Selective Recovery of Silver(I) Ions from E‐Waste using Cubically Multithiolated Cage Mesoporous Monoliths

Abstract

We report the selective engineering of hybrid organic mesoporous silica monolith adsorbents for the recovery of silver (Ag) ions from e‐waste samples. The AgI multithiolated adsorbent scales were synthesized through dense and continuous surface modifications of hierarchically ordered mesoporous (HOM) monoliths by active organic moieties. Captured subsets were created on the monolithic surfaces and in the orderly pore cavities for suitable AgI trapping. In addition, HOM monolithic carriers, with unique surface dominants, micrometer‐sized particles, high surface‐area/pore‐volume ratios, and uniform groove‐like cage cavities, form neat rooms for target ions. The decoration and depression of the extraordinary micrometer‐sized surface monoliths and the orderly neat grooves enable the adsorption of large quantities and well‐dispersed coverage of the multithiolated layers. These layers include sulfur‐ and nitrogen‐active sites that selectively improve AgI adsorption/trapping/capture among competitive matrices. Results indicate that the adsorption of AgI is strong at pH 6.5 and it appears to follow the Langmuir adsorption model, with a maximum capacity of 179.23 mg g–1. The hierarchical multithiolated adsorbent scales exhibit selectivity for Ag ions in the presence of coexisting cations. The retention of the organic structure and orientation along the HOM monoliths enables multiple‐use recovery, collection, and management of AgI, without altering their functionality and capacity. The results suggest that the hierarchical adsorbent scales are suitable for AgI recovery from aquatic samples.

Thorium ions recovery using activated carbon modified with triphenyl phosphine oxide: kinetic and equilibrium studies

“…The value of saturation capacity determined from Langmuir isotherm model was 71.94 mg/g at room temperature which is near to the experimental value of 71.2 mg/g. The tested modified AC showed high sorption capacity compared to other adsorbents [34][35][36][37][38][39][40]. From Langmuir assumptions, thorium uptake has occurred on a homogeneous surface as a monolayer and all the metal binding sites are energetically the same [41].…”

Fabrication of Silica Microspheres (HB/A@SI-MNS) for Hafnium and Zirconium Recovery from Zirconyl Leach Liquor

“…A decrease in the surface area (111.5 cm 2 g −1 ), pore volume (0.44 cm 3 g −1 ), and pore diameter (3.20 nm) after the functionalization of fabricated cylindrical mesoporous silica with HB provides further evidence that the organic moieties were embedded inside the mesopore of the modified silica. This may be attributed to the partial blocking obtained by the modifying silica that hinders the adsorption of nitrogen molecules [23][24][25]. The scanning electron microscope (SEM) showed uniform particles with a well-defined spherical morphology with particle sizes ranging from 250 to 300 nm ( Figure 3B).…”

“…At lower pH values, the active groups of the HB/A@Si-MNS get protonated and the interaction between the protonated HB/A@Si-MNS and cationic species of Zr(IV) and Hf(IV) is reduced. The interaction of Zr(IV) and Hf(IV) with the HB/A@Si-MNS may take place through a complex formation with the donor sites of amino groups, as well as the oxygen atoms of the phenolic hydroxyl group, and coordination type, as suggested in Figure 1 [1,2,9,21,24]. The observed decrease in the uptake of Zr(IV) and Hf(IV) at pH > 3 can be explained on the basis of the formation of various oligomeric and monomeric hydrolyzed species of Zr(IV) and Hf(IV) with lower adsorption affinities to HB/A@Si-MNS.…”

“…The values of the Langmuir parameters, Q max and K L , were calculated from the slopes and intercepts of the straight lines ( Figure 6) and were reported in Table 3 Langmuir adsorption isotherm can be expressed in terms of a dimensionless constant called the equilibrium parameter (R L ) [24,25]:…”

“…This implies that the adsorption process proceeds according to the pseudo-second-order kinetics and depends upon the metal ion and active site concentrations. In order to show the effect of the intraparticle diffusion (IPD) on the rate of the adsorption process, the plots between the amount of Zr(IV) and Hf(IV) adsorbed at different time intervals (q t ) and the square root of time (t 0.5 ) were carried out according to IPD model [22][23][24][25].…”