Chengyan Wang

Slurry electrolysis of ocean polymetallic nodule

Abstract The ocean poly-metallic nodule was leached by using slurry electrolysis process in HCl-NaCl medium. The leaching rates of Mn, Co, Cu and Ni in the ocean poly-metallic nodule are all above 97%. Meanwhile, the high purity of electrolytic MnO 2 is also obtained as an anode product. The effects of electrolysis electric quantity, acidity, temperature, slurry density, grain size and iron ions concentration were studied. The results show that the ocean poly-metallic nodule can be treated economically in the slurry electrolysis process.

Selective separation of copper and cadmium from zinc solutions by low current density electrolysis

Copper and cadmium ions were selectively separated from zinc sulphate aqueous solution or zinc ammonia/ammonium sulphate aqueous solution by low current density electrolysis. It was shown that the concentration of cadmium ion in zinc sulphate solution decreased from 4.56 g/L to 0.18 g/L in an electrolysis time of 8.5 h, whilst it decreased from 5.16 g/L to lower than 0.005 g/L in zinc ammonia/ammonium sulphate aqueous solution. On the other hand, the deposition rate of copper was so low that it was difficult to separate copper and cadmium ions from the zinc ammonia/ammonium sulphate aqueous solution during electrolysis. But copper ion could be decreased to 0.002 g/L in this solution through solvent extraction by using kerosene diluted LIX984N as extractant. Therefore, it is favorable to recover cadmium ion from the zinc ammonia/ammonium sulphate solution by electrolysis after solvent extraction of copper.

Recovery of iron from copper tailings via low-temperature direct reduction and magnetic separation: process optimization and mineralogical study

Currently, the majority of copper tailings are not effectively developed. Worldwide, large amounts of copper tailings generated from copper production are continuously dumped, posing a potential environmental threat. Herein, the recovery of iron from copper tailings via low-temperature direct reduction and magnetic separation was conducted; process optimization was carried out, and the corresponding mineralogy was investigated. The reduction time, reduction temperature, reducing agent (coal), calcium chloride additive, grinding time, and magnetic field intensity were examined for process optimization. Mineralogical analyses of the sample, reduced pellets, and magnetic concentrate under various conditions were performed by X-ray diffraction, optical microscopy, and scanning electron microscopy–energy-dispersive X-ray spectrometry to elucidate the iron reduction and growth mechanisms. The results indicated that the optimum parameters of iron recovery include a reduction temperature of 1150°C, a reduction time of 120 min, a coal dosage of 25%, a calcium chloride dosage of 2.5%, a magnetic field intensity of 100 mT, and a grinding time of 1 min. Under these conditions, the iron grade in the magnetic concentrate was greater than 90%, with an iron recovery ratio greater than 95%.

Solid-phase synthesis of Cu 2 MoS 4 nanoparticles for degradation of methyl blue under a halogen-tungsten lamp

The Cu2MoS4 nanoparticles were prepared using a relatively simple and convenient solid-phase process, which was applied for the first time. The crystalline structure, morphology, and optical properties of Cu2MoS4 nanoparticles were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and UV-vis spectrophotometry. Cu2MoS4 nanoparticles having a band gap of 1.66 eV exhibits good photocatalytic activity in the degradation of methylene blue, which indicates that this simple process may be critical to facilitate the cheap production of photocatalysts.

Cleaning of lead smelting flue gas scrubber sludge and recovery of lead, selenium and mercury by the hydrometallurgical route

ABSTRACT The expansion of the nonferrous metal smelting industry in the recent two decades has resulted in the generation of massive quantities of flue gas scrubber sludge containing hazardous heavy metals, such as cadmium, lead, arsenic, selenium and mercury (Hg), posing a potential environmental threat. In this work, lead smelting flue gas scrubber sludge was treated by a hydrometallurgical process to achieve sludge cleaning and economic recovery of metal values lead, selenium and mercury. The sludge was preliminarily leached by sodium chloride solution to extract lead. Under the optimum conditions, 99.8% of lead was selectively leached into the solution and subsequently precipitated by calcium oxide while almost the entire selenium and mercury remained in residue. Ninety-eight percent of selenium and 99.8% of mercury were further leached by hydrochloric acid solution with sodium chlorate. 99.3% of mercury was precipitated as red mercuric oxide from the Se–Hg leach liquor by adding sodium hydroxide. After the mercury was removed from the solution, 97.5% of selenium was reduced and precipitated as crude selenium by reduction with sodium sulfite. Recovery yields of lead, mercury and selenium by this process were 99.6%, 98.9% and 95.5%, respectively.

A simple and effective process for recycling zinc-rich paint residue

Continuous growth of the shipping industry and infrastructure has consumed large amounts of zinc-rich paint (ZP) for the protection of steel structures against corrosion. Consequently, a growing amount of waste zinc-rich paint residue (ZPR) is being generated from anticorrosion spraying. ZPR is classified as hazardous waste in most industrialized countries, but it contains considerable amounts of organic compounds with high calorific value and zinc species that can potentially be recycled. Most of the ZPR generated is not properly treated, and this study presents a simple and efficient process for recycling ZPR. The zinc in ZPR was recovered via a hydrometallurgical route through oxidative alkaline leaching and electrowinning. The results show that the leaching ratio of zinc was greater than 98% at 95 °C, NaOH concentration of 250 g/L, liquid/solid ratio of 10:1, air flow rate of 0.6 L/min, and leaching time of 1.5 h. The appropriate minimum concentration of zinc for electrowinning was determined to be 10 g/L. Adding 50 mg/L of gelatin to the electrolyte significantly refined the grain and the optimum current density was determined to be 200 A/m2. Fern shaped cathode zinc powders with a purity of 99.8% were obtained. A high current efficiency (92.7%) was also obtained with energy consumption of 2330.3 kWh per ton of zinc produced. The composition and thermal analysis of the leaching residue suggest that co-processing in cement kiln may be suitable for disposing the leaching residue of ZPR. The experimental results show that the proposed process is promising for ZPR recycling.

An Innovative Oxygen-Enriched Flash Smelting Technology for Lead Smelting and Its Industrial Application

This paper introduces an oxygen-enriched flash smelting (OFS) process for lead smelting. Compared with the bath smelting, OFS has many advantages, including wide adaptability, high yield, low energy consumption, little uncontrolled emission, and considerable metals recoveries. Test results showed that increasing CaO could effectively reduce lead content in the slag, and the appropriate mass ratios of FeO-to-SiO2 and CaO-to-SiO2 were 1.15 and 0.6, respectively. The testing and commissioning indicated when OFS was used to treat material containing 30% of lead, the residual lead in slag could decrease to 4–10%. Furthermore, after zinc volatilization using an ore-smelting electric furnace, contents of lead, zinc, silver, gold and copper in the final slag were below 2%, 2%, 6 g/L, 0.1 g/L and 1%, respectively. The total recoveries of lead, zinc, silver, gold, copper and sulfur were above 98, 90, 99.5, 99.5, 85 and 98%, respectively.

Facile synthesis of monodispersed copper oxalate flaky particles in the presence of EDTA

Monodispersed copper oxalate particles with flaky morphology were prepared via a simple one-pot synthesis method. Scanning electron microscope (SEM), X-ray diffraction (XRD), and fourier transform infrared (FTIR) spectra were used to characterize particle morphology, size, phase composition, and functional groups. It was found that the presence of ethylenediaminetetraacetic acid (EDTA) and the solution pH value had strong influence on the morphological and size evolution of the precipitated particles. On the basis of controlled release of copper ions from a Cu2+–EDTA complex and Weimarn’s law, a strategy for the controlled synthesis of monodispersed copper oxalate particles was designed by referring to the basic mode of the Stöber method. The inherent nature of crystallization to form the flaky solid in the early stage of precipitation as well as the driving force of the long-lasting low supersaturation in the growth stage was proposed to explain the size and morphological evolution of the copper oxalate precipitates. Thermodynamic equilibrium concentrations of copper(II) species in the Cu(II)–EDTA–oxalate–H2O solution system were calculated to help explain the possible formation mechanism of copper oxalate precipitates.

Deep cleaning of a metallurgical zinc leaching residue and recovery of valuable metals

Huge quantities of zinc leaching residues (ZLRs) generated from zinc production are dumped continuously around the world and pose a potential environmental threat because of their considerable amounts of entrained heavy metals (mainly lead). Most ZLRs have not been properly treated and the valuable metals in them have not yet been effectively recovered. Herein, the deep cleaning of a ZLR and recovery of valuable metals via a hydrometallurgical route were investigated. The cleaning process consists of two essential stages: acid leaching followed by calcium chloride leaching. The optimum conditions for extracting zinc, copper, and indium by acid leaching were a sulfuric acid concentration of 200 g·L−1, a liquid/solid ratio of 4:1 (mL/g), a leaching time of 2 h, and a temperature of 90°C. For lead and silver extractions, the optimum conditions were a calcium chloride concentration of 400 g·L−1, a pH value of 1.0, a leaching time of 1 h, and a temperature of 30°C. After calcium chloride leaching, silver and lead were extracted out and the lead was finally recovered as electrolytic lead by electrowinning. The anglesite phase, which poses the greatest potential environmental hazard, was removed from the ZLR after deep cleaning, thus reducing the cost of environmental management of ZLRs. The treatment of chlorine and spent electrolyte generated in the process was discussed.