Application of the Stover–Kincannon kinetic model to nitrogen removal by Chlorella vulgaris in a continuously operated immobilized photobioreactor system

BACKGROUND: The aim of this study was to evaluate the ammonium nitrogen removal performance of algae culture Chlorella vulgaris in a novel immobilized photobioreactor system under different operating conditions and to determine the biokinetic coefficients using the Stover–Kincannon model. RESULTS: The photobioreactor was continuously operated at different initial ammonium nitrogen concentrations (NH₄‐N₀ = 10–48 mg L⁻¹), hydraulic retention times (HRT = 1.7–5.5 days) and nitrogen/phosphorus ratios (N/P = 4/1–13/1). Effluent NH₄‐N concentrations varied between 2.1 ± 0.5 mg L⁻¹ and 26 ± 1.2 mg L⁻¹ with increasing initial NH₄‐N concentrations from 10 ± 0.6 mg L⁻¹ to 48 ± 1.8 mg L⁻¹ at θ_H = 2.7 days. The maximum removal efficiency was obtained as 79 ± 4.5% at 10 mg L⁻¹ NH₄‐N concentration. Operating the system for longer HRT improved the effluent quality, and the percentage removal increased from 35 ± 2.4% to 93 ± 0.2% for 20 mg L⁻¹ initial NH₄‐N concentration. The N/P ratio had a substantial effect on removal and the optimum ratio was determined as N/P = 8/1. Saturation value constant, and maximum substrate utilization rate constant of the Stover–Kincannon model for ammonium nitrogen removal by C. vulgaris were determined as K_B = 10.3 mg L⁻¹ d⁻¹, U_max = 13.0 mg L⁻¹ day⁻¹, respectively. CONCLUSION: Results indicated that the algae‐immobilized photobioreactor system had an effective nitrogen removal capacity when the operating conditions were optimized. The optimal conditions for the immobilized photobioreactor system used in this study can be summarized as HRT = 5.5 days, N/P = 8 and NH₄‐N₀ = 20 mg L⁻¹ initial nitrogen concentration to obtain removal efficiency greater than 90%. Copyright © 2008 Society of Chemical Industry     

Use of fly ash as an admixture for electromagnetic interference shielding

The use of fly ash as an admixture results in enhancement of the electromagnetic interference (EMI) shielding effectiveness from 4 to 8 dB at 1 GHz, whereas the use of silica fume as an admixture results in negligible effect on the shielding effectiveness. The DC electrical resistivity is decreased slightly by silica fume, but is essentially not affected by fly ash. Both fly ash and silica fume cause slight increases in the reflectivity. The effectiveness of fly ash for shielding is attributed to the Fe₂O₃ component (15.4 wt.%) in the fly ash.     

2D Ti3C2Tx MXene/aramid nanofibers composite films prepared via a simple filtration method with excellent mechanical and electromagnetic interference shielding properties

Electromagnetic shielding (EMI) materials are becoming more and more important because of the increasingly serious radiation pollution. The preparation of high mechanical strength, ultrathin, lightweight, flexible materials with excellent EMI shielding performance have so far been elusive. Here, we try to prepare an ultrathin, lightweight and flexible film with excellent EMI shielding performance using one-dimensional aramid nanofibers (ANFs) and two-dimensional few-layered Ti₃C₂T_x through a simple filtration method. The ultimate tensile strength and strain of the film are up to 116.71 MPa and 2.64%. The EMI shielding effectiveness and the specific EMI shielding efficiency are 34.71 dB and 21971.37 dB cm² g⁻¹, which will be no recession after 1000 times bending. Our results show that a practical EMI shielding material with excellent performances has been successfully prepared, which will be widely applied in wearable electronics, robot joints, and precision instrument protection and so on.     

Pfropfung von acrylmonomeren auf cellulose durch Ag(II)-salz-initiierung

Methyl acrylate has been grafted onto viscose using [Ag(II)(C₅H₅N)₄]S₂O₈ as initiator with grafting yields of up to 50%. Similar yields have been obtained in a system containing AgNO₃ and (NH₄)₂S₂O₈. In this case the amount of Ag-ions could be decreased to 0,005m without any loss in yield, if the concentration of the persulfate was increased adequately.     

Hydrothermal synthesis,crystal structure and fluorescent properties of a novel 1D polymer: VO2(C7H3O4N)Ag(C10H8N2)·H2O

The hydrothermal synthesis of V₂O₅, AgNO₃, pyridine-2,6-dicarboxylic acid (H₂pdc) and 2,2′-bipyridine (bpy) in water at 160 °C for 4 days yields a novel 1D coordination polymer VO₂(C₇H₃O₄N)Ag(C₁₀H₈N₂)·H₂O (1). Each V center chelates to a tridentate ligand pdc^2? and coordinates to two O atoms, while the square based pyramid conformation of Ag center consists of three O atoms and a bpy molecular. V and Ag polyhedra alternate by either carboxyl or oxo bridges to further form a unique 3d–4d heterometal-based 1D double-chain ribbon.     

Studies on the electromagnetic interference shielding effectiveness of metallized PVAc‐AgNO3/PET conductive films

A metal chelate polymer (MCP) of PVAc‐AgNO₃ was prepared by adding AgNO₃ salts into the PVAc matrix and was coated on to PET substrate to form PVAc‐AgNO₃/PET films. These films were then treated with NaBH₄ aqueous solution to become the reduced metallized conductive films (RMCF) of PVAc‐AgNO₃/PET. The electromagnetic interference shielding effectiveness (EMI/SE) and the characteristics of these films were investigated. The SE value was measured by the far‐field transmission line method. The surface resistivity (Rs) of RMCF with a AgNO₃ content of 15 wt % was found to be below 5 Ω/sq, and the SE value exceeded 20 dB over the frequency range 50–900 MHz. The Rs of RMCF with a AgNO₃ content of 30 wt % was less than 1 Ω/sq, and the SE value even reached 33 dB at 550–650 MHz. It was confirmed by X‐ray and scanning electronmicroscope (SEM) analysis that the conducting network, as formed by closely deposited silver atoms on the reduced coating surface, was the dominant pathway for effective electron propagation that contributed to the excellent conductivity of these RMCF (PVAc‐AgNO₃/PET). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 270–273, 2004     

Promoting the electromagnetic interference shielding of Ti3C2Tx flakes by loading Fe3O4 nanoparticles: Insights into the performance of oligo-layers exposed to microwave interferences

This study aims to provide insights into the absorption and shielding performances of Fe₃O₄ modified oligo-layered Ti₃C₂T_x towards microwave electromagnetic interference. Oligo-layered Ti₃C₂T_x was modified by Fe₃O₄ nanoparticles (60 nm) via a facile electrostatic assembly approach at different loading rates. This composite was shown to have high dielectric constant and high permeability compared with oligo-layered Ti₃C₂T_x. The microwave electromagnetic absorbing and shielding performances were monitored through a vector network instrument with focuses on the EMI performance. The sample Ti₃C₂T_x/Fe₃O₄ with a 5:1 mass ratio of Ti₃C₂T_x to Fe₃O₄ displayed the optimized EMI shielding performance. The average SE value was 62.19 dB, and the maximum value was 68.72 dB at 18 GHz with a 2.6 mm thickness. The EMI shielding mechanism was understood based on the conductive loss, magnetic loss, dipole polarization, and multiple scattering. Results suggests that Ti₃C₂T_x/Fe₃O₄ composites are expected to be superior EMI shielding material.     

Multifunctional nanocomposites integrate electromagnetic shielding,thermal, mechanical,and wear resistance properties

The SiC_nws/SiC nanocomposites were in situ synthesized by using nickel carbon foam as catalyst and skeleton. This technique has a series of advantages including simple operation, low cost, and high efficiency. Due to the excellent microwave absorption and thermal properties of SiC_nws, SiC_nws/SiC nanocomposites possess excellent electromagnetic shielding performance with a high SE_T value of 38.3 dB and good thermal properties with thermal conductivity of 13.77 ± 0.098 wm⁻¹k⁻¹ at room temperature. Meanwhile, the bending strength of the nanocomposites is 110.9 ± 7.7 MPa. The friction coefficient of nanocomposites is about 0.26 with a wear speed of about 67 um³/s. Therefore, the nanocomposites integrate many advantages including lightweight (2.0 g/cm³), excellent electromagnetic shielding, good heat conduction, high strength, and wear resistance.     

Suitability of Sodium Pyruvate as Decomposer of Carried-over Liquid Hydrogen Peroxide

The aim of the present study was to evaluate the concentration of sodium pyruvate in growth media by using the most-probable number method to decompose carried-over liquid hydrogen peroxide (H₂O₂) without negative influences on correct enumeration of Geobacillus stearothermophilus spores. An equivalent molar ratio of sodium pyruvate and H₂O₂ was verified to be sufficient for a complete decomposition. The results showed that by exposition of G. stearothermophilus spores in different liquid hydrogen peroxide and by carry-over of concentrations ranging from 3.56 · 10⁻⁶ up to 1.69 · 10⁻⁴ mol, a sodium pyruvate concentration of 0.05 mol L⁻¹ in growth media was most efficient for the recovery of spores.     

Polyaniline–antimony oxide composites for effective broadband EMI shielding

Conducting polyaniline (PAni)–antimony trioxide (Sb₂O₃) composites with different weight percentages (wt%) of Sb₂O₃ in PAni have been synthesized by in situ chemical oxidative polymerization. The composites were structurally and morphologically characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Measurements of electromagnetic interference (EMI) shielding, complex permittivity and microwave absorbing as well as reflecting properties of the composites were carried out in the frequency range of 8–18 GHz, encompassing the microwave X and Ku bands of practical relevance. All the computations are based on microwave scattering parameters measured by transmission line waveguide technique. It is observed that the presence of Sb₂O₃ in the PAni matrix affects the electromagnetic shielding and dielectric properties of the composites at microwave frequencies. The composites have shown better shielding effectiveness (SE) in both the X (SE in the range ?18 to ?21 dB) and Ku (?17.5 to ?20.5 dB) bands. ε′ and ε′′ values of the PAni–Sb₂O₃ composites are in the range of 64–37 and 63–30, respectively, in the frequency range of 8–18 GHz. Dielectric measurements indicated the decrease in dielectric constant with the increase in wt% of Sb₂O₃. The results obtained for the reflection and absorption coefficients indicated that PAni–Sb₂O₃ composites exhibit better electromagnetic energy absorption throughout the X and Ku bands. The results indicated that PAni–Sb₂O₃ composites can be used as potential microwave absorption and shielding materials.     

Bifunctional Ti3C2Tx–CNT/PANI composite with excellent electromagnetic shielding and supercapacitive performance

Ti₃C₂T_x exhibits excellent electromagnetic (EM) shielding and electrochemical properties. However, the inherent re-stacking tendency and easy oxidation of Ti₃C₂T_x limit its further application. In this study, a multi-walled carbon nanotube/polyaniline composite (CNT/PANI, denoted as C–P) was introduced into Ti₃C₂T_x nanosheets to obtain a Ti₃C₂T_x–CNT/PANI composite (T@CP). Owing to the integrated effects of Ti₃C₂T_x and C–P, the contribution of absorption was significantly improved, which finally enhanced the EM shielding performance of T@CP. The highest total EM shielding effectiveness (SE_T) was close to 50 dB (49.8 dB), which was substantially higher than that of pure Ti₃C₂T_x (45.3 dB). Moreover, T@CP demonstrated outstanding supercapacitive performance. The specific capacitance of T@CP (2134.5 mF/cm² at 2 mV/s) was considerably higher than that of pure Ti₃C₂T_x (414.3 mF/cm² at 2 mV/s). These findings provide a new route for the development of high-efficiency Ti₃C₂T_x-based bifunctional EM shielding and electrochemical materials.     

Electromagnetic shielding Janus membrane for direct current-type pressure and sliding sensing

Facing increasing electromagnetic radiation pollution, soft sensors with electromagnetic interference (EMI) shielding is highly desirable. Here, flexible electromagnetic shielding [polyacrylonitrile/Fe₃O₄/polyaniline]//[multiwalled carbon nanotube/polyvinyl pyrrolidone] (denoted [PAN/Fe₃O₄/PANI]//[MWCNT/PVP]) Janus membrane is reported for pressure and sliding sensing. The [PAN/Fe₃O₄/PANI] layer of Janus membrane as the force and sliding sensing unit can generate direct current-type (DC-type) voltage signals by conducting polymer/metal Schottky junction, whereas [MWCNT/PVP] layer serves as main electromagnetic shielding unit. Under the vertical force and horizontal sliding of aluminum (Al) foil, it can output DC-type voltage signals based on the Schottky contact. The performance of [PAN/Fe₃O₄/PANI]//[MWCNT/PVP] Janus membrane for pressure and sliding sensing is appropriately explored and assessed. Moreover, the Janus membrane exhibits excellent shielding effects with average EMI shielding effectiveness (SE) of 37.54 dB in 8.2–12.4 GHz (X-Band) frequency ranges. Thus, based on the asymmetrical double-layer structure, soft DC-type sensor with EMI shielding is achieved, showing utilization potential in wearable electronics and intelligent robots.     

Effectiveness of ozonation and catalytic ozonation (iron oxide) in the degradation of sunset yellow dye

Azo dyes present in industrial effluents represent a hurdle that regular treatments cannot overcome. In this study, the application of ozone and a catalytic (iron oxide) ozone treatment were proposed as a means of degrading aqueous sunset yellow dye. In order to understand the factors involved, a rotatable central composite design was applied using the variables time, initial dye concentration (C₀), pH, ozone inlet concentration (O₃), and mass of catalyst, which varied in each case. All variables were significant in colour removal. Extremes in pH, lower C₀, and higher ozone concentrations are conditions that favour dye degradation. A complete colour loss occurred for certain combinations of these parameters. The application of iron oxide as a catalyst did not present a satisfactory improvement in the reaction rate. Chemical oxygen demand and total organic carbon showed minimum values of 80% and 78%, respectively, for the worst experimental conditions (pH 7.0, C₀ of 45 mg · L⁻¹, and 5 g O₃ · m⁻³), while their values were 88% and 83% for the best conditions applied. There was no immobilization of Artemia salina nauplii, even for the experimental run where the maximum concentration of dye of the set was used (45 mg dye · L⁻¹). Ozonation is a promising alternative in the degradation of aqueous sunset yellow dye, being favoured in acidic or basic media, which is especially important since food effluents usually present low pH and show low toxicity. The mathematical model proposed can be useful in the design of wastewater treatment processes.     

Cost analysis for the degradation of highly concentrated textile dye wastewater with chemical oxidation H2O2/UV and biological treatment

The efficiency and cost‐effectiveness of H₂O₂/UV for the complete decolorization and mineralization of wastewater containing high concentrations of the textile dye Reactive Black 5 was examined. Oxidation until decolorization removed 200–300 mg g^?1 of the dissolved organic carbon (DOC). The specific energy consumption was dependent on the initial dye concentration: the higher concentration required a lower specific energy input on a weight basis (160 W h g^?1 RB5 for 2.1 g L^?1 versus 354 W h g^?1 RB5 for 0.5 g L^?1). Biodegradable compounds were formed, so that DOC removal could be increased by 30% in a following biological stage. However, in order to attain 800 mg g^?1 overall mineralization, 500 mg g^?1 of the DOC had to be oxidized in the H₂O₂/UV stage. A cost analysis showed that although the capital costs are much less for a H₂O₂/UV stage compared to ozonation, the operating costs are almost double those of ozonation. Thus, while H₂O₂/UV can compete with ozonation when the treatment goal only requires decolorization, ozonation is more cost‐effective in this case when mineralization is desired. Copyright © 2006 Society of Chemical Industry     

Enhanced impact resistance and electromagnetic interference shielding of carbon nanotubes films composites

High reliability and high-performance electromagnetic interference (EMI) shielding polymeric composite was fabricated by introducing carbon nanotube films (CNT_f) into an epoxy (EP) matrix as mechanical and EMI shielding reinforcement simultaneously. According to the computed tomography (CT) detection recorded by a high-speed camera, CNT_f exhibited excellent mechanical behavior and good energy absorption. While being introduced into laminated EP composite, the CNT_f enhanced both the mechanical performance and EMI shielding performance. The damage mechanism of CNT_f/EP was studied by CT detection of the impact process, indicating that the CNT_f absorbed the impact energy by improving the delamination resistance. Additionally, the multilayered CNT_f can trap and attenuate the entered electromagnetic microwaves by repeated adsorption, reflection, and scattering in the composite, resulting in excellent EMI shielding performance. Consequently, the energy absorption and the total shielding effectiveness of the CNT_f/EP reached to 4.58 × 10⁻³ J and 52.31 dB, respectively. Therefore, we demonstrated that the CNT_f was an ideal functional reinforcement for mechanically strong and high-performance EMI shielding polymeric composites and the CNT_f reinforced EP composite is promising in practical EMI-shielding applications.     

Multifunctional Shape-Stabilized Phase Change Materials with Enhanced Thermal Conductivity and Electromagnetic Interference Shielding Effectiveness for Electronic Devices

A paraffin-based shape-stabilized composite phase change material (CPCM) is fabricated with dramatically enhanced thermal conductivity and excellent electromagnetic interference (EMI) shielding capacity. The as-prepared CPCMs are supported by graphene-based frameworks with many bubble-like micropores that are prepared by the addition of polystyrene microspheres into graphene oxide hydrogel as hard templates. These bubble-like micropores can encapsulate paraffin wax (PW) due to the strong capillary force between the graphene-based framework and PW and leading to enhanced shape stability of the as-prepared CPCMs. Moreover, the continuous thermally and electrically conductive network formed by graphene nanoplatelets endows the as-prepared CPCMs with a high thermal conductivity and an excellent EMI shielding effectiveness. When the ratio of graphene-based framework is 23.0 wt%, the thermal conductivity and latent heat of CPCM reaches 28.7 W m⁻¹ k⁻¹ and 175.8 J g⁻¹, respectively, and the EMI shielding effectiveness is higher than 45 dB in the frequency of 8.2–12.4 GHz. Their outstanding thermal and EMI shielding performance makes the as-prepared CPCMs promising candidates for use in thermal management and EMI shielding of electronic devices.     

Electromagnetic interference shielding effectiveness of hybrid multifunctional Fe3O4/carbon nanofiber composite

Electromagnetic interference shielding effectiveness (EMI SE) of multifunctional Fe₃O₄/carbon nanofiber composites in the X-band region (8.2–12.4 GHz) is studied. Here, we examine the contributing effects of various parameters such as Fe₃O₄ content, carbonization temperature and thickness on total shielding efficiency (SE_total) of different samples. The maximum EMI SE of 67.9 dB is obtained for composite of 5 wt.% Fe₃O₄ (0.7 mm thick) with the dominant shielding by absorption (SE_A) of electromagnetic radiation. The enhanced electromagnetic shielding performance of Fe₃O₄/carbon nanofiber composites is attributed to the increment of both magnetic and dielectric losses due to the incorporation of magnetite nanofiller (Fe₃O₄) in electrically conducting carbon nanofiber matrix as well as the specific nanofibrous structure of carbon nanofiber mats, which forms a higher aspect ratio structure with randomly aligned nanofibers. Furthermore, we prove that the addition of elastomeric polydimethylsiloxane (PDMS) as a coating for carbon nanofiber composite strengthens the composite structure without interfering with its electromagnetic shielding efficiency.     

CuxS/PAN 3D Nanofiber Mats as Ultra‐Lightweight and Flexible Electromagnetic Interference Shielding Materials

Shielding materials are becoming increasingly important, but present materials suffer from either insufficient mechanical stability or limited shielding properties. In this study, 3D flexible copper sulfide (Cu_xS)/polyacrylonitrile (PAN) nanofiber mats are developed via air spinning followed by chemical reaction with copper salt. The Cu_xS/PAN nanofiber mats exhibit an ultra‐lightweight density of 0.044 g cm^?3 and a thickness of 0.423 mm. Stable electromagnetic interference (EMI) shielding effectiveness (SE) (29–31 dB) of the Cu_xS/PAN composite is achieved in the frequency range of 500–3000 MHz. EMI SE per unit surface density of 16 655.92 dB cm² g^?1 is several orders of magnitude higher than most copper sulfide containing EMI shielding materials reported in literature. In addition, the introduction of the Cu_xS improves the thermal stability and launderability of the PAN mats giving the mats thermal, mechanical, and aqueous stability. Finally, the shielding mechanism of the Cu_xS/PAN nanofiber mats for electromagnetic waves is proposed     

Rapid preparation,thermal stability and electromagnetic interference shielding properties of two-dimensional Ti3C2 MXene

Two-dimensional (2D) MXenes have attracted much attention due to their unique structural characteristics and novel performance in a variety of functions. The fabrication of 2D Ti₃C₂ MXene by acid etching usually requires a long period of over 10 h. In this work, we report on the rapid preparation, thermal stability and electromagnetic interference (EMI) shielding effectiveness of 2D Ti₃C₂ MXene. With the processing conditions optimized by adjusting the etching time and temperature, Ti₃C₂ MXene with a scattered accordion-like structure has been successfully achieved by etching Ti₃AlC₂ powders with 40% HF at 50 °C for only 0.5 h. The as-synthesized Ti₃C₂ was stable at temperatures up to 300 °C in air, but stable in vacuum at temperatures up to 800 °C. The as-synthesized Ti₃C₂ MXene has good EMI shielding performance. The total shielding effectiveness of Ti₃C₂ in a WAX matrix exceeded 20 dB in the whole frequency ranging from 2 to 18 GHz. The maximum shielding effectiveness value achieved to 34 dB at 18 GHz as the Ti₃C₂ content was up to 70 wt%. This work provides an approach for the large scale preparation of the Ti₃C₂ MXene.     

Preparation of NiCo2O4 Nanosheet Arrays and its High Catalytic Performance for H2O2 Electroreduction

Ni foam supporting‐NiCo₂O₄ nanosheet arrays (NiCo₂O₄/Ni foam) are successfully prepared by electrodeposition of the hydroxide precursor, followed by a thermal treatment in air without any template and surfactant. The morphology of NiCo₂O₄ nanosheet arrays is characterized by scanning electron microscope and transmission electron microscopy. The structure is analyzed using X‐ray diffractometer, X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The catalytic performance of NiCo₂O₄/Ni foam electrode for H₂O₂ electroreduction in KOH solution is evaluated by means of cycle voltammetry and chronoamperometry, which exhibits an excellent catalytic performance and superior stability for H₂O₂ electroreduction. The reduction current density of H₂O₂ on NiCo₂O₄/Ni foam electrode is 0.378 A cm⁻² at –0.4 V in the solution containing 3.0 mol L⁻¹ KOH + 0.4 mol L⁻¹ H₂O₂, which is much larger than that on other metal oxides reported previously.