脱硫灰与钾矿石复合生产钾钙硅镁硫肥料研究

对脱硫灰与钾矿石复合生产钾钙硅镁硫肥的研究意义、反应原理、生产流程、环境安全性能以及施肥方法等进行了介绍和评估,并对其应用前景进行了展望。研究结果表明:利用脱硫灰与钾矿石复合生产钾钙硅镁硫肥在理论上可行;生产出的产品中硫酸钾的含量达10.34%～12.0%,枸溶氧化钙19.06%～32.28%,枸溶二氧化硅10.98%～14.46%,枸溶氧化镁1.46%～1.82%。产品的pH值从原脱硫灰的10.65下降到9.60。重金属含量低于农用粉煤灰国家标准,生产过程中不会产生SO2等有害气体污染。肥料的生产成本低于350元/t,该肥料不但可以增加土壤中钾、钙、硅、镁和硫等中微量元素的含量,而且可以提高或改善农作物的产量和品质。达到变废为宝,促进循环经济发展之目的。     

Oxidative stress, cytoxicity, and cell mortality induced by nano-sized lead in aqueous suspensions

This paper reports on the effect of aqueous and nano-particulated Pb on oxidative stress (lipid peroxidation), cytoxicity, and cell mortality. As determined by the Thiobarbituric Acid Reactive Substances (TBARS) method, only 6 h after incubation aqueous suspensions bearing nano-sized PbO₂, soluble Pb(II), and brain-homogenate only suspensions, were determined to contain as much as ca. 7, 5, and 1 nmol TBARS mg protein⁻¹, respectively. Exposure of human cells (central nervous system, prostate, leukemia, colon, breast, lung cells) to nano-PbO₂ led to cell-growth inhibition values (%) ca. ≤18.7%. Finally, as estimated by the Artemia salina test, cell mortality values were found to show high-survival larvae rates. Microscopic observations revealed that Pb particles were swallowed, but caused no mortality, however.     

The use of chemical and statistical methods to identify sources of selected elements in ambient air aerosols in Karachi,Pakistan

Concentrations of 23 elements plus NO₃⁻, SO₄²⁻ and Cl⁻ were determined for samples collected continuously every 3 or 6 h during 22–27 July, 1985 at a suburban site in Karachi, Pakistan. Concentrations of lithophilic elements and several anthropogenic elements were ~ 80 % higher during daytime than at night. These elevated levels were attributed to daytime increases in wind velocity and anthropogenic activity. Factor analysis showed that ~ 50% of the variance was associated with soil, and ~ 14 % each with oceanic Na and Cl⁻, anthropogenic Sb and Pb, and Zn, Se and SO₄²⁻. A cement (limestone/dolomite) factor was not separated even though Ca and Mg concentrations were unusually high and a cement factory was located nearby. This led to an investigation of a chemical approach to determine the sources. Concentrations of Na, Mg and Ca were determined in water-extracts of the samples. Assuming soluble Na (~ 92 % of total) to be sea derived, marine components of Mg, SO₄²⁻, Ca and Br were determined. Solubility considerations were then used to reveal the cement source and apportion the aerosol sources. On the average, approximately 48 % of the total aerosol mass could be accounted for by the ‘cement’ and ‘soil’ components; about 12 % by the ‘sea salt’, about 3% by the ‘fossil fuel’ SO₄²⁻ (as (NH₄)₂SO₄); about 1 % by the NO₃⁻ (as NH₄NO₃); the remaining 36 % of the aerosol mass was unassigned.     

In vivo genotoxicity assessment of titanium,zirconium and aluminium nanoparticles,and their microparticulated forms,in Drosophila

As in vivo system, we propose Drosophila melanogaster as a useful model for study the genotoxic risks associated with nanoparticle exposure. In this study we have carried out a genotoxic evaluation of titanium dioxide (TiO₂), zirconium oxide (ZrO₂) and aluminium oxide (Al₂O₃) nanoparticles and their microparticulated forms in D. melanogaster by using the wing somatic mutation and recombination assay. This assay is based on the principle that loss of heterozygosis and the corresponding expression of the suitable recessive markers, multiple wing hairs and flare-3, can lead to the formation of mutant clones in treated larvae, which are expressed as mutant spots on the wings of adult flies. Third instar larvae were feed with TiO₂, ZrO₂ and Al₂O₃ nanoparticles, and their microparticulated forms, at concentrations ranging from 0.1 to 10 mM. Although a certain level of aggregation/agglomeration was observed in solution, it must be noted than the constant digging activity of larvae ensures that treated medium pass constantly through the digestive tract ensuring exposure. The results showed that no significant increases in the frequency of all spots (e.g. small single, large single, twin, total mwh and total spots) were observed, indicating that these nanoparticles were not able to induce genotoxic activity in the wing spot assay of D. melanogaster. Negative data were also obtained with the microparticulated forms. This indicates that the nanoparticulated form of the selected nanomaterials does not modify the potential genotoxicity of their microparticulated versions. These in vivo results contribute to increase the genotoxicity database on the TiO₂, ZrO₂ and Al₂O₃ nanoparticles.     

Toxicity of TiO2, ZrO2, Fe,Fe2O3, and Mn2O3 nanoparticles to the yeast, Saccharomyces cerevisiae

The growing application of engineered nanomaterials is leading to an increased occurrence of nanoparticles (NPs) in the environment. Thus, there is a need to better understand their potential impact on the environment. This study evaluated the toxicity of nanosized TiO₂, ZrO₂, Fe⁰, Fe₂O₃, and Mn₂O₃ towards the yeast Saccharomyces cerevisiae based on O₂ consumption and cell membrane integrity. In addition, the state of dispersion of the nanoparticles in the bioassay medium was characterized.     

Shape-dependent bactericidal activity of TiO2 for the killing of Gram-negative bacteria Agrobacterium tumefaciens under UV torch irradiation

This paper demonstrated the relative bactericidal activity of photoirradiated (6W-UV Torch, λ?>?340 nm and intensity?=?0.64 mW/cm²) P25–TiO₂ nanoparticles, nanorods, and nanotubes for the killing of Gram-negative bacterium Agrobacterium tumefaciens LBA4404 for the first time. TiO₂ nanorod (anatase) with length of 70–100 nm and diameter of 10–12 nm, and TiO₂ nanotube with length of 90–110 nm and diameter of 9–11 nm were prepared from P-25 Degussa TiO₂ (size, 30–50 nm) by hydrothermal method and compared their biocidal activity both in aqueous slurry and thin films. The mode of bacterial cell decomposition was analyzed through transmission electron microscopy (TEM), Fourier transform-infrared (FT-IR), and K⁺ ion leakage. The antimicrobial activity of photoirradiated TiO₂ of different shapes was found to be in the order P25–TiO₂?>?nanorod?>?nanotube which is reverse to their specific surface area as 54?<?79?<?176 m² g^?1, evidencing that the highest activity of P25–TiO₂ nanoparticles is not due to surface area as their crystal structure and surface morphology are entirely different. TiO₂ thin films always exhibited less photoactivity as compared to its aqueous suspension under similar conditions of cell viability test. The changes in the bacterial surface morphology by UV-irradiated P25–TiO₂ nanoparticles was examined by TEM, oxidative degradation of cell components such as proteins, carbohydrates, phospholipids, nucleic acids by FT-IR spectral analysis, and K⁺ ion leakage (2.5 ppm as compared to 0.4 ppm for control culture) as a measure of loss in cell membrane permeability.     

Evaluation of three common alkaline agents for immobilization of multi-metals in a field-contaminated acidic soil

We investigated three common alkaline agents (NaOH, CaO, and Mg(OH)₂) for immobilization of four heavy metals (Pb, Zn, Cu, and Cd) in a field-contaminated soil and elucidated the underpinning principles. NaOH caused the highest pH spike in the soil, while CaO and Mg(OH)₂ served as a longer-lasting source of OH^-. Amending the soil with CaO or Mg(OH)₂ at ≥0.1 mol as OH^- (kg·soil)^?1 for 24 h was able to immobilize all four metals, while NaOH failed. NaOH leached up to 3 times more organic carbon than CaO and Mg(OH)₂, resulting in elevated leachability of the metals. Column elution tests showed that amendments by CaO and Mg(OH)₂ lowered the leachable Pb²⁺, Zn²⁺, Cu²⁺, and Cd²⁺ by 52–54%, 71–75%, 69–73%, and 68%, respectively, after 1440 pore volumes of elution. Sequential extraction revealed that the soil amendments converted the exchangeable fraction of the metals to the much less available forms. XRD and FTIR analyses indicated that formation of metal oxide precipitates and complexation with soil organic matter were responsible for the metals immobilization. Taken together the chemical cost, technical effectiveness, and environmental impact, CaO is the most suitable alkaline agent for remediation of soil contaminated with heavy metals.

     

Silica-Enhanced Sorbents for Dry Injection Removal of SO2 from Flue Gas

Novel silica-enhanced lime sorbents were tested in a bench-scale sand-bed reactor for their potential for SO₂ removal from flue gas. Reactor conditions were 64°C (147°F), relative humidity of 60 percent [corresponding to an approach to saturation temperature of 10°C (18°F)], and inlet SO₂ concentration of 500 or 1000 ppm. The sorbents were prepared by pressure hydration of CaO or Ca(OH)₂ with siliceous materials at 100°C (101 kPa) [212°F (14.7 psi)] to 230°C (2793 kPa) [446°F (405 psi)] for 15 min to 4 h. Pressure hydration fostered the formation of a sorbent reactive with SO₂ from fly ash and Ca(OH)₂ in a much shorter time than did atmospheric hydration. The conversion of Ca(OH)₂ in the sand-bed reactor increased with the increasing weight ratio of fly ash to lime and correlated well with B.E.T. surface area, increasing with increasing surface area. The optimum temperature range for the pressure-hydration of fly ash with Ca(OH)₂ was between 110 and 160°C (230 and 320 °F). The pressure hydration of diatomaceous earth with CaO did not offer significant reactivity advantages over atmospheric hydration; however, the rate of enhancement of Ca(OH)₂ conversions was much faster with pressure hydration. Scanning electron microscope (SEM) and x-ray diffraction studies showed solids of different morphology with different fly ash/lime ratios and changing conditions of pressure hydration.     

Solubility products of six metal‐glyphosate complexes in water and forestry soils,and their influence on glyphosate toxicity to plants

Abstract

The solubility products (K_sp) of 1:1 complexes of glyphosate, [N‐(phosphonomethyl)glycine], with Mg²⁺, Ca²⁺, Mn²⁺, Zn²⁺, Cu²⁺ and Fe³⁺, were determined in buffered (pH 7.0) distilled water, moist Ottawa sand, sandy loam and clay loam soils, each adjusted to 0.02 M with respect to KNO₃. The K_sp values decreased in the order of Mg ? Ca > Mn > Zn > Cu > Fe, regardless of the medium in which they were determined. The constants measured in Ottawa sand were similar to those in water, but those in the forestry soils depended upon the type of metal ion involved. The values for the Mg, Ca, Mn and Zn complexes were about 2 to 3 times lower in sandy loam soil than those in water, but those in clay loam were about 3 to 10 times lower. The K_sp of the Cu and Fe complexes were similar to those in water regardless of the soil type used.

In a bioassay experiment using tomato plants, immersed in the saturated solutions of the complexes or planted in the sand and soils containing saturated solutions of the complexes, no mortality occurred although slight inhibition in growth was observed in all cases. The most soluble complexes of Mg and Ca caused the most reduction in plant height, while the least soluble complex of Fe caused little growth inhibition. The Zn, Cu and Mn complexes caused some growth inhibition depending on their K_sp values. The larger the solubility product, the greater the concentration of glyphosate ion in solution, and the greater the growth inhibition. In a similar experiment using white spruce seedlings, growth inhibition was insignificant over the 12‐d bioassay period.     

Photocatalytic Degradation of the Herbicide Erioglaucine in the Presence of Nanosized Titanium Dioxide: Comparison and Modeling of Reaction Kinetics

The present work mainly deals with photocatalytic degradation of a herbicide, erioglaucine, in water in the presence of TiO₂ nanoparticles (Degussa P-25) under ultraviolet (UV) light illumination (30 W). The degradation rate of erioglaucine was not so high when the photolysis was carried out in the absence of TiO₂ and it was negligible in the absence of UV light. We have studied the influence of the basic photocatalytic parameters such as pH of the solution, amount of TiO₂, irradiation time and initial concentration of erioglaucine on the photodegradation efficiency of erioglaucine. A kinetic model is applied for the photocatalytic oxidation by the UV/TiO₂ system. Experimental results indicated that the photocatalytic degradation process could be explained in terms of the Langmuir–Hinshelwood kinetic model. The values of the adsorption equilibrium constant, K, and the second order kinetic rate constant, k, were 0.116 ppm^{? 1} and 0.984 ppm min^{? 1}, respectively. In this work, we also compared the reactivity between the commercial TiO₂ Degussa P-25 and a rutile TiO₂. The photocatalytic activities of both photocatalysts were tested using the herbicide solution. We have noticed that photodegradation efficiency was different between both of them. The higher photoactivity of Degussa P-25 compared to that of rutile TiO₂ for the photodegradation of erioglaucine may be due to higher hydroxyl content, higher surface area, nano-size and crystallinity of the Degussa P-25. Our results also showed that the UV/TiO₂ process with Degussa P-25 as photocatalyst was appropriate as the effective treatment method for removal of erioglaucine from a real wastewater. The electrical energy consumption per order of magnitude for photocatalytic degradation of erioglaucine was lower with Degussa P-25 than in the presence of rutile TiO₂.     

Trichloroethylene decomposition and in-situ dry sorption of Cl-products by calcium oxides prepared from hydrated limes

A comparison of CaOs produced by calcining two types of hydrated lime and calcium carbonate was made for decomposition of trichloroethylene and in-situ dry sorption of the decomposed Cl-products using a lab-scale gas flow type tubular packed bed reactor. About 20 mg of CaO sample was mixed with about 2 g of Al₂O₃ particles and packed in the reactor and allowed to react with a flowing standard gas containing 500 ppm of C₂HCl₃ (N₂ balance) at 673 and 873 K, under the condition that the reaction of CaO with C₂HCl₃ might be completed within a few hours.It was found that no thermal decomposition of C₂HCl₃ at or below 673 K was observed in a reactor packed only with Al₂O₃ particles. However, a considerable amount of decomposition of C₂HCl₃ was obtained in a reactor packed with CaO and Al₂O₃, even at 673 K. For 1 mol of CaO prepared by calcining highly reactive Ca(OH)₂ at 673 K, decomposition of 0.42 mol of C₂HCl₃ and in-situ absorption product of 0.53 mol of CaCl₂ were obtained. At 873 K, about 46% of C₂HCl₃ was thermally decomposed. The total amount of C₂HCl₃ decomposed in CaO-Al₂O₃ particle bed at 873 K became nearly twice larger than that at 673 K. For 1 mol of CaO prepared by calcining highly reactive Ca(OH)₂ at 873 K, decomposition of 0.59 mol of C₂HCl₃ and in-situ absorption product of 0.67 mol of CaCl₂ were obtained. Small amounts of C₂Cl₂, C₂Cl₄, CCl₄, etc. were detected during decomposition of C₂HCl₃ at 673 and 873 K.It was recognized that the data on decomposition of C₂HCl₃ as well as in-situ dry sorption of Cl-products in CaO particle bed were correlated with specific surface area of the CaO employed.     

纳米Bi2O3/TiO2复合光催化剂的制备及性能研究

以光催化效果为评价标准,采用超声波作用下水解法制备Bi₂O₃/TiO₂复合光催化剂,考察了水解条件和Bi₂O₃掺入量等制备条件对复合光催化剂性能的影响。结果表明,与传统制备方法相比,该方法操作简单、快速;当水和乙醇的比例为4∶1时所得样品的光催化活性最好;Bi₂O₃的掺入拓宽了TiO₂对光的吸收范围,提高了TiO₂的光催化活性,掺入量(Bi₂O₃)为0.25%复合光催化剂催化活性最高;复合光催化剂对多种水溶性染料均具有较好的处理效果。     

Chemical composition of precipitation at Marion Island (sub-Antarctic)

Over a 1-year period 16.40g Cl⁻m⁻², 10.35 g Na m⁻², 2.11 g SO₄-S m⁻², 1.24g Mg m⁻², 0.39 g K m⁻², 0.37 g Ca m⁻² and 0.21 g inorganic N m⁻² were deposited in precipitation 450 m inland on the eastern coastal plain of sub-Antarctic Marion Island (46°54′S, 37°45′E). Dissolved PO₄-P and organic forms of N were not detected in the precipitation samples. Concentrations of Cl⁻, Na, Mg, Ca and K, as well as the total ionic concentration in the precipitation samples were significantly negatively correlated with the amount of precipitation. The ionic concentration order (Cl > Na > SO₄-S > Mg > K ≈ Ca) in the precipitation was very similar to that in the surrounding ocean. It is likely that most of the inorganic N found in the precipitation originated in penguin rookeries on the nearby shore zone. A comparison is made between precipitation inputs of nutrients at the island and those at other subpolar sites in the S and N Hemispheres.     

Visible light photocatalytic antibacterial activity of Ni-doped and N-doped TiO<Subscript>2</Subscript> on <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> and <Emphasis Type="Italic">Escherichia coli</Emphasis> bacteria

The Ni-doped and N-doped TiO₂ nanoparticles were investigated for their antibacterial activities on Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria. Their morphological features and characteristics such as particle size, surface area, and visible light absorbing capacity were compared and discussed. Scanning electron microscopy, X-ray diffraction, and UV–visible spectrophotometry were used to characterize both materials. The inactivation of E. coli (as an example of Gram-negative bacteria) and S. aureus (as an example of Gram-positive bacteria) with Ni-doped and N-doped TiO₂ was investigated in the absence and presence of visible light. Antibacterial activity tests were conducted using undoped, Ni-doped, and N-doped TiO₂. The N-doped TiO₂ nanoparticles show higher antibacterial activity than Ni-doped TiO₂. The band gap narrowing of N-doped TiO₂ can induce more visible light absorption and leads to the superb antibacterial properties of this material. The complete inactivation time for E. coli at an initial cell concentration of 2.7?×?10⁴ CFU/mL was 420 min which is longer than the 360 min required for S. aureus inactivation. The rate of inactivation of S. aureus using the doped TiO₂ nanoparticles in the presence of visible light is greater than that of E. coli. The median lethal dose (LD50) values of S. aureus and E. coli by antibacterial activity under an 18-W visible light intensity were 80 and 350 mg/ml for N-doped TiO₂, respectively.     

Photodegradation of the novel fungicide fluopyram in aqueous solution: kinetics,transformation products,and toxicity evolvement

The aqueous photodegradation of fluopyram was investigated under UV light (λ?≥?200 nm) and simulated sunlight irradiation (λ?≥?290 nm). The effect of solution pH, fulvic acids (FA), nitrate (NO₃ ^?), Fe (III) ions, and titanium dioxide (TiO₂) on direct photolysis of fluopyram was explored. The results showed that fluopyram photodegradation was faster in neutral solution than that in acidic and alkaline solutions. The presence of FA, NO₃ ^?, Fe (III), and TiO₂ slightly affected the photodegradation of fluopyram under UV irradiation, whereas the photodegradation rates of fluopyram with 5 mg L^?1 Fe (III) and 500 mg L^?1 TiO₂ were about 7-fold and 13-fold faster than that without Fe (III) and TiO₂ under simulated sunlight irradiation, respectively. Three typical products for direct photolysis of fluopyram have been isolated and characterized by liquid chromatography tandem mass spectrometry. These products resulted from the intramolecular elimination of HCl, hydroxyl-substitution, and hydrogen extraction. Based on the identified transformation products and evolution profile, a plausible degradation pathway for the direct photolysis of fluopyram in aqueous solution was proposed. In addition, acute toxicity assays using the Vibrio fischeri bacteria test indicated that the transformation products were more toxic than the parent compound.     

Copper ultrastructural localization, subcellular distribution, and phytotoxicity in Hydrilla verticillata (L.f.) Royle

Laboratory experiments were conducted to investigate copper (Cu) subcellular distribution and toxicity in Hydrilla verticillata. Fronds were subjected to different concentrations (15, 75, and 150 μM) of Cu for 7 days. Cu grains were found in cell walls, plasmodesmata, and within the nuclei and chloroplasts using the autometallographic technique. Subcellular fractionation of Cu-containing tissues indicated that in leaves subjected to high Cu concentrations, 59–65 % of the element was located in the cell wall fraction, followed by cell organelles (21–30 %) and the soluble fraction (10–14 %). The levels of K, P, Zn, and Mg declined under all Cu concentrations, but Ca, Mn, and Fe contents reached their peak at 15 μM Cu and decreased thereafter. F _v/F _m, F ₀, and F _m fell significantly in line with the decrease in pigment content. Cu exposure also caused significant damage to the chloroplasts, mitochondria, and nuclei, including disintegration of the chloroplasts and vacuolization of the mitochondria and nuclei, all of which suggested that Cu hastened plant senescence. The Cu maximum permissible concentration for H. verticillata was 10 μM, which was less than the existing general water quality standard. This suggested that H. verticillata could be used to assess Cu phytotoxicity.     

Solar CPC pilot plant photocatalytic degradation of bisphenol A in waters and wastewaters using suspended and supported-TiO2. Influence of photogenerated species

Photocatalytic degradation of bisphenol A (BPA) in waters and wastewaters in the presence of titanium dioxide (TiO₂) was performed under different conditions. Suspensions of the TiO₂ were used to compare the degradation efficiency of BPA (20 mg L^?1) in batch and compound parabolic collector (CPC) reactors. A TiO₂ catalyst supported on glass spheres was prepared (sol–gel method) and used in a CPC solar pilot plant for the photodegradation of BPA (100 μg L^?1). The influence of OH·, O₂ ^·?, and h ⁺ on the BPA degradation were evaluated. The radicals OH· and O₂ ^·? were proved to be the main species involved on BPA photodegradation. Total organic carbon (TOC) and carboxylic acids were determined to evaluate the BPA mineralization during the photodegradation process. Some toxicological effects of BPA and its photoproducts on Eisenia andrei earthworms were evaluated. The results show that the optimal concentration of suspended TiO₂ to degrade BPA in batch or CPC reactors was 0.1 g L^?1. According to biological tests, the BPA LC₅₀ in 24 h for E. andrei was of 1.7?×?10^?2 mg cm^?2. The photocatalytic degradation of BPA mediated by TiO₂ supported on glass spheres suffered strong influence of the water matrix. On real municipal wastewater treatment plant (MWWTP) secondary effluent, 30 % of BPA remains in solution; nevertheless, the method has the enormous advantage since it eliminates the need of catalyst removal step, reducing the cost of treatment.     

Larvicidal,ovicidal, and oviposition-deterrent activities of four plant extracts against three mosquito species

In mosquito control programs, insecticides of botanical origin have the potential to eliminate eggs, larvae, and adults. So, the larvicidal, ovicidal, and oviposition-deterrent activities of petroleum ether and ethyl acetate extracts of the leaves of Eugenia jambolana, Solidago canadensis, Euodia ridleyi, and Spilanthes mauritiana were assayed against the three vector mosquito species, namely Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus. The larval bioassay was conducted following the World Health Organization method. The maximum larval mortality was found with ethyl acetate extract of S. mauritiana against the larvae of A. stephensi, A. aegypti, and C. quinquefasciatus with LC₅₀ values of 11.51, 28.1, 14.10 ppm, respectively. The mean percent hatchability of the ovicidal activity was observed at 48-h post-treatment. The percent hatchability was found to be inversely proportional to the concentration of the extract and directly proportional to the number of eggs. The flower head extract of S. mauritiana gave 100 % mortality followed by E. ridleyi, S. canadensis, and E. jambolana against the eggs of the three mosquito vectors. For oviposition-deterrent effect, out of the five concentrations tested (20, 40, 60, 80, and 100 ppm), the concentration of 100 ppm showed a significant egg laying-deterrent capacity. The oviposition activity index value of E. jambolana, E. ridleyi, S. canadensis, and S. mauritiana against A. aegypti, A. stephensi, C. quinquefasciatus at 100 ppm were ?0.71, ?0.71, ?0.90, ?0.93, ?0.85, ?0.91, ?1, ?1, ?0.71, ?0.85, ?1, and ?1, respectively. These results suggest that the leaf/flower extracts of certain local plants have the potential to be developed as possible eco-friendly means for the control of mosquitoes.     

Effect of Nb doping on structural, optical and photocatalytic properties of flame-made TiO2 nanopowder

TiO₂:Nb nanopowders within a dopant concentration in the range of 0.1?C15?at.% were prepared by one-step flame spray synthesis. Effect of niobium doping on structural, optical and photocatalytic properties of titanium dioxide nanopowders was studied. Morphology and structure were investigated by means of Brunauer?CEmmett?CTeller isotherm, X-ray diffraction and transmission electron microscopy. Diffuse reflectance and the resulting band gap energy were determined by diffuse reflectance spectroscopy. Photocatalytic activity of the investigated nanopowders was revised for the photodecomposition of methylene blue (MB), methyl orange (MO) and 4-chlorophenol under UVA and VIS light irradiation. Commercial TiO₂-P25 nanopowder was used as a reference. The specific surface area of the powders was ranging from 42.9?m²/g for TiO₂:0.1?at.% Nb to 90.0?m²/g for TiO₂:15?at.% Nb. TiO₂:Nb particles were nanosized, spherically shaped and polycrystalline. Anatase was the predominant phase in all samples. The anatase-related transition was at 3.31?eV and rutile-related one at 3.14?eV. TiO₂:Nb nanopowders exhibited additional absorption in the visible range. In comparison to TiO₂-P25, improved photocatalytic activity of TiO₂:Nb was observed for the degradation of MB and MO under both UVA and VIS irradiation, where low doping level (Nb?<?1?at.%) was the most effective. Niobium doping affected structural, optical and photocatalytic properties of TiO₂. Low dopant level enhanced photocatalytic performance under UVA and VIS irradiation. Therefore, TiO₂:Nb (Nb?<?1?at.%) can be proposed as an efficient selective solar light photocatalyst.