Optimum Reduction Conditions Research Articles

Thermodynamic and Experimental Study on Efficient Extraction of Valuable Metals from Polymetallic Nodules

Polymetallic nodules are promising resources for the extraction of valuable metals such as copper, nickel, and cobalt, as well as manganese alloys. To achieve efficient extraction of useful metals from the emerging resource, high-temperature carbothermic reduction of nodules was investigated by optimizing the reductant addition, slag and alloy systems. Thermochemical software FactSage was used to predict the liquidus temperature of the slag system, which is not sensitive to FeO, CaO and Al2O3, but decreases significantly with decreasing MnO/SiO2 mass ratio. The experiments were designed to reduce the oxides of Cu, Co and Ni completely, and reduce FeOx partially depending on the amount of graphite addition while leaving the residual slag for further processing into ferromanganese and/or silicomanganese alloys. Co, Cu and Ni concentrations in the alloy decreased with increasing graphite addition. The optimal reduction condition was reached by adding 4 wt% graphite at the MnO/SiO2 mass ratio of 1.6 in slag. The most effective metal-slag separation was achieved at 1350 °C, which enables the smelting reduction to be carried out in various furnaces.

Carbothermic reduction of low-grade laterite-graphite composite pellets

The appropriate carbothermic reduction parameters of low-grade laterite-graphite pellets and the influence of calcined temperature on these for upgrading the nickel (Ni) content in pellets were evaluated. Afterward, the impact of the additive (Na2SO4) on Ni grade and Ni recovery of calcined pellets at optimal reduction conditions was also investigated. XRD analysis, thermodynamic calculation, isothermal reduction experiment, BET-specific surface area analysis, bromine methyl alcohol solution analysis, and chemical composition analysis were used in order to obtain the associated parameters. In this study, it showed the improvement of Ni grade and Ni recovery rate of 673 K-calcined laterite-graphite pellets can respectively reach > 30 mass % and 90.2 mass % under the conditions of reduction temperature = 1373 K, reduction time = 30 min, and the mole ratio of fixed carbon to reducible oxygen of iron and nickel in laterite nickel ore (C/O) = 0.6. The reasons were proposed that the 673 K-calcined laterite ores have the highest specific surface area of 46.8 m2/g with pores in the size of 29.7 Å to provide faster Ni reduction at the initial stage followed by reduction. The addition of 5 mass % additive resulted in the best Ni grade of > 30 mass % and the best Ni recovery rate of 93.8 mass % in pellets at the same reduction temperature, time and (C/O) molar ratio.

Photocatalytic degradation of swine wastewater on aqueous TiO2 suspensions: optimization and modeling via Box-Behnken design

Heterogeneous photocatalysis is a promising technology to treat many industrial wastewaters. To date, this potential has not been proven with wastewaters from agricultural origins, such as swine wastewater. In this work, the photocatalytic degradation of swine wastewater was studied by applying a response surface methodology based on the Box-Behnken design. The interactive effects of the variation of factors such as photocatalyst dosage (X1), wastewater concentration (X2), and irradiation time (X3) were analyzed to identify the optimal operating conditions for COD reduction. A second-order polynomial accurately represented organics degradation with a high adjusted R-squared (0.9666). The main effects of factor X2 and the quadratic effects of factors X2 and X3 were the most significant for COD reduction. The optimal conditions for COD degradation were 1.16 g L−1 for photocatalyst dosage, 1.68% for wastewater concentration, and irradiation time of 9.2 h. These results have been validated in a confirmation experiment and COD removal reached 91.7% (98.1 % predicted). Based on the Langmuir—Hinshelwood model, the reaction rate constant was 3.9×10−3 min−1. Besides, FTIR analysis indicated that Aeroxide® TiO2 reusability may be possible, especially for low wastewater concentrations. Heterogeneous photocatalysis can be applied as a technology for the integrated treatment of industrial wastewaters resulting from swine production.

Bio-fabrication of silver nanoparticles using naturally available wild herbaceous plant and its antibacterial activity

The irrational use of antibiotics has caused an increment in bacterial resistance to these compounds, leading humans to go in quest of alternative effective antimicrobial factors with less side effects as compared to antimicrobial compounds with less unwanted side effects. Silver Nanoparticles (AgNPs) could be considered as one of the most important antibacterial agents. In this study, the aqueous extract of Fumaria officinalis leaf was prepared and used in optimal conditions(pH=10, extract volume=8, metal salt concentration=10 mM, temperature 100 °C and time=120 min) for reduction of silver ions and synthesis of AgNPs. The resulted AgNPs were characterized by different techniques including UV-Vis, and XRD, FESEM, TEM, EDX and FTIR, respectively. Finally, the antibacterial activity of AgNPs on two pathogens (Escherichia coli (PTTC 1707), and Staphylococcus aureus (PTTC 1112)), was investigated using agar disk diffusion and minimum inhibitory concentration (MIC) test. The extract of Fumaria officinalis displayed high potential to synthesize of stable spherical AgNPs in shape with size below 25 nm. The nanoparticles showed considerable antibacterial effect on two tested bacteria. The minimum inhibitory concentration on Escherichia coli and Staphylococcus aureus for AgNPs was 12.5 and 6.25 μg / ml, respectively.

The Applications of Order Reduction Methods in Nonlinear Dynamic Systems

Two different order reduction methods of the deterministic and stochastic systems are discussed in this paper. First, the transient proper orthogonal decomposition (T-POD) method is introduced based on the high-dimensional nonlinear dynamic system. The optimal order reduction conditions of the T-POD method are provided by analyzing the rotor-bearing system with pedestal looseness fault at both ends. The efficiency of the T-POD method is verified via comparing with the results of the original system. Second, the polynomial dimensional decomposition (PDD) method is applied to the 2 DOFs spring system considering the uncertain stiffness to study the amplitude-frequency response. The numerical results obtained by the PDD method agree well with the Monte Carlo simulation (MCS) method. The results of the PDD method can approximate to MCS better with the increasing of the polynomial order. Meanwhile, the Uniform-Legendre polynomials can eliminate perturbation of the PDD method to a certain extent via comparing it with the Gaussian-Hermite polynomials.

Albumin-stabilized manganese-based nanocomposites with sensitive tumor microenvironment responsivity and their application for efficient SiRNA delivery in brain tumors.

Mn(iv)-Based nanoparticles (NPs) are effective in improving tumor oxygenation (hypoxia) and reducing endogenous hydrogen peroxide and acidity in the tumor region. However, the optimized reduction conditions of conventional Mn(iv)-based NPs are generally reported at pH ≤ 6.5, while the usual pH range of the tumor microenvironment (TME) is 6.5-7.0. The dissatisfactory imaging performance in the weakly acidic environment may limit their further application in tumor diagnosis. In this study, Mn(iii) was introduced in a nanoplatform, because it is reduced into Mn(ii) in weakly acidic environments. Arg-Gly-Asp (RGD) peptide-decorated bovine serum albumin (BSA) was employed as the stabilizer and scaffold to fabricate Mn(iii)- and Mn(iv)-integrated nanocomposites (RGD-BMnNPs) with suitable size, good stability, and excellent biocompatibility. The as-prepared NPs showed clear contrast enhancement at pH 6.5-6.9 in vitro as well as sensitive and rapid T1-weighted imaging performance within the tumor region in a glioblastoma (U87MG) orthotopic model, owing to the intrinsic disproportionation reaction of Mn(iii) in the weakly acidic environment. In addition, these NPs could be used for efficient siRNA delivery. They showed superior advantages in this process, including increased tumour uptake, improved tumor accumulation and enhanced therapeutic effects with the modulation of the TME. These novel albumin-stabilized manganese-based NPs combined with efficient drug delivery capacity hold great potential to serve as intelligent theranostic agents for further clinical translation.

Production of Ferronickel Concentrate from Low-Grade Nickel Laterite Ore by Non-Melting Reduction Magnetic Separation Process

The production of ferronickel concentrate from low-grade nickel laterite ore containing 1.31% nickel (Ni) was studied by the non-melting reduction magnetic separation process. The sodium chloride was used as additive and coal as a reductant. The effects of roasting temperature, roasting duration, reductant dosage, additive dosage, and grinding time on the grade and recovery were investigated. The optimal reduction conditions are a roasting temperature of 1250 °C, roasting duration of 80 min, reductant dosage of 10%, additive dosage of 5%, and a grinding time of 12 min. The grades of nickel and iron are improved from 2.13% and 51.12% to 8.15% and 64.28%, and the recovery of nickel is improved from 75.40% to 97.76%. The research results show that the additive in favor of the phase changes from lizardite phase to forsterite phase. The additive promotes agglomeration and separation of nickel and iron.

Sulfate Reduction and Heavy Metals Removal from Industrial Wastewater via Advanced Calcium-Aluminum Precipitation Method

The reduction of sulfate ions from the industrial wastewater using advanced calcium-aluminum precipitation method (ACAPM) has been evaluated. The ACAPM involved the precipitation of sulfate ions as minerals like gypsum and ettringite via calcium/ aluminum compounds. Factors affecting the reduction of sulfate ions such as: pH, Ca(OH)2 and NaAlO2 dosages have been investigated, while the optimal experimental conditions for sulfate ions reduction were determined. The precipitated solids have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS), respectively. Experimental results indicate that the ACAPM was effectively reduced sulfate with removal efficiency exceed 98%. It also effectively removed heavy metals including: Cr, Ni, Cd, Pb, Fe, Mn & Zn, with removal efficiencies up to 99%. Results showed that the ACAPM has remarkable sulfate ions removal efficiency with high concentrations.

Photoelectrochemical degradation of 2,4-dichlorophenoxyacetic acid using electrochemically self-doped Blue TiO2 nanotube arrays with formic acid as electrolyte

Blue TiO2 nanotube arrays (Blue-TNTs) were fabricated via an electrochemical reduction method with formic acid as the electrolyte. The optimum reduction conditions were obtained as bias potential of −1.3 V, reduction time of 5 min and formic acid of 3 M. Blue-TNTs were remarkably corroded compared with the intact TNTs. Similar crystal structures of the two catalysts were observed using X-ray diffraction, while red-shift was observed for Blue-TNTs using Raman spectra. X-ray photoelectron spectroscopy indicated of the presence of Ti3+ in Blue-TNTs that resulted from the reduction of Ti4+ and reduced the resistance of the catalyst. Blue-TNTs exhibited much stronger light-absorption than intact TNTs over the entire ultraviolet-visible region, especially in the visible region. The catalyst was used toward the photoelectrochemical oxidation of 2,4-dichlorophenoxyacetic acid (2,4-D) for the first time where the influencing factors were studied. Photoelectrocatalysis with Blue-TNTs presented a 2,4-D degradation rate constant (0.0295 min−1) more than twice the sum of that of electrocatalysis (0.0055 min−1) and photocatalysis (0.0089 min−1). Blue-TNTs fabricated in formic acid showed a better photoelectrocatalytic performance for 2,4-D removal compared with that prepared in ethylene glycol, Na2SO4 and NaNO3 solution. Blue-TNTs is considered to be a promising photoelectric anode for contaminant degradation.

Extraction of nickel and cobalt from a laterite ore using the carbothermic reduction roasting-ammoniacal leaching process

The carbothermic reduction roasting followed by ammoniacal leaching of a Ni-laterite ore from Bajaur (Pakistan) has been studied first time for its potential exploitation via the Caron process. The use of fuel oil as reductant can be costly in Pakistan, therefore, plenty available coal was employed in this study. The roasting parameters like coal mixing proportion (5–15 wt%), temperature (600–900 °C), additive dosage (3–12 wt%), and time (15–180 min) were varied to optimize the selective reduction of Ni and Co. The extent of goethite phase transformation of roasted products characterized through the X-ray diffraction (XRD) analysis could depict sharp peaks for the formation of Ni-Fe alloy phase in the presence of an additive, Na2SO4. The optimal reduction condition was observed to be laterite ore mix with 10 wt% coal and 9 wt% Na2SO4, and roasted at 800 °C for 120 min. Leaching of the roast-reduced product performed in NH4OH–(NH4)2CO3 solutions (150 g/L total NH3) was influenced by carbonate ion concentration and yielded >90% Ni and 67% Co. The apparent activation energy of Ni, 21.2 kJ/mole and Co, 7.6 kJ/mole indicated to follow intermediate-controlled and diffusion-controlled mechanism, respectively. Furthermore, the leach liquor was pre-oxidized and contacted to 10 vol% of LIX 84-I; yielding a selective extraction of >97% Ni over Co at the organic-to-aqueous ratio of 1. Results presented in this paper suggest that the extraction of Ni and Co from Bajaur lateritic ore is technically feasible through the Caron process, and can be useful to others as well.

An evaluation of effects of fuel parameters and flue gas recirculation on NOx emissions through detailed chemical kinetics simulations

In this work the effects of fuel parameters and under grate flue gas recirculation (FGR) are investigated when applying staged air combustion of solid fuel for the purpose of NOx reduction. In addition to temperatures, residence times and primary and overall excess air ratio, the fuel-N content and speciation, the relative fuel-C, fuel-H and fuel-O contents, the fuel moisture content, the fuel gas composition from the dry fuel and the use of FGR (in the primary and/or secondary combustion zone) influence the NOx reduction potential to a larger or smaller extent. To assess the influence of different parameters, a simulation matrix using one ideal plug flow reactor representing only the primary zone and a recent detailed chemical kinetics mechanism was carried out. The results show a large influence of the fuel-N content and speciation on the NOx reduction potential in the primary zone, and a significant influence of the fuel moisture content due to its fuel gas dilution effect. At the close to optimum NOx reduction conditions studied in this work (973 K, primary excess air ratio of 0.9), the influence of the fuel gas composition from the dry fuel on the achievable total fixed nitrogen reduction in the primary zone is relatively small, as well as its influence on the radical pool available for the fuel-N chemistry. The influence of the relative content of C, H and O in the fuel at a constant primary excess air ratio is also relatively small. From a kinetics point of view, there is a positive effect of applying under grate flue gas recirculation if the residence time is sufficiently long, however, the effect is relatively low compared to the other main influencing parameters. At higher temperatures the importance of the radical pool availability as well as its speciation increases, and a more significant part of the NH3 and especially HCN reduction in the primary zone results in increasing NO formation with increasing temperature.

Biological drying of municipal solid waste from landfill

The aim of this work was to investigate the process of biodrying of municipal solid waste from the old landfill to preparing it for pyrolysis or gasification. New aspect of this research is biodrying of waste from old landfill. Biodrying of wastes was carried out at different aeration rates (7, 35, and 175 dm3/kg dry matter/d) at two temperatures (23 and 50 °C). The research was carried out in the laboratory bioreactors of special design (lysimeters), which simulated the conditions prevailing in the landfill. The optimal conditions for reduction of moisture in waste (63.2%) has been attained for the highest aeration rate (175 dm3/kg dry matter/d) and temperature equal to 50 °C. The final moisture content of the obtained biodried product was 23% w/w. In the bioreactor, in which the greatest reduction of moisture was obtained, the total amount of produced CO2 was 44.9 gC/kg dry matter, and the biodrying efficiency was equal to 0.89. During biodrying of wastes in optimal conditions, higher heating value of waste increased from 4.3 to 11.0 MJ/kg. As a result of the performed pyrolysis of biodried waste at 900 °C, char, oil, and gas were obtained the respective yields of 47, 32, and 21% w/w. The gas emerging in the gasification process was characterized by higher heating value equal to 11.3 MJ/m3.

Improvement of the photoelectrochemical performance of vertically aligned WO3 nanosheet array film with a disordered surface layer by electroreduction

The search for efficient and powerful photoanode materials remains one of the toughest challenges in photoelectrochemical (PEC) water splitting because the oxygen evolution reaction on the photoanode is a rate-limiting process. On the other hand, the semiconductor/liquid interface is a key factor governing the water splitting efficiency due to its influence on charge separation and collection. Herein, we synthesized vertically aligned WO3 nanosheet array (NS) films on fluorine-doped tin oxide (FTO), and followed by electroreduction for tuning the surface structure of WO3 NSs. A disordered layer is formed on the surface of WO3 NSs by controlling the external bias voltage and reduction time of electroreduction, and its thickness of the disordered layer varies with reduction time. The optimal WO3 NSs with a 1.2 nm disorder layer thickness exhibit a remarkable photocurrent density of 1.07 mA cm−2 at 1.23 V vs reversible hydrogen electrode (RHE) under AM 1.5G illumination, which is 1.43 times of pristine WO3 NSs. The results indicate that the electroreduction voltage and reduction time exert great influence on the formation of the surface disordered layer, and the optimized reduction conditions can enhance charge transfer and charge separation efficiency, substantially improving the PEC performance of WO3 photoanode.

A clean process of lead recovery from spent lead paste based on hydrothermal reduction

Abstract An innovative process was proposed for recovering lead from spent lead paste, and it produced less pollution and used less energy than the traditional process. First, lead dioxide in lead paste was reduced by glucose under hydrothermal conditions. The effects of the reaction time, glucose excess coefficient, temperature and pH on the hydrothermal reduction were systematically investigated. Under the optimized reduction conditions (i.e., temperature of 175 °C, time of 120 min, glucose excess coefficient of 3.0 and pH of 5.5), 99.9% reduction ratio of lead dioxide is achieved, and only the PbO·PbSO4 and PbSO4 phases are observed in the reducing residue. Subsequently, the reducing residue is desulfurized in a NaOH solution, and approximately 99.40% of the sulfur is removed. The main lead phase in the desulfurization residue is 3PbO·H2O.

High expectancy and early response produce optimal effects in sertraline treatment for post-traumatic stress disorder.

Better indicators of prognosis are needed to personalise post-traumatic stress disorder (PTSD) treatments.AimsWe aimed to evaluate early symptom reduction as a predictor of better outcome and examine predictors of early response. Patients with PTSD (N = 134) received sertraline or prolonged exposure in a randomised trial. Early response was defined as 20% PTSD symptom reduction by session two and good end-state functioning defined as non-clinical levels of PTSD, depression and anxiety. Early response rates were similar in prolonged exposure and sertraline (40 and 42%), but in sertraline only, early responders were four times more likely to achieve good end-state functioning at post-treatment (Number Needed to Treat = 1.8, 95% CI 1.28-3.00) and final follow-up (Number Needed to Treat = 3.1, 95% CI 1.68-16.71). Better outcome expectations of sertraline also predicted higher likelihood of early response. Higher expectancy of sertraline coupled with early response may produce a cascade-like effect for optimal conditions for long-term symptom reduction. Therefore, assessing expectations and providing clear treatment rationales may optimise sertraline effects. None.

Issues Relevant to Recycling of Stainless-Steel Pickling Sludge

Stainless-steel pickling sludge is a hazardous solid waste. Harmless treatment and recycling of this sludge are major research topics. Based on the sludge formation process, two typical types of stainless-steel pickling sludge were chosen and their physiochemical properties determined by chemical analysis, differential thermal analysis/thermogravimetry, and x-ray diffraction analysis. Possible approaches to recycle the sludge were suggested, and relevant problems are discussed. Based on its high water and sulfur contents, as well as the valuable metals that could be recovered from sludge, drying, roasting, and reduction tests were carried out. It was found that Fe and Cr were mainly present in oxides, Ca in Ca(OH)2 and CaF2, and sulfur in CaSO4. Natural drying was a very slow process, but forced drying at temperatures above 423 K was effective. Sulfur could be partly removed from sludge through roasting and reduction at high temperatures, with most of the sulfur being transferred to gas and slag in the reduction process; however, this treatment did not allow sludge with high sulfur content to be used as a suitable raw material in terms of sulfur level requirements. It is suggested that prepickling and pickling waste liquors should be treated to reduce output of high-sulfur sludge to promote sludge recycling. Optimized reduction conditions were identified in terms of additional carbon content (1.3 times as suggested by theoretical data) and temperature (above 1673 K) for high metal recovery.

Optimization fluidization characteristics conditions of nickel oxide for hydrogen reduction by fluidized bed reactor

We evaluated the optimal conditions for fluidization of nickel oxide (NiO) and its reduction into high-purity Ni during hydrogen reduction in a laboratory-scale fluidized bed reactor. A comparative study was performed through structural shape analysis using scanning electron microscopy (SEM); variance in pressure drop, minimum fluidization velocity, terminal velocity, reduction rate, and mass loss were assessed at temperatures ranging from 400 to 600 °C and at 20, 40, and 60 min in reaction time. We estimated the sample weight with most active fluidization to be 200 g based on the bed diameter of the fluidized bed reactor and height of the stocked material. The optimal conditions for NiO hydrogen reduction were found to be height of sample H to the internal fluidized bed reactor diameter D was H/D=1, reaction temperature of 550 °C, reaction time of 60 min, superficial gas velocity of 0.011 m/s, and pressure drop of 77 Pa during fluidization. We determined the best operating conditions for the NiO hydrogen reduction process based on these findings.

Comparative study on cadmium column reduction and UV-induced reduction for online determination of nitrate in seawater

An online detection system for nitrate in seawater was designed and set up based on flow injection analysis and spectrophotometry. We used this system to compare and study the two reduction methods for nitrate in seawater: cadmium column reduction method and UV light-induced reduction method. The cadmium column could reach the optimal reduction condition in 300 s while the UV light could reach the optimal reduction condition in 480 s. The two methods both had good linear relationship in the range of 5-500 μg/L. The reduction efficiency for Cd-column and UV light were 95% and 80% respectively under the same conditions. The detection limit was 2.5 μg/L for Cd-column reduction method and was 3.4 μg/L for UV-induced reduction method. The relative standard deviation (RSD) for the two methods were both less than 3%. The recovery rate for Cd-column reduction method and UV-induced reduction method were 98.22% and 100.83% respectively.

Textile Wastewater Treatment Using Photonanocatalytic Process (UV/CuO Nanoparticles): Optimization of Experiments by Response Surface Methodology

: This study examines the efficiency of photodegradation process (color and COD removal) in textile wastewater treatment, using copper oxide nanoparticles (CuO-NPs) as photocatalyst to propose a suitable alternative for the available approaches. The experiments were developed, using a central composite design and response surface methodology (RSM). RSM was applied to evaluate the effects of different variables, including pH, CuO- NPs concentration, reaction time, and UV light intensity, as well as their interactions for achieving optimal conditions. The second-order model consisted of linear and quadratic terms, which seemed appropriate for color and COD removal. All the variables showed significant effects on color and COD degradation. The optimal conditions for maximum color degradation (83%) included pH of 6.9, contact time of 60 min, CuO- NPs concentration of 0.05 g/L, and UV light intensity of 30 W. In addition, the optimal conditions for maximum COD reduction (99%) were pH of 6.8, contact time of 60 min, CuO-NPs concentration of 0.02 g/L, and UV light intensity of 30 W. Based on the results of this study, CuO-NPs can be used for effective treatment of textile wastewater by high COD and color removal.

Synthesis of S-Licarbazepine by Asymmetric Reduction of Oxcarbazepine in Organic Solvent/Phosphate Buffer Biphasic System

S-licarbazepine was synthesized by asymmetric reduction of oxcarbazepine in organic solvent/phosphate buffer biphasic system with Bacillus anthracis CGMCC No.12337 as catalyst. Effects of many factors on reduction were studied. Dibutyl phthalate/phosphate buffer was selected as the optimal biphasic system for reduction. The optimum reduction conditions are as follows: volume ratio of dibutyl phthalate and phosphate buffer 1:1, 30 g/L iospropanol as co-substrate, phosphate buffer pH 5, substrate concentration 7.92 mmol/L, cell concentration 30 g/L, 32°C，180 rpm. The conversion and enantiometric excess of S-licarbazepine reached 97.32% and 99.80%. An efficient method for synthesis of S-licarbazepine was provided.