Porous Materials Modified with Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles for Arsenic Removal in Drinking Water

The contamination of drinking water with arsenic has been a problem in a lot of countries around the world because of its toxicological and carcinogenic effects on human health. Porous materials modified with Fe₃O₄ nanoparticles (Fe₃O₄ NPs) represent convenient removers for that contaminant. A co-precipitation method of Fe(III) and Fe(II) in alkaline media was applied to obtain Fe₃O₄ NPs. In a first stage, single nanoparticles were synthesized and stabilized with carboxylic acids. A characterization with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, and X-ray diffraction (XRD) confirms a magnetite-type structure. Moreover, transmission electron microscopy (TEM) and calculations from XRD data using Scherrer’s equation indicate an average particle size of 13 nm and an average crystallite size of 10 nm, both independent of the stabilizer used. Then, the co-precipitation method studied was applied to modify kaolin, bentonite, diatomite, and silica and thus prepare magnetic composites having support-magnetite weight ratios of 2:1. Among them, silica-modified material presented the best hydraulic characteristics, an important aspect for large-scale applications such as removal under gravity. This composite has the capacity to remove up to 80 and 70% for initial concentrations of 25 and 50 μg/L, respectively, representing a convenient remover for processes developed in subsequent stages or in continuous flow.     

Preparation of Highly Efficient CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/Zn<Subscript>2</Subscript>SnO<Subscript>4</Subscript> Composite Photocatalyst for the Degradation of Rhodamine B Dye from Aqueous Solution

CoFe₂O₄/Zn₂SnO₄ composite was synthesized using a simple two-step process and applied as a novel-efficient photocatalyst for the rhodamine B degradation from aqueous solution. Characterization techniques such as X-ray diffraction (XRD), N₂ adsorption-desorption isotherms, scanning electron microscopy (SEM), EDS analysis, and diffuse reflectance spectroscopy were employed in order to investigate the physical and chemical properties of composite. Higher values of the specific surface area, pore volume and diameter, and a smaller band-gap energy promoted a greater catalytic activity of CoFe₂O₄/Zn₂SnO₄ composite when compared to Zn₂SnO₄. A rapid decolorization of dye solution was observed at 40 min of reaction using the CoFe₂O₄/Zn₂SnO₄ catalyst, being 2.5 times faster than the Zn₂SnO₄ alone. Therefore, the CoFe₂O₄/Zn₂SnO₄ composite shows extraordinarily high photocatalytic activity toward the degradation of rhodamine B dye from aqueous solution.     

Removal of As(III) from Aqueous Solution Using Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles: Process Modeling and Optimization Using Statistical Design

In this study, Extran (biodegradable surfactant) was used for the preparation of Fe₃O₄ nanoparticles by microemulsion process to improve removal efficiency of As(III) from aqueous solution. Fe₃O₄ nanoparticles were characterized by XRD, FTIR, FESEM, TEM, HRTEM, and VSM instrumental techniques. The effect of different parameters such as adsorbent dose, initial As(III) concentration, and solution pH were studied by response surface methodology (RSM) based on Box-Behnken design (BBD). The optimized condition for adsorption of As(III) from aqueous solution was obtained as adsorbent dose of 0.70 mg/g, solution pH of 7.7, and initial As(III) concentration of 33.32 mg/L. In this optimum condition, about 90.5% of As(III) was removed from the aqueous solution. Isotherm studies have been done at optimal condition, and it was observed that the Langmuir isotherm models were fitted well with experimental data having a high correlation coefficient of 0.993. From the Langmuir isotherm data, the maximum adsorption capacity of Fe₃O₄ nanoparticles was found to be 7.18 mg/g at pH 7.7 in room temperature. This study revealed that Fe₃O₄ nanoparticles can be used as an efficient, eco-friendly, and effective material for the adsorptive removal of As(III) from aqueous system.     

pH-Based Strategies for an Efficient Addition of H<Subscript>2</Subscript>O<Subscript>2</Subscript> During Ozonation to Improve the Mineralisation of Two Contaminants with Different Degradation Resistances

Ozonation is an efficient process for the primary degradation of most substrates but not for their mineralisation. In this work, the ozonation enhanced with the addition of H₂O₂ was studied for two substrates with very different oxidation resistances: the dye rhodamine 6G (R6G) and the surfactant linear alkylbenzene sulfonate (LAS). With O₃ only, the primary degradation of R6G was completed in less than 10 min but its TOC removal only reached 45% in 1 h. By adding H₂O₂, TOC removal was increased to 70% with a molar ratio (mol H₂O₂/mol substrate) of 10. The analysis of pH decrease served to define the specific basicity loss (SBL). The optimum conditions for the R6G mineralisation were found to be associated with a SBL value between 1 and 10 ((min/g)/L)^?1, through an adequate addition of H₂O₂. Moreover, in the case of LAS, the addition of H₂O₂ for a greater efficiency should occur after the foaming period, above all formed at acid pH. LAS degradation was also considerably improved, and the optimum for primary degradation achieved in 10 min with a TOC removal of over 65% with a molar ratio (mol H₂O₂/mol substrate) of 20.

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Photodegradation of Bisphenol A with ZnO and TiO<Subscript>2</Subscript>: Influence of Metal Ions and Fenton Process

In this study, photocatalytic degradation of bisphenol A (BPA) was investigated using two types of catalysts (TiO₂ and ZnO) with various metal ion concentrations and amounts of added H₂O_2. A kinetic test was performed to observe the changes of BPA over time under UV irradiation in a photocatalytic reactor. Experimental results demonstrated that degradation efficiency of ZnO was higher than that of TiO₂. The degradation rate increased as catalyst dosage increased until reaching optimum dosage, after which degradation rate decreased. The addition of H₂O₂ improved the degradation efficiency of BPA, with the degradation efficiency increasing with the amount of H₂O₂. All metal ions, including Fe²⁺, Ni²⁺, and Cu²⁺, inhibited the degradation of BPA by ZnO at natural pH, whereas Fe²⁺ and Ni²⁺ enhanced degradation efficiency of BPA at acidic pH. Comparison of BPA degradation with H₂O₂ only, ZnO/H₂O₂, Fe²⁺/H₂O₂, and ZnO/Fe²⁺/H₂O₂ revealed that Fe²⁺/H₂O₂ was more efficient than other processes at lower pH (pH?=?3.44), whereas ZnO/H₂O₂ the most efficient at higher pH (pH?=?6.44). These results indicate that ZnO/H₂O₂ process was observed to be the most efficient of all processes. Degradation efficiency of BPA by ZnO was also influenced by additional parameters, including H₂O₂ concentration, metal ions, and solution pH.     

Efficient Photocatalytic Reduction of CO<Subscript>2</Subscript> Present in Seawater into Methanol over Cu/C-Co-Doped TiO<Subscript>2</Subscript> Nanocatalyst Under UV and Natural Sunlight

Photocatalytic reduction of CO₂ in seawater into chemical fuel, methanol (CH₃OH), was achieved over Cu/C-co-doped TiO₂ nanoparticles under UV and natural sunlight. Photocatalysts with different Cu loadings (0, 0.5, 1, 3, 5, and 7 wt%) were synthesized by the sol–gel method and were characterized by XRD, SEM, UV–Vis, FTIR, and XPS. Co-doping with C and Cu into TiO₂ remarkably promoted the photocatalytic production of CH₃OH. This improvement was attributed to lowering of bandgap energy, specific catalytic effect of Cu for CH₃OH formation, and the minimization of photo-generated carrier recombination. Co-doped TiO₂ with 3.0 wt% Cu was found to be the most active catalyst, giving a maximum methanol yield rate of 577 μmol g-cat^?1 h^?1 under illumination of UV light, which is 5.3-fold higher than the production rate over C-TiO₂ and 7.4 times the amount produced using Degussa P25 TiO₂. Under natural sunlight, the maximum rate of the photocatalytic production of CH₃OH using 3.0 wt% Cu/C-TiO₂ was found to be 188 μmol g-cat^?1 h^?1, which is 2.24 times higher than that of C-TiO₂, whereas, no CH₃OH was observed for P25.     

Organics Wastewater Degradation by a Mesoporous Chromium-Functionalized γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> with H<Subscript>2</Subscript>O<Subscript>2</Subscript> Assistance

In this study, a mesoporous chromium-functionalized γ-Al₂O₃ (Cr/γ-Al₂O₃) catalyst was prepared by an impregnation method, and the catalytic activity was evaluated by the degradation of organics wastewater. The prepared catalyst was characterized by X-ray photoelectron spectroscopy, X-ray diffraction, nitrogen adsorption-desorption experiments, and scanning electron microscopy. The characterization results confirmed that the pores in the Cr/γ-Al₂O₃ catalyst distributed broadly in the mesoporous region, and the active chromium species were highly dispersed on the catalyst surface. The catalytic activity tests showed that the Cr/γ-Al₂O₃ catalyst exhibited a superior performance for the degradation of organics wastewater with H₂O₂ assistance. And the methylene blue (MB) disappeared within 20 min and the COD removal reached 76.5% within 40 min for the MB-simulated wastewater; for the phenol-simulated wastewater, the phenol removal was above 95% and the corresponding COD removal reached 71% within 40 min. Such an excellent catalytic performance demonstrates that the Cr/γ-Al₂O₃ catalyst has a potential application in the degradation of complex organics wastewater simultaneously.     

Solar Decolorization of Methylene Blue by Magnetic MgFe<Subscript>2</Subscript>O<Subscript>4</Subscript>-MWCNT/Ag<Subscript>3</Subscript>VO<Subscript>4</Subscript> Visible Active Photocatalyst

MgFe₂O₄-MWCNT/Ag₃VO₄ photocatalyst was prepared for benefiting the visible region of solar spectrum. Prepared catalyst was characterized by using scanning electron microscope (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX). Photocatalytic activity was measured by methylene blue (MB) decolorization under visible light obtained from a 105-W tungsten light bulb. Dye decolorization and its kinetics were followed up by means of a UV-vis spectrophotometer. Kinetic model of decolorization was found to be compatible with first-order kinetics. The effects of pH and concentration of MB solution on the decolorization efficiency were determined. Low and high pH conditions were found to be more effective in increasing the MB decolorization yield and rate. On the other hand, due to the low transparency of concentrated MB solutions, an increase on decolorization time and a lowering in decolorization yield were encountered. Thanks to the magnetic MgFe₂O₃ nanoparticles, 96% of the catalyst could be recovered by a simple magnetic bar. It was observed that simulated wastewater containing MB was also successfully decolorized showing that visible region-sensitive MgFe₂O₄-MWCNT/Ag₃VO₄ photocatalyst can be benefited as a potential, efficient, and reusable material for the removal organic pollutants in aquatic environment.     

Improved Photodegradation Efficiency of 2,4-DCP Through a Combined Q<Subscript>3</Subscript>Fe(III)-Decorated Porous g-C<Subscript>3</Subscript>N<Subscript>4</Subscript>/H<Subscript>2</Subscript>O<Subscript>2</Subscript> System

Graphitic carbon nitride (g-C₃N₄) is a photocatalyst with wide application in removal of organic pollutants. In this study, we designed a porous g-C₃N₄ (p-g-C₃N₄)/8-quinolinolato iron(III) (Q₃Fe)/H₂O₂ system to enhance the organic pollutant removal efficiency by combining photocatalysis and Fenton interaction under neutral condition. The p-g-C₃N₄ was prepared through a two-step thermal oxidation reaction. Afterwards, Q₃Fe-coupled p-g-C₃N₄ was prepared by an impregnating method. The 2,4-dichlorophenol (2,4-DCP) photodegradation ratio and decomposition rate of the p-g-C₃N₄/Q₃Fe/H₂O₂ system are approximately 5 and 18 times as high as those of individual p-g-C₃N₄ system, respectively. Besides, its degradation rate is 4.3 times as high as that in the p-g-C₃N₄/H₂O₂ system. Meanwhile, Q₃Fe/g-C₃N₄ also exhibits higher activity than individual p-g-C₃N₄ in 2,4-DCP photo-decomposing. On the basis of the results of the radical trapping experiments and the Fe(II) concentration in different systems, the synergistic effect between photocatalysis and Fenton reaction is vital for the efficient pollutant degradation. The coupled system combining p-g-C₃N₄ with Q₃Fe and H₂O₂ shows potential for efficient treatment of recalcitrant organic pollutants. The combined system in this work indicated a new idea for the decomposition of organic pollutants.     

Effectiveness of Air,N<Subscript>2</Subscript> (gas), Fe<Superscript>+3</Superscript> and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles on the Sonication of Less and More Hydrophobic Polycyclic Aromatic Hydrocarbons (PAHs) and Toxicity

In this study, the effects of 1 h aeration, nitrogen gas N₂(g) sparging (15 and 30 min) and increasing ferric ions (Fe⁺³) as FeSO₄ (10, 20 and 50 mg L⁻¹) and Fe₃O₄ nanoparticles (1, 2 and 4 g L⁻¹) concentrations on three less hydrophobic and three more hydrophobic polycyclic aromatic hydrocarbons (PAHs) and toxicity removals from a petrochemical industry in Izmir (Turkey) were investigated in a sonicator with a power of 650 W and an ultrasound frequency of 35 kHz; 1 h aeration increased the yields in benzo[b]fluoranthene, benzo[k]fluoranthene and benzo[a]pyrene PAHs (less hydrophobic) from 62% to 67% to around 95–97% after 150 min sonication at 60°C. However, 1 h aeration did not contribute to the yields of more hydrophobic PAHs (indeno[1,2,3-cd]pyrene, dibenz[a,h]anthracene, benzo[g,h,i]perylene). The maximum yields were obtained at acidic and alkaline pH for more and less hydrophobic PAHs, respectively, after 60 and 120 min sonication at 30°C; 30 min N₂(g) sparging, 50 mg L⁻¹ Fe⁺³ increased the yields of less hydropobic PAHs after 150 min sonication at 60°C. Two milligrams per liter of Fe₃O₄ nanoparticles increased both less (87–88%) and more (96–98%) hydrophobic PAH yields. The Daphnia magna acute toxicity test showed that the toxicity decreased significantly with an hour aeration, 30 min N₂(g) sparging, 50 mg L⁻¹ Fe⁺³ and 2 g L⁻¹ Fe₃O₄ nanoparticles at 60°C after 120 and 150 min sonications. Vibrio fischeri was found to be more resistant to the sonicated samples than D. magna. Significant correlations were found between the physicochemical properties of sonicated PAHs and acute toxicities both organisms.     

Removal of Hazardous Hydrogen Fluoride (HF) from Water Through Homogeneous Nanostructured CaO-SiO<Subscript>2</Subscript> Sorbents: Optimization of Binder

In this study, we prepared a homogeneous dispersion of CaO-SiO₂ sorbent with advanced nanostructures as an efficient solid-reducing agent for the elimination of hazardous chemicals. The hydrophobic properties of SiO₂ ceramic particles are of interest for reducing the limitations and enhancing the chemical properties of highly hygroscopic materials. Nano-sized SiO₂ is introduced and composited with CaO through a facile synthetic route. The structural and microstructural characteristics and elemental compositional analyses confirm the uniform distribution of the CaO-SiO₂ nanocomposite. The as-prepared nanocomposites have particle sizes in the range of ~?20–100 nm. Optimization of the composition reveals that the 60 wt% CaO-SiO₂ can be considered as an efficient solid-reducing agent for the hydrogen fluoride (HF) removal process. In order to identify the catalytic effect and binder ratio, the specific surface area and HF removal performance was investigated and compared to CaO-SiO₂ nanostructures with individual CaO catalyst. The higher amount of HF concentration was absorbed by CaO-SiO₂ catalyst than the CaO only. In the first 2.5-h reaction, the outlet HF concentration is rapidly increased to 380 ppm by using CaO catalyst as a HF sorbent. However, the outlet HF concentration is sluggishly increased up to 180 ppm, when nanostructured CaO-SiO₂ catalyst used as a sorbent in RE-RCS. It has been found that the addition of hydrophobic properties of SiO₂ has prevented the reaction between water/moisture and CaO in CaO-SiO₂ catalyst system, which is a major reason for enhancement in HF removal process. Furthermore, the CaF₂ byproduct can be effectively used in the ceramic industry and building material applications.     

Biotreatment of Melanoidin-Containing Distillery Spent Wash Effluent by Free and Immobilized Aspergillus oryzae MTCC 7691

Humic acids (HA) are known as the precursors of carcinogenic compounds formed by the disinfection of drinking water. While conventional treatments were found to be inefficient HA removal processes in drinking water, advanced oxidation processes have been proven to have a significant effect in the treatment of HA. The degradation of HA was investigated using nano-sized zinc oxide (ZnO)/laponite composite (NZLC). The reactions occurred in a UVC reactor by considering following variables: pH, initial HA concentration, catalyst loading, addition of hydrogen peroxide (H₂O₂), and catalyst reuse. Water samples containing HA were analysed by ultraviolet/visible spectrophotometer and high-performance size-exclusion chromatography. Initial HA concentrations were tested by the Langmuir–Hinshelwood model with k and K _ads values, determined to be 0.126 mg/L.min and 0.0257 L/mg, respectively. The change in pH affected the HA degradation efficiency by the photocatalytic activity where it was higher under acidic conditions rather than alkaline ones. Optimal catalyst loading was proved to be a constrained factor in influencing the photocatalytic efficiency: the increase of catalyst concentration enhanced the HA decomposition efficiency up to an optimum value of 20 g/L, where there was no further degradation with excess loading. The addition of H₂O₂ was investigated through homogenous and heterogeneous photocatalysis, and, heterogeneous photocatalysis showed higher removal efficiency due to the combined effect of both catalysts and H₂O₂. Finally, NZLC was effective for reuse and exhibited an excellent stability after six times of usage.     

Physiological Effects and Fluorescence Labeling of Magnetic Iron Oxide Nanoparticles on Citrus (<Emphasis Type="Italic">Citrus reticulata</Emphasis>) Seedlings

Nanoparticles (NPs) have been reported to cause physiological effects on plant cells and tissue. This study traced the uptake and distribution of magnetic iron oxide nanoparticles (γ-Fe₂O₃ NPs) in citrus (Citrus reticulata) plants under hydroponic condition by fluorescent dye labeled γ-Fe₂O₃ NPs, and described a detailed evidence of physiological effects of 0–100 mg/L γ-Fe₂O₃ NPs on citrus plants by measuring the physiological parameters such as content of chlorophyll, malondialdehyde (MDA), soluble sugar, soluble protein, activity of antioxidant enzyme, and ferric reductase after 21 days exposure. Fluorescence images of citrus stem and root showed that citrus roots could absorb γ-Fe₂O₃ NPs but no translocation from roots to shoots was observed, since NPs aggregated or even clogged the vascular system. Physiological results showed that 20 mg/L γ-Fe₂O₃ NPs could significantly enhance chlorophyll content by 126.4%, while 50 and 100 mg/L of γ-Fe₂O₃ NPs decreased chlorophyll content by 27.8 and 35.4%, respectively. MDA contents in citrus leaves under 20–100 mg/L γ-Fe₂O₃ NPs exposure were increased by 37.8, 107.2, and 61.5%, respectively, while that in roots were decreased by 27.0,11.9, and 7.4%, respectively, with elevated SOD and CAT activity, suggesting that oxidative stress occurred in citrus leaves, but oxidative stress in roots was eliminated by antioxidant defense. It is noteworthy that although Fe(II)-EDTA treatment had a high level of chlorophyll content, it induced strong oxidative stress in citrus plants as well. Collectively, the various physiological responses of citrus plants to γ-Fe₂O₃ NPs exposure were closely correlated with the concentrations of NPs. γ-Fe₂O₃ NPs at proper concentrations, such as 20 mg/L, have the potential to ameliorate chlorosis of plants and be effective nanofertilizers for increasing agronomic productivity.     

Community Refinery Wastewater Photodegradation by Fe-Doped TiO<Subscript>2</Subscript> Films

Photocatalytic treatment of real community wastewater using Fe-doped TiO₂ nanofilm was prepared by modified sol-gel method together with a simple dip-coating technique. The process was investigated in a home-made batch photoreactor. The as-prepared nanocomposite film was characterized by UV-Vis diffuse, XRD, BET, and Fe-SEM analysis. The poultry processing wastewater was collected from Nakhonsawan Municipality. Subsequently, the photocatalytic treatment of the wastewater was performed using a home-made photoreactor operated in batch mode to demonstrate the effects of Fe-dopant concentration with various layer numbers. The catalysts were irradiated using four lamps of 15 W power that emitted visible light and performed at room temperature. The samples were collected every 15 min and analyzed for biochemical oxygen demand (BOD) and chemical oxygen demand (COD) removal efficiency compared to pure TiO₂ nanofilm and direct photolysis. From the results, the mixture of rutile and anatase was obtained with the maximum specific surface area of 150.12 mg²/g and the average particle size of 39.95 nm for 3 layers of 0.15% wt/v Fe-doped TiO₂. The BOD and COD value at 90 min time treatment was presented to be 8.87 and 32 mg L^?1, respectively, in the presence of 0.15% wt/v Fe-doped TiO₂ film photocatalysts. Moreover, atomic absorption spectrometric result ensured that no Ti contamination was detected in all parts of plants after watering by the treated water. Hence, the photocatalytic treatment markedly improved the quality of the community wastewater.     

Effects of O<Subscript>3</Subscript> stress on physico-chemical and biochemical properties and composition of main microbial groups of a soil cropped to soybean

Tropospheric O₃ (ozone) stress can negatively affect forest productivity and crop yields. Yet, relatively little attention has been paid to the effects of O₃ stress on belowground system. Here, a pot experiment was conducted in open top chambers to monitor the response of physico-chemical properties, main microbial groups, and potential enzyme activities of a soil cropped to soybean (Glycine max; a highly sensitive species to O₃) and exposed to background O₃ concentration (45?±?5 ppb, control) and O₃ stress (80?±?10 ppb, O₃+ and 110?±?10 ppb, O₃++) with sampling at branching, flowering, and podding stages. The growth of soybean was significantly inhibited by O₃ stress, which showed significant effects on soil microbial biomass C and pH during the whole growth of soybean at the highest concentration. The O₃++ stress significantly decreased soil pH at flowering stage, and increased soil pH at podding stage; the O₃+ stress and growth stage?×?O₃+ stress showed significant influences on the potential activities of acid phosphomonoesterase, invertase, and amylase. The O₃ stress significantly reduced the abundances of total PLFAs (phospholipid fatty acid), bacterial PLFAs, and AMF (arbuscular mycorrhizal) PLFAs at branching and podding stages. Our results suggest that the main soil microbial groups might be indirectly affected by the O₃ stress through the alteration of soil physico-chemical properties with changes in the potential enzyme activities of soil.     

Increases in soil CO<Subscript>2</Subscript> and N<Subscript>2</Subscript>O emissions with warming depend on plant species in restored alpine meadows of Wugong Mountain,China

Purpose

Ecosystem restorations can impact carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions which are important greenhouse gasses. Alpine meadows are degraded worldwide, but restorations are increasing. Because their soils represent large carbon (C) and nitrogen (N) pools, they may produce significant amounts of CO₂ and N₂O depending on the plant species used in restorations. In addition, warming and N deposition may impact soil CO₂ and N₂O emissions from restored meadows.

Materials and methods

We collected soils from degraded meadows and plots restored using three different plant species at Wugong Mountain (Jiangxi, China). We measured CO₂ and N₂O emissions when soils were incubated at different temperatures (15, 25 or 35 °C) and levels of N addition (control vs. 4 g m^?2) to understand their responses to warming and N deposition.

Results and discussion

Dissolved organic C was higher in restored plots (especially with Fimbristylis dichotoma) compared to non-restored bare soils, and their soil inorganic N was lower. CO₂ emission rates were increased by vegetation restorations, decreased by N deposition, and increased by warming. CO₂ emission rates were similar for the three grass species at 15 and 25 °C, but they were lower with Miscanthus floridulus at 35 °C. Soils from F. dichotoma and Carex chinensis plots had higher N₂O emissions than degraded or M. floridulus plots, especially at 25 °C.

Conclusions

These results show that the effects of restorations on soil greenhouse gas emissions depended on plant species. In addition, these differences varied with temperature suggesting that future climate should be considered when choosing plant species in restorations to predict soil CO₂ and N₂O emissions and global warming potential.

     

The Effect of Polyethylene Glycol (PEG) Modification on Fe Dispersal and the Catalytic Degradation of Phenol Wastewater

Modification of a catalyst with polyethylene glycol (PEG) created a dramatic increase in the catalytic activity for the degradation of phenol wastewater. The Fe/PEG-modified γ-Al₂O₃ catalyst was prepared by an impregnation method. The as-prepared catalyst was characterized by X-ray photoelectron spectroscopy, wide- and small-angle X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and N₂ adsorption-desorption experiments, and the results showed that the Fe species were highly dispersed on the surface of the PEG-modified support. At the same time, the PEG modification resulted in an increase in the Brunauer-Emmett-Teller surface area and pore volume. The catalytic activity test showed that the Fe/PEG-modified γ-Al₂O₃ catalyst exhibited a superior performance for the degradation of phenol wastewater in this study, and the phenol and COD removal values reached 94.1 and 88.9%, respectively, within 60 min. The results clearly show that PEG modification is a promising methodology for the preparation of a catalyst with good dispersal of the active component on the support.     

Photo-Assisted Degradation,Toxicological Assessment,and Modeling Using Artificial Neural Networks of Reactive Gray BF-2R Dye

This work investigates the degradation of Reactive Gray BF-2R dye (a blend of reactive yellow 145, reactive orange 122 and reactive black 5 dyes) using UV/H₂O₂, Fenton, and photo-Fenton-advanced oxidative processes, with artificial sunlight and UV-C radiations. The photo-Fenton process employing UV-C radiation was the most efficient under the conditions studied. The ideal conditions for the degradation of the dye, determined using a factorial design 2³ and a study of the concentration of hydrogen peroxide ([H₂O₂]), were [H₂O₂] equal to 40 mg L^?1, iron concentration [Fe] of 1 mg L^?1, and pH between 3 and 4. The Chan and Chu non-linear kinetic model predicted the kinetic data with a degradation of over 98% for color and 68% for aromatics after 60 min. The behavior of the chemical oxygen demand fitted the first-order kinetic model well, with a degradation of 64% after 60 min. The Multilayer Perceptron 7-11-2 artificial neural network model enabled to model the degradation process of the aromatics and accurately predict the experimental data. Toxicity tests indicated that the post-treatment samples were non-toxic for Escherichia coli bacteria, and Portulaca grandiflora and Basil sabory seeds. However, they inhibited the growth of Lactuca sativa seeds and Salmonella enteritidis bacteria. The photo-Fenton process with UV-C radiation degraded the dye studied efficiently and the degradation percentages were, on average, 7% and 5% higher for color than those observed when employing the Fenton and UV/H₂O₂ processes, respectively. With the aromatic, however, they were 84% and 62% higher, thus justifying the use of this process.     

TiO<Subscript>2</Subscript> photocatalytic degradation of 4-chlorobiphenyl as affected by solvents and surfactants

Purpose  

TiO₂ photocatalytic degradation of 4-chlorobiphenyl (PCB3) in aqueous solution under UV irradiation was investigated as affected by different environmental factors, including initial PCB3 concentration, TiO₂ content, UV intensity, H₂O₂ concentration, cosolvents, and surfactants.     

Short-term uptake of <Superscript>15</Superscript>NH<Subscript>4</Subscript><Superscript>+</Superscript> into soil microbes and seedlings of pine,spruce and birch in potted soils

Short-term competition between soil microbes and seedlings of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.) and silver birch (Betula pendula Roth) for N was assessed in a pot study using (¹⁵NH₄)₂SO₄ as a tracer. Seedlings were grown in organic and mineral soil, collected from a podsol soil; 3.18 mg (¹⁵NH₄)₂SO₄ per pot were injected into the soil, corresponding to 4 µg ¹⁵N g^-1 d.m. (dry matter) mineral soil and 17 µg ¹⁵N g^-1 d.m. organic soil. The amounts of N and ¹⁵N in the seedlings and in microbial biomass derived from fumigation-extraction were measured 48 h after addition of ¹⁵N. In the mineral soil, 19–30% of the added ¹⁵N was found in the plants and 14–20% in the microbial biomass. There were no statistically significant differences between the tree species. In the organic soil, 74% of the added ¹⁵N was recovered in the microbial biomass in birch soil, compared to 26% and 17% in pine and spruce soils, respectively. Correspondingly, about 70% of the ¹⁵N was recovered in pine and spruce seedlings, and only 23% in birch seedlings. In conclusion, plants generally competed more successfully for added ¹⁵NH₄ ⁺ than soil microbes did. An exception was birch growing in organic soil, where the greater amount of available C from birch root exudates perhaps enabled micro-organisms to utilise more N.