Jianguang Yang

Dissolution kinetics of low grade complex copper ore in ammonia-ammonium chloride solution

The leaching kinetics of Tang-dan refractory low grade complex copper ore was investigated in ammonia-ammonium chloride solution. The concentration of ammonia and ammonium chloride, the ore particle size, the solid-to-liquid ratio and the temperature were chosen as parameters in the experiments. The results show that temperature, concentration of ammonia and ammonium chloride have favorable influence on the leaching rate of copper oxide ores. But, leaching rate decreases with increasing particle size and solid-to-liquid ratio. The leaching process is controlled by the diffusion of the lixiviant and the activation energy is determined to be 23.279 kJ/mol. An equation was also proposed to describe the leaching kinetics.

Heavy metal removal and crude bio-oil upgrade from Sedum alfredii Hance harvest using hydrothermal upgrading.

In this study, heavy metals were removed and crude bio-oil was yielded from a heavy metal hyperaccumulator harvest, Sedum alfredii Hance, through hydrothermal upgrading process. This paper reports on the optimization of process parameters for the removal of heavy metals (zinc, lead, and copper) and for the upgrading of crude bio-oil from this biomass in an autoclave. Parameters such as granularity, temperature, pressure, and duration were examined for their effect on the removal efficiency of heavy metals and upgrading efficacy of crude bio-oil. Maximum heavy metal removal efficiency of >99% and crude bio-oil upgrading efficiency of >60% were attained with an 18 mesh (1 mm) granularity, and 22.1 MPa at 370 degrees C in the presence of 10 mg/L additives (K(2)CO(3)) for 60 s. Under these optimized conditions, an oil phase (mostly composed of phenolic hydrocarbons and derivatives), a water phase raffinate (containing Zn(2+) (0.39 g/L), Pb(2+) (0.10 g/L), Cu(2+) (0.15 g/L)), and a solid phase (the hydrothermal upgrading residue, which completely satisfies the limit set by China legislation related to biosolids disposal) were obtained.

Recovery of zinc from hyperaccumulator plants: Sedum plumbizincicola

Hyperaccumulator biomass harvested after heavy‐metal phytoremediation must be considered as hazardous waste that should be contained or treated appropriately before disposal or reuse. As a potential method to detoxify the biomass and to convert this material to a suitable fertilizer or mulch, leaching of heavy metals from Sedum plumbizincicola biomass was studied by using ammonia–ammonium chloride solution as a leaching agent. The research was carried out in two phases: (i) a leaching study to determine the heavy metal:zinc extraction efficiency of this leaching agent and (ii) a thermodynamic analysis to identify the likely reactions and stable Zn(II) species formed in the leaching systems. Experimentally, a Taguchi orthogonal experiment with four variable parameter elements: leaching temperature, nNH4Cl:nNH3 ratio, leaching time and solid–liquid ratio, each at three levels, was used to optimize the experimental parameters by the analysis of variances. Application of the Taguchi technique significantly reduced the time and cost required for the experimental investigation. The findings indicate that leaching temperature had the most dominant effect on metal extraction performance, followed by nNH4Cl:nNH3 ratio, solid–liquid ratio and leaching time. Accordingly, the optimum leaching conditions were determined as temperature: 60°C, nNH4Cl:nNH3 = 0.6, leaching time: 2 h and solid/liquid ratio: 5:1. The total zinc removal after leaching under the optimum conditions reached 97.95%. The thermodynamic study indicated that the dominant species produced by the leaching process should be the soluble species Zn(NH3)4 2+.

Thermodynamics of solubility of Cu2(OH)2CO3 in ammonia-ammonium chloride-ethylenediamine(En)-water system

Abstract In order to decrease the evaporating rate of ammonia and increase the solubility of copper in the solution, ethylenediamine was added into the ammonia-ammonium chloride system to leach the copper-containing oxide ores. The thermodynamic model was constructed and the solubility of malachite Cu 2 (OH) 2 CO 3 in the ammonia-ammonium chloride-ethylenediamine(En)-water system was calculated using the exponential computation method based on both mass balance and charge balance. It is found that the solubility of copper can be increased and the free ammonia concentration can be decreased by submitting partial ammonia with ethylenediamine. The lower free ammonia concentration in the solution is a guarantee to the lower evaporating rate of ammonia. The conditions of malachite Cu 2 (OH) 2 CO 3 converting to atacamite Cu(OH) 1.5 Cl 0.5 were also studied. A group of experiments were designed to validate the veracity of the results of the thermodynamic calculation. It is found that the thermodynamic model is reliable and it can guide the leaching process.

Zinc removal from hyperaccumulator Sedum alfredii Hance biomass

Abstract Leaching of heavy metals from Sedum alfredii Hance biomass was studied with ammonia-ammonium chloride solution as leaching agent. The research was carried out in two phases: 1) a leaching study to determine the zinc extraction efficiency of this leaching agent, and 2) a thermodynamic analysis to identify the likely reactions and stable Zn(II) species formed in the leaching systems. Taguchi orthogonal experiment, with four variable parameters, leaching temperature, molar ratio of NH 4 Cl to NH 3, leaching time and solid-to-liquid(L/S) ratio, and each at three levels, was used to optimize the experiment parameters by the analysis of variances. The results indicate that leaching temperature has the most dominant effect on metal extraction performance, followed by molar ratio of NH 4 Cl to NH 3 , solid-to-liquid ratio and leaching time. The optimum condition was obtained as follows: temperature of 60°C, molecular ratio of NH 4 Cl to NH 3 of 0.6, leaching time of 2 h and solid-to-liquid ratio of 5:1. The total zinc leaching efficiency under optimum conditions reaches 97.95%. The thermodynamic study indicates that the dominant species produced by the leaching process should be the soluble Zn(NH 3 ) 42 + .

Separation of Bismuth From a Bismuth Glance Concentrate Through a Low-Temperature Smelting Process

The present study aims to characterize and separate bismuth from a bismuth glance concentrate through a low-temperature sulfur-fixing smelting process. It reports on the effects of the optimization of process parameters such as sodium carbonate (Na2CO3) and zinc oxide (ZnO) weight percentage in charging, smelting temperature, and smelting duration on the bismuth yield and resultant crude bismuth grade. A maximum bismuth recovery rate of 97.31% and a crude bismuth grade of 96.93% are obtained when a charge (containing 63.5 wt% Na2CO3, 22.5 wt% bismuth glance, and 5% in excess of the stoichiometric requirement of ZnO dosage) is smelted at 900°C for 150 min. Based on the results of the chemical content analysis of separated ZnS, more than 93% ZnS can be recovered, and the recovered ZnS grade can reach 60.2%.

Erratum to: The Membrane Electrowinning Separation of Antimony from a Stibnite Concentrate

Fig. 5—An SEM image of the antimony electrodeposit (the NaCl concentration in catholyte is 5 g/L). JIAN-GUANG YANG, Associate Professor, is with the Department of Metallurgical Science and Engineering and the Institute of Powder Metallurgy Research, Central South University, Changsha 410083 P.R. China. Contact e-mail: jianguang_yang@hotmail.com SHENG-HAI YANG and CHAO-BO TANG, Associate Professors, are with the Department of Metallurgical Science and Engineering, Central South University, Changsha 410083, P.R. China. The online version of the original article can be found under doi: 10.1007/s11663-010-9353-9. Article published online February 12, 2013.