scholarly journals Mechanism and Kinetics of Malachite Dissolution in an NH4OH System

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 833
Author(s):  
Alvaro Aracena ◽  
Javiera Pino ◽  
Oscar Jerez
Keyword(s):  
Ammonium Hydroxide ◽  
Copper Recovery ◽  
X Ray Diffraction ◽  
Solution Ph ◽  
Acid Dissolution ◽  
Acid Consumption ◽  
Mechanism And Kinetics ◽  
Solid Liquid ◽  
Kinetics Of ◽  
Highly Porous

Copper oxide minerals composed of carbonates consume high quantities of leaching reagent. The present research proposes an alternative procedure for malachite leaching (Cu2CO3(OH)2) through the use of only compound, ammonium hydroxide (NH4OH). Preliminary studies were also carried out for the dissolution of malachite in an acid system. The variables evaluated were solution pH, stirring rate, temperature, NH4OH concentration, particle size, solid/liquid ratio and different ammonium reagents. The experiments were carried out in a stirred batch system with controlled temperatures and stirring rates. For the acid dissolution system, sulfuric acid consumption reached excessive values (986 kg H2SO4/ton of malachite), invalidating the dissolution in these common systems. On the other hand, for the ammoniacal system, there was no acid consumption and the results show that copper recovery was very high, reaching values of 84.1% for a concentration of 0.2 mol/dm3 of NH4OH and an experiment time of 7200 s. The theoretical/thermodynamic calculations indicate that the solution pH was a significant factor in maintaining the copper soluble as Cu(NH3)42+. This was validated by the experimental results and solid analysis by X-ray diffraction (XRD), from which the reaction mechanisms were obtained. A heterogeneous kinetic model was obtained from the diffusion model in a porous layer for particles that begin the reaction as nonporous but which become porous during the reaction as the original solid splits and cracks to form a highly porous structure. The reaction order for the NH4OH concentration was 3.2 and was inversely proportional to the square of the initial radius of the particle. The activation energy was calculated at 36.1 kJ/mol in the temperature range of 278 to 313 K.

Applications of Rietveld-based QXRD analysis in mineral processing

2014 ◽  
Vol 29 (S1) ◽  
pp. S89-S95 ◽  
Author(s):  
Jian Li ◽  
Robbie G. McDonald ◽  
Anna H. Kaksonen ◽  
Christina Morris ◽  
Suzy Rea ◽  
...  
Keyword(s):  
Ferrous Iron ◽  
Rheological Behaviour ◽  
Lower Grade ◽  
X Ray Diffraction ◽  
Mineralogical Characterization ◽  
Pressure Oxidation ◽  
Oxidation Rates ◽  
Acid Consumption ◽  
Micro Organisms ◽  
Kinetics Of

Rietveld-based quantitative X-ray diffraction (QXRD) has been extensively used for mineralogical characterization in order to understand the reaction chemistry, and kinetics of minerals leaching and formation. This work presents examples where QXRD has been applied to understanding fundamental aspects of these two processes. Firstly, the co-processing of nickel laterites and sulphidic materials has the potential to offer several advantages that include the use of lower grade (including non-smeltable) concentrates, improvement in the rheological behaviour of the blends, and reduction in the use of sulphuric acid. The leaching kinetics and chemistry of mixed nickel laterite ore and sulphide concentrate were explored by the QXRD analysis of feed materials and, intermediates and final leach residues produced using controlled oxidation rates. Under high temperature (250 °C) and pressure oxidation (~40 to 45 atm.) conditions, sulphide minerals in the nickel concentrate underwent several oxidative hydrothermal transformations, and ferrous iron was oxidized and precipitated primarily as hematite. High recovery of nickel can be achieved with low acid consumption under these conditions. Secondly, iron precipitation/removal is an important down-stream process in hydrometallurgy. Moderate concentrations of ferrous iron can be oxidized using micro-organisms with oxidation rates several orders of magnitude faster compared with abiotic oxidation at ambient temperature and pressure. QXRD and chemical analysis have indicated that after oxidation, iron at pH ~2 mostly precipitates as jarosite with various amounts of K+, Na+, NH4+, and H3O+ incorporated into the structure. Bio-catalysed iron removal can be achieved with minimum copper and nickel losses at relatively low pH conditions.

Diffusion Mechanism and Kinetics of Diffusion Bonded Mg/Ni/Al Joint

2014 ◽  
Vol 616 ◽  
pp. 286-290
Author(s):  
Jian Zhang ◽  
Qiang Guo Luo ◽  
Qiang Shen ◽  
Lian Meng Zhang
Keyword(s):  
Heating Temperature ◽  
Diffusion Mechanism ◽  
Diffusion Activation Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atom Diffusion ◽  
Mechanism And Kinetics ◽  
Ni Interlayer ◽  
Kinetics Of ◽  
Diffusion Activation

Mg and Al were bonded successfully by means of diffusion bonding using Ni interlayer. The microstructure, diffusion mechanism and regulation of atom diffusion were investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron probe microanalysis analysis (EPMA). The results showed that the joints consisted of Mg-Ni interface and Al-Ni interface, and there were Mg2Ni formed in the Mg-Ni interface and Al3Ni formed in the Al-Ni interface, respectively. Diffusion activation energy of Mg and Al were lower than that of Ni in the Mg-Ni and Al-Ni interface. The thickness (x) of Mg2Ni and Al3Ni can be expressed as x2=3.97×10-4 exp (-139600/RT) (t-t0) and x2=8.62×10-3 exp (-174200/RT) (t-t0) with heating temperature (T) and holding time (t).

Preparation of modified sorbents from rehydrated clay materials

Clay Minerals ◽  
2012 ◽  
Vol 47 (2) ◽  
pp. 251-258
Author(s):  
M. Lhotka ◽  
V. Machovič ◽  
B. Doušová
Keyword(s):  
Chemical Properties ◽  
Solution Ph ◽  
Adsorption Capacities ◽  
Modification Method ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Modified Sorbents ◽  
Highly Porous ◽  
Clay Materials

AbstractThe use of clay materials as selective sorbents for different contaminants requires very efficient methods. A natural kaolinite was calcined to metakaolinite and than rehydrated at different temperatures to produce a highly porous sorbent. The kinetics of this process were measured, with subsequent IR characterization of the phases formed. The surface and pore distribution of new phases were also assigned. In addition, the kaolinite obtained was pre-treated with Fe3+ ions to improve its sorption affinity for anionic particles. The rehydrated kaolinite and its Fe-modification were used for the adsorption of toxic cations (Zn, Cd, Pb) and anions (As, Se). Adsorption capacities depending on the physical chemical properties of the initial solution (pH, concentration of toxic ions) and the surface properties of the sorbent (specific surface area, modification method) were investigated. The adsorption properties of the sorbents were defined by the Langmuir model.

scholarly journals Evaluation of Kinetic and Equilibrium Parameters of NiFe2O4 Nanoparticles on Adsorption of Reactive Orange Dye from Water

2016 ◽  
Vol 10 (2) ◽  
pp. 51-58
Author(s):  
Raziyeh Zandi Pak ◽  
◽  
Soheil Sobhan Ardakani2 ◽  
Keyword(s):  
Contact Time ◽  
Magnetic Nanomaterials ◽  
X Ray Diffraction ◽  
Anionic Dyes ◽  
Solution Ph ◽  
Removal Capacity ◽  
Pseudo Second Order ◽  
Nife2o4 Nanoparticles ◽  
Reactive Orange ◽  
Kinetics Of

Background: Among different pollutants released into the environment, dyes are considered as one of the most dangerous contaminants. In recent years, magnetic nanomaterials have attracted much attention for their dye removal capacity. The aim of this study was to explore the adsorption kinetics of an anionic dye (Reactive Orange 13 (RO)) by NiFe2O4 nanoparticles (NiFe2O4 NPs) under various conditions. Methods: NiFe2O4 nanoparticles (NiFe2O4 NPs) were prepared and characterized by X-ray diffraction (XRD), transmission electronic microscopy (TEM), pHpzc and BET methods. The adsorption characteristics of the NiFe2O4 NPs adsorbent were examined using Reactive Orange 13 as an adsorbate. The influences of parameters including pH, dose of adsorbent and contact time were investigated to find the optimum adsorption conditions. Results: Decreasing solution pH and increasing contact time were favorable for improving adsorption efficiency. The kinetic and isotherm data of RO adsorption on NiFe2O4 NPs were well fitted by pseudo-second-order and Langmuir models, respectively. Conclusion: The maximal adsorption capacity of RO was 243.9 mg g-1 at 25◦C and pH 3.0 and the adsorption of RO on the NiFe2O4 NPs follows a monolayer coverage model. NiFe2O4 NPs might be an effective and potential adsorbent for removing anionic dyes from aqueous solutions.

scholarly journals Mass Transfer in the Solid-Liquid System: Mechanism and Kinetics of the Extraction Process

2020 ◽  
Vol 14 (1) ◽  
pp. 121-128
Author(s):  
Yevgen Semenyshyn ◽  
◽  
Volodymyr Atamanyuk ◽  
Tetiana Rymar ◽  
Oleksandr Ivashchuk ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Extraction Process ◽  
Liquid System ◽  
Mechanism And Kinetics ◽  
Solid Liquid ◽  
Kinetics Of ◽  
System Mechanism

HYDROTHERMAL SYNTHESIS AND ENHANCED VISIBLE-LIGHT PHOTOCATALYTIC ACTIVITY OF CdS QUANTUM DOTS SENSITIZED CARBON NANOTUBES (CNTs) NANOCOMPOSITE

NANO ◽  
2014 ◽  
Vol 09 (02) ◽  
pp. 1450017 ◽  
Author(s):  
XINLIN LIU ◽  
YANFENG TANG ◽  
CHANGCHANG MA ◽  
YAN YAN ◽  
PENG LV ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Photocatalytic Activity ◽  
Visible Light ◽  
X Ray Diffraction ◽  
Composite Photocatalyst ◽  
Transmission Electron ◽  
Excellent Photocatalytic Activity ◽  
New Type ◽  
Mechanism And Kinetics ◽  
Kinetics Of

A new-type photocatalyst of cadmium sulfide carbon nanotubes ( CdS /CNTs) was prepared by the hydrothermal method. This as-prepared CdS /CNTs composite photocatalyst was proved to exhibit an excellent photocatalytic activity for degradation of tetracycline (TC). Specially, the 95%- CdS –5%-CNTs composite photocatalyst played the best degradation rate (81.2%) in 60 min under the visible light irradiation. Moreover, this 95%- CdS –5%-CNTs composite photocatalyst possessed great stability and could be used at least four cycles with almost no loss of photocatalytic efficiency. Furthermore, the as-synthesized CdS /CNTs composite photocatalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis diffused reflectance spectra (UV-Vis), Raman and thermal gravimetry (TG). In addition, the possible mechanism and kinetics of photodegradation of TC with CdS /CNTs photocatalyst was also discussed.

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