Objectives

-Recover the maximum of Zn -Recirculate the leaching solution (no changes in pH and reactants concentrations)

Electrodeposition in two steps (Fig. 5).

Precipitation by aluminum nitrate allows to reach a zinc recovery of 92% and it's a selective operation because the copper concentration remains constant during the precipitation step. No pH change is necessary or observed. Reactants : Ammonia chemical grade and ammonium chloride salt

𝐶𝑢 2+ + 4𝑁𝐻 4 + + 4𝐻 2 𝑂 ↔ 𝐶𝑢 𝑁𝐻 3 4 2+ + 4𝐻 3 𝑂 +
After copper electrodeposition, leachate is recirculated to leach again the column.

Also, the cathodic deposit is redissolved in acidic media to perform to the electrowinning step.

Conclusions

The leaching step is a key step to improve efficiencies. By identifying leaching limiting and improving factors it's possible to drastically improve total recovery for both metals.

Fig. 4 :

 4 Fig. 4 : XRD spectrum of calcinated zinc precipitate corresponding to a pure ZnAl 2 O 4 phase.

Fig. 3 :

 3 Fig. 3 : SEM back scattered electrons snapshot of 0.063-2 mm bottom ash fraction (original on the right and identification based on EDS analysis on the left)

Fig

  Fig. 6: Leachate color evolution during electrodeposition step

  of leachable sulfates content prior to the leaching step. Experimental setup : down-flow percolating column filled with 50 g to 2 kg of MSWI. Reactants : saline solutions to enhance sulfate solubilization (increasing ionic strength and cationic exchange capacity) -NaCl 1M Fine fraction of municipal solid waste incinerator : zinc and copper urban mine PERRIN Mathilde, DESEURE Jonathan, SVECOVA Lenka LEPMI-Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, Grenoble INP, CNRS -Funding : ADEME

Fig. 1 :

 1 Fig. 1: Evolution of world municipal solid waste production, compared with zinc and copper ore grades evolution and copper and zinc world consumption since 1860