Co-combustion of coal and sewage sludge: Chemical and ecotoxicological properties of ashes

The co-combustion of sewage sludge (SS) and coal is widely used for the treatment and thermal valorization of SS produced in wastewater treatment plants. The chemical and ecotoxicological properties of the ashes produced in this thermal treatment have not been fully studied. Two combustion tests were performed in a fluidized bed combustor. Colombian coal was used as fuel in test A. A blend (1 + 1) of this coal and a stabilized SS (Biogran^®) was used in a second test B. Samples of the bottom and fly ashes trapped in two sequential cyclones were collected. The characterization of the ashes was focused on two main aspects: (1) the bulk content of a set of metals and (2) the characterization of eluates produced according to the European Standard leaching test EN 12457-2. The eluates were submitted to an ecotoxicological characterization for two bio-indicators. In what concerns the bulk content of ashes, both combustion tests have produced ashes with different compositions. The ashes formed during the co-combustion test have shown higher concentrations of metals, namely Cr, Cu, Ni, Pb, Zn and Fe for all ashes. The leaching test has shown low mobility of these elements from the by-products produced during the combustion and co-combustion tests. Cr and Cr(VI) were mainly detected in the eluates of the 1st cyclone ashes produced in both combustion tests and in the 2nd cyclone ashes produced in the co-combustion test.Considering the ecotoxicity assays, the eluates of bottom and fly ashes for both combustion and co-combustion tests have shown low ecotoxic levels. The micro-crustacean Daphnia magna was generally more sensitive than the bacterium Vibrio fischeri. CEMWE criterion has allowed to classify the bottom ashes for both combustion and co-combustion tests as non-toxic residues and the fly ashes collected in both cyclones as toxic.     

Nickel (II) ions sensing properties of dimethylglyoxime/poly(caprolactone) electrospun fibers

A novel dimethylglyoxime (DMG)/poly(caprolactone) (PCL) blend was electrospun into fibers to serve as an optical sensor for the nickel detection based on the formation of a red Ni(DMG)₂ complex. DMG was mixed with PCL at 10, 20 and 30% (w/w) in a mixture of N, N-dimethylformamide (DMF) and dichloromethane (DCM) (50/50, v/v) prior electrospunning process. The best fibers were prepared under an electric field of 20 kV and a distance between needle and collector of 20 cm. From scanning electron microscopy (SEM), the average diameter of the fibers remained nearly constant with increasing amount of DMG. The optimum mass ratio of DMG and PCL was found to be 20:80 as it produced fibers with the smallest diameter distribution and the best sensing property. The formation of the Ni(DMG)₂ complex was confirmed by Fourier transform infrared spectroscopy (FT-IR). The colorimetric response of the PCL/DMG electrospun fibers were then tested against the nickel ions over a concentration range of 1-10 ppm using reflectance spectroscopy. Good linearity between the reflectance values at 547 nm and the concentrations was obtained (R² = 0.9925). These proposed DMG and PCL fibers could be used as the naked-eye sensor for nickel in waste water.     

Using response surface methodology to assess the effects of iron and spent mushroom substrate on arsenic phytotoxicity in lettuce (Lactuca sativa L.)

The effects of iron (Fe) and spent mushroom substrate (SMS) arsenic (As) phytotoxicity towards lettuce in artificial soils were investigated to separate the adverse soil parameters relating to As toxicity using a response surface methodology. SMS induced the root elongation of lettuce in both control and As-treated soils. However, in phytotoxicity test using a median effective concentration (EC₅₀) of As, Fe and the interaction between both parameters (Fe*SMS) significantly affected EC₅₀, which explained 71% and 23% of the response, respectively. The refined model was as follows: EC₅₀ of As (mg kg⁻¹) = 10.99 + 60.03 × Fe − 10.50 × Fe*SMS. The results confirmed that the soil parameters relating to the As mobility in soils were important factors affecting its toxicity. In conclusion, Fe significantly reduced the As phytotoxicity. However, although SMS enhanced the root elongation, SMS in As-treated soils decreased EC₅₀ of As on the root growth via its interaction with Fe. Despite the limitations of the artificial soils and range of parameters studied, the application of this statistical tool can be considered a powerful and efficient technique for interpretation and prediction of the complicated results caused by the interactions between many factors within the soil environments.     

Preparation and nonlinear optical properties of hybrid films containing dicyanomethylenepyran-based chromophores

A new nonlinear optical (NLO) chromophore 4-dicyanomethylene-2-methyl-6- {4-[4-(N-ethyl-N-hydroxyethylamino)phenylazo]}styryl-4H-pyran (AZP), which features extended conjugated chain based on DCM laser dye, was synthesized and functionalized with alkoxysilane for materials processing. Hybrid films containing chromophore AZP and DCM were prepared via a sol-gel processing. The d₃₃ values of films containing AZP are 39-48 pm/V varying with concentration of chromophores, which is similar to that containing DCM. By tuning the organic content, the thermal stability of d₃₃ values can be significantly improved by about 30 °C, about 15 °C higher than those containing DCM. The residual rotational stress, along with cavity between chromophores and matrix, is proposed to contribute to the stability of NLO activity of hybrid films.     

Soft magnetic properties of hybrid ferromagnetic films with CoFe, NiFe, and NiFeCuMo layers

Two-layered ferromagnetic alloy films (NiFe and CoFe) with intermediate NiFeCuMo soft magnetic layers of different thicknesses were investigated to understand the relationship between coercivity and magnetization process by taking into account the strength of hard-axis saturation field. The thickness dependence of H_EC (easy-axis coercivity), H_HS (hard-axis saturation field), and χ (susceptibility) of the NiFeCuMo thin films in glass/Ta(5 nm)/[CoFe or NiFe(5 nm-t/2)]/NiFeCuMo(t = 0, 4, 6, 8, 10 nm)/[CoFe or NiFe(5 nm-t/2)]/Ta(5 nm) films prepared using the ion beam deposition method was determined. The magnetic properties (H_EC, H_HS, and χ) of the ferromagnetic CoFe, NiFe three-layers with an intermediate NiFeCuMo super-soft magnetic layer were strongly dependent on the thickness of the NiFeCuMo layer.     

Study on the interaction of phthalate esters to human serum albumin by steady-state and time-resolved fluorescence and circular dichroism spectroscopy

Phthalate esters (PAEs) are globally pervasive contaminants that are considered to be endocrine disruptor chemicals and toxic environmental priority pollutants. In this paper, the interactions between PAEs and human serum albumin (HSA) were examined by molecular modelling, steady state and time-resolved fluorescence, ultraviolet-visible spectroscopy (UV-vis) and circular dichroism spectroscopy (CD). The association constants between PAEs and HSA were determined using the Stern-Volmer and Scatchard equations. The binding of dimethyl phthalate (DMP) to HSA has a single class of binding site and its binding constants (K) are 4.08 × 10³, 3.97 × 10³, 3.45 × 10³, and 3.20 × 10³ L mol⁻¹ at 289, 296, 303, and 310 K, respectively. The Stern-Volmer and Scatchard plots both had two regression curves for HSA-butylbenzyl phthalate (BBP) and HSA-di-2-ethylhexyl phthalate (DEHP), which indicated that these bindings were via two types of binding sites: the numbers of binding site for the first type were lower than for the second type. The binding constants of the first type binding site were higher than those of the second type binding site at corresponding temperatures, the results suggesting that the first type of binding site had high affinity and the second binding site involved other sites with lower binding affinity and selectivity. The thermodynamic parameters of the binding reactions (ΔG°, ΔH° and ΔS°) were measured, and they indicated the presences of hydrophobic forces and hydrogen interactions in the PAEs-HSA interactions, which agreed well with the results from molecular modelling. The alterations of protein secondary structure in the presence of PAEs were confirmed by UV-vis and CD spectroscopy. The time-resolved fluorescence study showed that the lifetime of Trp residue of HSA decreased after the addition of PAEs, which implied that the Trp residue of HSA was the main binding site.     

Toxicity of mercury on in vitro development of parthenogenetic eggs of a freshwater cladoceran Daphnia carinata

Chronic toxicity test duration of 21 days for daphnid is time consuming and expensive. Therefore, the developmental stages of Daphnia carinata eggs that could be used as potential endpoints for sublethal and chronic toxicity tests have been investigated and defined. Daphnid egg test is simple, easy to conduct and handle in the laboratory, and cost-effective. The 72 h ‘egg arrest’ bioassay system could be an alternative to the classic 21-day chronic test with neonates of daphnid. The main aims of the study were to establish easy to identify stages of D. carinata egg that could be used as potential endpoints for toxicity tests with in vitro cultures of daphnid parthenogenetic eggs. Commonly available Indian freshwater cladoceran Daphnia carinata parthenogenetic eggs in vitro were exposed to water borne mercury concentrations, ranging from 0.1 to 32 μg l⁻¹. Adult female cladoceran D. carinata have eight main developmental stages of parthenogenetic reproduction based on the release of external and internal membranes, formation of cephalic and body regions, appearance of secondary antennae, presence of two pink eyes, than a single black eye, and finally caudal or shell spine separation and finally free-swimming neonate within 65–72 h. At 1, 3.2 and 10 μg l⁻¹ of Hg concentrations; the 25, 50 and 70% embryonic developmental arrests were observed. The lower concentrations of Hg (0.32, 1, and 3.2 μg l⁻¹) tested in the present study are not generally harmful to the neonates and adults daphnid species, but the same are highly toxic to the embryos of D. carinata. The 48 h and 72 h EC₅₀s and their 95% confidence limits for survival and hatchability were lower than previously reported 48 h EC₅₀s for Daphnia magna immobilization assay. The egg of D. carinata turned out to be a suitable alternative model for ecotoxicological and water quality assessment studies.     

Effectiveness of nonlinear ultrasonic and acoustic emission evaluation of concrete with distributed damages

Nonlinear ultrasonic (NLU) and acoustic emission (AE) techniques are used for nondestructive evaluation of concrete, damaged under compression loading. Experiments were carried out in 18 cubic specimens (150 × 150 × 150 mm) cast with three different w/c (six specimens for each w/c). Three specimens at each w/c were used for AE monitoring and three others for NLU evaluation. The NLU evaluation is based on measuring the change in fundamental amplitude with increasing damage and output power level. In acoustic emission testing technique four sensors were used to listen to the wide range of events under various loading and unloading cycles. An increase in AE hits was observed with increasing damage. Each loading and unloading stage was carefully examined for Kaiser and Felicity effects in order to assess the concrete deterioration. It was proposed to measure Felicity ratio at three different loading levels, corresponding to AE hits at 3%, 5%, and 10% of the AE hits at the previous maximum load, respectively. Normalized values of Felicity ratio were plotted and compared with the NLU test data. Correlation between acoustic emission and nonlinear ultrasonic techniques in assessing damage growth in concrete was investigated.     

Preparation and mechanical properties of silicon oxycarbide fibers from electrospinning/sol-gel process

Silicon oxycarbide (SiOC) fibers were produced through the electrospinning of the solution containing vinyltrimethoxysilane and tetraethoxysilane in the course of sol-gel reaction with pyrolysis to ceramic. The effect of the amount of spinning agent Polyvinylpyrrolidone (PVP) on the dope spinnability was investigated. At a mass ratio of PVP/alkoxides = 0.05, the spinning sol exhibited an optimal spinnable time of 50 min and generated a large quantity of fibers. Electrospun fibers were characterized by Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis-differential scanning calorimetry (TGA-DSC), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The SEM results revealed that the SiOC fibers had a smooth surface and dense cross-section, free of residue pores and cracks. The XPS results gave high content of SiC (13.99%) in SiOC fibers. The SiOC fibers prepared at 1000 °C had a high tensile strength of 967 MPa and Young's modulus of 58 GPa.     

Sorption, diffusion, and pervaporation characteristics of dimethylformamide/water mixtures using sodium alginate/polyvinyl pyrrolidone blend membranes

Separation of aqueous dimethylformamide (DMF) solutions in the concentration range of 0-100 wt% were studied using sodium alginate (NaAlg)/polyvinyl pyrrolidone (PVP) blend membranes. The NaAlg was blended in different ratios with PVP. Prepared membranes were crosslinked with CaCl₂ for testing in pervaporation (PV) separation of DMF/water mixtures. Effects of feed composition (0-100 wt%), operating temperature (30-50 °C), and membrane thickness were investigated. Best results were obtained at the conditions of 75/25 NaAlg/PVP blend ratio (w/w), 40 °C temperature, 20 wt% DMF concentration, and 70 μm membrane thickness. Blending of PVP with NaAlg increased permeation flux whereas it decreased the separation factor. NaAlg/PVP membranes gave separation factors of 5.5-27 for permeation flux of 0.96-1.81 kg/m²h depending on the operating temperature and the feed mixture composition. Arrhenius plot of permeation flux data versus reciprocal of temperature exhibited linear trends. Permeation activation energy of DMF and water in the PV was calculated as 6.76 and 1.88 kcal/mol, respectively, using an Arrhenius type relationship. Sorption-diffusion properties of the NaAlg/PVP membranes were also investigated at the operating temperature and the feed composition.     

Treatment of anaerobic sludge digester effluents by the CANON process in an air pulsing SBR

The CANON (Completely Autotrophic Nitrogen removal Over Nitrite) process was successfully developed in an air pulsing reactor type SBR fed with the supernatant from an anaerobic sludge digester and operated at moderately low temperatures (18–24 °C). The SBR was started up as a nitrifying reactor, lowering progressively the dissolved oxygen concentration until reaching partial nitrification. Afterwards, an inoculation with sludge containing Anammox biomass was carried out. Nitrogen volumetric removal rates of 0.25 g N L⁻¹ d⁻¹ due to Anammox activity were measured 35 d after inoculation even though the inoculum constituted only 8% (w/w) of the biomass present in the reactor and it was poorly enriched in Anammox bacteria. The maximal nitrogen removal rate was of 0.45 g N L⁻¹ d⁻¹. By working at a dissolved oxygen concentration of 0.5 mg L⁻¹ in the bulk liquid, nitrogen removal percentages up to 85% were achieved.     

Clean hydrometallurgical route to recover zinc, silver, lead, copper, cadmium and iron from hazardous jarosite residues produced during zinc hydrometallurgy

A hydrometallurgical process for treating the hazardous jarosite residue from zinc hydrometallurgy was proposed, for not only detoxifying the residue, but also recovering the contained valuable metal components. The jarosite was initially activated and decomposed by sintering at 650 °C for 1 h. The sintered residue was leached in 6 mol L⁻¹ aqueous NH₄Cl solution at 105 °C, followed by filtration. The leaching extraction of Zn, Pb, Cu, Cd and Ag are more than 95%. During reduction with Zn powder, more than 93% of Pb, Cu, Ag and Cd can be simultaneously recovered. Then the NH₄Cl leaching residue were leached again in 30 wt% aqueous NaOH solution for 1 h at 160 °C, and about 94% of As and 73% of Si were removed from the residue. The final residue was almost completely detoxified, and contains about 55 wt% Fe, which can be used as an iron concentration.     

Fracture behavior under mixed-mode loading of ceramic plasma-sprayed thermal barrier coatings at ambient and elevated temperatures

The fracture behavior under modes I and II loading of ceramic plasma-sprayed thermal barrier coatings was determined in air at 25 and 1316 °C in asymmetric four-point flexure. The mode I fracture toughness was found to be K_Ic = 1.15 ± 0.07 and 0.98 ± 0.13 MPa , respectively, at 25 and 1316 °C. The respective ‘nominal’ mode II fracture toughness values were K_IIc = 0.73 ± 0.10 and 0.65 ± 0.04 MPa . The empirical mixed-mode fracture criterion best described the coatings’ fracture behavior under mixed-mode loading. The angle of crack propagation was in reasonable agreement with the minimum strain energy density criterion.     

Evaluation of persulfate oxidative wet scrubber for removing BTEX gases

Soil vapor extraction (SVE) coupled with air sparging of groundwater is a method commonly used to remediate soil and groundwater contaminated with volatile organic petroleum contaminants such as gasoline. These hazardous contaminants are mainly attributable to the compounds-benzene, toluene, ethylbenzene, and xylenes (known collectively as BTEX). Exhaust gas from SVE may contain BTEX, and therefore must be treated before being discharged. This study evaluated the use of iron-activated persulfate chemical oxidation in conjunction with a wet scrubbing system, i.e., a persulfate oxidative scrubber (POS) system, to destroy BTEX gases. The persulfate anions can be activated by citric acid (CA) chelated Fe(2+) to generate sulfate radicals (SO(4)(*-), E degrees =2.4V), which may rapidly degrade BTEX in the aqueous phase and result in continuous destruction of the BTEX gases. The results show that persulfate activation occurred as a result of continuous addition of the citric acid chelated Fe(2+) activator, which readily oxidized the dissolved BTEX. Based on initial results from the aqueous phase, a suitable Fe(2+)/CA molar ratio of 5/3 was determined and used to initiate activation in the subsequent POS system tests. In the POS system, using persulfate as a scrubber solution and with activation by injecting Fe(2+)/CA activators under two testing conditions, varying iron concentrations and pumping rates, resulted in an approximate 50% removal of BTEX gases. During the course of the tests which in corporate activation, a complete destruction of BTEX was achieved in the aqueous phase. It is noted that no removal of BTEX occurred in the control tests which did not include activation. The results of this study would serve as a reference for future studies into the practical chemical oxidation of waste gas streams.     

Compressive strength of HPC containing CNI and fly ash after long-term exposure to a marine environment

This study addressed the effect of calcium nitrite based corrosion inhibitor (CNI) and fly ash (FA) on the long-term compressive strength of high performance concrete (HPC). A 3³ full factorial design was developed to evaluate the influence of CNI at addition rates of 0, 12.5 and 25 L/m³ on the compressive strength of HPC manufactured with 8% silica fume blended cement in combination with 0%, 20% and 40% FA replacements and mixed at 0.29, 0.37 and 0.45 water to cementing materials ratios (w/cm). Standard 100 × 200 mm cylinders were prepared and tested for compressive strength at 28 days and 1 year. The 9-year old concrete specimens were obtained from small-scale reinforced concrete slabs that were exposed to a marine environment. Results indicate that the interaction of CNI and FA does not adversely affect the short and long term compressive strength of concrete. In fact, an enhancement on the compressive strength was observed in concretes containing such combination even after long-term exposure to a marine environment.     

Electrospun PVdF-PVC nanofibrous polymer electrolytes for polymer lithium-ion batteries

Nanofibrous membranes based on Poly (vinyl difluoride) (PVdF)-Poly (vinyl chloride) (PVC) (8:2, w/w) were prepared by electrospinning and then they were soaked in a liquid electrolyte to form polymer electrolytes (PEs). The morphology, thermal stability, function groups and crystallinity of the electrospun membranes were characterized by scanning electron microscope (SEM), thermal analysis (TG), Fourier transform infrared spectra (FT-IR) and differential scanning calorimetry (DSC), respectively. It was found that both electrolyte uptake and ionic conductivity of the composite PEs increased with the addition of PVC. The composite PVdF-PVC PEs had a high ionic conductivity up to 2.25 × 10⁻³ S cm⁻¹ at 25 °C. These results showed that nanofibrous PEs based on PVdF-PVC were of great potential application in polymer lithium-ion batteries.     

Preparation of a modified flue gas desulphurization residue and its effect on pot sorghum growth and acidic soil amelioration

A modified flue gas desulphurization residue (MFGDR) was prepared and its effects on sorghum growth and acidic soil amelioration were evaluated in this paper. The MFGDR was prepared by calcining a mixture of dry/semi-dry flue gas desulphurization (FGD) residue from a coal-fired power plant, sorted potash feldspar and/or limestone powder. The available nutrients from the MFGDR were determined with 4.91 wt% K⁺, 1.15 wt% Mg²⁺, 22.4 wt% Ca²⁺, 7.01 wt% Si⁴⁺ and 2.07 wt% SO₄²⁻-S in 0.1 mol L⁻¹ citric acid solution. Its pH value was held at 9.60 displaying slightly alkaline. The results of sorghum pot growth in both red and crimson acidic soil for 30 days indicated that adding the MFGDR at a dosage of 2 g kg⁻¹ in total soil weight would increase the growth rate of biomass by 24.3-149% (wet weight basis) and 47.3-157% (dry weight), the stem length and thickness increase by 5.75-22.1% and 4.76-30.9% in contrast with CK treatment for two test cuttings, respectively. The effect on sorghum growth was attributed to the increase of available nutrients, the enhancement of soil pH value and the reduction of aluminum toxicity in acidic soil due to the addition of the MFGDR. The experimental results also suggested that the MFGDR could be effectively used to ameliorate the acidic soil which is widely distributed throughout the southern China.     

Addressing materials and integration issues for NiSi silicide contact metallization in nano-scale CMOS devices

As the industry approaches sub-100 nm technology nodes, the trend is to replace cobalt silicide with nickel monosilicide (NiSi) since the use of NiSi for contact metallization shows a number of technological advantages, including its line-width independent low resistivity, less Si consumption and low thermal budget for its formation, and compatibility with Si_1 − xGe_x substrate technology. However, NiSi has not been considered as a serious candidate until recently mainly due to its poor morphological/thermal stability. Recent studies have shown that the morphological/thermal stability of NiSi can be enhanced substantially through the addition of a small amount of impurities, resulting in much improved silicided shallow junction integrity. Moreover, it has also been demonstrated that the addition of certain impurities, such as Ti, effectively reduces the sensitivity of NiSi formation to surface contaminants (e.g., residual interfacial oxide). This paper will present and discuss the details of these experimental results.     

Multimodal grain size distribution and high hardness in fine grained tungsten fabricated by spark plasma sintering

Preparation of fine grained, hard and ductile pure tungsten for future fusion reactor applications was tested using the bottom-up approach via powder consolidation by spark plasma sintering (SPS) at different temperature (1300-1800 °C) and pressure (90-266 MPa) conditions. Pure tungsten powders with an average particle size of about 1 μm were sintered to high density (about 94%) with almost no grain growth at a temperature below 1400 °C and an applied pressure up to 266 MPa. These samples had a multi-modal grain size distribution (resembling the size distribution of the initial powder) and a very high Vickers hardness (up to 530 kg/mm²). Above 1500 °C fast grain growth occurred and resulted in a drop in hardness. XRD on the surface of bulk samples showed a small amount of tungsten oxides; however, XPS and EDS indicated that these oxides were only surface contaminants and suggested a high purity for the bulk samples. The results demonstrate that SPS can lead to ultrafine and nanocrystalline tungsten if used to consolidate pure nano tungsten powders.     

Aerobic fate and impact of canola oil in aquatic media

The fate of canola oil in water under aerobic conditions was studied in respirometry tests. First-order biodegradation rates were estimated for a refined oil (commercial canola oil, CCO), 0.0037 h⁻¹, and for two synthetic oils, one prepared with mono-acid triacylglycerols (TAO) 0.0048 h⁻¹, and the other with free fatty acids and glycerol (FAO) 0.0038 h⁻¹. Two abiotic factors limited substrate bioavailability: the autoxidation of the oleoyl chains and the insolubility of fully saturated triacylglycerols. In addition, the ecotoxic impact of the oils was assessed by Microtox^? toxicity. For the acylglycerol oils, luminescent bacteria inhibition was not detected in the water phase, whereas solid-phase EC₅₀ values below 1.8% sample volume were measured. Toxicity was observed in the aqueous phase (EC₅₀ < 16%) during the biodegradation of FAO. In this case, however, solid-phase toxicity was extremely high at the beginning of the test (0.02%) but the toxicity dissipated 480 h into the experiment.