scholarly journals Refining of Precious Metal Bearing Materials from Secondary Sources-Methanesulfonic Acid Leaching of Raw Silver Granules as a Promising Approach towards a Green Way of Silver Refining

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6095
Author(s):  
Johannes Hopf ◽  
Aaron Weigelt ◽  
Hartmut Bombach ◽  
Michael Stelter ◽  
Alexandros Charitos

The state-of-the-art technology of raw silver refining in a silver nitrate-based electrorefining process (Moebius-electrolysis) is accompanied by several disadvantages, both from a technological and from an ecological point of view. In addition, increasing concentrations of critical impurities from secondary sources, like palladium, in raw silver are a further challenge for the future of silver refining. Thus, there is strong motivation for the development of an adequate, alternative process of raw silver refining to substitute the existing Moebius-electrolysis. Due to its less environmentally toxic character and the high aqueous solubility of its silver salt, methanesulfonic acid (MSA) is a possible base chemical for the design of an efficient refining method based on leaching of raw silver followed by electrowinning, with less ecological and technological complications. In this paper the results of some fundamental investigations on the leaching of raw silver granules, containing approx. 94% silver, with methanesulfonic acid and hydrogen peroxide as an oxidation agent are presented. Agitation leaching experiments were conducted on a laboratory scale and the effects of the solid concentration, the hydrogen peroxide dosage and the temperature as leaching parameters were studied. The obtained results indicate that silver leaching yields of more than 90% are achievable with leaching at elevated temperatures of 65 °C or 80 °C, solid concentrations of 500 g/L and at a stoichiometric H2O2:Ag-ratio of 3:1. Increased solid concentrations greater than 500 g/L and elevated temperatures of 65 °C or 80 °C additionally improved the selectivity of the process regarding the leaching of Pd.

Author(s):  
Jihao Guo ◽  
Hongao Xu ◽  
Bo Li ◽  
Yonggang Wei ◽  
Hua Wang

Abstract Multiple purification of zinc sulfate solution is an important process for zinc hydrometallurgy, and large quantities of copper-cadmium residues are generated as byproducts in this process. Copper-cadmium residues contain a large number of valuable metals that must be recovered. A comprehensive extraction process has been proposed using sulfuric acid as the leaching reagent and hydrogen peroxide as the oxidizing reagent. The effects of acid concentration, leaching temperature, leaching time, liquid-to-solid ratio, hydrogen peroxide dosage and stirring speed on the leaching efficiency were investigated. The optimum conditions were determined as an acid concentration of 150 g/L, liquid-to-solid ratio of 4:1, hydrogen peroxide amount of 20 mL, time of 60 min, temperature of 30 °C, particle size of −d75 μm, and agitation rate of 300 r/min. It was concluded that the leaching efficiency of copper and cadmium reached 97%, but because of the existence of zinc sulfide in the residues, a lower leaching efficiency of zinc was obtained. Furthermore, the leaching kinetics of copper was also studied based on the shrinking core model. The activation energy for copper leaching was 5.06 kJ/mol, and the leaching process was controlled by the diffusion through the product layer.


Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2797 ◽  
Author(s):  
Chongsei Yoon ◽  
Buil Jeon ◽  
Giwan Yoon

In this paper, we present zinc oxide (ZnO)-based flexible harvesting devices employing commercially available, cost-effective thin aluminum (Al) foils as substrates and conductive bottom electrodes. From the device fabrication point of view, Al-foils have a relatively high melting point, allowing for device processing and annealing treatments at elevated temperatures, which flexible plastic substrate materials cannot sustain because of their relatively low melting temperatures. Moreover, Al-foil is a highly cost-effective, commercially available material. In this work, we fabricated and characterized various kinds of multilayered thin-film energy harvesting devices, employing Al-foils in order to verify their device performance. The fabricated devices exhibited peak-to-peak output voltages ranging from 0.025 V to 0.140 V. These results suggest that it is feasible to employ Al-foils to fabricate energy-efficient energy harvesting devices at relatively high temperatures. It is anticipated that with further process optimization and device integration, device performance can be further improved.


2013 ◽  
Vol 591 ◽  
pp. 122-125
Author(s):  
Li Jiao Yang ◽  
Si Chen ◽  
Yan Zhang ◽  
Nan Chun Chen ◽  
Jun Gao ◽  
...  

Extracting indium from water quenching slag, which contains poor indium, by two process of leaching, the effect of different oxidants and dosages on the leaching rate of indium in water quenching slag were studied. The leaching conditions: temperature 80 °C, leaching time 2 h, the liquid to solid ratio of neutral leaching 8︰1, the liquid to solid ratio of acid leaching 2︰1, initial concentration of sulfuric acid 500 g·L-1, adding different oxidants, the concentration was detected by crystal violet spectrophotometry. Test results showed that the leaching rate of indium was significantly improved by adding hydrogen peroxide and potassium permanganate. Compared with the effect of different oxidants, the effect of potassium permanganate was significantly higher than that of hydrogen peroxide on the leaching rate of indium.


Author(s):  
CHE MOHD AZIZ BIN YAACOB ◽  
NOR AZURA A RAHMAN

Pergolakan antara etnik Uighur dan Kerajaan China sudah lama diperkatakan. Bermula pada tahun 1949 sehingga kini, konflik ini masih belum reda malah mengakibatkan ribuan nyawa terkorban dan harta benda musnah. Kedua-dua pihak masih memperjuangkan matlamat dan kepentingan masing-masing dan belum bersedia untuk mencari penyelesaian. Penulisan ini memfokuskan kepada pendekatan Segi tiga Konflik sebagai alternatif untuk memahami konflik yang bersifat berulang-ulang ini (Protracted Social Conflict). Terdapat tiga elemen utama dalam Pendekatan Segi tiga Konflik iaitu Situasi, Sikap dan Tingkah laku. Ketiga elemen ini saling berkaitan antara satu sama lain yang mendorong kepada turun dan naik intensiti konflik. Penulisan ini merujuk kepada sumber-sumber sekunder yang melibatkan perbincangan dalam buku, jurnal, hasil kajian, laporan media dan lain-lain lagi. Data yang diperoleh ini kemudiannya dianalisis melalui pengaplikasian elemen Segi tiga Konflik sebagai alternatif memahami konflik yang berpanjangan tersebut. Kebergantungan antara tiga elemen ini membolehkan kita memahami punca-punca konflik tersebut terperangkap di intensiti yang ekstrem. Hasil daripada pengaplikasian elemen Segi tiga Konflik ini mendapati bahawa dari sudut ‘Situasi’, konflik tersebut berlaku akibat perebutan Wilayah Xinjiang (konflik material) antara etnik Uighur dan Kerajaan China dan kini telah bertukar kepada konflik nilai (agama dan identiti) sehingga sukar dikompromi dan diselesaikan. Begitu juga dengan elemen ‘Sikap’, apabila konflik yang berpanjangan tersebut telah meningkat elemen psikologi yang tidak terkawal seperti marah, benci, cemburu, imej musuh, stereotaip dan prejudis. Akhirnya, ia membentuk elemen ‘Tingkah laku’ yang memaksa, memujuk, mengugut, ancaman, diskriminasi, asimilasi  dan pembunuhan. Salah satu contoh ialah penahanan kem pendidikan dan vokasional ke atas etnik Uighur di Xinjiang yang merupakan tingkah laku asimilasi yang melibatkan ancaman dan ugutan; ia berkaitan dengan elemen psikologi stereotaip dan double standard Kerajaan China ke atas etnik Uighur.   The unrest between the Uighurs and the Chinese government has elongated for quite a long time. Since 1949, the conflict has not subsided and resulted in thousands of lives lost and property destruction. Both sides are still fighting for their respective goals and interests, and not ready to find solutions. This paper focuses on the Galtung’s Conflict Triangle Approach as an alternative to understand this recurring conflict (Protracted Social Conflict). There are three main elements in the Conflict Triangle Approach namely Situation, Attitude and Behavior. These three elements are interconnected, leading to escalated and de-escalated of conflict intensity. This paper has made reference to secondary sources involving discussions in books, journals, research results, media reports and others. In order to understand the protracted social conflict, the data obtained are analyzed using the application of the Conflict Triangle. The interdependence between these three elements allows us to understand the causes of this conflict is trapped in extreme intensity. As a result of the application of the Conflict Triangle elements, it is found that from the ‘Situation’ point of view, there is a dispute over Xinjiang province (material conflict) between the Uighur ethnic group and the Chinese government in which has turned into a values conflict (religion and identity) that is difficult to compromise and resolve. Attitude is found as an element from the protracted social conflict which was resulted to an uncontrollable psychological element such as anger,hatred, jealousy, enemy images, stereotypes and prejudice. Eventually, it forms the behavior element of coercion, persuasion, intimidation, threats,discrimination, assimilation and murder. One example is the establishment of educational and vocational detention camps for the Uighur ethnic group in Xinjiang. The camps are part of the assimilation strategy of the government to asimilate the Uighurs. The camps are reported to execute inhuman behavior involving threats and intimidation which relate to the stereotypical psychological elements and the Chinese government’s double standard on the Uighur ethnic group.


2021 ◽  
Vol 14 (3) ◽  
pp. 273-292
Author(s):  
Victoria I. Zhuravleva ◽  

The article focuses on the debatable issues of Russian-American relations from 1914 until the fall of Tsarism, such as the degree of the two countries’ rapprochement, ethnic questions, the positive dynamics of mutual images and the intensified process of Russians and Americans studying each other. Based on primary and secondary sources, this work intends to emphasize that the conflict element in bilateral relations did not hamper cooperation between the two states. The author’s multipronged and interdisciplinary approach allowed her to conclude that the United Sates was ready to engage in wide-ranging interaction with the Russian Empire regardless of their ideological differences. From the author’s point of view, it was the pragmatic agenda that aided the states’ mutual interest in destroying the stereotypes of their counterpart and stimulated Russian Studies in the US and American Studies in Russia. Therefore, the “honeymoon” between the two states had started long before the 1917 February Revolution. However, Wilson strove to turn Russia not so much into an object of US’ “dollar diplomacy”, but into a destination of its “crusade” for democracy. The collapse of the monarchy provided an additional impetus for liberal internationalism by integrating the Russian “Other” into US foreign policy. Ultimately, an ideological (value-based) approach emerged as a stable trend in structuring America’s attitude toward Russia (be it the Soviet Union or post-Soviet Russia).


2018 ◽  
Vol 60 (1) ◽  
pp. 69-78
Author(s):  
Ridoan Karim ◽  
Imtiaz Mohammad Sifat

Purpose This paper aims to provide a comparative discussion on silence as a misrepresentation in contractual obligations between common law and Islamic law. The objective of this paper is to – from a legal pluralism point of view – highlight the contrasts between the two traditions and provide recommendations for best practices to achieve fairness and equity among the contracting parties. While common law does not treat silence as conscious misrepresentation, in Islamic law, silence does not constitute affirmative will. This has repercussions for the contracting parties because if future disputes arise, the aggrieved party in Islamic law reserves the option to rescind or nullify the contract – an opportunity not afforded by common law. We have discussed and analyzed the implementations of the different contractual terms, such as fraud, misrepresentation, trickery and deception in relation with Islamic law principles and common law practices. This research is an effort to draw the attention for further development in both Islamic law and common law practices on contractual obligation. The notion of misrepresentation – subset of a broader gamut of fraud – is arguably nebulous in Islamic literature as well. We delve into these nuances and provide examples both from common law and Islamic law precedents and provide recommendations for reform in both traditions. Design/methodology/approach This paper operates under qualitative methodological framework and uses secondary sources for analysis. Sources include journal databases, review of cases, classical/medieval Islamic scripts, etc. Findings This paper provides a general comparative study between common law’s principle and practice and Islamic law’s principle to forge a better understanding of fine-tuning existing practice and contribute to the debate on determining the best practices to unify international trade and custom exercise. Common law principle, obviously, holds a historical and traditional reputation as those principles are derived from long years of practice and judicial interpretation. Such historical legal system should accommodate fresh ideas in their repertoire and welcome novel ideas which would positively influence its own practice. This paper affords the freedom to the reader to interpret which general principle is acceptable in terms of contractual obligation. Originality/value Previous works exist on the issue of misrepresentation. However, those are mostly explanations of fraud and deceit in Islamic law or common law. The treatment of silence as affirmative will is seldom touched upon. To the authors’ knowledge, this is the first attempt at contrasting the treatment of silence in common and Islamic law. They have also advocated pluralistic practices and argued for legal reform whereby both traditions can benefit from each other.


2020 ◽  
Vol 12 (5) ◽  
pp. 1778 ◽  
Author(s):  
Pedro Cuesta-Valiño ◽  
Fadoua Bolifa ◽  
Estela Núñez-Barriopedro

Information and Communication Technology (ICT) tools are perfect for developing tourism. Several countries are making an effort to become smart and sustainable tourist destinations, making it easier for tourists to interact with their environment while at the same time improving the quality of life for local people. There are many studies of this process and the benefits it brings, although most of them approach the subject from a western traveler’s point of view. This article aims to study the benefits of being a smart and Muslim-friendly tourist destination. An exploratory study was therefore carried out, including a bibliographical review of over one hundred secondary sources. We analyze the Muslim-friendly online services provided by nine destinations, and one of our principal conclusions is that these online services are of the greatest importance for a destination to be truly Muslim-friendly. We also conclude that such services allow companies to design tailored proposals and promote them through digital channels aimed at Muslim people.


Processes ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 376 ◽  
Author(s):  
Qian Zhang ◽  
Qicheng Feng ◽  
Shuming Wen ◽  
Chuanfa Cui ◽  
Junbo Liu

In this work, oxidizing roasting was combined with leaching to separate copper, lead, and zinc from a concentrate obtained by bulk flotation of a low-grade ore sourced from the Jiama mining area of Tibet. The flotation concentrate contained 7.79% Cu, 22.00% Pb, 4.81% Zn, 8.24% S, and 12.15% CaO; copper sulfide accounted for 76.97% of the copper, lead sulfide for 25.55% of the lead, and zinc sulfide for 67.66% of the zinc. After oxidizing roasting of the flotation concentrate, the S content in the roasting slag decreased to 0.22%, indicating that most sulfide in the concentrate was transformed to oxide, which was beneficial to leaching. The calcine was subjected to sulfuric acid leaching for separation of copper, lead, and zinc; i.e., copper and zinc were leached, and lead was retained in the residue. The optimum parameters of the leaching process were: a leaching temperature of 55 °C; sulfuric acid added at 828 kg/t calcine; a liquid:solid ratio of 3:1; and a leaching time of 1.5 h. Under these conditions, the extents of leaching of copper and zinc were 87.43% and 64.38%, respectively. Copper and zinc in the leaching solution could be further separated by electrowinning. The effects of leaching parameters on the extents of leaching of copper and zinc were further revealed by X-ray diffraction and scanning electron microscopy analysis.


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