Current situation and prospects for the clean utilization of gold tailings.

Gold tailings are characterized by low-grade, complex composition, fine embedded particle size, environmental pollution, and large land occupation. This paper describes the mineralogical properties of gold tailings, including chemical composition, phase composition, particle size distribution, and microstructure; summarizes the recycling and utilization of components such as mica, feldspar, and valuable metals in gold tailings; reviews harmless treatment measures for harmful elements in gold tailings; and adumbrated the research progress of gold tailings in the application fields of building materials, ceramics, and glass materials. Based on these discussions, a new technology roadmap that combines multistage magnetic separation and cemented filling is proposed for the clean utilization of all components of gold tailings.

Eco-friendly approach for enhancing the floatability of non-metallic components in waste printed circuit boards: Adding gutter oil during dry grinding.

Waste printed circuit boards (WPCBs) are an attractive secondary resource that is challenging to dispose of due to its complexity. Reverse flotation is an effective method to remove non-metallic particles (NMPs) to obtain metals from WPCBs. Nevertheless, the removal of NMPs is usually inadequate in the present flotation practice.

Synthesized Zeolite Based on Egyptian Boiler Ash Residue and Kaolin for the Effective Removal of Heavy Metal Ions from Industrial Wastewater.

The increase of global environmental restrictions concerning solid and liquid industrial waste, in addition to the problem of climate change, which leads to a shortage of clean water resources, has raised interest in developing alternative and eco-friendly technologies for recycling and reducing the amount of these wastes. This study aims to utilize Sulfuric acid solid residue (SASR), which is produced as a useless waste in the multi-processing of Egyptian boiler ash. A modified mixture of SASR and kaolin was used as the basic component for synthesizing cost-effective zeolite using the alkaline fusion-hydrothermal method for the removal of heavy metal ions from industrial wastewater.

WSe-loaded co-catalysts CuP and CNTs: Improving photocatalytic hydrogen precipitation and photocatalytic memory performance.

Photocatalytic decomposition of water for hydrogen production using semiconductor photocatalysts in visible light is considered one of the most promising environmentally friendly ways to produce hydrogen. In this work, the calcination method was adopted to prepare an efficient CuP/WSe/CNTs composite photocatalysts. CuP and carbon nanotubes (CNTs) were used as co-catalysts to reduce the composite rate of the photogenerated supports of the photocatalyst.

Enhanced cleaner flotation behavior of non-metallic particles in waste printed circuit boards: From the perspective of particle size.

Flotation is an attractive method for separating the different components of waste printed circuit boards (WPCBs) due to its cleanliness and efficiency. Non-metallic particles (NMPs) with good floatability usually need to be floated, however, it is difficult to achieve complete removal. The effect of particle size on the flotation behavior of NMPs, which is usually ignored in previous studies, is concerned in this paper.

Does microplastic really represent a threat? A review of the atmospheric contamination sources and potential impacts.

Microplastics (MPs) are regarded as one of the major atmospheric contaminants that have gained wide attention across the globe in the current dispensation. Airborne MPs have been collected in atmospheric fallouts, in indoor and outdoor air as well as along roadways and indoor dust. The most dominating constituent shapes and forms of identified airborne MPs are fibers and synthetic textiles, respectively.

Effects of physicochemical properties of Au cyanidation tailings on cyanide microbial degradation.

The initial cyanide (CN) concentration and amount of co-contaminants in GCTs can inhibit bacterial growth and reduce the CN-degrading ability of bacteria. Several microorganisms can biotransform a wide range of organic and inorganic industrial contaminants into nontoxic compounds. However, active enzymatic CN metabolism processes are mostly constrained by the physical and chemical characteristics of GCTs.

Kelp-derived N-doped biochar activated peroxymonosulfate for ofloxacin degradation.

N-doped carbon materials have been proven to be effective catalysts for activating peroxymonosulfate (PMS). Marine algae biomass is rich in nitrogenous substances , which can reduce the cost of N-doping process and can obtain excellent N-doped catalysts cheaply and easily. In this study, kelp biomass was selected to prepare N-doped kelp biochar (KB) materials.

Advanced utilization of copper in waste printed circuit boards: Synthesis of nano-copper assisted by physical enrichment.

The copper in the waste printed circuit boards (WPCBs) is cleanly recycled by physical methods and presented in the form of nano copper particles by hydrometallurgical, which provides environmental approach to the advanced utilization of metal copper. Copper in WPCBs was first pre-concentrated by gradient enrichment process including gravity separation, mechanical grinding and flotation. The leaching method was then used to dissolve copper from the flotation concentrate in ammoniacal/ammonium salt solutions.

Mechanical activation to enhance the natural floatability of waste printed circuit boards.

The metal in the waste printed circuit boards (WPCBs) is an excellent secondary metal resource. WPCBs were ground to dissociate, and impurities in the dissociated product were removed by gradient flotation to recover valuable metals in this study. The effects of crushing methods on size composition and dissociation state of the crushed products were studied.

Flotation dynamics of metal and non-metal components in waste printed circuit boards.

Flotation is an effective and clean separation technology to realize the recovery of metal in waste printed circuit boards (WPCBs). The flotation kinetic of metal and non-metal components was concerned in this study. In addition, the loading of bubbles, the collision and shedding of particles and bubbles were used to assist in proving the particle dynamics results.

Enhanced Photocatalytic Activity of SiC-Based Ternary Graphene Materials: A DFT Study and the Photocatalytic Mechanism.

A graphene-like semiconductor composite is one of the most promising photocatalyst that does not use noble metals. These composites have excellent photocatalytic properties and have attracted great attention for water splitting. Here, a facile method called the hydrothermal method was used to prepare graphene oxide (GO)/SiC/MoS composites.

Determination and detoxification of cyanide in gold mine tailings: A review.

Cyanide is among the most toxic chemicals widely employed in the cyanidation process to leach precious minerals, such as gold and silver, by the minerals processing companies worldwide. This present article reviews the determination and detoxification of cyanide found in gold mine tailings. Most of the cyanide remains in the solution or the slurries after the cyanidation process.

Effect of Layer Charge Density on Hydration Properties of Montmorillonite: Molecular Dynamics Simulation and Experimental Study.

Four kinds of Ca-montmorillonite with different layer charge density were used to study the effect of charge density on their hydration properties by molecular dynamics simulation and experiments. The research results of Z-density distribution of water molecules, H (hydrogen in water molecules), and Ca in the interlayer of montmorillonite show that the hydration properties of montmorillonite are closely related to its layer charge density. If the charge density is low, the water molecules in the interlayers are mainly concentrated on the sides of the central axis about -1.

Effect of Layer Charge Characteristics on the Distribution Characteristics of HO and Ca in Ca-Montmorillonites Interlayer Space: Molecular Dynamics Simulation.

The charge characteristics of montmorillonite have significant effects on its hydration and application performances. In this study, a molecular dynamics simulation method was used to study the influence of the charge position and charge density of montmorillonite on the distribution of HO and Ca in layers. The results showed that when the layer charge is mainly derived from the substitution among ions in the tetrahedron, a large number of H and O are combined into a hydrogen bond in the interlayer, thus the water molecules are more compactly arranged and the diffusion of water molecules among the layers is reduced.

Cr-Dopant Induced Breaking of Scaling Relations in CoFe Layered Double Hydroxides for Improvement of Oxygen Evolution Reaction.

Monodentate adsorption of oxygen intermediates results in a theoretical overpotential limit of ≈0.35 V for oxygen evolution reaction (OER), which causes the sluggish kinetics of the OER process. In this work, nonprecious chromium dopant is introduced into the self-supported CoFe layered double hydroxides (LDHs) on nickel foam (Cr-CoFe LDHs/NF) via a facile one-step hydrothermal method, which exhibits a preeminent electrocatalytic activity toward the OER with an ultralow overpotential of 238 mV to obtain 10 mA cm and a high stability after cyclic voltammetry for 5000 cycles in alkaline solution (1 m KOH).

Recovery of metals in waste printed circuit boards by flotation technology with soap collector prepared by waste oil through saponification.

Recycling metal from waste printed circuit boards (WPCBs) through green flotation technology has been concerned in this paper. For the sake of environmentally friendly of flotation process, a renewable collector was prepared from waste oil by saponification reaction. The collector composition was analyzed by GC-MS, and results show that the main compositions are n-Hexadecanoic acid, oleic acid and octadecanoic acid.

Flexible vanadium-doped NiP nanosheet arrays grown on carbon cloth for an efficient hydrogen evolution reaction.

Tuning the electronic structure, morphology, and structure of electrocatalysts is of great significance to achieve a highly active and stable hydrogen evolution reaction (HER). Herein, combining hydrothermal and low temperature phosphidation methods, V-doped Ni2P nanosheet arrays grown on carbon cloth (V-Ni2P NSAs/CC) were successfully prepared for the HER. It is found that the prepared V-Ni2P NSAs/CC exhibits preeminent performance for the HER.

N-doping nanoporous carbon microspheres derived from MOFs for highly efficient removal of formaldehyde.

Indoor formaldehyde (HCHO) removal is very important to reduce public health risk. Herein, we report a facile method for preparing N-doped nanoporous carbon through direct carbonization of metal-organic frameworks (ZIF-8) to remove harmful formaldehyde. The prepared N-doped nanoporous carbon exhibited uniform morphology and large specific surface area.

MnMoO nanosheet array: an efficient electrocatalyst for hydrogen evolution reaction with enhanced activity over a wide pH range.

We report the preparation of MnMoO nanosheet array on nickel foam (MnMoO NSA/NF) as an excellent 3D hydrogen evolution reaction (HER) electrocatalyst with good catalytic performance applied under basic, acidic and neutral conditions. In 0.5 M HSO, this MnMoO NSA/NF electrode needs an overpotential of 89 mV to drive current densities of 10 mA cm, to achieve the same current density, it demands overpotentials of 105 mV in 1.

Periodic Porous Alloyed Au-Ag Nanosphere Arrays and Their Highly Sensitive SERS Performance with Good Reproducibility and High Density of Hotspots.

Periodic porous alloyed Au-Ag nanosphere (NS) arrays with different periodic lengths and tunable composition ratios were prepared on Si substrates on a large scale (∼cm) using stepwise metal deposition-annealing and subsequent chemical corrosion from a monolayer of colloidal polystyrene (PS) microspheres as the initial template. The porous alloyed Au-Ag NSs possessed a high porosity and bicontinuous morphology composed of hierarchically interconnected ligaments, which were obtained from an optimized dealloying process in nitric acid. Interestingly, when the dealloying time was prolonged, the average size of the porous alloyed NSs slightly decreased, and the width of the ligaments gradually increased.

Mn doped porous cobalt nitride nanowires with high activity for water oxidation under both alkaline and neutral conditions.

We report the successful synthesis of Mn doped CoN nanowires on a carbon fiber cloth substrate (CFC) by a two-step strategy, which can be used as an efficient and stable OER electrocatalyst under both alkaline and neutral conditions. Benefiting from enhanced electronic interaction, high active area and electrical conductivity, the Mn doped CoN nanowires/CFC exhibits enhanced kinetics and improved cycling stability for the OER under both alkaline and neutral conditions. To achieve a current density of 10 mA cm, the Mn doped CoN nanowires/CFC requires an overpotential of 265 mV in alkaline solution and 285 mV in neutral solution.

Mo doped NiP nanowire arrays: an efficient electrocatalyst for the hydrogen evolution reaction with enhanced activity at all pH values.

We report the successful synthesis of Mo doped NiP nanowires (NWs) on a Ni foam (NF) substrate by a two-step strategy, which could be used as an efficient and stable hydrogen evolution reaction (HER) electrocatalyst over the whole pH range (0-14). Electrochemical investigations demonstrated that Mo doping made the catalytic activity of NiP significantly enhanced. To achieve a current density of 10 mA cm, Mo-NiP NWs/NF required an overpotential of 67 mV in acidic solution, 78 mV in alkaline solution and 84 mV in neutral solution.