Ultrasound effects on zinc recovery from EAF dust by sulfuric acid leaching

In this work, an ultrasound-assisted leaching process was studied for the recovery of zinc from electric arc furnace （EAF） dust, in which zinc was mainly present in the form of franklinite （60%）. HydrometaUurgy is emerging as a preferred process for the recovery of a va- riety of metals, and the use of ultrasound could offer advantages over the conventional leaching process, especially for the dissolution of franklinite. Franklinite is a refractory phase that is difficult to leach and represents the main obstacle in conventional hydrometallurgy proc- essing. Atmospheric leaching with different sulfuric acid concentrations （0.2-2.0 M） at two temperatures （323 and 353 K） was performed. The tests were conducted using both conventional and ultrasound-assisted leaching. After the leaching tests, the solid residues were charac- terized by scanning electron microscopy （SEM） and X-ray diffraction （XRD） techniques, whereas the leach liquor was analyzed by induc- tively coupled plasma spectroscopy OCP）. The use of ultrasound facilitated the dissolution of franklinite at low acid concentrations and re- suited in a greater zinc recovery under all of the investigated operating conditions.

Laboratory Study on the Removal of Fluorine from High Fluorine Bearing Zinc Oxide Ore

An ever increasing demand for zinc has resulted in worldwide efforts to exploit complex and lean grade reserves of zinc oxide ore. In this study experiments were done on zinc recovery from high-fluorine bearing zinc oxide ore. First the effect of different variables on fluorine removal was investigated. Optimum experimental conditions occurred when the temperature was 1173 K, roasting time was 90 min and air flow was at a velocity of 5 m/min, the fluorine removal from the samples reached over 93%. The results obtained indicate that fluorine removal is not enhanced by adding diluted sulfuric acid or water as a binder. Second the roasted materials were leached with a diluted sulfuric acid, neutralized, flocculated and filtrated. The which satisfies the requirement of fluorine residual fluorine content in the leached content in the leached solutions for the solutions was less than 38 mg/L production of electrolytic zinc.

Recovery of zinc from Zn-Al-Fe alloys by gas pressure filtration

The recovery of zinc from galvanizing dross and the removal of iron contained dross particles by gas pressure filtration were investigated using the model of Zn-Fe-Al alloys.The majority of molten zinc was separated after filtration,and the residue intercepted by the filter consisting mostly of dross particles.The effects of the pressure differential(p),separation temperature(T)and alloy composition on the zinc recovery and iron removal were investigated.At p=0.30 MPa and T=723 K,86.2 wt.%zinc was recovered from the Zn-4Al-2Fe alloy,and up to 99.9 wt.%of the iron was concentrated in the residue.Applying a higher pressure differential led to the improved filtration efficiency,and the desired separation temperature was about 723 K.The aluminum content in the Zn-Al-Fe alloy had little effect on separation efficiency,whereas increasing the iron content led to a decrease in the separation efficiency.Our findings demonstrate the potential of the gas pressure filtration method for the recovery of zinc from galvanizing dross.

Solvent Extraction Developments in Southern Africa

The largest solvent-extraction plant in the world at the time, the Nchanga Copper Operation, was in Zambia. The first commercial process using solvent extraction for the refining of the platinum-group metals was in South Africa. More recently, the Southern African region has seen the implementation of solvent extraction for other base metals, precious metals, and specialty metals. These include the world firsts of primary production of zinc at Skorpion Zinc in Namibia and the large-scale refining of gold by Harmony Gold in South Africa. Several other flowsheets that use solvent-extraction technology are currently under commissioning, development, or feasibility study for implementation in this part of the world, including those for the recovery of copper, cobalt, nickel, tantalum, and niobium.