Evaluating and Enhancing Iron Removal via Filterable Iron Precipitates Formation during Coal-Waste Bioleaching

Iron removal via jarosite precipitate formation is a commonly used technique in various hydrometallurgical processes. Excess iron removal often becomes essential to an overall metal recovery circuit. This is particularly important to processes involving iron-bearing minerals. A technique, which involved the use of pyrite to generate acid for leaching, for iron removal is critical to enabling the process. Iron removal using CaO or similar reagents is expensive and often results in lost product. In the present study, various compounds that facilitate jarosite formation, namely Na2SO4, NH4OH, KCl, and KOH, were utilized and their effect in precipitation was observed. Visual Minteq assisted simulations were run in order to evaluate favorable conditions for iron removal. Morphology and elemental composition of precipitates were analyzed using scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, and the phase purity was identified using X-ray diffraction analysis

Secondary crystalline phases identification in Cu2ZnSnSe4 thin films: contributions from Raman scattering and photoluminescence

In this work, we present the Raman peak positions of the quaternary pure selenide compound Cu2ZnSnSe4 (CZTSe) and related secondary phases that were grown and studied under the same conditions. A vast discussion about the position of the X-ray diffraction (XRD) reflections of these compounds is presented. It is known that by using XRD only, CZTSe can be identified but nothing can be said about the presence of some secondary phases. Thin films of CZTSe, Cu2SnSe3, ZnSe, SnSe, SnSe2, MoSe2 and a-Se were grown, which allowed their investigation by Raman spectroscopy (RS). Here we present all the Raman spectra of these phases and discuss the similarities with the spectra of CZTSe. The effective analysis depth for the common back-scattering geometry commonly used in RS measurements, as well as the laser penetration depth for photoluminescence (PL) were estimated for different wavelength values. The observed asymmetric PL band on a CZTSe film is compatible with the presence of CZTSe single-phase and is discussed in the scope of the fluctuating potentials’ model. The estimated bandgap energy is close to the values obtained from absorption measurements. In general, the phase identification of CZTSe benefits from the contributions of RS and PL along with the XRD discussion.info:eu-repo/semantics/publishedVersio

Enhanced Photoelectrochemical Response from Copper Antimony Zinc Sulfide Thin Films on Transparent Conducting Electrode

Copper antimony sulfide (CAS) is a relatively new class of sustainable absorber material, utilizing cost effective and abundant elements. Band gap engineered, modified CAS thin films were synthesized using electrodeposition and elevated temperature sulfurization approach. A testing analog of copper zinc antimony sulfide (CZAS) film-electrolyte interface was created in order to evaluate photoelectrochemical performance of the thin film of absorber materials. Eu3+/Eu2+ redox couple was selected for this purpose, based on its relative band offset with copper antimony sulfide. It was observed that zinc has a significant effect on CAS film properties. An enhanced photocurrent was observed for CAS film, modified with zinc addition. A detailed investigation has been carried out by changing stoichiometry, and corresponding surface and optical characterization results have been evaluated. A summary of favorable processing parameters of the films showing enhanced photoelectrochemical response is presented

An Investigation of Nanocrystalline and Electrochemically Grown Cu2ZnSnS4 Thin Film Using Redox Couples of Different Band Offset

Alternative electrolytes were examined to evaluate photoelectrochemical response of Cu2ZnSnS4 films at different biasing potential. Selections of the electrolytes were made on the basis of relative Fermi level position and standard reduction potential. Our search was focused on some cost-effective electrolytes, which can produce good photocurrent during illumination. Thin films were grown on FTO substrate using ink of nanocrystalline Cu2ZnSnS4 particles as well as electrodeposition-elevated temperature sulfurization approach. Our investigations suggest that photoelectrochemical response is mostly due to conduction band-mediated process. Surface topography and phase purity were investigated after each electrochemical test, in order to evaluate film quality and reactivity of electrolytes. Raman examination of film and nanocrystals was conducted for comparison. The difference in photocurrent response was explained due to various parameters such as change in charge transfer rate constant, presence of dangling bond, difference in concentration of adsorbed species in electrode

Evaluating and Enhancing Iron Removal via Filterable Iron Precipitates Formation during Coal-Waste Bioleaching

Iron removal via jarosite precipitate formation is a commonly used technique in various hydrometallurgical processes. Excess iron removal often becomes essential to an overall metal recovery circuit. This is particularly important to processes involving iron-bearing minerals. A technique, which involved the use of pyrite to generate acid for leaching, for iron removal is critical to enabling the process. Iron removal using CaO or similar reagents is expensive and often results in lost product. In the present study, various compounds that facilitate jarosite formation, namely Na2SO4, NH4OH, KCl, and KOH, were utilized and their effect in precipitation was observed. Visual Minteq assisted simulations were run in order to evaluate favorable conditions for iron removal. Morphology and elemental composition of precipitates were analyzed using scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, and the phase purity was identified using X-ray diffraction analysis

Phosphorus-Doped SnTe-Type Needle-like Crystals: Band Structure Modifications and Electronic Properties

SnTe has recently emerged as a 3D crystalline topological insulator exhibiting band inversion at the L point where certain crystalline symmetries allow the protection of robust topological surface states. Synthesis and development of new Dirac materials by disturbing the SnTe symmetry was accomplished by substitution of a Sn vacancy by P that maintains the intrinsic band inversion at the L point but also the direct bandgap reduction upon the incorporation of spin orbit coupling. The exotic morphology of the synthesized P-doped SnTe microneedles produces signal amplification arising from the topological surface states due to the alteration of surface area to volume ratio. Moreover, the modified effective mass, lattice imperfection, and conductivity results in a large memory window ∼3.1 V for field effect transistors accompanied by a large change in current within a certain potential range