A Novel Calcium Oxalate/Sepiolite Composite for Highly Selective Adsorption of Pb(II) from Aqueous Solutions

Abstract

Synthesizing functional nanomaterials from naturally abundant clay has always been of vital importance for resource utilization, however, the lack of new methods to effectively utilize low-grade clay presents a significant challenge. Herein, a calcium oxalate/sepiolite nanocomposite (SMN-x) was prepared by using the water bath heating method to convert the associated calcium carbonate in low-grade sepiolite into calcium oxalate. The developed composite was subsequently used to remove Pb(II) from the aqueous solutions. The SMN-3 adsorbent prepared by heating in a water bath at 90 °C for 3 h (with a high specific surface area of 234.14 m2·g−1) revealed the maximum Pb(II) adsorption capacity of 504.07 mg·g−1 at pH 5, which was about five times higher than that of sepiolite (105.57 mg·g−1). Further, the SMN-3 adsorbent possessed a much higher selectivity for Pb(II) as compared to the other metal ions. Moreover, the residue was noted to be stable and safe. The adsorption kinetics and isotherms conformed to the quasi-second-order kinetic and Langmuir models. During the adsorption process, ion exchange was noted to the main mechanism, however, it was also accompanied by electrostatic attraction. This study provides a novel strategy for the sustainable development of simple and efficient adsorbents by utilizing low-grade clay minerals.

Facile Preparation of Millimeter‐Sized Sodium Alginate‐Silica Composite Spheres for Highly Selective Adsorption of Heavy Metal Ions

“…As shown in Figure 3a, the broadband around 3441 cm −1 is attributed to the stretching vibration of the terminal −OH and/or adsorbed water, [27] and the bands that appeared at 1619 cm −1 and 1425 cm −1 are due to the asymmetric and symmetric stretching vibration of −COOH, respectively [28–30] . By a careful comparing, it can be found that the vibration bands of −COO − (1610 cm −1 ) and the vibration bands of Si−O−Si located at around 1097, 805, and 472 cm −1 shift to lower wave number for the functional samples due to the influence of −NH 2 and −SH [31,32] . Furthermore, a new weak band around 2558 cm −1 belongs to the vibration of −SH appeared in the spectra of SH‐SiO 2 /SA [33] .…”

“…[28][29][30] By a careful comparing, it can be found that the vibration bands of À COO À (1610 cm À 1 ) and the vibration bands of SiÀ OÀ Si located at around 1097, 805, and 472 cm À 1 shift to lower wave number for the functional samples due to the influence of À NH 2 and À SH. [31,32] Furthermore, a new weak band around 2558 cm À 1 belongs to the vibration of À SH appeared in the spectra of SH-SiO 2 /SA. [33] Therefore, it seems reasonable to believe that the synthesized materials had been successfully functionalized by -SH and -NH 2 groups.…”

Calcium Oxalate Crystallization: Influence of pH, Energy Input, and Supersaturation Ratio on the Synthesis of Artificial Kidney Stones

“…Furthermore, ζ potential indicates the surface charge and surface composition, which determine how particles grow and how adhesives and other particulates can be attached to particles. Hence, the ζ potential is important to make estimations on the electrochemical double layer forming around the particles and the resulting effects on adsorption of metal ions to the oxalate particles . The ζ potential is strongly dependent on the surface structure and composition and on the ionic strength of the solution .…”

“…Hence, the ζ potential is important to make estimations on the electrochemical double layer forming around the particles and the resulting effects on adsorption of metal ions to the oxalate particles. 53 The ζ potential is strongly dependent on the surface structure and composition and on the ionic strength of the solution. 54 In human kidneys, the ionic strength is usually isotonic and the pH is slightly acidic.…”

Mesoporous maltose/calcium oxalate hybrid material with abundant reaction sites and its efficient Pb(ii) removal from diverse water bodies

“…8,9 As a pollution elimination strategy, the economic and ecological benefits of adsorption are an important index to evaluate the feasibility of the technology. Therefore, some cheap and environment-friendly natural minerals adsorbents such as carbonate, 10,11 Mg(OH) 2 /talc, 12 oxalate, 13 hydroxyapatite, 14 magnetic iron oxide, 15 alumina 16 and amorphous silicon dioxide 17 have attracted the attention. Among them, calcium carbonate has excellent adsorption performance for lead, but the carbonate is unstable under acidic conditions.…”