Synthesis of new dithiocarbamate-based organosilanes for grafting on silica

Synthesis of Mesoporous Silica Using the Sol-Gel Approach: Adjusting Architecture and Composition for Novel Applications

The sol-gel chemistry of silica has long been used for manipulating the size, shape, and microstructure of mesoporous silica particles. This manipulation is performed in mild conditions through controlling the hydrolysis and condensation of silicon alkoxide. Compared to amorphous silica particles, the preparation of mesoporous silica, such as MCM-41, using the sol-gel approach offers several unique advantages in the fields of catalysis, medicament, and environment, due to its ordered mesoporous structure, high specific surface area, large pore volume, and easily functionalized surface. In this review, our primary focus is on the latest research related to the manipulation of mesoporous silica architectures using the sol-gel approach. We summarize various structures, including hollow, yolk-shell, multi-shelled hollow, Janus, nanotubular, and 2D membrane structures. Additionally, we survey sol-gel strategies involving the introduction of various functional elements onto the surface of mesoporous silica to enhance its performance. Furthermore, we outline the prospects and challenges associated with mesoporous silica featuring different structures and functions in promising applications, such as high-performance catalysis, biomedicine, wastewater treatment, and CO2 capture.

Speciation of Inorganic Compounds in Aquatic Systems Using Diffusive Gradients in Thin-Films: A Review

The speciation of trace metals in an aquatic system involves the determination of free ions, complexes (labile and non-labile), colloids, and the total dissolved concentration. In this paper, we review the integrated assessment of free ions and labile metal complexes using Diffusive Gradients in Thin-films (DGT), a dynamic speciation technique. The device consists of a diffusive hydrogel layer made of polyacrylamide, backed by a layer of resin (usually Chelex-100) for all trace metals except for Hg. The best results for Hg speciation are obtained with agarose as hydrogel and a thiol-based resin. The diffusive domain controls the diffusion flux of the metal ions and complexes to the resin, which strongly binds all free ions. By using DGT devices with different thicknesses of the diffusive or resin gels and exploiting expressions derived from kinetic models, one can determine the labile concentrations, mobilities, and labilities of different species of an element in an aquatic system. This procedure has been applied to the determination of the organic pool of trace metals in freshwaters or to the characterization of organic and inorganic complexes in sea waters. The concentrations that are obtained represent time-weighted averages (TWA) over the deployment period.

Development and evaluation of a 99mTc(V)-nitrido complex derived from estradiol for breast cancer imaging

Estrogen receptors are overexpressed in 70% of breast cancer and identification of their presence is important to select the appropriate treatment. This work proposes the preparation and evaluation of an estradiol derived as potential ER imaging agent. Ethinylestradiol was derivatized to introduce a dithiocarbamate function for Tc coordination. Labeling was achieved through the formation of a symmetric Tc(V)-nitrido complex with a radiochemical purity (RCP) > 95%. Physicochemical evaluation, cell uptake, biodistribution in normal animals and in nude mice bearing induced ER + breast tumors showed promising results.

Magnetic dithiocarbamate functionalized reduced graphene oxide for the removal of Cu(II), Cd(II), Pb(II), and Hg(II) ions from aqueous solution: Synthesis, adsorption, and regeneration

In this study, dithiocarbamate(DTC)-modified magnetic reduce graphene oxide (rGO-PDTC/Fe₃O₄) was synthesized for the removal of heavy metal ions (Cu(II), Cd(II), Pb(II), and Hg(II)) in synthetic waste water. The rGO-PDTC/Fe₃O₄ nanocomposite was prepared via a novel synthesis route that includes GO bromination, nucleophilic substitution of polyethylenimine (PEI), the reaction with carbon disulphide (CS₂) and Fe₃O₄ nanoparticle loading. The prepared rGO-PDTC/Fe₃O₄ nanocomposite was characterised by XPS, FTIR, TEM and XRD, suggesting that DTC functional groups were chemically bonded to rGO surfaces. N₂ adsorption-desorption results revealed that rGO-PDTC/Fe₃O₄ nanocomposite exhibited high BET surface area (194.8 m²/g) and large pore volume (0.33 cm³/g) which are crucial to the function of adsorbent. Adsorption experiments showed that rGO-PDTC/Fe₃O₄ nanocomposite is an excellent adsorbent for heavy metal removal, which exhibits large adsorption capacities, fast kinetics and solid-liquid separation. The pseudo-second-order kinetic model and Langmuir adsorption model were used to unveil the adsorption mechanisms. The maximum adsorption capacities of the Langmuir model were 113.64, 116.28, 147.06, and 181.82 mg/g for Cu(II), Cd(II), Pb(II), and Hg(II) ions, respectively. After adsorption and desorption process, the spent rGO-PDTC/Fe₃O₄ nanocomposite was easily regenerated via one-step organic reaction. The regenerated rGO-PDTC/Fe₃O₄ composite exhibited good adsorption capacities for different metals in five adsorption-desorption-regeneration cycles.

New Trend for Acceleration Solid Phase Extraction Process Based on Using Magnetic Nano-adsorbents along with Surface Functionalization through Microwave Assisted Solvent-free Technique

The use of a microwave assisted solvent-free technique for silica coating of iron magnetic nanoparticles (Fe3O4-MNPs) and their functionalization with three aliphatic diamines: 1,2-ethylenediamine (1,2EDA), 1,5-pentanediamine (1,5PDA) and 1.8-octanediamine (1,8-ODA), were successfully achieved in a very short time. Only 60 min were needed for the nano-adsorbent modification as compared with more than 1000 min using conventional methods under reflux conditions. Their surface characteristics (observed by TEM, XRD and FT-IR), in addition to Cu(II) adsorption capacities (1.805, 1.928 and 2.116 mmol g(-1)) and time of equilibration (5 s) were almost the same. Thus, the time required to accomplish the solid phase extraction process is greatly reduced. On the other hand, the phenomenon of the fast equilibration kinetics was successfully extended on using the functionalized aliphatic diamines magnetic nano-adsorbents as precursors for further microwave treatment. Three selective magnetic nano-adsorbents (Fe3O4-MNPs-SiO2-1,2EDA-3FSA, Fe3O4-MNPs-SiO2-1,5PDA-3FSA and Fe3O4-MNPs-SiO2-1,8ODA-3FSA) were obtained via the reaction with 3-formayl salicylic acid (3FSA) as a selective reagent for Fe(III). At 5 s contact time, they exhibited maximum Fe(III) uptake equal to 4.512, 4.987 and 5.367 mmol g(-1), respectively. Furthermore, modeling of values of metal uptake capacity obtained at different shaking time intervals supports pseudo-second order kinetics.

Core-shell magnetite-silica dithiocarbamate-derivatised particles achieve the Water Framework Directive quality criteria for mercury in surface waters

The sorption capacity of nanoporous titanosilicate Engelhard titanosilicate number 4 (ETS-4) and silica-coated magnetite particles derivatised with dithiocarbamate groups towards Hg(II) was evaluated and compared in spiked ultra-pure and spiked surface-river water, for different batch factors. In the former, and using a batch factor of 100 m(3)/kg and an initial Hg(II) concentrations matching the maximum allowed concentration in an effluent discharge, both materials achieve Hg(II) uptake efficiencies in excess of 99 % and a residual metal concentration lower than the guideline value for drinking water quality. For the surface-river water and the same initial concentration, the Hg(II) uptake efficiency of magnetite particles is outstanding, achieving the quality criteria established by the Water Framework Directive (concerning Hg concentration in surface waters) using a batch factor of 50 m(3)/kg, while the efficiency of ETS-4 is significantly inferior. The dissimilar sorbents' Hg(II) removal efficiency is attributed to different uptake mechanisms. This study also highlights the importance of assessing the effective capacity of the sorbents under realistic conditions in order to achieve trustable results.

Synthesis of a novel silica-supported dithiocarbamate adsorbent and its properties for the removal of heavy metal ions

Silica-supported dithiocarbamate adsorbent (Si-DTC) was synthesized by anchoring the chelating agent of macromolecular dithiocarbamate (MDTC) to the chloro-functionalized silica matrix (SiCl), as a new adsorbent for adsorption of Pb(II), Cd(II), Cu(II) and Hg(II) from aqueous solution. The surface characterization was performed by FT-IR, XPS, SEM and elemental analysis indicating that the modification of the silica surface was successfully performed. The effects of media pH, adsorption time, initial metal ion concentration and adsorption temperature on adsorption capacity of the adsorbent had been investigated. Experimental data were exploited for kinetic and thermodynamic evaluations related to the adsorption processes. The characteristics of the adsorption process were evaluated by using the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption isotherms and adsorption capacities were found to be 0.34 mmol g(-1), 0.36 mmol g(-1), 0.32 mmol g(-1) and 0.40 mmol g(-1) for Pb(II), Cd(II), Cu(II) and Hg(II), respectively. The adsorption mechanism of Hg(II) onto Si-DTC is quite different from that of Pb(II), Cd(II) or Cu(II) onto Si-DTC, which is demonstrated by the XPS and FT-IR results.

Energetic features of copper and lead sorption by innovative aminoalcohol-functionalized cobalt phyllosilicates

Inorganic-organic cobalt phyllosilicate hybrids were synthesized by the sol-gel procedure under mild non-hydrothermal conditions with a silicon precursor, formed through individual reactions between the silane 3-glycidoxypropyltriethoxysilane and the aminoalcohols ethanol- or diethanolamine. These procedures generated talc-like phyllosilicates containing pendant organic chains with nitrogen and oxygen basic centres located in the interlamellar region. For organofunctionalized phyllosilicates the lamellar structure obtained through the sol-gel method was confirmed by X-ray powder diffraction, while elemental analysis indicated that the densities of the organic groups attached to the new matrices were 3.31 ± 0.05 and 3.08 ± 0.07 mmol g(-1) for hybrids functionalized with ethanol- and diethanolamines, respectively. Infrared spectroscopy and nuclear magnetic resonance in the solid state for (13)C and (29)Si showed that the organic groups are indeed covalently bonded to the inorganic structures and the process of functionalization did not affect the original structures of the silylating agents employed. The thermally stable hybrids presented well-formed particles with a homogeneous distribution of cobalt and nitrogen atoms. Their abilities for copper removal from aqueous solutions gave maximum capacities of sorption of 2.01 ± 0.11 and 2.55 ± 0.15 mmol g(-1) for phyllosilicates containing ethanol- and diethanolamine groups, respectively. For lead sorption the values of 2.59 ± 0.11 and 2.43 ± 0.12 mmol g(-1) were found for this same sequence. These sorption data were adjusted to the non-linear regression of the Langmuir equation. Energetic features related to the interactions between the cations and the pendant basic centres were determined through calorimetric titrations. The acid-basic interactions reflect the spontaneity of the reactions, which are also enthalpically and entropically favourable for these chelating processes at the solid-liquid interface.

Silica coated magnetite particles for magnetic removal of Hg2+ from water

The magnetic removal of Hg(2+) from water has been assessed using silica coated magnetite particles. The magnetite particles were first prepared by hydrolysis of FeSO(4) and their surfaces were modified with amorphous silica shells that were then functionalized with organic moieties containing terminal dithiocarbamate groups. Under the experimental conditions used, the materials reported here displayed high efficiency for Hg(2+) uptake (74%) even at contaminant levels as low as 50 μg l(-1). Therefore these eco-nanomagnets show great potential for the removal of heavy metal ions of polluted water, via magnetic separation.