Removal and stabilization of arsenic from anode slime by forming crystal scorodite

A process was proposed for removing and stabilizing arsenic(As) from anode slime. The anode slime with high arsenic concentration was pretreated by circular alkaline leaching process. Then, the arsenic in the leaching solution can be further precipitated as a form of scorodite crystalline(FeAsO4·2H2O). In the precipitating arsenic reaction, in which ferrous ions were oxidized by air gas, the effects of acidity(p H), reaction temperature, air flow rate, initial concentration of arsenic and initial molar ratio of Fe(II) to As(V) on arsenic precipitation were investigated. The results showed that sufficiently stable crystal scorodite could be achieved under the condition of initial arsenic concentration of 10 g/L, pH 3.0-4.0, Fe/As molar ratio of 1.5, the temperature of 80-95 °C, and the air flow rate higher than 120 L/h. Under the optimal condition, more than 78% of arsenic could be precipitated as a form of scorodite crystalline. The As leaching concentration of the precipitates was less than 2.0 mg/L and the precipitates may be considered to be safe for disposal.

Sequential removal of selenium and tellurium from copper anode slime with high nickel content

A process using soda roasting-alkaline leaching-acid leaching to remove selenium, tellurium and copper sequentially from the copper anode slime with high content of Ni was tested. The mechanism of this process was outlined based on thermodynamic analysis and the change in the XRD patterns of different intermediate products. During soda roasting, copper which occurs as Cu4SeTe in the slime was oxidized to CuO and Cu3TeO6, while selenium and tellurium were oxidized to Ag2SeO4 and Cu3TeO6, respectively. Ag2SeO4 in the calcine is easily leached in the subsequent alkaline leaching, but CuTeO3 resulted from the decomposition of CCu3TeO6 remains inactive in this process through which selenium is leached out in preference to tellurium. The CuTeO3 and Cu O in the alkaline leaching residue can be leached in the following sulfuric acid leaching process. More than 97% of selenium was leached with little tellurium leached under the optimal condition. Then, more than 96% of copper and almost all the tellurium were leached out in the following acid leaching process.

Occurrence of lead and silver minerals and their interaction with xanthate in slurry of zinc electrolysis anode slime

The background pulp potential of zinc anode slime,and its influence on the occurrence of lead,silver and xanthate,were investigated with thermodynamic method.The thermodynamic conclusion and XRD analysis pointed out that in zinc anode slime,the thermodynamically stable compound of xanthate is dixanthogen,anglesite is the only mineral of lead,and kerargyrite is one of silver minerals occurring.Microflotation tests on single minerals of anglesite and kerargyrite in sulfuric acid solution by amyl dixanthogen indicated that dixanthogen has a much stronger collecting ability to kerargyrite than to anglesite.Molecular dynamic simulation indicated that amyl dixanthogen can only be adsorbed on the surface of kerargyrite in the presence of SO42-.The FTIR tests also verified the selective adsorption of amyl dixanthogen on the surface of kerargyrite in the presence of SO42-.

Leaching kinetics of selenium from copper anode slimes by nitric acid-sulfuric acid mixture

The leaching kinetics of selenium from copper anode slimes was studied in a nitric acid?sulfuric acid mixture.The effects of main parameters on selenium leaching showed that the leaching rate of selenium was practically independent of stirring speed,while dependent on temperature and the concentrations of HNO3and H2SO4.The leaching of selenium includes two stages.The activation energy in the first stage is103.5kJ/mol,and the chemical reaction is the rate controlling step.It was almost independent of H2SO4concentration and dependent on HNO3concentration since the empirical reaction order with respect to HNO3concentration is0.5613.In the second stage,the activation energy is30.6kJ/mol,and the process is controlled by a mixture of diffusion and chemical reaction.The leaching of selenium was almost independent of HNO3concentration.

Preparation of pure SbCl_3 from lead anode slime bearing high antimony and low silver

A novel treatment process of lead anode slime bearing high antimony and low silver was developed by a potential-controlled chloridization leaching and continuous distillation.The experimental results show a high Sb 3+ concentration,489.2 g/L,in the leaching solution for two-stage countercurrent leaching process,and the leaching rates of Sb,Cu,Bi more than 99% when the potential is controlled at 450 mV.When the leaching solution is distillated and concentrated at 120°C,almost all the silicon compound is evaporated into the concentration distillate and exists as amorphous hydrated silica.By the continuous distillation,high pure SbCl3 could be prepared,and AsCl3 is enriched in the distillate while metals Bi,Cu are enriched in the continuous distillation residue.As a result,the recovery rate of Sb is more than 95%.

φ-pH diagram of As-N-Na-H_2O system for arsenic removal during alkaline pressure oxidation leaching of lead anode slime

In order to illustrate the thermodynamic characteristics of arsenic during alkaline pressure oxidation leaching process oflead anode slime(NaNO3as oxidant;NaOH as alkaline reagent),theφ-pH diagrams of As-Na-H2O,N-H2O,As-N-Na-H2Osystems at ionic mass concentration of0.1mol/kg and temperatures of298,373,423and473K were established according tothermodynamic calculation.The results show that the existence forms of arsenic are associated with pH value,which mainly exists inthe forms of H3AsO4,24H AsO-,24HAsO-,H2AsO2-and As2O3in lower pH region,while it mainly exists in the form of3AsO4-when pH>11.14.High alkali concentration and high temperature are advantageous to the arsenic leaching.The alkaline pressureoxidation leaching experiments display that the tendency of arsenic leaching rate confirms the thermodynamic analysis resultsobtained from theφ-pH diagrams of As-N-Na-H2O system,and the highest leaching rate of arsenic reaches95.85%at453K.

Intensification of pretreatment and pressure leaching of copper anode slime by microwave radiation

The application of microwave irradiation for pretreatment of copper anode slime with high nickel content prior to pressure sulfuric acid leaching has been proposed.The microwave-assisted pretreatment is a rapid and efficient process.Through the technology of microwave assisted pretreatment-pressure leaching of copper anode slime,copper,tellurium,selenium and nickel are almost completely recovered.Under optimal conditions,the leaching efficiencies of copper,tellurium,selenium and nickel are 97.12%,95.97%,95.37% and 93.90%,respectively.The effect of microwave radiation on the temperature of copper anode slime and leaching solution is investigated.It is suggested that the enhancement on the recoveries of copper,tellurium and selenium can be attributed to the temperature gradient which is caused by shallow microwave penetration depth and super heating occurring at the solid–liquid interface.The kinetic study shows that the pressure leaching of copper anode slime,with and without microwave assisted pretreatment,are both controlled by chemical reactions on the surfaces of particles.It is found that the activation energy calculated for microwave-assisted pretreatment-pressure leaching(49.47 kJ/mol) is lower than that for pressure leaching which is without microwave assisted pretreatment(60.57 kJ/mol).

Selective extraction of gold(Ⅲ) from hydrochloric acid-chlorine gas leach solutions of copper anode slime by tri-butyl phosphate(TBP)

The oxidative leaching causes to dissolve various impurities such as Fe, Cu, Pd, Se in copper anode slime. Organicextractant tri-butyl phosphate (TBP) was used to purify leach solution. Several parameters, such as TBP, HCl and chloride inorganicsalt concentrations were chosen in order to determine efficient state for impurities separation. Standard solvent extraction tests forextraction and separation of Au, Pd, Pt, Fe, Cu and Se were conducted with equal volume of aqueous and organic phases in batchexperiments. The effect of hydrochloric acid, organic phase and metals initial concentration were examined at ambient temperature. Itwas found that 0.25 mol/L TBP in the presence of 2.5 mol/L hydrochloric acid can cause high extraction of gold. Meanwhile, in theseconditions the extraction of other impurities is negligible. After extraction, pregnant organic phase was scrubbed by distilled waterand some impurities were removed. Finally, gold was stripped by sodium thiosulfate solution. The stripping solution does not haveany impurities. By adding H2SO4 to stripping solution containing Na2S2O2, SO2 gas is released and Au3+ ions could be reduced.

Ultra fast microwave-assisted leaching for the recovery of copper and tellurium from copper anode slime

The decomposition of copper anode slime heated by microwave energy in a sulfuric acid medium was investigated. Leaching experiments were carried out in a multi-mode cavity with microwave assistance. The leaching process parameters were optimized using response surface methodology（RSM）. Under the optimized conditions, the leaching efficiencies of copper and tellurium were 99.56% ± 0.16% and 98.68% ± 0.12%, respectively. Meanwhile, a conventional leaching experiment was performed in order to evaluate the influence of microwave radiation. The mechanism of microwave-assisted leaching of copper anode slime was also investigated. In the results, the microwave technology is demonstrated to have a great potential to improve the leaching efficiency and reduce the leaching time. The enhanced recoveries of copper and tellurium are believed to result from the presence of a temperature gradient due to the shallow microwave penetration depth and the superheating at the solid-liquid interface.

Ag recovery from copper anode slime by acid leaching at atmospheric pressure to synthesize silver nanoparticles

In this paper, recovery of silver from anode slime of Sarcheshmeh copper complex in lran and subsequent synthesis of silver nanoparticles from leaching solution is investigated. Sarcheshmeh anode slime is mainly consisted ofCu, Ag, Pb and Se. Amount of Ag in the considered anode slime was 5.4% （by weight）. The goal was to recover as much as possible Ag from anode slime at atmospheric pressure to synthesize Ag nanoparticles. Therefore, acid leaching was used for this purpose. The anode slime was leached with sulfuric and nitric acid from room to 90 ~C at different acid concentrations and the run which yielded the most recovery of Ag was selected for Ag nanoparticles synthesis. At this condition, Cu, Pb and Se are lea- ched as well as Ag. To separate Ag from leach solution HCI was added and silver was precipitated as AgCl which were then dissolved by ammonia solution. The Ag nanoparticles are synthesized from this solution by chemical reduction method by aid of sodium borohydride in the presence of PVP and PEG as stabilizers. The synthesized Ag nanoparticles showed a peak of 394 nm in UV-vis spectrum and TEM images showed a rather uniform Ag nanoparticles of 12 nm.

Effects of anode slime removing by Fe^(2+)dissolution method on electrochemical properties of Pb−0.6%Ag anode and zinc electrowinning

Fe^(2+)dissolution method and manual method were used to remove the anode slime and their effects on properties of cast Pb−0.6wt.%Ag anode and zinc electrowinning were compared.The results reveal that the Fe^(2+)dissolution method can avoid mechanical damage to the oxide film layer on the anode surface,which cannot be achieved by traditional manual method.This can lower the anode corrosion rate by 57.14%,thus reducing Pb contamination in electrolyte and zinc products.Meanwhile,compared with manual method,Fe^(2+)dissolution method can significantly improve the electrocatalytic activity of the anode and lower the initial power consumption of zinc electrowinning to 2720 kW·h/t after removing anode slime.

Selenium(Ⅵ) removal from caustic solution by synthetic Ca-Al-Cl layered double hydroxides

To extract selenium(Ⅵ)from the highly caustic leachate of copper anode slime,the Ca-Al-Cl layered double hydroxides(Ca-Al-Cl-LDHs)with a formula of Ca2 Al(OH)6 Cl·2 H2 O by three co-precipitation methods were synthesized.A plate-like morphology and hexagonal crystal structure with typical mineral phases and functional groups were identified by the FESEM,XRD,FTIR,BET and XPS analysis.The forward feeding sample exhibits the best adsorption capacity of Se(Ⅵ).The factor experiments then reveal a favorable adsorption process with low temperature,low NaOH concentration and high adsorbent dosage.Furthermore,the adsorption kinetics and isotherm parameters can be well described by the Langmuir isotherm and the pseudo-second-order models,respectively.Accordingly,the maximum adsorption amount of Se(Ⅵ)onto Ca-Al-Cl-LDHs reaches188.6 mg/g at 50 ℃.