TY - JOUR
T1 - Chameleon behaviour of iodine in recovering noble-metals from WEEE
T2 - Towards sustainability and "zero" waste
AU - Serpe, Angela
AU - Rigoldi, Americo
AU - Marras, Claudia
AU - Artizzu, Flavia
AU - Mercuri, Maria Laura
AU - Deplano, Paola
N1 - Publisher Copyright:
© The Royal Society of Chemistry.
PY - 2015/4/1
Y1 - 2015/4/1
N2 - An effective and sustainable method for the selective leaching of metals from the non-ferrous metal fraction of Waste Electric and Electronic Equipment (WEEE) is described here. This method consists of a sequence of steps which involve the selective leaching of the different metals from the shredded sample by using environmentally friendly lixiviants in water. In particular: (1) a refluxing citric acid (3 M) solution which dissolves Sn, Zn, Pb, Ni, and other base metals; (2) NH3in combination with an IO3 -/I-mixture which allows one to oxidize Cu and Ag, and to separate them by selective AgI precipitation; (3) an I-/I2mixture (5.3:1 molar ratio) which is capable of leaching quantitatively Au metal from the solid residue. Each step is followed by a further treatment for: (i) high-rate metal and reagent recovery, in the case of NMs; (ii) inertization, in the case of heavy metals. The "chameleon" behaviour of iodine, which shows versatile redox/complexing/precipitating capabilities, allows one to achieve, on the one hand, a selective noble-metal (NM) leaching and, on the other hand, a simple and effective reagent and metal recovery. The comparison of the above described method with a similarly effective one previously patented by some of the same authors, allows one to point out that a significant improvement in sustainability is achieved in terms of lixiviant employment, which is of low cost, easily available and recyclable, and able to work in water solutions, while maintaining or improving its environmentally friendly character.
AB - An effective and sustainable method for the selective leaching of metals from the non-ferrous metal fraction of Waste Electric and Electronic Equipment (WEEE) is described here. This method consists of a sequence of steps which involve the selective leaching of the different metals from the shredded sample by using environmentally friendly lixiviants in water. In particular: (1) a refluxing citric acid (3 M) solution which dissolves Sn, Zn, Pb, Ni, and other base metals; (2) NH3in combination with an IO3 -/I-mixture which allows one to oxidize Cu and Ag, and to separate them by selective AgI precipitation; (3) an I-/I2mixture (5.3:1 molar ratio) which is capable of leaching quantitatively Au metal from the solid residue. Each step is followed by a further treatment for: (i) high-rate metal and reagent recovery, in the case of NMs; (ii) inertization, in the case of heavy metals. The "chameleon" behaviour of iodine, which shows versatile redox/complexing/precipitating capabilities, allows one to achieve, on the one hand, a selective noble-metal (NM) leaching and, on the other hand, a simple and effective reagent and metal recovery. The comparison of the above described method with a similarly effective one previously patented by some of the same authors, allows one to point out that a significant improvement in sustainability is achieved in terms of lixiviant employment, which is of low cost, easily available and recyclable, and able to work in water solutions, while maintaining or improving its environmentally friendly character.
UR - http://www.scopus.com/inward/record.url?scp=84927589291&partnerID=8YFLogxK
U2 - 10.1039/c4gc02237h
DO - 10.1039/c4gc02237h
M3 - Article
SN - 1463-9262
VL - 17
SP - 2208
EP - 2216
JO - Green Chemistry
JF - Green Chemistry
IS - 4
ER -