Three-dimensional mesoporous calcium carbonate–silica frameworks thermally activated from porous fossil bryophyte: adsorption studies for heavy metal uptake

Abstract

In this paper, three-dimensional mesoporous calcium carbonate-silica frameworks have been created from the straw tufa (ST) originating from porous fossil bryophyte by a thermal activation technique. A batch of adsorption kinetic and thermodynamic experiments were used to investigate the adsorption capacity of Cd (II) The adsorption capacities of Cd(II) and Pb(II) both decrease with the addition of the other heavy metal cations, indicating that the adsorption is hindered by the competitive adsorption and the adsorption active sites on the mineral surface are readily exchangeable. The adsorption of Cd(II) and Pb(II) followed the pseudo-second order kinetics model well. In addition, the Langmuir model could accurately describe the adsorption isotherms. Based on the results of characterization with TEM, XRD and XPS, the adsorption mechanisms could be primarily explained as formation of Cd(OH) 2 and CdCO 3 as well as Cd(HCO 3 ) 2 precipitation on the surface of ST. These characteristics of ion-exchange and the adsorptive property for ST modified allow it to be widely used in artificial wetland landfill and environmental protection.

Cd(ii) removal by Fe(ii) surface chemically modified layered double hydroxide–graphene oxide: performance and mechanism

“…S4(a), † the doublet characteristics of Cd appeared at 406 and 412 eV were in line with those of Cd(OH) 2 , which indicated the precipitation form of cadmium. 20,46 Combined with XRD pattern, it is clear that in this study, the removal of Cd(II) from aqueous solution was mainly conducted by surface-induced precipitation as hydroxides. Notably, the peaks of Fe 2p were impaired aer Cd(II) adsorption ( Fig.…”

Contribution to the study of the seasonal dynamics of trace metals in the open waters at the water-sediment interface from a tropical lagoon estuary

“…Over the entire study period, the slight basicity and probably reducing character of these open waters over all the study period would have been favorable for the solubilization in them of the trace metals studied by their release from Fe and Mn (oxy)hydroxides on the particulate phases [12,13] and; from the mineralization of the relative important particulate organic matter in the form of soluble organometallic complexes [4;10] , particularly from the degradation of macrophytes of the genus Eicchornia crassipes [45] . The same would have been true for their relatively important salinity and conductivity [4;16,17] , and of the solubilization of other trace metals than Cd, Ni, Pb, and Zn from carbonates on the particulate phases [10,11] . These processes would explain the relative important trace metal contents of these open waters over the entire study period, despite the retention of these trace metals on the particulate phase by sulphides [8,9] and organic matter [4;10] .…”

“…The pH, temperature, salinity, conductivity, as well as dissolved oxygen, organic matter, carbonates, sulphide, Fe, and Mn contents, of the open waters at water-sediment interface play an important role in the dynamics of trace metals. In neutral to basic and reducing aquatic environments, trace metals are immobilized on the particulate phase by sulphides and carbonates [8][9][10][11] ; while Fe and Mn (oxy)hydroxides promote their solubilization in these conditions [12,13] . In acidic to neutral and oxidizing aquatic environments, the reverse of these reactions takes place.…”

“…In acidic to neutral and oxidizing aquatic environments, the reverse of these reactions takes place. However, for some trace metals such as Cd, Ni, Pb, and Zn, their immobilization by carbonates on the particulate phase is observed under slight acidic to neutral conditions [10,11] .…”

Production of Activated Carbon from Waste PET’ Chars

“…According to the International Union of Pure and Applied Chemistry (IUPAC) classification, the ZnCl325 and ZnCl350 activated carbons belonged to typical type IV adsorption isotherms with an H1 hysteresis loop characteristic of mesoporous structures (Figure 4) [20]. In addition, as seen in Figure 5, it was observed that the BET surface area increased proportionally with high relative pressure (p/p0) [21].…”