Recovery of molybdenum from residues by simultaneous ultrafine milling and alkali leaching

Late expansions due to alkali-silica reaction were observed in field samples for some aggregates and supplementary cementing materials (SCM) combinations despite meeting the 2-year expansion criterion of the concrete prism test. This fosters a research into the effect of sample geometry and aggregate reactivity on alkali leaching and expansion of lab samples. Larger samples showed less leaching compared to standard prisms. Cylinders of 100 mm-diameter showed higher expansion than 75 mm-standard prisms; however, both sample shapes showed similar expansions for one tested aggregate when used with SCM. Alkali leaching from concrete samples and alkali release from some aggregates could lead to cylindrical samples having higher expansion and better correlation to field samples compared to standard concrete prisms.

Download Full-text

Alkali leaching features of 3-year-old alkali activated fly ash-slag-silica fume: For a better understanding of stability

Composites Part B Engineering ◽

10.1016/j.compositesb.2021.109469 ◽

2021 ◽

pp. 109469

Author(s):

Yingcan Zhu ◽

Marlon A. Longhi ◽

Aiguo Wang ◽

Dongshuai Hou ◽

Hao Wang ◽

...

Keyword(s):

Fly Ash ◽

Silica Fume ◽

Alkali Leaching ◽

Alkali Activated

Download Full-text

Influence of Impurity Dissolution on Surface Properties and NH3-SCR Catalytic Activity of Rare Earth Concentrate

Minerals ◽

10.3390/min9040246 ◽

2019 ◽

Vol 9 (4) ◽

pp. 246

Author(s):

Zhang ◽

Zhu ◽

Zhang ◽

Li ◽

Luo ◽

...

Keyword(s):

Rare Earth ◽

Active Sites ◽

Catalytic Effect ◽

Catalytic Reduction ◽

Weak Acid ◽

Active Components ◽

Catalyst Sample ◽

Nh3 Scr ◽

O2 Concentration ◽

Alkali Leaching

Impurity removal and modification of rare earth concentrate powder were conducted by roasting weak acid-weak alkali leaching to obtain the active components of denitrification catalysts. NH3 selective catalytic reduction catalyst samples were prepared by mixing and kneading with pseudo-γ-Al2O3 boehmite as carrier. The results showed that the Ce7O12 content in the active component samples increased and dispersed more evenly. The grain size of the samples was refined, the specific surface area increased, and the active sites exposed more. Ce coexists in the form of Ce3+ and Ce4+. Fe coexists in the form of Fe3+ and Fe2+, but Fe3+ is abundant. Some Ce, La, Nd, Pr, Fe, Mn, and other components formed solid melts during preparation, which increased the synergistic catalytic effect. The denitrification efficiency of the catalyst sample was 92.8% under the conditions of reaction temperature 400 °C, NO content was 600 ppm, NH3/NO ratio was 1.5, and O2 concentration was 4%.

Download Full-text

Determining alkali leaching during accelerated ASR performance testing and in field exposed cubes using cold water extraction (CWE) and µXRF

MATEC Web of Conferences ◽

10.1051/matecconf/201819903004 ◽

2018 ◽

Vol 199 ◽

pp. 03004

Author(s):

Jan Lindgård ◽

Tone Østnor ◽

Benoit Fournier ◽

Øyvind Lindgård ◽

Tobias Danner ◽

...

Keyword(s):

Fly Ash ◽

Laboratory Testing ◽

Alkali Metals ◽

Ordinary Portland Cement ◽

Cold Water ◽

Performance Testing ◽

Field Samples ◽

Alkali Leaching ◽

Cast Surface ◽

Paste Content

Considerable leaching of alkali metals was documented, both in concrete samples exposed to accelerated laboratory testing and field samples. CWE allowed to quantitatively determine the free alkali metal profiles as a function of the depth. However, CWE cannot account for the changes in the paste content towards a cast surface leading to a seemingly increase in alkali metals. The μXRF allowed to distinguish paste and aggregates. It allowed thereby to determine qualitative Na and K profiles in the cement paste phase of the concrete samples. The laboratory exposed samples showed a clear leaching profile into a depth of about 15 mm after 21 weeks of exposure at 60°C. Corresponding numbers for the 12 years field exposed cube were 50-60 mm. Alkali sorption by alkali silica gel was detected using the μXRF. For the laboratory exposed samples, the prisms prepared with Portland fly ash cement leached less alkali compared to the prisms prepared with ordinary Portland cement, as expected. The leaching in the middle of the prisms estimated based on the μXRF profiles agreed rather well with the level of alkali leaching determined based on the analysis of the leachate (i.e. the water below the samples during exposure).

Download Full-text

An effective separation process of arsenic, lead, and zinc from high arsenic-containing copper smelting ashes by alkali leaching followed by sulfide precipitation

Waste Management & Research ◽

10.1177/0734242x20927473 ◽

2020 ◽

Vol 38 (11) ◽

pp. 1214-1221

Author(s):

Yuhui Zhang ◽

Xiaoyan Feng ◽

Bingjie Jin

Keyword(s):

Separation Efficiency ◽

Separation Process ◽

Copper Smelting ◽

Solid Ratio ◽

Effective Separation ◽

Lead And Zinc ◽

Valuable Metals ◽

Alkali Leaching ◽

Sulfide Precipitation ◽

High Arsenic

Separation of arsenic and valuable metals (Pb, Zn, Cu, Bi, Sn, In, Ag, Sb, etc.) is a core problem for effective utilization of high arsenic-containing copper smelting ashes (HACSA). This study developed an effective separation process of arsenic, lead, and zinc from HACSA via alkali leaching followed by sulfide precipitation. The separation behaviors and optimum conditions for alkali leaching of arsenic and sulfide precipitation of lead and zinc were established respectively as follows: NaOH concentration 3.81 M; temperature 80°C; time 90 minutes; liquid-to-solid ratio 4:1; agitation speed 450 revolutions/minute (r/min) and 2.0 times of theoretical quantity of sodium sulfide (Na2S); temperature 70°C; and time 60 minutes. The results indicated that the leaching rates of As, Pb, and Zn were 92.4%, 36.9% and 13.4%, respectively. More than 99% of lead and zinc were precipitated from the alkali leachate. The scanning electron microscopy/energy dispersive X-ray spectroscopy study confirmed that arsenic was dissolved from HACSA into the alkali leachate. Furthermore, lead and zinc were precipitated as sulfides from the alkali leachate. The proposed process was a good technique for separation of arsenic and enrichment of valuable metals for further centralized treatment separately. It provided high separation efficiency of arsenic and valuable metals, as well as low environmental pollution.

Download Full-text

Recovery of molybdenum from alkali leaching solution of low-grade molybdenum concentrate by ion exchange

Green Processing and Synthesis ◽

10.1515/gps-2015-0033 ◽

2015 ◽

Vol 4 (4) ◽

Author(s):

Zhaoguo Gao ◽

Bo Zhang ◽

Hongzhao Liu ◽

Wei Wang ◽

Yaohua Cao

Keyword(s):

Ion Exchange ◽

Adsorption Capacity ◽

Ammonia Solution ◽

National Standard ◽

Precipitation Process ◽

Low Grade ◽

Loaded Resin ◽

Dynamic Experiments ◽

Alkali Leaching ◽

Leaching Solution

AbstractIn order to extract molybdenum (Mo) from alkali leaching solution of low-grade Mo concentrate, static and dynamic ion exchange experiments were performed. The static experiments results indicated that the adsorption capacity of D201 resins reached 93.50% at pH 3.5, while the adsorption capacity of D314 resins was 95.47%. Therefore, D314 resin was adopted for further experiments. The dynamic experiments results indicated that the adsorption capacity of Mo reached 96.77% when the flow rate of leaching solution was 1 ml/min. The loaded resin could be desorbed by 10% ammonia solution. In consequence, the maximum concentration of Mo in eluate was 122 g/l. In the precipitation process, the Mo recovery reached 97.81%, and the obtained Mo oxide products met the requirement of YMo 55 national standard in GB/T24482-2009 and Grade A standard of ASTM A146-04 (2014).

Download Full-text

A Novel Technique of Flyash Utilization: Preparation of Silica from Flyash by Alkali Leaching

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.434-435.814 ◽

2010 ◽

Vol 434-435 ◽

pp. 814-815

Author(s):

An Ran Guo ◽

Jia Chen Liu ◽

Yi Bing Sun ◽

Wen Jun Lian ◽

Lu Yang

Keyword(s):

High Purity ◽

Sodium Hydroxide Solution ◽

X Ray Diffraction ◽

X Ray ◽

Novel Technique ◽

Reinforcing Agent ◽

Alkali Leaching ◽

A New Technique ◽

Fluorescence Spectrometer ◽

Scanning Electron

A new technique of flyash utilization was presented and high-purity silica was prepared by alkali leaching. The flyash was added into sodium hydroxide solution, and then the suspension was heated to 115 °C for 30 min. After filtrated, the filtrate was collected and carbon dioxide was imported into the solution. Finally, the silica would precipitate from the solution. The silica was characterized by scanning electron microscopy, X-ray diffraction and X-ray fluorescence spectrometer. The high-purity silica prepared from flyash was qualified for the rubber reinforcing agent used in shoemaking.

Download Full-text

Concentration of Rare Earth Elements (Sc, Y, La, Ce, Nd, Sm) in Bauxite Residue (Red Mud) Obtained by Water and Alkali Leaching of Bauxite Sintering Dust

Minerals ◽

10.3390/min10060500 ◽

2020 ◽

Vol 10 (6) ◽

pp. 500 ◽

Cited By ~ 1

Author(s):

Leonid Chaikin ◽

Andrei Shoppert ◽

Dmitry Valeev ◽

Irina Loginova ◽

Julia Napol’skikh

Keyword(s):

Rare Earth ◽

Rare Earth Elements ◽

Red Mud ◽

Electrostatic Precipitator ◽

Bauxite Residue ◽

X Ray ◽

Before And After ◽

Shrinking Core ◽

Alkali Leaching ◽

Rotary Kilns

One of the potential sources of rare-earth elements (REE) is the industrial waste known as red mud (bauxite residue), in which the majority of REE from the initial bauxite are concentrated via the Bayer process. Therefore, the studies of the subject, both in Russia and outside, focus almost exclusively on red mud processing. This article looks into the possibility of REE concentration into red mud by leaching an intermediate product of the bauxite sintering process at Russian alumina refineries, namely electrostatic precipitator (ESP) dust. The experimental works were performed by X-ray diffraction (XRD)and electron probe microanalysis (EPMA) of the sinter and sinter dust. The determination of major and rare-earth elements in the sinter from the rotary kilns and in the ESP dust before and after leaching was carried out by X-ray fluorescence (XRF) and plasma mass spectrometry (ICP-MS). The study showed that it is possible to obtain red mud that contains three times more REE than traditional waste red mud after two-stage leaching ESP dust in the water at 95 °C followed by leaching in an alkaline-aluminate liquor at 240 °C. The shrinking core model was used to study the kinetics of leaching of the original ESP dust and water-treated dust in alkaline-aluminate liquor. The study showed the change in the limiting stage of the alkaline leaching process after water treatment, with the activation energy growing from 24.98 to 33.19 kJ/mol.

Download Full-text