P25 TiO2 Nanoparticles Research Articles

A mechanistic study on photocatalytic activity of hydrothermally synthesized titanium dioxide nanowires decorated by silver phosphate

Heterostructure semiconductors have attracted increasing attention in the energy, environment, and catalysis domains. This study employed the hydrothermal method to synthesize titanium dioxide nanowires (TNWs) from TiO2–P25 nanoparticles. An effective strategy was used for coupling TNWs with a proper semiconductor with a narrow bandgap (Ag3PO4) for the purpose of enhancing absorption capacity in the visible light area and preventing the recombination of the photo-generated electrons and holes. The Ag3PO4/TNWs heterostructures consisted of Ag3PO4 nanoparticles firmly attached to the TNWs surfaces in varying ratios. The synthesized nanostructures were investigated by the Transmission Electron Microscopy (TEM), BET-BJH, and UV–Vis Diffusion Reflectance Spectra (DRS) techniques, as well as the X-ray diffractometer instrument. The photocatalytic degradation of RhB showed that the Ag3PO4/TNWs heterostructures manifested better photocatalytic performance than the pure TNWs and Ag3PO4. Likewise, the Ag3PO4/TNWs heterostructure photocatalyst reduced the loading of the noble Ag metal and thus decreased the practical application costs of the Ag3PO4 photocatalyst. A detailed mechanism study revealed the effective roles of holes and anion radical superoxides in the photocatalytic activity of the Ag3PO4/TNWs heterostructures.

Synthesis of 2D anatase TiO2 with highly reactive facets by fluorine-free topochemical conversion of 1T-TiS2 nanosheets.

Two-dimensional (2D) anatase titanium dioxide (TiO2) is expected to exhibit different properties as compared to anatase nanocrystallites, due to its highly reactive exposed facets. However, access to 2D anatase TiO2 is limited by the non-layered nature of the bulk crystal, which does not allow use of top-down chemical exfoliation. Large efforts have been dedicated to the growth of 2D anatase TiO2 with high reactive facets by bottom-up approaches, which relies on the use of harmful chemical reagents. Here, we demonstrate a novel fluorine-free strategy based on topochemical conversion of 2D 1T-TiS2 for the production of single crystalline 2D anatase TiO2, exposing the {001} facet on the top and bottom and {100} at the sides of the nanosheet. The exposure of these faces, with no additional defects or doping, gives rise to a significant activity enhancement in the hydrogen evolution reaction, as compared to commercially available Degussa P25 TiO2 nanoparticles. Because of the strong potential of TiO2 in many energy-based applications, our topochemical approach offers a low cost, green and mass scalable route for production of highly crystalline anatase TiO2 with well controlled and highly reactive exposed facets.

Mechanical Stability Is Key for Large-Scale Implementation of Photocatalytic Surface-Attached Film Technologies in Water Treatment

Replacement of classical tertiary water treatment by chemical-free sunlight-driven photocatalytic units has been often proposed. Photocatalysts are required to be cost-effective, inert, chemically stable, reusable, and easy to separate and also that they are mechanically stable. The effect of mechanical stress on a photoactive TiO2 layer, and on its effectivity for degradation of phenol as a model pollutant, has been studied during photocatalytic water treatment using NUV–vis light. Sol–gel (SG) and liquid phase deposition (LPD) methods have been used to coat spherical glass beads with the photocatalyst (TiO2). Physicochemical characterization of coated glass beads has been performed by N2 adsorption–desorption isotherms, SEM, EDXS, and AFM. Phenol photocatalyzed degradation was carried out both in stirred batch and flow reactors irradiated with a medium-pressure Hg-vapor lamp (λ > 350 nm). Phenol concentration was determined by HPLC, and its photoproducts were identified using HPLC/MS. In the stirred batch reactor, all LPD-coated glass beads displayed higher catalytic activity than SG-coated ones, which increased with calcination temperature, 700°C being the most efficient temperature. Preliminary etching of the glass beads surface yielded dissimilar results; whereas, phenol photodegradation with SG-coated etched glass beads is twice faster than with unetched SG ones, the rate reduces to one-third using LPD etched instead of unetched LPD glass beads. Phenol photodegradation using LPD is similar both in stirred batch and flow reactors, despite the latter uses a lower catalyst load. LPD-etched catalyst was recovered and reused in the stirred batch reactor; its activity reduced sharply after the first use, and it also lost activity in successive runs, ca. 10% of activity after each “use and recover” cycle. In the flow reactor, activity loss after the first experiment and recycling (ca. 30%) was much larger than in the following runs, where the activity remained rather constant through several cycles. LPD is more adequate than SG for TiO2 immobilization onto glass beads, and their calcination at 700°C leads to relatively strong and reactive photocatalytic films. Still, TiO2-coated glass beads exhibited very low photoactivity compared to TiO2-P25 nanoparticles, though their separation is much easier and almost costless. The durability of the catalytic layer increases when using a flow reactor, with the pollutant solution flowing in a laminar regime through the photocatalyst bed. In this way, the abrasion of the photocatalytic surface is largely reduced and its photoactivity is better maintained.

Integration of water collection and purification on cactus- and beetle-inspired eco-friendly superwettable materials

Freshwater shortage has been a terrible threat for the sustainable progress and development of human society in 21st century. Inspired from natural creatures, harvesting water from atmosphere has been a feasible and effective method to alleviate water shortage crisis. However, the recent works related to water collection just focuses on how to optimize fog-harvesting manners and efficiencies, the safety and availability of collected water are always ignored. In this paper, we proposed a new strategy accessed to freshwater resources through combining water collection and purification together on eco-friendly superwettable material inspired by cactus spines and desert beetles. Six superhydrophilic wedge-shaped patterns prepared by P25 TiO2 nanoparticles (NPs) were constructed on candle soot@polydimethylsiloxane (CS@PDMS) superhydrophobic coating. The special superhydrophilic regions not only effectively captured water from foggy environment but generated Laplace pressure gradient to faster drive water away. The bioinspired material exhibited an efficient water collection rate (WCR) of 14.9 ± 0.2 mg min−1 cm−2, which was 5.3 and 2.5 times larger than that on uniformed superhydrophilic and superhydrophobic surfaces, respectively. Because of the existence of photocatalytic P25 NPs in wetting areas, the harvested wastewater containing nine kinds of pesticides (0.5 mg/L) could be purified in low concentrations (< 5%) under UV light (365 nm, 5.0 ± 0.6 mW cm−2). Ten zebrafishes were still alive in such purified water for 72 h, as a contrast, the same number of fishes would almost die in untreated harvested wastewater in just 7 h. This work indeed opens up a new sight to freshwater accessibility, aiming to a promising project for alleviating water shortage around the world.

Photocatalytic oxidation of ceftiofur sodium under UV–visible irradiation using plasmonic porous Ag-TiO2 nanospheres

In this study, 250 nm sized porous anatase TiO2 nanospheres (TiO2 NSPs) composed of ∼ 10 nm sized anatase TiO2 nanoparticles are obtained through a green synthetic route and their surfaces have been decorated with 3–4 nm sized plasmonic silver nanoparticles (AgNPs). Photoluminescence studies confirm that the AgNPs presence on TiO2 NSPs surface effectively inhibits the radiative charge recombination and thus facilitates charge separation process at the Ag-TiO2 NSPs interface, causing an enhanced photocatalytic activity. About 92% of the ceftiofur sodium (CFS) antibiotic taken initially is oxidized by Ag-TiO2 NSPs upon 90 min white light irradiation, while Ag loaded Degussa P25 TiO2 nanoparticles effects only 71% CFS oxidation. The synergistic effect given by plasmonic AgNPs and the continuous framework of anatase TiO2 NPs contributes to inhibit the electron-hole recombination in the Ag-TiO2 NSPs. Oxidation products of CFS in different water sources and their eco-toxicity effects identified through LC-MS and microtox-bioassays, respectively, indicate that the obtained oxidation products are non-toxic compared to pure CFS. Therefore, porous Ag-TiO2 NSPs could be successfully applied in photocatalytic oxidation technologies, exploiting sunlight for the effective removal of pharmaceutical pollutants from wastewater.

Controlled growth of ultrasmall Cu2O clusters on TiO2 nanoparticles by atmospheric-pressure atomic layer deposition for enhanced photocatalytic activity

This work presents a gas-phase approach for the synthesis of Cu2O/TiO2 powder-based photocatalysts using atomic layer deposition (ALD). The process is carried out in a fluidized bed reactor working at atmospheric pressure using (trimethylvinylsilyl)-hexafluoroacetulacetonate copper(I) as the Cu-precursor and H2O vapor as the oxidizer. The saturating regime of the chemical reactions and the linear growth of ALD are achieved. In combination with the unsaturated regime, the ALD approach enables the deposition of ultrasmall Cu2O clusters with average diameters in the range of 1.3–2.0 nm, narrow particle size distributions and tunable Cu2O loadings on P25 TiO2 nanoparticles. The photocatalytic performance of Cu2O/TiO2 photocatalysts is investigated by the degradation of organic dyes, including Rhodamine B (RhB), methyl orange, and methylene blue; the results demonstrate that the surface modification of TiO2 nanoparticles by Cu2O nanoclusters significantly enhances the photocatalytic activity of TiO2. This is attributed to the efficient charge transfer between Cu2O and TiO2 that reduces the charge recombination. The photocatalytic reaction mechanism is further investigated for the degradation of RhB, revealing the dominating role of holes, which contribute to both direct hole oxidation and indirect oxidation (i.e. via the formation of hydroxyl radicals). Our approach provides a fast, scalable and efficient process to deposit ultrasmall Cu2O clusters in a controllable fashion for surface engineering and modification.

Ag nanoparticle-decorated SiO2@TiO2 hierarchical microspheres improve the efficiency of dye-sensitized solar cells

SiO2@TiO2-Ag (STA) microspheres decorated with Ag nanoparticles (Ag NPs) were prepared and assembled into the photoanode. The photoanode composed of STA microspheres and TiO2 nanoparticles (P25) was prepared by doctor blade method. UV–vis measurement indicates that the introduction of a few STA microspheres observably enhances the light scattering and capturing ability of the photoanode. The photoelectric conversion efficiency of the DSSCs with 2wt% STA photoanode increased to 7.4% from 4.3% comparing with pure P25 TiO2 nanoparticles. The configuration DSSCs have the maximum short circuit current density (Jsc) of 16.0 mA cm−2 and open-circuit voltage (Voc) of 0.780 V, which are significantly higher than the pure TiO2 DSSCs. The significant improvement of the DSSCs performance can be due to the synergistic effect of the superior light scattering of STA and the localized surface plasma resonance (LSPR) effect of Ag NPs modified on the microspheres surface.

Interparticle effects in the cotransport of viruses and engineered nanoparticles in saturated porous media

The effects of P25 TiO2 nanoparticles on the transport in saturated porous media of the bacteriophage PP7 was investigated. Two levels of ionic strength were considered, given by monovalent and divalent cations, Na+ and Ca2+. The viruses and the P25 particles were characterized with respect to size and surface charge, by dynamic light scattering and electron microscopy. The breakthrough curves were obtained for suspensions of each particle and both combined, using UV absorbance to quantify P25 and RT-qPCR for PP7. In the single transport experiments, P25 was retained, while the viruses mostly eluted the sand bed. However, in the cotransport experiments, retention increased for the virus and decreased for the TiO2 nanoparticles under high viral content, due to heteroaggregation among the colloids in the incoming suspension, electrostatic interactions, and ripening. The interparticle interactions were modeled by DLVO theory, resulting in agreement with the experimental observations, which highlights the electrostatic nature.

Novel TiO2 Nanoparticles/Polysulfone Composite Hollow Microspheres for Photocatalytic Degradation.

Nanosized titanium oxide (TiO2) material is a promising photocatalyst for the degradation of organic pollutants, whereas the difficulty of its recycling hinders its practical application. Herein, we reported the preparation of a novel titanium oxide/polysulfone (TiNPs/PSF) composite hollow microspheres by the combination of Pickering emulsification and the solvent evaporation technique and their application for the photodegradation of methyl blue (MB). P25 TiO2 nanoparticles dispersed on the surface of PSF microspheres. The porosity, density and photoactivity of the TiNPs/PSF composite microsphere are influenced by the TiO2 loading amount. The composite microsphere showed good methyl blue (MB) removal ability. Compared with TiO2 P25, and PSF, a much higher MB adsorption speed was observed for TiNPs/PSF microspheres benefited from their porous structure and the electrostatic attractions between the MB+ and the negatively charged PSF materials, and showed good degradation efficiency. For TiNPs/PSF composite microsphere with density close to 1, a 100% MB removal (10 mg L−1) within 120 min at a catalyst loading of 2.5 g L−1 can be obtained under both stirring and static condition, due to well dispersing of TiO2 particles on the microsphere surface and its stable suspending in water. For the non-suspended TiNPs/PSF composite microsphere with density bigger than 1, the 100% MB removal can be only obtained under stirring condition. The removal efficiency of MB for the composite microspheres retained 96.5%, even after 20 cycles. Moreover, this composite microsphere also showed high MB removal ability at acidic condition. The high catalysis efficiency, excellent reusability and good stability make this kind of TiNPs/PSF composite microsphere a promising photocatalyst for the water organic pollution treatment.

Photocatalytic activity of TiO2-P25@n-TiO2@HAP composite films for air depollution.

We report on an elaboration of new composite photocatalysts (TiO2-P25@ n-TiO2@HAP) based on grafted size-selected 5-nm titanium-oxo-alkoxo nanoparticles on P25-TiO2 nanoparticles and HAP obtained by co-precipitation of salts. The 5-nm oxo-TiO2 particles were prepared in a sol-gel reactor with rapid reagents micromixing. The photocatalytic test of ethylene degradation, in a continuous-flow fixed-bed reactor, showed an increase of the photocatalytic yield for the composite photocatalysts with an addition of HAP. This result was interpreted by a synergy between adsorption and photo-oxidation.

Cobalt carbide nanosheets as effective catalysts toward photothermal degradation of mustard-gas simulants under solar light

Here, ultrathin cobalt carbide (Co2C) nanosheets are firstly illustrated as effective and robust catalysts toward photothermal degradation of sulfur mustard simulants (e.g., 2-chloroethyl ethyl sulfide, CEES) under solar light. Under the optimal conditions, the degradation rate of CEES by Co2C nanosheets is up to 98 %, which is much higher than the widely used P25 and anatase TiO2 nanoparticles. Moreover, the degradation performance is comparable or even better than those typical photothermal catalysts, including MnO2, MnOx-TiO2 and Co3O4, under identical conditions. Experimental evidences and density functional theory (DFT) calculations reveal that the superior activity is attributed to three main reasons: (i) the high photo-to-heat conversion efficiency of Co2C enables an elevated surface temperature for chemical bond breaking, (ii) the feasible binding of CEES on Co2C surface via CoS and CoCl coordination promotes the process of degradation, and (iii) the surface hydroxyl groups (OH) on Co2C nanosheets favor the degradation of CEES. Obviously, this work provides new insights into practical and large-scale application of transition metal carbides (TMCs) as novel photothermal catalysts in the decontamination of chemical warfare agents (CWAs) under ambient conditions (i.e., solar light and room temperature).

New application for TiO2 P25 photocatalyst: A case study of photoelectrochemical sensing of nitrite ions

Developing photoelectrochemical (PEC) sensors based on photocatalytic materials has recently attracted great interest as an emerging technology for environmental monitoring. TiO2 P25 is a well-known highly active photocatalyst, cheap, and produced commercially on a large scale. In the current work, a practical and durable TiO2-based PEC sensor has been fabricated by immobilizing TiO2 P25 nanoparticles at disposable screen-printed carbon substrates using drop-casting method. The fabricated PEC sensor has been applied for the anodic-detection and determination of nitrite (NO2−) ions under UV(A) light (LED, 365 nm) using chronoamperometry (CA) and differential pulse voltammetry (DPV). Linear calibration curves were obtained between the photocurrent responses and the concentrations of NO2− ions in the ranges of 0.1–5.0 and 0.5–10 mg L−1 for CA and DPV, respectively. Surprisingly, the detection limits (sensitivities) of the fabricated sensor towards NO2− ions under light were enhanced by a factor of 4.75 (4.1) and 8.3 (37.4) for CA and DPV, respectively, in comparsion with those measured in the dark. It is found that the photo-excitation of TiO2 facilitates the photooxidation of NO2− ions via the photo-generated holes whereas the photogenerated electrons contribute to the enhanced photocurrent and consequently the enhanced detection limit and sensitivity. The fabricated TiO2-based PEC sensor exhibits a good stability, durability, and satisfying selectivity for NO2− ions determination. These results indicate that the TiO2-based PEC sensor fabricated by utilizing cheap and commercially available components has great potential for being transferred from lab-to-factory.

Shift the Photocatalytic Activity of P25 TiO2 Nanoparticles toward the Visible Region upon Surface Modification with Organic Hybrid of Phosphotungstate

In this study, a visible-light-driven P25 TiO2 was prepared upon surface modification with a colored organic hybrid of phosphotungstic acid that makes titanium dioxide suitable for photocatalytic degradation of organic pollutants under visible and sunlight irradiation. Visible shifting of the photocatalytic activity of surface-modified TiO2 was examined by studying the decolorization of methylene blue (MB) and rhodamine B (RhB). The results show that colored TiO2 is, unlike bare TiO2, a good photocatalyst in the degradation of dyes under visible and sunlight irradiation. Surface-modified Al2O3 and reduced graphene oxide (RGO) with organic hybrid of phosphotungstate failed to degrade RhB under sunlight irradiation, which prove the role of TiO2 in the photochemical process.

Photocatalytic degradation of pharmaceutically active compounds (PhACs) in urban wastewater treatment plants effluents under controlled and natural solar irradiation using immobilized TiO2

The degradation of pharmaceutically active compounds (PhACs) under controlled and natural solar irradiation using immobilized TiO2 was studied in model solution and real urban wastewater effluents. The TiO2 coatings were prepared via the sol–gel method with two different configurations, using simple (thin films) and the “sandwich” approach. Prepared coatings were characterized employing X-ray diffraction (XRD), scanning electron microscopy (SEM), ellipsometry and UV–Vis diffuse reflectance spectroscopy. Decomposition of PhACs detected in urban wastewater effluents (diclofenac, carbamazepine, atenolol, propranolol, albuterol, ofloxacin, ciprofloxacin, azithromycin, erythromycin, hydrochlorothiazide, and furosemide) was monitored using Ultra Performance Liquid Chromatography-Triple Quadrupole Mass Spectrometry (UPLC-QqQ-MS/MS). Among detected PhACs three are included in the Watch List (EU Decision 2018/840). The “sandwich” coatings (deposited on frosted support) with the following structure: anatase layer, TiO2 P25 nanoparticles and anatase layer (sealing film) demonstrated the highest photocatalytic activity among all tested TiO2 coatings and were used for elimination of PhACs from real urban wastewater effluents. Photocatalytic treatment of urban wastewater effluents under controlled and natural solar irradiation led to moderate and high removal (>40%) of all detected PhACs except carbamazepine and atenolol, for which poor removal efficiency was observed (~20%). Some of the PhACs compounds present in wastewater effluents, such as diclofenac, ofloxacin, ciprofloxacin, hydrochlorothiazide and furosemide were sensitive to solar photolysis. The efficiency of solar photocatalytic inactivation of Escherichia coli present in urban wastewater effluent was similar to that of solar disinfection (SODIS).

Tuning the photocatalytic activity of TiO2 nanoparticles by ultrathin SiO2 films grown by low-temperature atmospheric pressure atomic layer deposition

We employed atomic layer deposition (ALD) to deposit ultrathin SiO2 layers on P25 TiO2 nanoparticles to fabricate TiO2/SiO2 core/shell nanostructures. The ALD process was carried out in a fluidized bed reactor working at atmospheric pressure using SiCl4 and H2O as precursors, enabling the deposition of SiO2 at 100 °C with the ability to control the thickness at the sub-nanometer level. By controlling the thickness of the SiO2 in a very narrow range, i.e., below 2 nm, the photocatalytic activity of TiO2 can be tuned. In particular, an enhancement was obtained for the SiO2 layers with a thickness below 1.4 nm, in which the layer with a thickness of about 0.7 nm exhibited the highest photocatalytic activity; for SiO2 layers thicker than 1.4 nm, the photocatalytic activity was strongly suppressed. The photocatalytic activity enhancement and the degradation mechanism of RhB by the TiO2/SiO2 photocatalysts were investigated by combining X-ray photoelectron spectroscopy, UV–Vis absorption spectroscopy, photoluminescence spectroscopy and the aid of charge carrier and radical scavengers. Our findings have revealed an improvement of photogenerated charge separation due to the SiO2 coating and the dominating role of hydroxyl radicals in the degradation of RhB.

Artificial Neural Network Modelling of Photocatalytic Degradation of Diclofenac as a Pharmaceutical Contaminant

In this work, the photocatalytic removal of diclofenac (DCF) was investigated using TiO2-P25 nanoparticles immobilized on glass beads in a packed bed photoreactor. DCF is one of the non-steroidal anti-inflammatory drugs used as an analgesic drug. DCF is monitored in urban sewage and surface waters as a stable contaminant that can harm the environment. Advanced oxidation processes (AOPs) are promising methods for degradation and removal of environmental pollutants. The heterogeneous photocatalysis process is one of the AOPs so that the contaminants are decompose in the presence of UV light and a photocatalyst (TiO2). Holes and hydroxyl radicals are the main active species in the UV/TiO2 process. A thin layer of TiO2-P25 nanoparticles was immobilized by heat attachment method on glass beads. The effect of five operational parameters, the initial concentration of DCF, the power of the light source, the flow rate of the fluid in the photoreactor, irradiation time and pH, has been studied experimentally in the efficiency of the photoreactor. The DCF removal percent is 99% for the initial DCF concentration of 10 mg L–1, the power of the light source of 16 W, the fluid flow rate of 240 mL min–1 and pH 6 for 120 min irradiation time. The effect of operational parameters on the DCF removal percent was modeled using the artificial neural network (ANN). ANN modeling with a 5 : 9 : 1 feed-forward back propagation neural network demonstrated the appropriate consistency of the experimental and predicted data. The R2 values for all data (training, validation and test) were close to 1, confirming ANN reasonable predictive performance. Using the weights of the ANN model in the Garson equation, indicated that pH and irradiation time had the highest effect on the DCF removal percent.

Response surface methodology and artificial neural network for remediation of acid orange 7 using TiO2-P25: optimization and modeling approach.

The primary responsibility for continuously discharging toxic organic pollutants into water bodies and open environments is the increase in industrial and agricultural activities. Developing economical and suitable methods to continuously remove organic pollutants from wastewater is highly essential. The aim of the present research was to apply response surface methodology (RSM) and artificial neural networks (ANNs) for optimization and modeling of photocatalytic degradation of acid orange 7 (AO7) by commercial TiO2-P25 nanoparticles (TNPs). Dose of TNPs, pH, and AO7 concentration were selected as investigated parameters. RSM results reveal the reflective rate of AO7 removal of ~ 94.974% was obtained at pH7.599, TNP dose of 0.748g/L, and AO7 concentration of 28.483mg/L. The resulting quadratic model is satisfactory with the highest coefficient of determination (R2) between the predicted and experimental data (R2 = 0.98 and adjusted R2 = 0.954). On the other hand, ANNs were successfully employed for modeling of AO7 degradation process. The proposed ANN model was absolutely fitted with experimental results producing the highest R2. Furthermore, root mean square error (RMSE), mean average deviation (MAD), absolute average relative error (AARE), and mean square error (MSE) were examined more to compare the predictive capabilities of ANN and RSM models. The experimental data was well fitted into pseudo-first-order and pseudo-second-order kinetics with more accuracy. Thermodynamic parameters, namely enthalpy, entropy, Gibbs' free energy, and activation energy, were also evaluated to suggest the nature of the degradation process. The increase of temperature was analyzed to be more suitable for the fast removal of AO7 over TNPs. Graphical abstract.

Scattering phase function of fractal aggregates of TiO2 particulate photocatalyst simulated with discrete dipole approximation

The aggregate structures of photocatalyst particles are critical for their light absorption and scattering properties and thus significantly impact the photocatalytic performance toward solar hydrogen production. Herein, taking P25 TiO2 nanoparticles as model photocatalysts, we calculate the optical properties of the aggregates of nanoparticles with the Discrete Dipole Approximation (DDA). A scattering phase function, which can reveal and predict the structural information of photocatalyst particles, is accordingly obtained. Specifically, it is found that the forward scattering is dominant when light is scattered on the particles, and this scattering mode becomes more intense with the increment of the particle size. Our results show that the scattering phase function is also in agreement with the Rayleigh-Gans-Debye (RGD) approximation.

Removal of titanium dioxide nanoparticles from wastewater using traditional chemical coagulants and chitosan

AbstractAlum and ferric chloride were used individually as coagulants to remove P25 TiO2 nanoparticles (NPs) from a simulated wastewater. Previous studies have addressed the use of alum, polyaluminum chloride, chitosan, and polyaluminum chloride with chitosan for coagulation of NPs. A goal of this study was to reduce chemical usage associated with wastewater treatment by examining the coagulation effectiveness of chitosan in conjunction with alum. To further reduce chemical consumption during coagulation, the initial solution pH was limited to 6 or 8. A range of alum doses removed NPs from pH 8 wastewater to achieve residual turbidity &lt;1 NTU. NP removal from pH 6 solutions produced water with residual turbidity &lt;2 NTU only at lower initial NP concentrations. For pH 8 solutions, ferric chloride produced treated water with residual turbidity &lt;1 NTU but at higher doses than required for alum. While chitosan alone did not significantly reduce turbidity, the use of alum and chitosan together reduced the optimal alum dose by 10% and also reduced alum treatment acidification. Therefore, the use of chitosan in coagulation can potentially reduce chemical usage during water treatment and the energy and water consumption associated with chemical production. Use of alum with low chitosan concentrations produces faster settling floc, which can potentially reduce settling tank volume and produce an effluent containing lower aluminum concentrations.

Structural and magnetic properties of P25 TiO2 nanoparticles doped by Co

The present work reports on the structural and magnetic properties of TiO2 P25 Degussa powder doped with cobalt. Dissolution of cobalt in TiO2 matrix was achieved by precipitation of tris(diethyldithiocarbamato) cobalt(III) (CoDtc - Co[S2CN(C2H5)2]3 in chloroform (CHCl3) and consequent thermal treatment. Five different Co atomic percentage contents were chosen, e.g., 0.5%, 1%, 2%, 5% and 10%. It was shown that cobalt atoms are uniformly distributed across TiO2 matrix and exhibit antiferromagnetic interactions at low temperatures.