scholarly journals Fractal kinetic characteristics of hard-rock uranium leaching with sulfuric acid

2018 ◽  
Vol 5 (9) ◽  
pp. 180403 ◽  
Author(s):  
Sheng Zeng ◽  
Jinzhu Li ◽  
Kaixuan Tan ◽  
Shuwen Zhang
Keyword(s):  
Particle Size ◽  
Fractal Dimension ◽  
Flow Rate ◽  
Sampling Rate ◽  
Acid Leaching ◽  
Diffusion Reaction ◽  
Uranium Mine ◽  
Uranium Leaching ◽  
Leaching Experiment ◽  
Leaching Solution

In order to study the fractal dynamic properties of uranium leach mining and discuss the influence of ore crushing on the dynamics of leach mining, uranium mine ore rocks in southern China were selected as the research object and an acid leaching experiment was performed on the ore samples with different fractal dimensions of 1.1, 1.4, 1.7, 2.0, 2.3 and 2.6. In the column leaching experiment, a PVC pipe with an inner diameter of 112 mm and a height of 1500 mm was used. The uranium content was determined by using titanium trioxide that was placed into a 0.1 mg ml −1 standard uranium solution, and a sampling rate of once daily with a 5 ml volume of leaching solution was adopted after 8 h drenching time. The results show that the flow rate of the leaching solution depends on the distribution of the ore's particle size, that is, a larger fractal dimension results in a smaller flow rate. The concentration of the uranium leaching solution reaches a maximum value which subsequently decreases with time on the third day of the experiment, and it seems that the changes in the uranium concentration tend to be stable at around 15 days. Moreover, the concentration seems to increase with the increasing fractal dimension, and the fractal dimension of the ore particle size has a significant impact on the leaching kinetics. When the fractal dimension is between 1.1 and 2.6, the uranium dissolution rate, K , increases with the increasing fractal dimension. The kinetic reaction of the uranium leaching is a liquid–solid one, which is controlled by chemical reactions in the earlier phase. While the middle reaction phase is mainly chemical-diffusion reaction coupling, and the latter part of the reaction is controlled by diffusion. As the fractal dimension increases, the liquid–solid reaction controlled by diffusion appears at earlier phases. When the fractal dimension is greater than 2.0, the time of entering the diffusion control phase only changed little with the increasing of the fractal dimension. At last, a fractal dimension of 2.0 is suggested for the acid leaching of uranium ore crushing.

Pyrolysis of brown algae (Bifurcaria Bifurcata) in a stainless steel tubular reactor: From a review to a case study

2018 ◽  
Vol 14 (1) ◽  
pp. 31-60 ◽  
Author(s):  
M. Y. Guida ◽  
F. E. Laghchioua ◽  
A. Hannioui
Keyword(s):  
Particle Size ◽  
Stainless Steel ◽  
Flow Rate ◽  
Brown Algae ◽  
Tubular Reactor ◽  
Nitrogen Flow ◽  
Nitrogen Flow Rate ◽  
Bifurcaria Bifurcata ◽  
Bio Oil

This article deals with fast pyrolysis of brown algae, such as Bifurcaria Bifurcata at the range of temperature 300–800 °C in a stainless steel tubular reactor. After a literature review on algae and its importance in renewable sector, a case study was done on pyrolysis of brown algae especially, Bifurcaria Bifurcata. The aim was to experimentally investigate how the temperature, the particle size, the nitrogen flow rate (N2) and the heating rate affect bio-oil, bio-char and gaseous products. These parameters were varied in the ranges of 5–50 °C/min, below 0.2–1 mm and 20–200 mL. min–1, respectively. The maximum bio-oil yield of 41.3wt% was obtained at a pyrolysis temperature of 600 °C, particle size between 0.2–0.5 mm, nitrogen flow rate (N2) of 100 mL. min–1 and heating rate of 5 °C/min. Liquid product obtained under the most suitable and optimal condition was characterized by elemental analysis, 1H-NMR, FT-IR and GC-MS. The analysis of bio-oil showed that bio-oil from Bifurcaria Bifurcata could be a potential source of renewable fuel production and value added chemicals.

Utilization of Waste of Enzymes Biomass as Biosorbent for the Removal of Dyes from Aqueous Solution in Batch and Fluidized Bed Column

2020 ◽  
Vol 71 (1) ◽  
pp. 1-12
Author(s):  
Salman H. Abbas ◽  
Younis M. Younis ◽  
Mohammed K. Hussain ◽  
Firas Hashim Kamar ◽  
Gheorghe Nechifor ◽  
...  
Keyword(s):  
Experimental Data ◽  
Aqueous Solution ◽  
Particle Size ◽  
Adsorption Capacity ◽  
Fluidized Bed ◽  
Flow Rate ◽  
Fungal Biomass ◽  
Solution Flow Rate ◽  
Maximum Adsorption Capacity ◽  
Solution Flow

The biosorption performance of both batch and liquid-solid fluidized bed operations of dead fungal biomass type (Agaricusbisporus ) for removal of methylene blue from aqueous solution was investigated. In batch system, the adsorption capacity and removal efficiency of dead fungal biomass were evaluated. In fluidized bed system, the experiments were conducted to study the effects of important parameters such as particle size (701-1400�m), initial dye concentration(10-100 mg/L), bed depth (5-15 cm) and solution flow rate (5-20 ml/min) on breakthrough curves. In batch method, the experimental data was modeled using several models (Langmuir,Freundlich, Temkin and Dubinin-Radushkviechmodels) to study equilibrium isotherms, the experimental data followed Langmuir model and the results showed that the maximum adsorption capacity obtained was (28.90, 24.15, 21.23 mg/g) at mean particle size (0.786, 0.935, 1.280 mm) respectively. In Fluidized-bed method, the results show that the total ion uptake and the overall capacity will be decreased with increasing flow rate and increased with increasing initial concentrations, bed depth and decreasing particle size.

Study on leaching kinetics of hexavalent chromium from aged calcium-free chromium slag

2021 ◽  
pp. 1-13
Author(s):  
Quan Qi ◽  
Liang Li ◽  
Liangyu Wei ◽  
Baoming Hu ◽  
Zheng Liu ◽  
...  
Keyword(s):  
Hexavalent Chromium ◽  
Resource Utilization ◽  
Scientific Basis ◽  
Diffusion Reaction ◽  
Leaching Kinetics ◽  
Leaching Rate ◽  
Chromium Slag ◽  
Leaching Solution ◽  
Main Components ◽  
Kinetics Of

To provide a scientific basis for the resource utilization of chromium slag, this article studies the release law of hexavalent chromium in the aged calcium-free chromium slag. XRD (X-ray diffractometer) and MLA (Mineral Liberation Analyzer) were used to analyze the composition of the chromium slag; using sulfuric acid-nitric acid as the leaching solution, the release law of hexavalent chromium in chromium slag and the leaching kinetics were studied. The results show that main components of the chromium slag are magnesioferrite, chromite, hematite, hydrargillite, and spinel; chromium is mainly present in chromite and magnesioferrite; the leaching rate of hexavalent chromium increases with the increase of temperature or the decrease of pH. The analysis of leaching kinetics shows the leaching rate is controlled by the internal diffusion reaction, and the apparent activation energy is 11.93 kJ·mol–1. The chromium slag is aged in high temperature seasons, which is conducive to the precipitation of hexavalent chromium in the chromium slag, can increase the yield of chromate in the roasting kiln, and is conducive to resource utilization; chromium slag should be stored in order to prevent acid rain erosion which leads to environmental pollution risk (e.g. drinking water).

scholarly journals Effect of flow rate, particle size and modifier ratio on the supercritical fluid extraction of anthocyanins from Hibiscus sabdariffa (L).

2020 ◽  
Vol 932 ◽  
pp. 012031
Author(s):  
Zuhaili Idham ◽  
Ahmad Syahmi Zaini ◽  
Nicky Rahmana Putra ◽  
Nurfarhain Mohamed Rusli ◽  
Noor Sabariah Mahat ◽  
...  
Keyword(s):  
Particle Size ◽  
Supercritical Fluid Extraction ◽  
Supercritical Fluid ◽  
Flow Rate ◽  
Hibiscus Sabdariffa ◽  
Fluid Extraction

Empirical Model to Estimate Mn2+ Precipitation Rate from a Leaching Solution Using SO2/O2 as Oxidizing Agent

2012 ◽  
Vol 1380 ◽  
Author(s):  
S. Bello-Teodoro ◽  
R. Pérez-Garibay
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Reaction Rates ◽  
Precipitation Process ◽  
Low Grade ◽  
Gas Flow Rate ◽  
Oxidative Precipitation ◽  
Leaching Solution ◽  
Good Concordance ◽  
Main Influence

ABSTRACTA method, based in leaching with SO2, to process low grade pyrolusite minerals has shown good results at laboratory scale. After the separation of the solid impurities, the dissolved manganese is subsequently precipitated using the SO2/O2 gas mixture as oxidising agent. In this research it was obtained a mathematical model to estimate the oxidative precipitation process, as a function of temperature, pH and SO2 gas flow rate. It was found that pH and temperature have the main influence in the reaction rate. An optimal SO2 concentration in the mixture must be used to avoid generation of reductive conditions. It was observed a most efficient reaction with a low gas flow rate injection. The predicted reaction rates presents a good concordance with the experimental results (R2=0.97), showing a worthy potential for practical uses.

Effect of Surface State of Die on Flow Rate of Steamed Bamboo Powder in Thermal Flow Test Using Capillary Rheometer

2015 ◽  
Vol 651-653 ◽  
pp. 830-835
Author(s):  
Shohei Kajikawa ◽  
Riku Sakagami ◽  
Takashi Iizuka
Keyword(s):  
Particle Size ◽  
Flow Rate ◽  
Surface State ◽  
Flow Behavior ◽  
Thermal Flow ◽  
Average Roughness ◽  
Arithmetic Average ◽  
Flow Test ◽  
Die Surface ◽  
Bamboo Powder

Thermal flow tests were performed on steamed bamboo powder using capillaries that were processed under different conditions in order to investigate the effect of the die surface state on the fluidity of the woody powder. The capillaries were processed by wire-cut electric discharge machining, reaming or drilling, and the arithmetic average roughness (Ra) varied from 0.5 to 2.5 μm. The bamboo powder was first steamed at 200 °C for 20 min, and its particle size was then controlled using different mesh screens. The thermal flow temperature was set at 200 °C. The results indicated that the flow behavior improved with increasing particle size. For the capillaries processed by WEDM, the flow rate for samples with particle sizes of 75~150 and 150~300 μm decreased with increasing Ra. On the other hand, when reaming or drilling was used to process the capillaries, the flow rate was almost independent of Ra, regardless of the particle size.

STRUCTURAL PARAMETERS OF AQUEOUS COLLOIDAL DISPERSIONS OF FULLERENE C60

2019 ◽  
pp. 31-37
Author(s):  
V.Yu. Fokina ◽  
E.А. Kizima ◽  
I.V. Miheev ◽  
A.I. Ivankov ◽  
V.M. Garamus
Keyword(s):  
Particle Size ◽  
Fractal Dimension ◽  
Particle Size Distribution ◽  
Structural Parameters ◽  
Colloidal Dispersions ◽  
Fullerene C60 ◽  
Solvent Exchange ◽  
X Ray ◽  
Dense Nucleus ◽  
Exchange Technique

Two types of fullerene C60 water dispersions were investigated by a small-angle X-ray and neutron scattering. As a result, structural parameters of fullerene aggregates were obtained. The water dispersions were obtained by the solvent-exchange technique and by huge dilution of initial C60/Nmethylpyrrolidone solution. The structure organization of water dispersions is considered in respect to their technique preparation. It was shown that fullerene aggregates were characterized by highly polydispersity in size for all dispersions. In the case of son/nC60 dispersion it was found that fullerenes formed aggregates with a dense nucleus (namely a surface fractal) with a radius of 58 ± 1 nm and a fractal dimension of 2.3. In turn, the nmp/nC60 system was characterized by the branched aggregates with fractal dimension 1.5 and bimodal particle size distribution.

Removal of Fe(III) from sulfuric acid leaching solution of phosphate ores with bisphosphonic acids

2021 ◽  
pp. 105799
Author(s):  
Chengjin Xu ◽  
Ling Li ◽  
Miaomiao Zhang ◽  
Xiao Meng ◽  
Xiujing Peng ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Acid Leaching ◽  
Sulfuric Acid Leaching ◽  
Leaching Solution ◽  
Bisphosphonic Acids ◽  
Phosphate Ores

scholarly journals Green Preparation, Spheroidal, and Superior Property of Nano-1,3,5,7-Tetranittro-1,3,5,7-Tetrazocane

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Xinlei Jia ◽  
Jingyu Wang ◽  
Conghua Hou ◽  
Yingxin Tan
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Fractal Dimension ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Fractal Theory ◽  
Crystal Form ◽  
Decomposition Temperature ◽  
Scanning Calorimetry ◽  
The Impact

Herein, a green process for preparing nano-HMX, mechanical demulsification shearing (MDS) technology, was developed. Nano-HMX was successfully fabricated via MDS technology without using any chemical reagents, and the fabrication mechanism was proposed. Based on the “fractal theory,” the optimal shearing time for mechanical emulsification was deduced by calculating the fractal dimension of the particle size distribution. The as-prepared nano-HMX was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). And the impact sensitivities of HMX particles were contrastively investigated. The raw HMX had a lower fractal dimension of 1.9273. The ideal shearing time was 7 h. The resultant nano-HMX possessed a particle size distribution ranging from 203.3 nm to 509.1 nm as compared to raw HMX. Nano-HMX particles were dense spherical, maintaining β-HMX crystal form. In addition, they had much lower impact sensitivity. However, the apparent activation energy as well as thermal decomposition temperature of nano-HMX particles was decreased, attributing to the reduced probability for hotspot generation. Especially when the shearing time was 7 h, the activation energy was markedly decreased.

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