Yang Jianguang

A new membrane electro-deposition based process for tin recovery from waste printed circuit boards.

The current research investigated a process combining leaching, purification and membrane electrodeposition to recover tin from the metal components of WPCBs. Experimental results showed that with a solid liquid ratio of 1:4, applying 1.1 times of stoichiometric SnCl4 dosage and HCl concentration of 3.5-4.0 mol/L at a temperature of 60-90°C, 99% of tin can be leached from the metal components of WPCBs. The suitable purification conditions were obtained in the temperature range of 30-45°C with the addition of 1.3-1.4 times of the stoichiometric quantity of tin metal and stirring for a period of 1-2h; followed by adding 1.3 times of the stoichiometric quantity of Na2S for sulfide precipitation about 20-30 min at room temperature. The purified solution was subjected to membrane electrowinning for tin electrodeposition. Under the condition of catholyte Sn(2+) 60 g/L, HCl 3 mol/L and NaCl 20 g/L, current density 200 A/m(2) and temperature 35°C, a compact and smooth cathode tin layer can be obtained. The obtained cathode tin purity exceeded 99% and the electric consumption was less than 1200 kW h/t. The resultant SnCl4 solution generated in anode compartment can be reused as leaching agent for leaching tin again.

Preparation of tetrapod-like ZnO whiskers from waste hot dipping zinc

Large and uniform tetrapod-like ZnO whiskers (T-ZnO) were prepared from waste hot dipping zinc by vapor oxidation and examined by means of X-ray diffraction and ICP-AES analysis and scanning electron microscope. The products are pure hexagonal wurtzite crystals with tetrapod shape and edge size of center body 5–6 µm and needle length of 100–130 µm. The size and shape of ZnO particles are fully controlled by the growth conditions and T-ZnO can be obtained only at 850–1000 °C and total gas flow rate ranging from 40 to 250 L · h−1 in which the size of the T-ZnO particles varies slightly with temperature. The process of the formation of T-ZnO is that T-ZnO may nucleate at the initial stage with a complete tetrapod shape and develop to the large size, but not the process of preferential growth of octahedral nuclei and subsequent growth of the needles. The experiment presents a new method to prepare T-ZnO economically by using the waste hot dipping zinc.

Thermodynamic Research of Leaching Copper Oxide Materials with Ammonia-ammonium Chloride-water Solution

Abstract The solubilities of copper hydroxide Cu(OH)2, copper oxide CuO, atacamite Cu(OH)1.5Cl0.5, malachite Cu2(OH)2CO3 and chessylite Cu3(OH)2(CO3)2 in an ammonia-ammonium chloride-water solution were calculated using an exponential computation method based on both mass balance and charge balance equations. The range of stability of each solid phase was also established. A group of experiments were designed to validate the veracity of the results of the thermodynamic calculation.