Magnetic Mesoporous Calcium Carbonate-Based Nanocomposites for the Removal of Toxic Pb(II) and Cd(II) Ions from Water

Abstract

Calcium carbonate (CaCO 3 )-based nanoadsorbents have gained widespread attention due to their superiority in removing toxic heavy metal ions. Considering that the inherent structure of the material determines its performance, it is important to fully understand the effect of different crystals of CaCO 3 on the removal of heavy metals. On the other hand, the difficult separation of nanoadsorbents during in situ remediation may cause the potential risk of secondary pollution by the remaining adsorbents. Herein, the magnetic calcium carbonate adsorbents with nanostructure (MCCR-X, X represent the annealing temperature) were fabricated with a tunable crystal structure of CaCO 3 by adjusting the annealing temperature. Results from batch experiments revealed the crystal structure (CaCO 3 )-dependent adsorption performance of MCCRs toward Pb(II) and Cd(II). MCCR-350 with an aragonite phase showed the outstanding adsorption toward both Pb(II) and Cd(II) with maximum adsorption capacity of 1179 and 821 mg/g, and MCCR-RAW with a vaterite/aragonite phase also has similar adsorption properties. However, MCCR-550 with the calcite phase displayed a superhigh adsorption toward Pb(II) only but very weak adsorption toward Cd(II) with a capacity of 1350 and 30 mg/g in the initial concentration of 300 mg/g. The findings indicated that the efficiently tunable removal of the heavy metal ion Pb(II) or Cd(II) by MCCRs can be realized by regulating the crystal phase of CaCO 3 . X-ray photoelectron spectroscopy technology (XPS) was employed to clarify the possible mechanism of the crystal phase of CaCO 3 -dependent adsorption ability for Pb(II)/Cd(II) removal by MCCRs. This work provides an understanding of the crystal-structure-related adsorption properties of CaCO 3 and also gives guidance for designing a CaCO 3 -based adsorbent for removal/recovery of heavy metal ions.

Multifunctional Binding Sites on Nitrogen-Doped Carboxylated Porous Carbon for Highly Efficient Adsorption of Pb(II), Hg(II), and Cr(VI) Ions

“…Finally, it should be noted that the developed ND-CPC adsorbent exhibits one of the highest maximum adsorption capacity ( q max ) of Pb(II) ions reported in the literature for a variety of organic, inorganic, hybrid, and metal–organic framework (MOF) adsorbents. 18 , 31 , 33 , 34 , 39 − 59 Table S10 ( Supporting Information ) compares the values of q max of Pb(II) ions measured at comparable experimental conditions by several adsorbents developed in the literature. 41 − 53 It is clear that the removal capacity for lead ions by the ND-CPC (721 ± 14 mg/g) adsorbent is higher than most of the reported values by other adsorbents such as thiol-functionalized mesoporous silica (91.5 mg/g), 41 calcium alginate/graphene oxide (GO) composite aerogel (368 mg/g), 42 polymer-based ZrP (398 mg/g), 43 and GO–ZrP (363 mg/g).…”

“…Therefore, the ND-CPC adsorbent is clearly among the very top-performing adsorbents reported in the literature for lead removal from contaminated industrial and wastewater. 39 − 59 …”

Melamine-based functionalized graphene oxide and zirconium phosphate for high performance removal of mercury and lead ions from water

“…12 Finally, it should be noted that the developed M-ZrP adsorbent exhibits one of the highest maximum adsorption capacity (q max ) of Pb(II) ions reported in literature for a variety of organic, inorganic, hybrid, and MOF adsorbents. [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64] The removal capacity for lead ions by M-ZrP is 680.4 mg g À1 and 1000 mg g À1 using an adsorbent dose of 1 g L À1 and 2 g L À1 , respectively. This removal capacity is higher than most of the reported values for Pb(II) removal by other ZrP-modied adsorbents such as ZrPchloromethylated polystyrene (556.0 mg g À1 ), 51 polymer based-ZrP (398.0 mg g À1 ), 19 Go-ZrP (363.4 mg g À1 ), 21 ZrP-polysulfone (302.1 mg g À1 ), 52 and ZrP-polyvinyl alcohol (121.1 mg g À1 ).…”

“…Therefore, the M-ZrP adsorbent is clearly among the very top performing adsorbents reported in literature for the lead removal from contaminated industrial and wastewater. [19][20][21][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64]…”

Syntheses of Nanostructured Magnesium Carbonate Powders with Mesoporous Structures from Carbon Dioxide

“…Shahwan et al report that MgCO 3 is a better adsorbent of Pb 2+ and Zn 2+ ions than clay minerals [11]. Mesoporous calcium carbonates have also been reported as good adsorbents for heavy metal ions (Pb 2+ and Cd 2+ ); the removal efficiency depended on the crystal structure [12]. Shan et al showed that synthetic nesquehonite is a highly efficient agent for removing Cu 2+ , which was precipitated as a mixture of hydroxides and carbonates [13].…”