Synthetic dyes are commonly used for graphite depression in poly-metallic flotation circuits; however,these dyes can be very expensive. The aim of this study is to evaluate performance of certain low-cost alternative ...Synthetic dyes are commonly used for graphite depression in poly-metallic flotation circuits; however,these dyes can be very expensive. The aim of this study is to evaluate performance of certain low-cost alternative depressants for a complex lead-zinc(Pb-Zn) ore rich in graphite(Gr-C) on a conventional mini pilot-scale flotation circuit. The reagents used were commercial and industrial grade starch; agro-based waste-sugarcane bagasse and charred(burnt) bagasse powder. The primary evaluation criteria were quality(grades) of lead and zinc concentrates, their recoveries(%), and graphite rejection(%) in the tails.Benchmark tests using nigrosine as graphite depressant showed 94.3% rejection of Gr-C. The results with commercial starch were found as effective with 93.8% graphite rejection. Furthermore, bagasse powder showed potential in improving product quality(36.4% and 65.6% Pb grade and recovery) with an intermediate effectiveness in graphite rejection(85.6%). The order of effectiveness in Gr-C rejection follows nigrosine % commercial starch > bagasse > industrial starch > charred bagasse. In addition, the effect these depressants on silver(byproduct) grade and recovery was also investigated.展开更多
Low-cost, highly efficient catalysts for hydrogen evolution reaction(HER) are very important to advance energy economy based on clean hydrogen gas. Intensive studies on two-dimensional molybdenum disulfides(2 D Mo S2)...Low-cost, highly efficient catalysts for hydrogen evolution reaction(HER) are very important to advance energy economy based on clean hydrogen gas. Intensive studies on two-dimensional molybdenum disulfides(2 D Mo S2) have been conducted due to their remarkable catalytic properties.However, most of the reported syntheses are time consuming,complicated and less efficient. The present work demonstrates the production of Mo S2/graphene catalyst via an ultra-fast(60 s) microwave-initiated approach. High specific surface area and conductivity of graphene delivers a favorable conductive network for the growth of Mo S2 nanosheets, along with rapid charge transfer kinetics. As-produced Mo S2/graphene nanocomposites exhibit superior electrocatalytic activity for the HER in acidic medium, with a low onset potential of62 m V, high cathodic currents and a Tafel slope of43.3 m V/decade. Beyond excellent catalytic activity, Mo S2/graphene reveals long cycling stability with a very high cathodic current density of around 1000 m A cm^-2 at an overpotential of 250 m V. Moreover, the Mo S2/graphene-catalyst exhibits outstanding HER activities in a temperature range of 30 to 120°C with low activation energy of36.51 k J mol^-1, providing the opportunity of practical scalable processing.展开更多
A foundation of the modern technology that uses single-crystal silicon has been the growth of highquality single-crystal Si ingots with diameters up to 12 inches or larger. For many applications of graphene, large-are...A foundation of the modern technology that uses single-crystal silicon has been the growth of highquality single-crystal Si ingots with diameters up to 12 inches or larger. For many applications of graphene, large-area high-quality(ideally of single-crystal) material will be enabling. Since the first growth on copper foil a decade ago, inch-sized single-crystal graphene has been achieved. We present here the growth, in 20 min, of a graphene film of(5 ×50) cm^2 dimension with >99% ultra-highly oriented grains.This growth was achieved by:(1) synthesis of metre-sized single-crystal Cu(1 1 1) foil as substrate;(2)epitaxial growth of graphene islands on the Cu(1 1 1) surface;(3) seamless merging of such graphene islands into a graphene film with high single crystallinity and(4) the ultrafast growth of graphene film.These achievements were realized by a temperature-gradient-driven annealing technique to produce single-crystal Cu(1 1 1) from industrial polycrystalline Cu foil and the marvellous effects of a continuous oxygen supply from an adjacent oxide. The as-synthesized graphene film, with very few misoriented grains(if any), has a mobility up to ~23,000 cm^2 V^(-1)s^(-1)at 4 K and room temperature sheet resistance of ~230 Ω/□. It is very likely that this approach can be scaled up to achieve exceptionally large and high-quality graphene films with single crystallinity, and thus realize various industrial-level applications at a low cost.展开更多
基金The author is grateful to the management and staff of Center Research Development laboratory(HZL,Debari),India for their support with this research and permitting to publish the work.
文摘Synthetic dyes are commonly used for graphite depression in poly-metallic flotation circuits; however,these dyes can be very expensive. The aim of this study is to evaluate performance of certain low-cost alternative depressants for a complex lead-zinc(Pb-Zn) ore rich in graphite(Gr-C) on a conventional mini pilot-scale flotation circuit. The reagents used were commercial and industrial grade starch; agro-based waste-sugarcane bagasse and charred(burnt) bagasse powder. The primary evaluation criteria were quality(grades) of lead and zinc concentrates, their recoveries(%), and graphite rejection(%) in the tails.Benchmark tests using nigrosine as graphite depressant showed 94.3% rejection of Gr-C. The results with commercial starch were found as effective with 93.8% graphite rejection. Furthermore, bagasse powder showed potential in improving product quality(36.4% and 65.6% Pb grade and recovery) with an intermediate effectiveness in graphite rejection(85.6%). The order of effectiveness in Gr-C rejection follows nigrosine % commercial starch > bagasse > industrial starch > charred bagasse. In addition, the effect these depressants on silver(byproduct) grade and recovery was also investigated.
基金supported by Auburn UniversityIntramural Grants Program (AU-IGP)
文摘Low-cost, highly efficient catalysts for hydrogen evolution reaction(HER) are very important to advance energy economy based on clean hydrogen gas. Intensive studies on two-dimensional molybdenum disulfides(2 D Mo S2) have been conducted due to their remarkable catalytic properties.However, most of the reported syntheses are time consuming,complicated and less efficient. The present work demonstrates the production of Mo S2/graphene catalyst via an ultra-fast(60 s) microwave-initiated approach. High specific surface area and conductivity of graphene delivers a favorable conductive network for the growth of Mo S2 nanosheets, along with rapid charge transfer kinetics. As-produced Mo S2/graphene nanocomposites exhibit superior electrocatalytic activity for the HER in acidic medium, with a low onset potential of62 m V, high cathodic currents and a Tafel slope of43.3 m V/decade. Beyond excellent catalytic activity, Mo S2/graphene reveals long cycling stability with a very high cathodic current density of around 1000 m A cm^-2 at an overpotential of 250 m V. Moreover, the Mo S2/graphene-catalyst exhibits outstanding HER activities in a temperature range of 30 to 120°C with low activation energy of36.51 k J mol^-1, providing the opportunity of practical scalable processing.
基金supported by National Key R&D Program of China (2016YFA0300903, 2016YFA0300802, 2014CB932500 and 2016YFA0200101)National Natural Science Foundation of China (51522201, 11474006, 11327902, 11234001, 21525310, 91433102 and 21573186)+1 种基金Postdoctoral Innovative Personnel Support Program (BX201700014)National Program for Thousand Young Talents of China and the Institute for Basic Science (IBS-R019-D1) of Korea
文摘A foundation of the modern technology that uses single-crystal silicon has been the growth of highquality single-crystal Si ingots with diameters up to 12 inches or larger. For many applications of graphene, large-area high-quality(ideally of single-crystal) material will be enabling. Since the first growth on copper foil a decade ago, inch-sized single-crystal graphene has been achieved. We present here the growth, in 20 min, of a graphene film of(5 ×50) cm^2 dimension with >99% ultra-highly oriented grains.This growth was achieved by:(1) synthesis of metre-sized single-crystal Cu(1 1 1) foil as substrate;(2)epitaxial growth of graphene islands on the Cu(1 1 1) surface;(3) seamless merging of such graphene islands into a graphene film with high single crystallinity and(4) the ultrafast growth of graphene film.These achievements were realized by a temperature-gradient-driven annealing technique to produce single-crystal Cu(1 1 1) from industrial polycrystalline Cu foil and the marvellous effects of a continuous oxygen supply from an adjacent oxide. The as-synthesized graphene film, with very few misoriented grains(if any), has a mobility up to ~23,000 cm^2 V^(-1)s^(-1)at 4 K and room temperature sheet resistance of ~230 Ω/□. It is very likely that this approach can be scaled up to achieve exceptionally large and high-quality graphene films with single crystallinity, and thus realize various industrial-level applications at a low cost.
