Formation Of NH Research Articles

Electrocatalytic Reduction of NO3- to Ultrapure Ammonia on {200} Facet Dominant Cu Nanodendrites with High Conversion Faradaic Efficiency.

Nitrate (NO3-) reduction reaction (NtRR) is considered as a green alternative method for the conventional method of NH3 synthesis (Haber-Bosch process), which is known as a high energy consuming and large CO2 emitting process. Herein, the copper nanodendrites (Cu NDs) grown along with the {200} facet as an efficient NtRR catalyst have been successfully fabricated and investigated. It exhibited high Faradaic efficiency of 97% at low potential (-0.3 V vs RHE). Furthermore, the 15NO3- isotope labeling method was utilized to confirm the formation of NH3. Both experimental and theoretical studies showed that NtRR on the Cu metal nanostructure is a facet dependent process. Dissociation of NO bonding is supposed to be the rate-determining step as NtRR is a spontaneously reductive and protonation process for all the different facets of Cu. Density functional theory (DFT) calculations revealed that Cu{200} and Cu{220} offer lower activation energy for dissociation of NO compared to that of Cu{111}.

Diversity of non-symbiotic nitrogen-fixing bacteria and their potential in andisols affected by the eruption of Mount Sinabung, North Sumatra, Indonesia

Abstract. Sembiribg M, Sabrina T. 2021. Diversity of non-symbiotic nitrogen-fixing bacteria and their potential in andisols affected by the eruption of Mount Sinabung, North Sumatra, Indonesia. Biodiversitas 22: 3539-3544. Nitrogen is the main macro-nutrient that is very important for plant growth. Nitrogen is absorbed by plants in the form of NO3-or NH4+ ions from the soil. The andisols affected by the eruption of Mount Sinabung alter the chemical, physical and biological characteristics of the soil. As a result, the population of beneficial microbes in the soil decreased, so soil fertility also decreased. The aim of this research is to determine the diversity of nitrogen-fixing microbes in andisol soil affected by the Mt. Sinabung eruption. The soil samples used in this research were collected from andisols affected by the eruption of Mount Sinabung. The isolation of non-symbiotic nitrogen-fixing bacteria was carried out using a nitrogen-free Jensen medium. The results showed that five non symbiotic N-fixing bacteria can increase the N content in andisols affected by Mount Sinabung eruption. Enterobacter cloacae can increase soil N by 111.76% as compared to without microbial application.

Oxygen Defect Engineering of β-MnO2 Catalysts via Phase Transformation for Selective Catalytic Reduction of NO.

The catalysts for low-temperature selective catalytic reduction of NO with NH3 (NH3 -SCR) are highly desired due to the large demand in industrial furnaces. The characteristic of low-temperature requires the catalyst with rich active sites especially the redox sites. Herein, the authors obtain oxygen defect-rich β-MnO2 from a crystal phase transformation process during air calcination, by which the as-prepared γ-MnO2 nanosheet and nanorod can be conformally transformed into the corresponding β-MnO2 . Simultaneously, this transformation accompanies oxygen defects modulation resulted from lattice rearrangement. The most active β-MnO2 nanosheet with plentiful oxygen defects shows a high efficiency of >90% NO conversion in an extremely wide operation window of ≈120-350°C. The detailed characterizations and density functional theory (DFT) calculations reveal that the introduction of oxygen defects enhances the adsorption properties for reactants and decreases the energy barriers of *NH2 formation more than 0.3eV (≈0.32-0.37eV), which contributes to a high efficiency of low-temperature SCR activity. The authors finding provides a feasible approach to achieve the oxygen defect engineering and gains insight into manganese-based catalysts for low-temperature NO removal or pre-oxidation.

Enhancing Electrocatalytic N2 Conversion to NH3 by MnO2 Ultralong Nanowires with Oxygen Vacancies

Background: At present, industrial synthesis of NH3 mainly relies on the Haber-Bosch process, which is characterized by harsh reaction conditions and high energy consumption. Electrochemical nitrogen reduction is considered to be a mild and sustainable alternative method for producing NH3, but efficient electrocatalyst under ambient conditions is the prerequisite for NH3 production. Objective: To demonstrate that CP@MnO2 ultralong nanowires are a highly-efficient electrocatalyst for N2 reduction reaction (NRR) under ambient conditions. Methods: The α-phase MnO2 synthesized by one-step hydrothermal method has an ultralong nanowires structure and oxygen vacancy defects. The catalysts were characterized by XRD, TEM, XPS, etc. The produced NH3 was estimated by indophenol blue method by UV-vis absorption spectra. Results: Such catalyst attains high Faradaic efficiency (FE) of 8.8% and a large NH3 yield of 1.13×10−10 mol cm−2 s−1 at −0.7 V versus reversible hydrogen electrode in 0.1 M Na2SO4. In addition, the catalyst also shows high electrochemical stability and selectivity for NH3 formation. Conclusion: MnO2 ultralong nanowires can expose higher density of active sites and the spontaneously formed oxygen vacancies can manipulate the electronic structure of manganese oxides and provide coordination unsaturation sites (CUS) to enhance the adsorption of N2, which is the main reason for the high activity of the catalyst.

Synergistic effects of lanthanum ferrite perovskite and hydrogen to promote ammonia production during microalgae catalytic pyrolysis process

Ammonia (NH3) production from nitrogen-enriched renewable resources pyrolysis is a green, clean, and sustainable technology. In this paper, lanthanum ferrite perovskite (LaFeO3) and hydrogen (H2) atmosphere were combined to enhance NH3 production during microalgae pyrolysis. The catalytic pyrolysis of microalgae pyrolysis was carried out in a fixed bed reactor. The results show that the synergistic effects between H2 and LaFeO3 promote the fuel-nitrogen transfer into gas phase, while nitrogen in biochar and bio-oil significantly decreases. H2 and LaFeO3 not only favor the conversion of protein-N to pyridinic-N, pyrrolic-N, and quaternary-N in char, but also accelerate the deamination of amides, pyrroles, and pyridines, thus facilitating the formation of NH3. Pyrolysis temperature plays a considerable role in distribution and conversion of N-species. Increasing temperature increases NH3 and HCN yields, the maximum NH3 yield reaches 47.40 wt% at 800 °C. Moreover, LaFeO3 shows considerable stability during 10 cyclic operations.

Activation of N2 on Manganese Nitride-Supported Ni3 and Fe3 Clusters and Relevance to Ammonia Formation.

Dual-site models were constructed to represent manganese nitride (Mn4N)-supported Ni3 and Fe3 clusters for NH3 synthesis. Density functional theory calculations produced an energy barrier of approximately 0.55 eV for N-N bond activation at the interfacial nitrogen vacancy sites (Nv); also, the hydrogenation and removal of interfacial N is promoted by earth-abundant Ni and Fe metals. Steady-state microkinetic modeling revealed that the turnover frequencies of NH3 production follow an order of Fe3@Mn4N ≈ Ni3@Mn4N > Mn4N > Fe ≫ Ni. Moreover, we present clear evidence that, before NH3 formation, NH migrates from Nv onto the metallic sites. Using N binding energy (BEN) and the transition-state energy of N2 activation (ETS) as descriptors, we concluded that the beneficial effects owing to interfacial Nv sites are the most pronounced when BEN is either too strong or too weak while ETS is high; otherwise, excessive Nv sites may hinder catalyst performance.

Enhanced sustainable electro-generation of a Ni (I) homogeneous electro-catalyst at a silver solid amalgam electrode for the continuous degradation of N2O, NO, DCM, and CB pollutants

This paper reports the sustainable and enhanced generation of a Ni(I) active electro-catalyst using AgSAE as a cathode material for the sustainable degradation of N2O, NO, dichloromethane (DCM), and chlorobenzene (CB) by electroscrubbing in a series operation. The AgSAE electrode showed 1.66 times higher Ni(I) formation than the Ag metal electrode. The AgSAE achieved 20% ± 2% Ni(I) generation in a highly concentrated alkaline medium, whereas Ag metal only achieved 12% ± 2% Ni(I) generation at the same current density. Electrochemical impedance spectroscopy and voltammetric studies determined that the kinetics of the charge-transfer reaction was also preferential at the AgSAE, with the cathodic peak at −1.26 V vs. Ag/AgCl confirming Ni(I) formation. Initially, the change in the oxygen reduction potential and reduction efficiency of Ni(I) confirmed the removal of N2O, NO, DCM and CB. In addition, the gas Fourier transform infrared (FTIR) spectrum revealed 99.8% removal efficiency of toxic pollutants. Therefore, the regeneration of Ni(I) confirmed the sustainable removal of toxic pollutants. Furthermore, the FTIR spectra revealed the formation of NH3 during the reduction of N2O and NO. On the other hand, DCM and CB were reduced to benzene derivatives in the solution phase. In addition, a plausible reduction mechanism was derived. As a result, the AgSAE cathode exhibited two-fold higher removal efficiency of N2O, NO, DCM, and CB than the previously reported electrodes.

Nitrogen Starvation Effect Versus its Excess on the Performance of Arthrospira maxima in Zarrouk’s Medium

Providing a new cheap medium in terms of biomass and pigment production from Arthrospira maxima is an important issue. In order to determine the effect of nitrogen starvation versus its excess, urea was used as a cheap nitrogen source in two different modes (alternative and additive) at four different concentrations (0, 1.25, 2.5, 5 gL-1). It was indicated that an alternative method is better than additive method due to accelerate the ammonia synthesis (NH3) and pH changes in the period of the growth that is directly related to biomass and pigments production. Moreover, the intensive production of biomass concentration, PC, APC, Ca, and C(X+C) content were 1.403, 0.074, 0.093,10.72, and 3.17 mgL-1 with nitrogen starvation medium. Urea considered being one of the inhibition sources of biomass growth due to the formation of NH3. Analyzing final results by general factorial design concluded that omitting nitrogen sources had the potential possibility for growing A. maxima in order to reduce the production costs in large-scale cultivation,which yields better performance than cost-effective Zarrouk’s medium.

Current Density Calculations of an Octahedral Fe Nanocluster for Selective Electrocatalytic for Nitrogen Reduction

In this work, an octahedral-shaped iron nanocluster (NC) electrocatalyst has been modeled to examine the pathways of electrochemical nitrogen reduction reaction (NRR) and analyze the catalytic activity over the (110) surface. The Heyrovsky-type associative and dissociative NRR mechanisms on the (110) facet and edge of the NC are systematically elucidated by calculating reaction free energies for all the possible elementary reaction steps in NRR. Our results show that the most of the NRR intermediates (*N2, *N2H, *N2H2, *N, *NH, *NH2, and *NH3) bind weakly on different sites of the NC in comparison to that on the periodic Fe(110) surface. Importantly, the reaction free energy change for the potential determining step (PDS) in the distal associative mechanism with the formation of *NNH on the NC facet is lower than the edge of NC and periodic Fe(110) surface. Our study also indicates that the PDS (*NH2 formation) associated with the periodic Fe(110) surface is no longer the same as the reaction is catalyzed by the NC. The calculated value of working potential is observed lower for Fe85 NC in comparison to that of the periodic Fe(110) surface. Furthermore, the current density plot indicates that the NC shows less hydrogen evolution reaction (HER) activity compared to other considered Fe based systems. Apart from the working potential study, the positive shift of dissolution potential has also been considered for dissolution behavior of Fe from the NC with respect to surface, confirming its stability in an electrochemical environment. The Fe85 NC electrocatalyst possess quite a low overpotential of 0.29 V for NRR with reduced HER activity, which is further lower compared to that of the well-established Re(111) and enhanced stability toward Fe dissolution in comparison to that of the periodic Fe(110) surface. Therefore, such an NC system may perform as an efficient catalyst for an electrochemical NRR.

Detailed NOX precursor measurements within the reduction zone of a novel small-scale fuel flexible biomass combustion technology

A novel biomass combustion technology with a compact fixed-bed operated with a low oxygen content and double air staging was investigated. Minimized flue gas emissions at high fuel flexibility were achieved only with primary measures. The fuel nitrogen conversion mechanisms were investigated in detail in the secondary zone of a 30 kW lab-reactor, designed as efficient reduction zone. Experimental investigations were carried out to determine the distribution of gas temperatures, main dry product gas components as well as NOX precursors such as NH3 and HCN along the height of the reduction zone. The objective was to determine and understand the various fuel nitrogen conversion mechanisms in the reduction zone that can minimize NOX emissions.It was found that the HCN/NH3 ratio increases with the fuel nitrogen content. This corresponds to an unexpected opposite trend to typical biomass grate furnaces. It was concluded that it is crucial for the HCN/NH3 ratio whether the released nitrogen tars are already cracked in the fixed-bed or only in the gas phase, as in the novel technology. Furthermore, the influence of gas temperature, air ratio, mixing, recirculated flue gas and residence time on the formation and reduction of NH3, HCN and NO is discussed.Finally, this novel technology achieves NOX emissions of<95 mg·m−3 and 175 mg·m−3 for woody and herbaceous fuels, respectively, which is well below the small-scale state-of-the-art for the respective N contents and it achieves fuel nitrogen conversions to NOX in flue gas of 35% and 25%, respectively.

Ammonia Generation from 2D MoS2 Catalysts

We use metallic MoS2 as a catalyst for N2 fixation and NH3 generation. Based on the current literature with regard to MoS2 catalytic performance for NH3 generation, it is tracking with catalytic performance for hydrogen evolution. For example, if you increase edge sites with 2D MoS2 structuring or incorporate more vacancies/defect sites, the hydrogen evolution reaction improves. The same is true of NH3 formation. If we take this one step further, hydrogen generation further increases if MoS2 is converted to its thermodynamically unstable metallic state and is stabilized in this state with functional groups. Therefore, we extend this correlation to NH3 generation. We expect that the N2 fixation and NH3 generation will improve and be stable if we use metallic, functionalized MoS2 nanosheets. This hypothesis is tested and reported. We will also comment on the selectivity for the H2 versus NH3 generation from this catalyst with various functional groups.

First-principles mechanistic study on nitrate reduction reactions on copper surfaces: Effects of crystal facets and pH

As a beneficial technology for nitrate removal and ammonia synthesis, electrocatalytic nitrate reduction reaction (NO3RR) has received much attention in experimental and theoretical studies. Previous work suggests that Cu is one of the most active electrocatalysts for NO3RR. However, the fundamental reaction mechanism, governing the activity and selectivity of Cu towards NO3RR with various facets and pH, remains elusive. Herein, a hybrid model is developed by combining the explicit water layer and the implicit solvation scheme to simulate the water/Cu interface based on theoretical density functional theory simulations. The hybrid model is used to elucidate the effects of crystal facets and pH on NO3RR mechanism over Cu. Our simulation results illustrate that NO3RR in acidic media proceeds via the formation of *NOH to produce NH3 on both (100) and (111) facets. While in alkaline media, Cu(100) prefers the formation of NH2OH via *NHO at low overpotentials, and Cu(111) kinetically favors the formation of NH3. In general, the (100) facet is more active towards NO3RR than the (111) facet, especially at higher pH, due to lower thermodynamic and kinetic barriers. Our results provide deeper mechanistic insights into the effects of both crystal facets and pH on the electrocatalytic activity and product selectivity of Cu towards NO3RR. The hybrid model developed here can be applied to other electrochemical reactions at water/metal interfaces.

Synergetic effect between Fe and Ti species on Fe–Ti–O x for hydrogen cyanide purification

ABSTRACT The Fe–Ti–O x catalysts with the different Fe contents were used for the catalytic hydrolysis of hydrogen cyanide (HCN) in the presence of H2O, which investigated the roles of Fe chemical valence and oxygen species in HCN removal and the production (NH3 and CO). The results implied that more amounts of Fe3+ species over Fe–Ti–Ox could increase the catalytic hydrolysis activity of HCN while Fe2+ species contributed to the formation of NH3 at high temperatures. Furthermore, the abundance of surface oxygen species was in favour of the catalytic performance of HCN.

Zirconium Metal-Organic Frameworks Integrating Chloride Ions for Ammonia Capture and/or Chemical Separation.

Ammonia capture by porous materials is relevant to protection of humans from chemical threats, while ammonia separation may be relevant to its isolation and use following generation by emerging electrochemical schemes. Our previous work described both reversible and irreversible interactions of ammonia with the metal-organic framework (MOF) material, NU-1000, following thermal treatment at either 120 or 300 °C. In the present work, we have examined NU-1000-Cl, a variant that features a modified node structure-at ambient temperature, Zr6(μ3-O)4(μ3-OH)4(H2O)812+ in place of Zr6(μ3-O)4(μ3-OH)4(OH)4(H2O)48+. Carboxylate termini from each of eight linkers balance the 8+ charge of the parent node, while four chloride ions, attached only by hydrogen bonding, complete the charge balance for the 12+ version. We find that both reversible and irreversible uptake of ammonia are enhanced for NU-1000-Cl, relative to the chloride-free version. Two irreversible interactions were observed via in situ diffuse-reflectance infrared Fourier-transform spectroscopy: coordination of NH3 at open Zr sites generated during thermal pretreatment and formation of NH4+ by proton transfer from node aqua ligands. The irreversibility of the latter appears to be facilitated by the presence chloride ions, as NH4+ formation occurs reversibly with chloride-free NU-1000. At room temperature, chemically reversible (and irreversible) interactions between ammonia and NU-1000-Cl result in separation of NH3 from N2 when gas mixtures are examined with breakthrough instrumentation, as evinced by a much longer breakthrough time (∼9 min) for NH3.

ISOLASI DAN IDENTIFIKASI BAKTERI PENAMBAT NITROGEN UNTUK PEMBUATAN BIOFERTILIZER

Nitrogen is a macro nutrient needed by plants. Generally, people use inorganic fertilizers to fulfill nitrogen nutrients in plants. The problem then is, the continuous use of synthetic nitrogen fertilizers has a direct negative impact on the soil and a derivative impact on human health. The use of microorganisms, in this case bacteria, to provide nitrogen to plants can be done by isolating it and making it a biological fertilizer agent. Nitrogen fixing bacteria was isolated on the land of the oil palm plantation of PT Astra Agro Lestari. The isolated nitrogen-fixing bacteria were then tested quantitatively for their ability to fix nitrogen. The bacteria with the highest nitrogen fixing ability were then identified by sequencing their DNA nucleotide bases so that the bacterial strains were identified. The result is that there are 13 bacteria that are able to fix nitrogen with the codes J1, J3, Q5, L1, L11, J31, D1, M6, M5, R1, P2, J4 and C7. The quantitative test shows that bacteria with code D1 are the best at fixing nitrogen in the form of NH4, namely 0.27 ppm. The results of D1 bacterial DNA nucleotide base sequencing showed that the putitive Bacillus aerius strain 24K with identical values ​​and query cover reach&#x0D; &#x0D;

Photocatalytic degradation of amoxicillin from aqueous solutions by titanium dioxide nanoparticles loaded on graphene oxide.

The photocatalytic degradation of amoxicillin (AMX) by titanium dioxide nanoparticles loaded on graphene oxide (GO/TiO2) was evaluated under UV light. Experimental results showed that key parameters such as initial pH, GO/TiO2 dosage, UV intensity, and initial AMX concentration had a significant effect on AMX degradation. Compared to the photolysis and adsorption processes, the AMX degradation efficiency was obtained to be more than 99% at conditions including pH of 6, the GO/TiO2 dosage of 0.4 g/L, the AMX concentration of 50 mg/L, and the intensity of 36 W. Trapping tests showed that all three hydroxyl radical (OH•), superoxide radical (O2•-), and hole (h+) were produced in the photocatalytic process; however, h+ plays a major role in AMX degradation. Under UV irradiation, GO/TiO2 showed excellent stability and recyclability for 4 consecutive reaction cycles. The analysis of total organic carbon (TOC) suggested that AMX could be well degraded into CO2 and H2O. The formation of NH4+, NO3-, and SO42- as a result of AMX degradation confirmed the good mineralization of AMX in the GO/TiO2/UV process. The toxicity of the inlet and outlet samples of the process has been investigated by cultivation of Escherichia coli and Streptococcus faecalis, and the results showed that the condition is suitable for the growth of organisms. The photocatalytic degradation mechanism was proposed based on trapping and comparative tests. Based on the results, the GO/TiO2/UV process can be considered as a promising technique for AMX degradation due to photocatalyst stability, high mineralization efficiency, and effluent low toxicity.

Effect of Na on the migration and release of pyridine nitrogen during coal pyrolysis

Based on density functional theory (DFT) and transition state theory, the effect of alkali metal Na on the formation mechanism and path of NH3 and HCN during coal pyrolysis was studied at the M06-2X/6-311G(d) level. The seven membered ring containing pyridine was selected as the coal model, and the adsorption structure of Na on the coal surface was used as the coal model containing Na. The results show that the presence of Na significantly strengthens the bonding between N and C atoms in pyridine ring, which makes the stripping of N atom from benzene ring requires higher activation energy, thus inhibiting the formation of HCN. However, Na can improve the surface activity of coal, and the energy barrier of NH3 formation rate determination step in the presence of Na is 271.35 kJ/mol lower than that in the absence of Na, which significantly promotes the formation of NH3.

Interplay of Alkali, Transition Metals, Nitrogen, and Hydrogen in Ammonia Synthesis and Decomposition Reactions.

ConspectusThe fixation of dinitrogen to ammonia is critically important for the biogeochemical cycle on earth. Ammonia also holds promise as a sustainable energy carrier. Tremendous effort has been devoted to the development of green processes and advanced materials for ammonia synthesis and decomposition under milder conditions, and encouraging progress has been made.The reduction of dinitrogen to ammonia needs electrons and protons, which hydridic hydrogen H- could supply. Polarized, electron-rich NxHy intermediates, on the other hand, can be stabilized by alkali or alkaline earth metal cations to lower kinetic barriers in the transformation. The inherent properties of alkali/alkaline earth metal hydrides (denoted as AH) endow them with a unique function in ammonia synthesis.In this Account, recent efforts in the exploration of alkali or alkaline earth metal hydrides (denoted as AH), amides, and imides (denoted as ANH hereafter) for ammonia synthesis and decomposition reactions will be summarized and discussed. We begin with an introduction to the chemistry of A with N2, NH3, and H2, highlighting the interconversion between AH and ANH that has profound implications on the formation and decomposition of NH3. We then present our finding on the strong synergistic effect between ANH and transition metals (TM) in ammonia decomposition catalysis, which stimulated our subsequent research on AH for ammonia synthesis. We discuss the effect and function mechanism of AH in the thermocatalytic and chemical looping ammonia synthesis processes. In the thermocatalytic process, AH cooperates with both early and late TM forming either composite catalysts with two active centers or complex metal hydride catalysts with electron- and hydrogen-rich ionic centers facilitating ammonia synthesis with high activities at lower temperatures. Very interestingly, AH levels the catalytic performances of TMs and intervenes in the energy-scaling relations of TM-only catalysts. Moreover, ANH serves as a new type nitrogen carrier effectively mediating ammonia synthesis via a low-temperature chemical looping process, in which N2 is fixed by AH forming ANH. Subsequently, ANH is hydrogenated to ammonia and AH. Late TMs have a strong catalytic effect on the chemical looping process. The unique interplay of A, N, TM, and H- offers plenty of opportunities for achieving dinitrogen conversion under mild conditions, while further efforts are needed to address the challenges in the fundamental understanding and practical application.

Plasma-Assisted Catalysis of Ammonia Using Tungsten at Low Pressures: A Parametric Study

The production of ammonia (NH3) with low-pressure, radiofrequency plasmas is studied in this paper in a wide range of experimental conditions using tungsten as a catalyst. The relative position of the tungsten foil in the pyrex tube was observed to dramatically impact ammonia formation. By positioning the catalyst in the middle of the tube, the concentration of NH3 peaked at 120 W with ≈20 mol %, while it decreased by more than a factor of 2 at 300 W. When the foil was placed close to the end of the tube, the production of NH3 was rather stable beyond 120 W. These results provide clear evidence of the surface’s role in the local enhancement of the NH3 formation rates. In the plasma volume, at some distance from the foil, the decomposition of NH3 is the major occurring process and the decomposition rate increases with the power primarily due to a higher electron density. The optimum production of NH3 was found to be at 45 mol % N2 and 120 W, and the position of the maximum was observed to slightly decrease to <40 mol % N2 with an RF power of 60 W, highlighting that not only the material characteristics play a role but also the discharge conditions. The measured NH3 decreased by increasing the pressure from 3 to 5 Pa, which is associated with a decrease in the electron temperature. The temperature of the discharge was found to have a negligible effect on NH3 formation up to 673 K, demonstrating one of the key features of plasma catalysis in respect to thermal catalysis. The largest energy yield of 0.075 g-NH3 kW h–1 was obtained with an equimolar mixture of N2–H2 at 30 W and 3 Pa. Overall, our results show that the changes in the electron density, electron temperature, and gas composition allow a more effective tuning of the catalytic properties of tungsten than varying the bulk gas temperature.

A novel approach for metal extraction from metal sulfide ores with NH4Cl: A combined DFT and experimental studies

Chalcocite (Cu2S) is the main source for metallurgical production of copper worldwide but it usually co-exist with nickel sulfide in nature. To develop an efficient and green process for the separation and extraction of valuable metals from high-grade matte, we performed density functional theory (DFT) calculations and experimental studies to elucidate chlorination mechanism of Cu2S with ammonium chloride (NH4Cl). First, NH4Cl can react with Cu2S directly in the absence of O2, leading to the formation of H2S and NH3 with negative adsorption energies. Second, O2 can promote the chlorination process by providing adsorbed O and promoting the dissociation of HCl decomposed from NH4Cl, leading to the formation of H2O and CuCl species eventually. Besides, SO2 generated at the Cu2S surface after O2 dissociative adsorption, may leading to the generation of Cl2. Finally, the chlorination can also be achieved by the interaction between Cu2S and Cl2, which is favored thermodynamically and kinetically. Based on the computational results, low-temperature roasting experiments were performed. Cu2S was successfully converted into the corresponding metal chloride (CuCl) by NH4Cl in the absence of O2, but the chlorination process is incomplete with unreacted Cu2S. However, the conversion from Cu2S to CuCl is complete under air atmosphere, consistent with our computational results. Furthermore, metallic copper was successfully obtained at the cathode through electrodeposition with CuCl. The present study reveals detailed reaction mechanism between Cu2S and NH4Cl, and shows the chlorination of Cu2S by NH4Cl followed by electrodeposition of the resulting CuCl as a highly efficient and green process.