Search

Refereed/Peer-reviewed Imogolite belongs to the family of nanotubular metal oxides which are useful for the construction of new materials in nanotechnology. This study aims to develop a simple waste valorization method to obtain imogolite from cement kiln dust (CKD) via solubilization of CKD and subsequent precipitation of imogolite (Imo-CKD) in a hydrothermal process. The newly synthesized Imo-CKD and a conventional imogolite (Imo) showed similar diameter (Ø) and length (L) of nanotubes [Ø≅ 1.9 nm and L ≅ 200 nm] and crystallinity grade but different values of isoelectric point (IEP) [IEPImo−CKD=8.86 and IEPImo=9.92]. The shift in the IEP value of Imo-CKD to a lower value was attributed to the presence of allophane as a subproduct during Imo-CKD synthesis. Arsenite [As(III)] removal from water by both the imogolites was a rapid (t ≤ 20 min) and spontaneous process. The kinetic As(III) removal data obeyed the pseudo-second order model, while surface diffusion also controlled the As(III) adsorption process. The activation energy (Ea > 40 kJ mol−1) suggested a chemical adsorption of As(III) in both materials. The Imo-CKD (0.377 mmol g−1) removed As(III) from water more efficiently than Imo (0.334 mmol g−1), despite the formation of allophane byproduct in the synthesis process. Results of this study can promote the reuse of inexpensive CKD as a viable alternative to replace costly tetraethyl orthosilicate for imogolite synthesis and use of imogolite for water pollutant removal.

usc This study aims to understand how properties of modified aluminosilicate geomaterials influence the antibacterial performance of nanocomposites when prepared with bimetallic nanoparticles (NPs). Copper/silver (Cu/Ag) bimetallic NPs were synthesized in the presence of imogolite (Imo), montmorillonite (Mtt), or zeolite (Zeo) using a simple one-pot method and characterized for their crystal phases, micro- and nanomorphologies, particle size, elemental composition, and electrophoretic mobility. The antibacterial activity was evaluated through minimum inhibition concentration assays of NPs and nanocomposites for Gram (−) Escherichia coli and Gram (+) Staphylococcus aureus bacteria. Deposition of metallic Cu0, Ag0, and cuprite NPs was confirmed in Zeo_Cu/Ag and Imo_Cu/Ag nanocomposites, whereas only Cu0 and Ag0 were identified in Mtt_Cu/Ag. The bimetallic NPs were more uniformly distributed on Zeo and Mtt than Imo. Particle sizes of 28.1 ± 5.0, 9.4 ± 2.3, 10.1 ± 1.7, and 12 ± 1.3 nm were determined for Cu/Ag NPs, Imo_Cu/Ag, Mtt_Cu/Ag, and Zeo_Cu/Ag, respectively. The release rate of Cu and Ag ions from Zeo_Cu/Ag was higher than those of pristine Cu/Ag NPs and the other two nanocomposites. The antimicrobial action of bimetallic NPs and nanocomposites was dose-dependent in relation to the concentration of concerned materials and their stability in the medium. The physicochemical characteristics of Zeo resulted in a homogeneous distribution and low oxidation and agglomeration of Cu/Ag NPs, consequently increasing the antibacterial activity. Results of this study highlight the benefits of using a geomaterial support to achieve high antibacterial activity of bimetallic NPs, which could help reduce the consumption of pure Cu/Ag salts in NP-based antibacterial applications. Refereed/Peer-reviewed

A novel hybrid nanomaterial, nanoscale zero-valent iron (nZVI)-grafted imogolite nanotubes (Imo), was synthesized via a fast and straightforward chemical procedure. The as-obtained nanomaterial (Imo-nZVI) was characterized using transmission electron microscopy (TEM), electrophoretic mobility (EM) and vibrating sample magnetometry (VSM). The prepared Imo-nZVI was superparamagnetic at room temperature and could be easily separated by an external magnetic field. Sorption batch experiments were performed in single- and multicomponent system and showed that Hg2+ and Pb2+ could be quantitatively adsorbed at pH 4.0 with maximum adsorption capacities of 62.3 and 73.8 mg·g− 1, respectively. It was observed that the functional groups in Imo-nZVI interact preferentially with analytes according to Misono Softness parameter. The higher performance of Imo-nZVI compared with Imo and nZVI is related to the increased adsorption sites in the functionalized nanomaterial. The sorption equilibrium data obeyed the Langmuir model, while kinetic studies demonstrated that the sorption processes of Hg2+ and Pb2+ followed the pseudo-second-order model. This study suggests that the Imo-nZVI composite can be used as a promising sorbent and provides a simple and fast separation method for the removal of Hg and Pb ions from contaminated water.

Nanoscale zero-valent iron (NZVI) and NZVI supported onto montmorillonite (NZVI-Mt) were synthetized and used in this study to remove Se-VI and As-V from water in monoand binary-adsorbate systems. The adsorption kinetics and isotherm data for Se-VI and As-V were adequately described by the pseudo-second-order (PSO) (r(2)>0.94) and Freundlich (r(2)>0.93) equations. Results from scanning electron microscopy showed that the dimension of the NZVI immobilized on the Mt was smaller than pure NZVI. Using 0.05 g of adsorbent and an initial 200 mg L-1 As-V and Se-VI concentration, the maximum adsorption capacity (q(max)) and partition coefficient (PC) for As-V on NZ(VI)-Mt in monocomponent system were 54.75 mg g(-1) and 0.065 mg g(-1).mu M-1, which dropped respectively to 49.91 mg g(-1) and 0.055 mg g(-1).mu M-1 under competitive system. For Se-VI adsorption on NZ(VI)-Mt in monocomponent system, q(max) and PC were 28.63 mg g(-1) and 0.024 mg g(-1).mu M-1, respectively. Values of q(max) and PC were higher for NZVI-Mt than NZVI and montmorillonite, indicating that the nanocomposite contained greater adsorption sites for removing both oxyanions, but with a marked preference for As-V. Future research should evaluate the effect of different operational variables on the removal efficiency of both oxyanions by NZVI-Mt. usc Refereed/Peer-reviewed

Imogolite and magnetic imogolite-Fe oxide nanocomposites (Imo-Fe50 and Imo-Fe25, at 50 and 25 % Fe loading (w/w), respectively) were synthesized and tested for the removal of aqueous copper (Cu), cadmium (Cd), and arsenic (As) pollutants. The materials were characterized by transmission electron microscopy, and specific surface area and isoelectric point measurements. The Fe-containing samples were additionally characterized by Mössbauer spectroscopy and vibrating-sample magnetometry. Significant differences were found in the morphological, electrophoretic, and magnetic characteristics between imogolite and the nanocomposites. The in-situ Fe-oxide precipitation process modified the active surface sites of the imogolite. The Fe–oxide, mainly magnetite, favored the contaminants’ adsorption over the pristine imogolite. The adsorption kinetics of these pollutants were adequately described by the pseudo-second order and intraparticle diffusion models. The kinetic models showed that surface adsorption was more important than intraparticle diffusion in the removal of the pollutants by all the adsorbents. The Langmuir-Freundlich model described the experimental adsorption data, and both nanocomposites showed greater adsorption capacity than the imogolite. The adsorption of Cu and Cd was sensitive to cationic competition, showing a decrease of the adsorption capacity when the two cations coexisted, while their adsorption increased in the presence of arsenate. Refereed/Peer-reviewed

To evaluate the potential role of phenolic compounds in Al and Cd stress tolerance mechanisms, Vaccinium corymbosum cv. Legacy plantlets were exposed to different metal concentrations. The present study used an in vitro plant model to test the effects of the following treatments: 100μM Al; 100μMAl + 50μMCd; and 100μMAl + 100μMCd during periods of 7, 14, 21 and 30 days. The oxidative damage was determined by the accumulation of malondialdehyde (MDA) and hydrogen peroxide (H2O2). The antioxidant activity values were determined using 1,1-diphenyl-2-picrylhydrazine (DPPH) and the ferric reducing antioxidant power test (FRAP). Additionally, the phenolic compound concentrations were determined using HPLC-DAD. The exposure to Al and Cd increased the MDA and H2O2 contents differentially, while the antioxidant capacity values showed differences between DPPH and FRAP with the largest changes in FRAP relative to Cd. SOD had the highest activity in the first 7 days, leading to a significant increase in phenolic compounds observed after 14 days, and chlorogenic acid was the major compound identified. Our results revealed that phenolic compounds seem to play an important role in the response to ROS. Therefore, the mechanisms of tolerance to Al and Cd in V. corymbosum will be determined by the type of metal and time of exposure.

The application of iron nanoparticles (FeNPs) to the removal of various pollutants has received wide attention over the last few decades. A synthesis alternative to obtain these nanoparticles without using harmful chemical reagents, such as NaBH 4 , is the use of extracts from different natural sources that allow a lesser degree of agglomeration, in a process known as green synthesis. In this study, FeNPs were synthesized by ‘green’ (hereafter, BB-Fe NPs) and ‘chemical’ (hereafter, nZVI) methods. Extracts of leaves and blueberry shoots ( Vaccinium corymbosum ) were used as reducing agents for FeCl 3 ·6H 2 O solution in the green synthesis method. FeNPs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), electrophoretic migration, Brunauer-Emmett-Teller (BET) surface area analysis and X-ray diffraction (XRD) and evaluated for the removal of As(V) from aqueous systems. In both synthesis methods, XRD analysis confirmed the presence of the different kinds of iron nanoparticles. SEM analysis showed that the average size of BB-Fe NPs was 52.4 nm and that a variety of nanoparticles of different forms and associated structures, such as lepidocrocite, magnetite, and nZVI, were present, while the dimensions of nZVI were 80.2 nm. Comparatively significant differences regarding the electrophoretic mobility were found between both materials pre- and post-sorption of As(V). The velocity of As(V) removal by BB-Fe NPs was slower than that by nZVI, reaching equilibrium at 120 min compared to 60 min for nZVI. The removal kinetics of As(V) were adequately described by the pseudo-second-order kinetic model, and the maximum adsorbed amounts of this analyte are in close accordance with the experimental results. The Langmuir-Freundlich model is in good agreement with our experimental data, where the sorption capacity of nZVI and BB-Fe NPs was found to be 52.23 ± 6.06 and 50.40 ± 5.90 (mg·g −1 ), respectively. The use of leaves of Vaccinium corymbosum affords an easy-to-synthesize, low-cost, and eco-friendly material with capabilities similar to nZVI. BB-Fe NPs are promising for arsenic remediation, which has emerged as a new alternative for water purification and sanitation.

Cadmium (Cd(2+)) can affect plant growth due to its mobility and toxicity. We evaluated the effects of Cd(2+) on the production of phenolic compounds and antioxidant response of Vaccinium corymbosum L. Plantlets were exposed to Cd(2+) at 50 and 100µM for 7, 14 and 21 days. Accumulation of malondialdehyde (MDA), hydrogen peroxide (H2O2) and the antioxidant enzyme SOD was determined. The profile of phenolic compounds was evaluated using LC-MS. The antioxidant activity was measured using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the ferric reducing antioxidant power test (FRAP). Cd(2+) increased the content of MDA, with the highest increase at 14 days. The presence of Cd(2+) resulted in changes in phenolic compounds. The main phenolic compound found in blueberry plantlets was chlorogenic acid, whose abundance increased with the addition of Cd(2+) to the medium. The changes in the composition of phenolic compounds showed a positive correlation with the antioxidant activity measured using FRAP. Our results suggest that blueberry plantlets produced phenolic compounds with reducing capacity as a selective mechanism triggered by the highest activity of Cd(2+).