Characterization Of Solid Residues Research Articles

Effect of mechanical activation on biooxidation and gold extraction of a high-grade flotation concentrate using mesophilic and moderately thermophilic microorganisms

The effect of mechanical activation and biooxidation on the gold extraction from a high-grade (168 g/t) gold sulfide concentrate was investigated using a mixed culture of iron- and sulfur-oxidizing microorganisms. The influence of mechanical activation pretreatment, the nutrient medium type (Norris and 9K), initial pH, and microbial culture type was investigated on the biooxidation ability of mixed cultures of mesophilic and moderately thermophilic microorganisms. Results showed that gold extraction from the non-activated non-biooxidized concentrate was 83.9%, while after biooxidation, it reached 98.8%. The gold recovery from the mechanically activated non-biooxidized concentrate was 77.3%, which reached 97.6% after biooxidation. Therefore, biooxidation was found to have a significant positive effect on gold extraction, but mechanical activation had a negative effect on it in both abiotic and biotic media. The characterization of solid residues was performed by SEM/EDS and chemical analyses. Jarosite and gypsum were the main precipitates formed during biooxidation, especially in 9K nutrient medium. It was found that mechanical activation reduced the efficiency of biooxidation process mainly as a result of overcoming negative effects such as weak bacteria-mineral attachment, the release of toxic species, increasing pulp viscosity, and the coating of gold grains by less soluble solids on the positive effects such as the enhancing of surface area and the disordering of the crystal structure of refractory sulfide phases.

CARACTERIZAÇÃO DE RESÍDUOS SÓLIDOS INDUSTRIAIS POR ANÁLISE TÉRMICA: PERSPECTIVAS DE USO COMO MATERIAL FILTRANTE PARA ÁGUAS RESIDUÁRIAS

CHARACTERIZATION OF SOLID RESIDUES THROUGH THERMAL ANALYSIS: UTILIZATION PERSPECTIVE AS FILTER MATERIAL FOR WASTEWATER TREATMENT. Metallurgical waste and vermiculite are solid residues that have potential of utilization as filtering material. Nevertheless, they are commonly discarded. These materials have chemical sites like Si-O, Si-O-Si in vermiculite or have good ionic exchange properties like iron oxide compounds that can be used in adsorption processes. When these materials are combined with a synthetic blanket (OH, C=C, CO and C-H groups), it composes a filter layer with potential to be used in wastewater treatment. In this article, these materials were chemically treated and characterized by Thermogravimetry (TG), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR) and coupled TG-FTIR. The results suggest that organic compound contamination was not found after chemical treatment, which could have remained over the unity operations in the Metallurgical processes. The thermal and acid treatments influenced a major formation of iron oxide formation, but its oxidation degree (FeO, Fe2O3, or Fe2O3.FeO) were dependent on the sample granulometry. The Vermiculite shows an irreversible chemical modification after thermal treatment. The characterization of these residues shows its potential use as material in filter construction. Hence, it is fundamental to minimize the environmental impacts as well as to diminish the production costs in wastewater treatment.

Coating layer formation from deposited droplets: A comparison of nanofluid, microfluid and solution

An experimental investigation regarding the build-up of small coating layers from deposited droplets dried under forced convection is presented. The structural and morphological evolution from single droplet residue to multi-deposit coating layer is analyzed, as well as the development of porosity during this incremental layer formation. Three model substances are compared, representing the behavior of nano- and microsuspensions, as well as solutions, respectively. The morphologies, porosities and characteristic phenomena of the resulting layers, obtained via sessile droplet drying on a flat, partially wetting substrate, are also investigated in-depth. In all associated experimental series, focus is laid on the dependency on drying conditions, as well as the development during the consecutive addition of droplets. Characterization of solid residues was performed foremost by white-light interferometry, with complementary X-ray micro-tomography measurements.

Lipid-rich bacterial biomass production using refinery wastewater in a bubble column bioreactor for bio-oil conversion by hydrothermal liquefaction

In this study, a bubble column reactor (BCR) was evaluated for producing lipid rich biomass of Rhodococcus opacus using refinery wastewater as the substrate. The biomass obtained was used for bio-oil production by hydrothermal liquefaction (HTL) process. Initially, the effect of three media constituents viz. NH4Cl, KH2PO4, and Na2HPO4 and three physicochemical parameters i.e., pH, agitation and temperature on refinery wastewater treatment by R. opacus was studied employing Placket Burman experimental design. From the results, it was observed that variation in the levels of these parameters does not have any significant effect on the wastewater treatment efficiency indicating the robust nature of R. opacus in treating refinery wastewater. During the continuous wastewater treatment using BCR, a very high chemical oxygen demand (COD) removal efficiency of 97 % was obtained along with 2.4 g L−1 of biomass and 1.33 g L−1 lipid yield. The lipid rich bacterial biomass was later subjected to HTL treatment which resulted in production of bio-oil with 26.5 % yield on biomass. Detailed characterization of the bio-oil revealed that it primarily contains different complex organic hydrocarbons. Characterization of solid residue (bio-char) obtained as a byproduct of HTL process contained a high amount of carbon (41.8 %) of large porosity and many active groups over its surface indicating its potential high application value. Overall, this study serves as an excellent example of zero waste strategy for recovering energy in the form of bio-oil from industrial wastewater.

Characterization of Solid Residues from Entrained Flow Gasification of Coal Bio-Oil Slurry

Char and soot characterization was performed on samples obtained from pilot-scale entrained flow gasification of coal bio-oil slurry (CBS) and coal/water slurry (CWS) at different operating conditions. The compositions and gasification reactivity of char and soot have been investigated to reveal the difference of CBS and CWS slurries. The results show that both char and soot obtained from CBS gasification contain alkali and alkaline earth metals which come from the bio-oil. These CBS char and soot alkali-containing samples exhibit higher gasification reactivity than those from CWS gasification. For CBS gasification, soot has higher gasification reactivity compared with char. The gasification reactivity may be caused by the catalytic effect of KCl and K(2)SO(4 )existing in char and soot. The reactivity of char and soot is also influenced by the gasification conditions (such as H2O/C ratio), and high CO2 gasification reactivity is observed for chars exposed to high H2O/C ratios in the entrained flow reactor.

Green template-free synthesis and characterization of mesoporous alumina as a high value-added product in aluminum black dross recycling strategy

Aluminum black dross (ABD) is a solid waste of aluminum smelting process that causes serious environmental and public health problems. In addition, it imposes significant disposal costs to the aluminum industry. In this study, synthesis and characterization of mesoporous alumina (MA) from the ABD using a novel recycling procedure consisting of leaching at low temperature (85 °C) and atmospheric pressure, co-precipitation, separation through selective dissolution, re-precipitation, aging and finally calcination at 600 °C for 2 h. No hard or soft template was used during the formation of the gel. The as-synthesized MA had a specific surface area, total pore volume and average pore diameter of 123–162 m2/g, 0.37 cm3/g and 10.6 nm, respectively which were obtained by nitrogen sorption analysis. The as-synthesized MA possessed more than 98% purity. Its XRD pattern exhibited the characteristic peaks of gamma, eta, theta, and delta phase alumina. FESEM and TEM analyses revealed nanoscale morphology of the as-synthesized MA; having crystal size of ∼11 nm. The TGA analysis showed that the as-synthesized MA is thermally stable and exhibits only ∼5 wt% mass loss for heating from 30 to 800 °C. The characterization of solid residue at the end of the proposed process proved that it contains mainly silica phase which can alternatively be reused as filling agent or aggregate in concrete materials applications. It is quite clear that the process of production of MA from the ABD is feasible and practical and provides a novel mitigation to the environmental problems of the ABD.

Post treatment of UASB effluent by using inorganic coagulants: Role of zeta potential and characterization of solid residue

In the present study, potential of four coagulants (ferric chloride, FC; ferrous sulfate, FS; poly aluminum chloride, PAC; and aluminum sulfate, AlS) was investigated in terms of removal of traditional water pollution indexes such as COD and TSS for the treatment of upflow anaerobic sludge blanket (UASB) reactor effluents. In particular, the effect of various process parameters such as coagulant dosage (m) and pH on treatment efficiency was examined along with characterization of coagulant sludge residue to evaluate its usability in future applications. The results achieved were also verified using zeta potential (ζ) measurement and particle size distribution (PSD) of coagulants in reaction mixture. Among the all investigated coagulants, maximum removal efficiency was found to be 85.5%, 80.2% and 97.4% for COD, TSS and turbidity respectively, at m=150mg/L and pH 8.5 with FC coagulant. Confirmation experiments also demonstrated that ζ measurement and PSD is a powerful and useful tool in optimization of coagulation process for the treatment of UASB reactor effluent. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), surface area, pore size distribution analysis and thermo-gravimetric analysis (TGA/DTA) were used for characterize the solid residue obtained after coagulation experiments. These investigation results revealed that solid residues, produced by different coagulants, have good calorific value, mesoporous in nature and possess higher surface area.

Characterization of Solid Residues from High Temperature Gasification of Olive Kernel

In this study, a fixed-bed downdraft gasifier (70 kWe–245 kWth) with gas cooling and cleaning system, combined with a gas engine, was tested using olive kernel as fuel. The primary scope of this paper is to identify the most prominent utilization paths for the solid residues of the process. After a 3-day experimental work and the respective sampling campaigns, a thorough characterization study was conducted: the mineralogy of collected residues was examined by means of XRD, Loss on Ignition tests were carried out by the use of TGA up to 850 °C, their morphology was examined by means of EDS-SEM, their energetic content and elemental composition were determined by means of proximate and ultimate analysis, respectively, while their major and trace metal characterization was conducted by means of AAS. Due to its high calorific value, relatively low moisture content, and high loss-on-ignition value, it has been concluded that the olive kernel gasification residue can be utilized as a primary fuel in combustion boilers. Moreover, its reduced chlorine and sulfur content suggest minimal corrosion-related problems. Alternative utilization options, based on their morphology, are also suggested in this study, while modifications in the current gasification conditions are proposed as well.

Understanding the Mechanism of Cypress Liquefaction in Hot-Compressed Water through Characterization of Solid Residues

The mechanism of hydrothermal liquefaction of cypress was investigated by examining the effects of temperature and retention time on the characteristics of the solid residues remaining after liquefaction. The solid residues were divided into acid-soluble and acid-insoluble residues. Results showed the polymerization reactions also mainly occurred at low temperatures. The reactive fragments transformed into acid-insoluble solid residue in the form of carbon and oxygen through polymerization reactions. The process of cellulose degradation consists of two steps: an initial hydrolysis of the more solvent- accessible amorphous region and a later hydrolytic attack on the crystalline portion. Hemicelluloses were decomposed into small compounds during the initial stage of the cypress liquefaction process, and then these compounds may rearrange through polymerization to form acid-insoluble solid residues above 240 °C. The higher heating value of the solid residues obtained from liquefaction at 260–300 °C was 23.4–26.3 MJ/kg, indicating that they were suitable for combustion as a solid fuel.

Multifaceted Approach for Characterization of Solid Residues from Sludge Incineration

The Italian Water Research Institute (IRSA) carried out sludge incineration tests on a demonstrative plant equipped with a circulating fluidized bed furnace. Aim of this paper is to present the potential applicability of non-conventional techniques for solid residues characterization. Results of five tests performed under different operating conditions are discussed. Incineration solid residues were sampled from the cyclone, downstream the furnace (cyclone ash, CA), and from the bag filter (filter ash, FA). Different techniques were used by the Mechanical and Industrial Engineering Department of the “Roma TRE” University, which cooperated with IRSA in the research project, to characterize incineration products and to correlate with process parameters. The X-ray Diffraction (XRD) technique was used to estimate the amount of sand, lost from the furnace, in CA and FA samples. Particle size distribution was measured using Low Angle Laser Light Scattering (LALLS). Scanning Electron Microscopy associated with Energy Dispersive Spectroscopy (SEM/EDS) was used to correlate size and shape of individual particles with chemical composition.This multifaceted approach to characterize incineration residues appears promising, providing additional and complementary information to the traditional chemical characterization.

The Effect of Nanometals on the Flammability and Thermooxidative Degradation of Polymer Materials

It was found that finely dispersed metals (nanometals) at low addition (≤1% wt.) increase flammability of neat polypropylene in spite of strong enhancement of char yield. The nanometals do not seriously affect flammability of neat epoxy resins. On the other hand, it was shown that the nanometals are very efficient co-additives in combination with some phosphorus containing fire retardants in both polypropylene (thermoplastic) and epoxy resin (thermoset). At the specific content of the metals, a sharp maximum is observed on the dependence of oxygen index on concentration of fire retardant additives which proves occurrence of strong synergistic effect. Thermal analysis and characterization of solid residues allowed to approach to the mode of fire retardant action of the nanometals.

The characterization of solid residues from PFBC boilers

AbstractPFBC is one of the two important advanced fossil fuel technologies, now available. It permits the combustion of fossil fuels with extremely low emissions, while also achieving high electrical conversion efficiencies. However, relatively little is known about the ash characteristics, despite the existence of several demonstration units. This study looks at bed and cyclone ash from two of these boilers, the Spanish PFBC plant at Escatron in Spain, and the Tidd plant in Brilliant, Ohio. In particular, these ashes are examined using both conventional and some newly developed techniques in order to determine their chemical speciation. This work confirms the ashes have extremely low free lime contents (1% or less), and extremely low elemental carbon. More surprisingly, the existence of significant amounts of dolomite in the cyclone ashes from the Tidd plant has been demonstrated, and significant quantities of other calcium compounds (i.e. silicates, ferrites etc.) have also been shown in the bed ashes from the Spanish plant. One other interesting observation is the presence of low levels of sulphides in the ashes from the Escatrón unit, and its total absence from the Tidd unit which used dolomite rather than calcitic limestone. These results also clearly indicate that ashes from PFBC plants are likely to be significantly easier to dispose of in landfills than AFBC ashes, and should have considerably better potential for use in cemen‐titious applications.

Effect of Melamine and its Salts on Combustion and Thermal Decomposition of Polyamide 6

Melamine and its salts added to polyamide 6 (PA-6, nylon 6) improve its fire retardancy as measured by oxygen index and UL94 tests. The mechanism of the fire-retardant action of the additives was studied using thermogravimetry, kinetics of thermal decomposition and characterization of solid residues and evolved high-boiling products. It was found that melamine, melamine oxalate, melamine phthalate and melamine cyanurate facilitate thermal decomposition of PA-6 with increasing evolution of oligomeric chain fragments instead of caprolactam, which is the principal product evolved from the nonfire-retarded PA-6. These additives promote non-combustible flow dripping and help extinguishment of the flame. The observed increase in solid residue from the thermal decomposition of the formulations or the endothermic cooling due to melamine evaporation might give an additional but less important contribution to fire retardancy. In the case of dimelamine phosphate and melamine pyrophosphate, PA-6 reacts with liberated phosphoric acids producing phosphoric esters which give char upon further thermal decomposition. The fire-retardant effect of these two salts is mostly attributed to polymer mass retention and intumescent layer protection mechanisms. © 1997 John Wiley & Sons, Ltd.

Effect of Melamine and its Salts on Combustion and Thermal Decomposition of Polyamide 6

Melamine and its salts added to polyamide 6 (PA-6, nylon 6) improve its fire retardancy as measured by oxygen index and UL94 tests. The mechanism of the fire-retardant action of the additives was studied using thermogravimetry, kinetics of thermal decomposition and characterization of solid residues and evolved high-boiling products. It was found that melamine, melamine oxalate, melamine phthalate and melamine cyanurate facilitate thermal decomposition of PA-6 with increasing evolution of oligomeric chain fragments instead of caprolactam, which is the principal product evolved from the nonfire-retarded PA-6. These additives promote non-combustible flow dripping and help extinguishment of the flame. The observed increase in solid residue from the thermal decomposition of the formulations or the endothermic cooling due to melamine evaporation might give an additional but less important contribution to fire retardancy. In the case of dimelamine phosphate and melamine pyrophosphate, PA-6 reacts with liberated phosphoric acids producing phosphoric esters which give char upon further thermal decomposition. The fire-retardant effect of these two salts is mostly attributed to polymer mass retention and intumescent layer protection mechanisms. © 1997 John Wiley & Sons, Ltd.