -26.6 adsorbent.…”

Enhanced phosphate sequestration by Fe(iii) modified biochar derived from coconut shell

“…On the other hand, as mentioned above, phosphate adsorption by the Fe-CSB was slightly affected by the different concentrations of nitrate (0-50 mg L À1 ), suggesting that the inner-sphere complexation may have been involved in the phosphate uptake by the Fe-CSB. 46,47 Furthermore, according to the results of the intraparticle diffusion model, the phosphate uptake process consisted of two steps. Firstly, the phosphate anions (H 2 PO 4 À , HPO 4 2À and PO 4…”

Investigation of Zinc and Phosphorus Elements Incorporated into Micro-Arc Oxidation Coatings Developed on Ti-6Al-4V Alloys

“…C 1s spectrum was divided into two peaks at binding energy of 284.6 and 286.0 eV ( Figure 6 b), separately corresponding to C–C or C–H and C–O [ 6 ]. The P 2p spectrum exhibited three peaks at 133.4, 134.3 and 140.8 eV, which were the phosphorus peaks of Zn 3 (PO 4 ) 2 [ 18 ]. The Zn 2p peaks at 1022.5 and 1045.6 eV were well assigned to Zn 3 (PO 4 ) 2 [ 18 ].…”