Recovery of plutonium and cerium from alumina crucible

Journal of Radioanalytical and Nuclear Chemistry - Plutonium recovery is inevitable from plutonium bearing alumina crucibles generated over the years as part of carbon analysis during chemical...     

Hydrogen production from paper sludge hydrolysate

The main objective of this study was to develop a system for the production of “renewable” hydrogen. Paper sludge is a solid industrial waste yielding mainly cellulose, which can be used, after hydrolysis, as a feedstock in anaerobic fermentation by (hyper)thermophilic organisms, such as Thermotoga elfii and Caldicellulosiruptor saccharolyticus. Tests on different medium compositions showed that both bacteria were able to produce hydrogen from paper sludge hydrolysate, but the amount of produced hydrogen and the requirement for other components differed. Hydrogen production by T. elfii strongly depended on the presence of yeast extract and salts. By contrast, C. saccharolyticus was less dependent on medium components but seemed to be inhibited by a component present in the sludge hydrolysate. Utilization of xylose was preferred over glucose by C. saccharolyticus.     

Physical and chemical transformations of calcium in aluminate solutions from alumina production

The data available from the literature are analyzed. The complex behavior of calcium in aluminate solutions was studied. The scattered results obtained in studying the calcium transformations in aqueous solutions containing aluminate ion are summarized and presented in the form of a scheme and phase diagram, which are useful for the development of lime technologies in various industries, including alumina production. In addition, the phase diagram outlines the most technologically important fields of research intended for obtaining desired products and is also suitable for forecasting processes.     

Scale-up of microwave heating process for the production of bio-oil from sewage sludge

A pilot-scale microwave heating apparatus was constructed for the production of bio-oil from sewage sludge, and the effects of important microwave processing parameters and chemical additives on the quality and yield of bio-oils were investigated. It was found that bio-oil was mainly formed at the pyrolysis temperature range of 200–400 °C. A higher heating rate (faster pyrolysis) not only increased the yield of bio-oil, but also improved the quality of bio-oil according to the elemental composition and calorific values. The maximum bio-oil yield was 30.4% of organic fraction, obtained from the pyrolysis of original sewage sludge at microwave radiation power of 8.8 kW and final pyrolysis temperature of 500 °C. All of five simple additives (KOH, H₂SO₄, H₃BO₃, ZnCl₂, and FeSO₄) reduced the bio-oil yield, but the composition and property of bio-oil varied with the additive types greatly. KOH, H₂SO₄, H₃BO₃ and FeSO₄ were found to improve the quality of bio-oils remarkably according to the calorific value, density, viscosity and carbon content of bio-oils, but ZnCl₂ treatment went against that. GC–MS analysis of the bio-oils showed that, alkali treatment promoted the formation of alkanes and monoaromatics, while acid treatment favored the formation of heterocyclics, ketones, alcohols and nitriles. Compared with sulfate slat FeSO₄, chloride salt ZnCl₂ was a better catalyst for selective catalytic pyrolysis of sewage sludge. The addition of ZnCl₂ only promoted the formation reactions of a few kinds of nitriles and ketones remarkably. It is technologically feasible to produce bio-oil form microwave-induced pyrolysis of sewage sludge by optimizing pyrolysis conditions and selecting appropriate additives.     

Low-waste production of alumina catalysts for gas sulfur recovery

A new low-waste technology for production of the alumina catalyst at the Claus process has been developed. The catalytic activity of the Claus alumina catalysts (IC-27-22) produced by this technology is close to that of the best foreign samples (CR and S-100).VNIIGAS     

Optimal production of polyhydroxyalkanoates in activated sludge biomass

Polyhydroxyalkanoates (PHAs) have been recognized as good candidates for biodegradable plastics, but their high price compared with conventional plastics has limited their use. In this study, actiated sludge microorgan isms from a conventional wastewater treatment process were induced, bycontrol-lingthe carbon: nitrogen (C:N) ratioin the reacorliquor, toaccumulate PHAs. In addition, an intermittent nitrogen feeding program was established to optimize the volumetric PHA productivity in a wastewater treatment process. The optimal overall polymer production yield of 0.111 g of polymer/g of carbonaceous substrate consumed was achieved under a C:N ratio of 96:1 by feeding nitrogen in the reactor liquor onceevery four cycles. At the same time, the amount of excess sludge generated from the wastewater treatment process was reduced by22.9%.     

Ethanol production from spent sulfite liquor fortified by hydrolysis of pulp mill primary clarifier sludge

Applied Biochemistry and Biotechnology - Some low-yield sulfite pulping operations ferment spent sulfite liquor (SSL) to remove biochemical oxygen demand associated with dissolved sugars while at...     

Sphaerotilus natans isolated from activated sludge and its production of poly (3-hydroxybutyrate-co-3-hydroxyvalerate)

Sphaerotilus natans is a sheathed bacterium existing in the activated sludge of wastewater treatment plants. IT is one of the filamentous bacteria causing the bulking and foaming difficulties of activated sludge. Isolating the strain and culturing it in an axenic environment could not only provide the metabolic knowledge of the strains that would be useful in the development of wastewater treatment methods, but also could enable us to gain an understanding of the mechanism by which poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (poly[3-HB-co-3-HV]) is produced by this strain. This article reports the screening and isolation of the strain from the activated sludge using the Nile blue staining method together with Fourier transform infrared analysis. We investigated the ability of the selected strain to produce poly(3-HB-co-3-HV) copolymer using glucose and peptone, or by adding valeric acid or sodium propionate as precursor. Proper precursor feeding could dramatically enhance its 3HV content in the copolymer P(3HB-co-3HV). By controlling the different feeding times in fed-batch fermentation, different desired copolymers were obtained with 15, 40, and 70% 3HV mole fraction of the copolymer. Polymer properties were analyzed by gas chromatography, differential scanning calorimetry, thermo-gravimetry, and nuclear magnetic resonance analysis. Open laboratory of Chirotechnology of the Institute of Molecular Technology for Drug Discovery and Synthesis The University Grants Committee Area of Excellence Scheme (Hong Kong).     

Use of drinking water sludge in the production process of zeolites

This study reports the synthesis of zeolites A, X, and P, cancrinite, and sodalite using sludge generated in a drinking water plant. Two experimental steps were carried out: (1) fusion and (2) hydrothermal treatment. Crystallization was achieved by means of a 2³ experimental design with central point with the following factors: temperature, time, and solid/liquid ratio. The sludge presented Si and Al contents (SiO₂/Al₂O₃ = 1.7) which allow the synthesis of zeolites with high cation exchange capacity. The content of organic matter was considerable (loss on ignition 26.1 %), but is eliminated in the fusion step at 550 °C. This process also permits the conversion of the initial aluminosilicates into zeolite precursors (sludge–NaOH mix of 1:0.785 g/g). Hydrothermal treatment then permits the crystallization of the aforementioned zeolites. These materials showed high cation exchange capacities as compared to other commercial and experimentally synthesized zeolites, and can be used in the removal of heavy metals such Cd²⁺, Pb²⁺, Cu²⁺, Fe²⁺, and ammonium present in water, providing an interesting new option in wastewater treatment and remediation of soils.     

Recovery and stabilization of heavy metal sludge (Cu and Ni) from etching and electroplating plants by electrolysis and sintering

This work dealt with the recovery and stabilization of the sludge with heavy metals (Cu and Ni) produced from etching and electroplating plants. The heavy metals in the sludge were deprived of by acid leaching, followed by precipitation with 28% NH₄OH, and finally by electrolysis. In the electrolysis, the recovery percentage and purity were investigated at different electronic currency and temperature. The metal-deprived sludge was stabilized by mixing with glass powder and clay, followed by sintering at high temperature. How the ratio of glass powder to metal-deprived sludge affected final products (sludge bricks) was explored, in terms of specific gravity, absorption capacity, unconfined compressive strength, morphology, the volume shrinkage ratio and burn-up ratio. The volume shrinkage ratio and burn-up ratio of sludge bricks increased with metal-deprived sludge contents. The heavy metal remaining in sludge bricks was assessed through TCLP (toxicity characteristic leaching procedure) and by the analysis of SEM and EDX. The results from TCLP showed that the contents of leached metals were all below the regulatory criteria. This fact approved the feasibility of our method.     

Synthesis of indenes from phenylpropanones using alumina catalyst

1,3-Diphenylpronan-2-one undergoes dehydration over alumina at around 400° C to form 1,3-diphenylallene which cyclizes to 2-phenylindene. Since the parent ketone can be obtained under the reaction conditions from phenylacetic acid, the present reaction forms a one step syntheses of 2-phenylindene from phenylacetic acid. 3- and 4-methylphenylacetic acids also give the corresponding indenes. 1,3-Diphenylpropan-1-ones also give phenylindenes, presumably by a direct cyclodehydration reaction.     

Porosity of anodic alumina membranes from electrochemical measurements

A procedure based on the high-field mechanism of the growth of anodic oxides was developed in order to evaluate the morphological features of porous layers. Since the thickness of the barrier film, separating the porous layer from the metal, does not change during the steady-state growth of an anodic porous layer, the rate of displacement of the metal-oxide interface to the metal direction must be equal to the rate of displacement of the pore base to the oxide direction. As a consequence, porosity can be expressed in terms of the ratio i _diss/i _ion, where i _diss is the dissolution current density at the pore base, and i _ion is the ionic current density at the metal-oxide interface. Pore diameter can be determined from geometrical considerations, while average pore population can be obtained from the ratio of porosity to the average surface area of a single pore. This procedure was checked by comparison with experimental results relative to membranes prepared in various conditions. The satisfactory agreement between theoretical and experimental findings indicates that porosity can be evaluated by current density data and vice-versa. Therefore, anodic alumina membranes may be tailored for different applications by choosing operative conditions giving the desired value of i _diss/i _ion.     

Municipal wastewater treatment by periodic biofilter without excess sludge production

The paper reports the results of an investigation aimed at evaluating the performances of a periodic biofilter (SBBR) for treating municipal wastewater. The investigation was carried out at laboratory scale on real primary effluent coming from a municipal wastewater treatment plant located in Southern Italy. The SBBR was designed for carbon and nitrogen removal through one single stage. The results have shown that even at maximum organic load (i.e., 7 kg COD/m3.d), the COD in the effluent was lower than 60 mg/L. TKN removal efficiencies resulted high (i.e. 90-95%) up to an organic load of 5.7 kg COD/m3.d corresponding to a nitrogen load of 0.8 kg TKN/m3.d. NO3-N concentration in the treated effluent was lesser than 6 mg/L although in the SBBR treatment cycle no anoxic phase was scheduled. This indicated that denitrification extensively took place in the biofilter. The process was characterized by high suspended solids removal (about 90%) and by a negligible sludge production (lower than 0.01 kgVSS/kgCODremoved). In the SBBR, biomass grew as granules and was characterised by different measurements (biomass concentration, cellular protein and biomass density). Biomass density resulted very high, i.e. 200 gTSS/Lbiomass, and this permitted to achieve a biomass concentration such high as 40 gTSS/Lbed. Such biomass concentration did not cause any decrease of biomass metabolic activity as proved by its total protein content (29% of organic matter) and maximum oxygen uptake rate value (i.e. 50 mgO2/gVSS h).     

Extraction of uranium in caustic sludge from the production of nuclear fuel components by countercurrent dissolution and acid curing

Journal of Radioanalytical and Nuclear Chemistry - The uraniferous caustic sludge (UCS) produced in the production of uranium fuel components was hardly to leach directly, due to its very low-grade...     

Separation of iodine produced from fission using silver-coated alumina

A method developed for the preparation of silver-coated alumina, a new material for retention of iodine from alkaline solution is described. Experiments were carried out, oriented to the purification step of ⁹⁹Mo produced by uranium fission, based on the retention of radioiodine in this material. Iodine retention, as well as molybdenum non-retention, were found, both with excellent results. Further tests showed that the incorporation of this material has no influence on the subsequent ⁹⁹Mo retention in ion exchange resins. The elution of the radioiodines retained was tested with satisfactory results. This new material can be used not only for improving the ⁹⁹Mo purification and working conditions, but also as the basis of a method for recovering the fission produced ¹³¹I.     

Uniform gold nanorod arrays from polyethylenimine-coated alumina templates

Monolithic Au nanorod arrays can be grown by electrodeposition in Au-backed nanoporous alumina templates using polyethylenimine (PEI) as an adhesion layer, with excellent height control between 300 nm and 1.4 microm. The local height distribution can be extremely narrow with relative standard deviations well below 2%. The uniform growth rate appears to be determined by the adsorbed PEI matrix, which controls the growth kinetics of the grains comprising the nanorods. The nanorods can be retained as free-standing 2D arrays after careful removal of the AAO template. Reflectance spectroscopy reveals a collective plasmon mode with a maximum near 1.2 microm, in accord with recent calculations for 2D arrays of closely spaced cylindrical nanoparticles.     

New epoxidation reagents derived from alumina and silicon

Hydrogen peroxide or tert butyl hydroperoxide in contact with basic alumina will epoxidize olefins. Triphenylsilyl hydroperoxide behaves similarly to peracids toward olefins, ketones and allylic alcohols.     

Thermoluminescence characteristics of different phase transitions from nanocrystalline alumina

Journal of Radioanalytical and Nuclear Chemistry - Nanocrystalline boehmite material was synthesized using the hydrothermal method. Different annealing temperatures have been used to transform...     

Thermal analysis of soil amended with sewage sludge and biochar from sewage sludge pyrolysis

The main objective of the present study is to study the behaviour of sewage sludge and biochar from sewage sludge pyrolysis after addition to soil in a context of a temperate agricultural soil. For this, an incubation experiment was designed during 200 days. Carbon mineralization of soil amended with sewage sludge and biochar at two different rates (4 and 8 wt%) was evaluated. Differential thermal analysis, thermogravimetry and the first derivate of the TG were performed in oxidizing conditions on soil samples before and after incubation. Biochar obtained from sewage sludge pyrolysis at 500 °C was more stable in soil than original sewage sludge. After incubation experiment, the reduction of soil organic matter content was significantly lower in soil amended with biochar than in soil amended with sewage sludge. The thermostability index WL₃/WL₂ decreases after incubation in soil amended with biochar, however it increases in case of soil treated with sewage sludge.