scholarly journals Technologies for metal recycling from electrical - electronic wastes

2021 ◽  
Vol 62 (3b) ◽  
pp. 58-68
Author(s):  
Toi Trung Tran ◽  
Chinh Thi Vu ◽  
Nhung Thi Pham ◽  
Keyword(s):  
Precious Metals ◽  
Operating Conditions ◽  
Electronic Equipment ◽  
Chemical Extraction ◽  
Base Metals ◽  
Separation Processes ◽  
Physical Separation ◽  
Metal Recycling ◽  
New Directions ◽  
Extraction Processes

Wastes from electrical - electronic equipment (WEEE) are of huge concerns worldwide. With the decreasing life cycle of most electrical - electronic equipment (EEE), the WEEE growth rate is fast, about 3÷5% annually. This is considered as the fastest growing waste stream among municipal wastes. WEEE contains, in addition to plastic, glass etc., high contents of base metals and precious metals. They are regarded as potential secondary resources of metals in addition to primary resources of metals from metallic ores. Over the past decades, many metal recycling technologies from WEEE have been developed including physical separation processes and chemical extraction processes. This article summarizes the characteristics, recycling principles, separation processes and optimal operating conditions of the world's most currently common technologies for metal recycling from WEEE. So that one can derive new directions for metal recycling from electrical - electronic wastes in the Vietnam case.

A mini-review of heavy metal recycling technologies for municipal solid waste incineration fly ash

2021 ◽  
pp. 0734242X2110039
Author(s):  
Huan Wang ◽  
Fenfen Zhu ◽  
Xiaoyan Liu ◽  
Meiling Han ◽  
Rongyan Zhang
Keyword(s):  
Fly Ash ◽  
Municipal Solid Waste ◽  
Solid Waste ◽  
Waste Incineration ◽  
Electrochemical Process ◽  
Chemical Extraction ◽  
Air Pollution Control ◽  
Municipal Solid Waste Incineration ◽  
Mswi Fly Ash ◽  
Metal Recycling

This mini-review article summarizes the available technologies for the recycling of heavy metals (HMs) in municipal solid waste incineration (MSWI) fly ash (FA). Recovery technologies included thermal separation (TS), chemical extraction (CE), bioleaching, and electrochemical processes. The reaction conditions of various methods, the efficiency of recovering HMs from MSWI FA and the difficulties and solutions in the process of technical development were studied. Evaluation of each process has also been done to determine the best HM recycling method and future challenges. Results showed that while bioleaching had minimal environmental impact, the process was time-consuming. TS and CE were the most mature technologies, but the former process was not cost-effective. Overall, it has the greatest economic potential to recover metals by CE with scrubber liquid produced by a wet air pollution control system. An electrochemical process or solvent extraction could then be applied to recover HMs from the enriched leachate. Ongoing development of TS and bioleaching technologies could reduce the treatment cost or time.

The Chemical Technology for Producing Precious Metals from Enrichment Rejects of Copper-Pyrite Ores

2021 ◽  
Vol 316 ◽  
pp. 625-630
Author(s):  
Nadezhda L. Medyanik ◽  
Anton P. Ponomarev ◽  
Olga V. Yershova
Keyword(s):  
Economic Effect ◽  
Precious Metals ◽  
Payback Period ◽  
Chemical Technology ◽  
Chemical Extraction ◽  
Two Stage ◽  
Flotation Tailings ◽  
Metallurgical Combine ◽  
Copper Pyrite ◽  
Pyrite Ores

The chemical technology for recovery precious metals Au and Ag from mature flotation tailings of copper-pyrite ores by two-stage sintering with chlorine-ammonium reagents and leaching of bakes with water is developed. The chemical extraction of gold and silver is carried out, using NH4Cl and NH4NO3 reagents in the ratios of 1:1 at a temperature of 250 °C, and 2:1 at 200 °C. In accordance with the obtained results, a chemical technology of enrichment rejects of copper-pyrite ores processing and a scheme of primary apparatus chain for implementing this technology are proposed. The economic effect of the technology realization is calculated. This effect is 96.3 million rubles with a payback period of 8 years when processing enrichment rejects of copper-pyrite ores in amount of 109.5 thousand tons per year under the conditions of JSC “Uchaly Mining and Metallurgical Combine”.

scholarly journals Application of NEAT for the Simulation of Liquid-liquid Extraction Processes with Poorly Specified Feeds

2021 ◽  
Author(s):  
Fabian Jirasek ◽  
Jakob Burger ◽  
Hans Hasse
Keyword(s):  
Liquid Extraction ◽  
Target Component ◽  
Test Cases ◽  
Separation Processes ◽  
Nmr Spectrum ◽  
Liquid Liquid Extraction ◽  
Full Knowledge ◽  
Extraction Processes ◽  
Chemical Groups ◽  
Fluid Separation

The conceptual design of fluid separation processes is particularly challenging if the considered mixtures are poorly specified, since classical thermodynamic models cannot be applied when the composition is unknown. We have recently developed a method (NEAT) to predict activity coefficients in such mixtures. It combines the thermodynamic group contribution concept with the ability of NMR spectroscopy to quantify chemical groups. In the present work, we describe how NEAT can be applied to equilibrium stage simulations of liquid–liquid extraction processes with poorly specified feeds. Only a single 13C NMR spectrum of the feed is needed for predicting the distribution of a target component for different process parameters, such as temperature or extracting agent. The predictions from several test cases are compared to results that are obtained using the full knowledge on the composition of the feed and surprisingly good agreement is found.

scholarly journals Evaluation of bio-coagulants for colour removal from dye synthetic wastewater: characterization, adsorption kinetics, and modelling approach

Water SA ◽  
2020 ◽  
Vol 46 (2 April) ◽  
Author(s):  
IA Obiora-Okafo ◽  
OD Onukwuli ◽  
NC Eli-Chukwu
Keyword(s):  
Adsorption Kinetics ◽  
Molecular Layer ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Synthetic Wastewater ◽  
Organic Polymer ◽  
Good Prediction ◽  
Colour Removal ◽  
Separation Processes ◽  
Coagulant Dosage

Dye usage for industrial applications has been on the increase and these activities generate large amounts of dye-constituted wastewater that should be treated before environmental discharge or reuse. Various studies have shown the application of natural organic polymer (NOP) coagulants in dye removal from industrial wastewater. In this research, the coagulation performances of Vigna unguiculata (VU) and Telfairia occidentalis (TO) for colour removal from crystal Ponceau 6R dye synthetic wastewater was studied. The proximate compositions, structure, and surface morphologies of the coagulants were investigated using standard methods, i.e. Fourier-Transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). Colour removal was evaluated through the time-dependent decrease in particle concentration and thus growth of flocs. Effects of the process parameters, including pH, coagulant dosage, dye concentration (DC), settling time, and temperature were preliminarily tested and the best range experimentally determined. The optimal operating conditions established were pH 2, 800 mg∙L−1 coagulant dosage, 100 mg∙L−1 dye concentration, 300 min, and 303 K. The order of greatest removal was VUC > TOC with optimum efficiency of 93.5% and 90.7%, respectively. The values of K and α obtained for VUC and TOC were 8.09 x 10−4 L∙mg−1∙min−1, 1.7 and 9.89 x 10-4 L∙mg−1∙min−1, 1.6, respectively. Coagulation time, Tag, calculated and deduced from the particle distribution plot, showed a rapid coagulation process. Coagulation-adsorption kinetics indicated agreement with the pseudo-second-order model deducing that chemisorption is the rate-controlling step. It further indicates that particle adsorption on the polymer surfaces occurred mostly as a mono-molecular layer and according to the chemisorption mechanism. Cross-validation showed good prediction of the experimental data. The selected coagulants have the potential for application as efficient coagulants while also showing significant adsorption characteristics. The application of kinetics and modelling in separation processes involving particle transfer is especially required in wastewater treatment.

The Mining of the Romans in Spain

1928 ◽  
Vol 18 (2) ◽  
pp. 129-143 ◽  
Author(s):  
T. A. Rickard
Keyword(s):  
Precious Metals ◽  
The State ◽  
Base Metals ◽  
Republican Period ◽  
Mineral Wealth ◽  
Roman People ◽  
State Monopoly ◽  
Mining Districts ◽  
Copper Lead

During the Republican Period a number of mining districts were exploited in the territory that the Romans annexed. Mines in conquered countries that had belonged to the former rulers became the property of the Roman people, and others were acquired by confiscation or forced purchase from private owners. But the industry was not entirely a State monopoly: on the contrary, a number of mines remained in private hands, more particularly those yielding the base metals—copper, lead and tin—whereas those that yielded the precious metals—gold and silver—were retained by the State. Under the Empire the mines became a special object of bureaucratic concern: as mineral wealth had been the spoil of conquest, so in due course it became the prize of usurpation.

scholarly journals Systematic Experimental Investigation of Segregation Direction and Layer Inversion in Binary Liquid-Fluidized Bed

Processes ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 177
Author(s):  
Alberto Di Renzo ◽  
Giacomo Rito ◽  
Francesco P. Di Maio
Keyword(s):  
Experimental Investigation ◽  
Operating Conditions ◽  
Industrial Processes ◽  
Process Unit ◽  
Separation Processes ◽  
Solids Concentration ◽  
Expansion Range ◽  
Surface Expansion ◽  
Density Ratios ◽  
Inversion Phenomenon

Multi-component liquid-fluidized beds are encountered in a variety of industrial processes. Often, segregation severely affects the performance of the process unit. Unfortunately, size-driven and density-driven separation processes may occur with a complex interplay, showing prevailing mechanisms that change with the operating conditions. For example, when the solids exhibit contrasting differences in size and density, even the direction of segregation can turn out hard to predict, giving rise for some systems to the so-called “layer inversion phenomenon”. A systematic experimental investigation is presented on 14 different binary beds composed of glass beads and ABS spheres with different size and density ratios and different bed composition. The analysis allows assessing the reliability of a model for predicting the segregation direction of fluidized binary beds (the Particle Segregation Model, PSM). By measurements of the solids’ concentration at the surface, expansion/segregation properties and the inversion voidage are compared with the PSM predictions, offering a direct means of model validation. Both the segregation direction throughout the expansion range and the value of the inversion voidage are compared. Extensive qualitative agreement is obtained for 12 out of 14 fluidized mixtures. Quantitatively, the average discrepancy between predicted and measured inversion voidage is below 5%, with a maximum of 17%.

PCR-DGGE analysis of denitrifying bacteria in a metallurgic wastewater treatment process

2002 ◽  
Vol 46 (1-2) ◽  
pp. 333-336 ◽  
Author(s):  
N. Noda ◽  
S. Yoshie ◽  
T. Miyano ◽  
S. Tsuneda ◽  
A. Hirata ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Denaturing Gradient Gel Electrophoresis ◽  
Precious Metals ◽  
Packed Bed ◽  
Population Diversity ◽  
Operating Conditions ◽  
Industrial Wastes ◽  
Wastewater Treatment Process ◽  
Dgge Analysis ◽  
Gradient Gel Electrophoresis

The wastewater generated from the processes of recovering precious metals from industrial wastes contains high concentrations of acids such as nitric acid and of salts. Biological nitrogen removal from this wastewater was attempted by using a circulating bioreactor system equipped with an anoxic packed bed or an anoxic fluidized bed and an aerobic three-phase fluidized bed. The system was found to effectively remove nitrogen from the diluted wastewater (T-N; 1,000–4,000 mg litre−1). The microbial population structure of activated sludge in an anoxic reactor was analyzed by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA (rDNA) fragments. DGGE analysis under different operating conditions demonstrated the presence of some distinguishable bands in the separation pattern, which were most likely derived from many different species constituting the microbial communities. Furthermore, the population diversity varied in accordance with the nitrate-loading rate, water temperature and reactor condition. Some major DGGE bands were excised, reamplified and directly sequenced. It was revealed that the dominant population in the anoxic reactor were affiliated with the β subclass of the class Proteobacteria.

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