Reach Zinc - Leach residues, cadmium cake (EC 293-309-7)

Leach residues, cadmium cake (EC 293-309-7)

Substance description/characteristics

Name and other identifiers of the substance:

The substance Leach residues, cadmium cake is a UVCB (origin: inorganic)

Public name: cadmium cake

Substance identity:
EC number:	293-309-7
EC name:	Leach residues, cadmium cake
CAS number (EC inventory):	91053-44-0
IUPAC name:	Insoluble cadmium-containing residue after precipitation of cadmium bearing solutions
Description:	Cadmium-rich precipitate obtained by adding of a reducing agent –i.e. Zinc powder, Fe-powder, Al-powder, H2, ...- to the Cadmium loaded Sulphate solution. The precipitate is separated in dedicated settler, then optionally re-pulped in a second reaction tank with a slightly acidic sulphate solution i.o.t. dissolve the excess of un-reacted reducing agent powder . Eventually, the Cadmium-rich precipitate is washed and filtered out of the suspension using press-filters. This Intermediate is typically used in production units of Cadmium metal or Cadmium compounds.
Molecular formula:	n.a.
Molecular weight range:	n.a.
Physical state:	solid at 20°C and 1013 hPa

Source, Process and Conclusion

Source	Cadmium loaded Zinc Sulphate solution
Process	During the hydrometallurgical production of metal and/or metal-compounds, redox-potential variations (cementation) result in the selective precipitation of a ‘Cadmium-cake’ that concentrates the Cd and Cd-compounds from the feed; it is extracted and isolated for further processing in production units of Cadmium metal or Cadmium compounds. The cadmium-precipitate is a wet filtercake with an average Cadmium-content of 25-75% w/w. A reducing agent (e.g. Zinc powder, Fe-powder, Al-powder, H2,...) is added to the cadmium loaded Zinc Sulphate solution and a cadmium-rich precipitate is precipitated (cementation). The precipitate is seperated in a dedicated settler before being optionally re-pulped in a second reaction tank with a slightly acidic sulphate solution in order to dissolve the excess of un-reacted reducing agent powder. Eventually, the Cadmium-rich precipitate is washed and filtered out of the suspension using press-filters. It is then stored (covered) and the filter-cake is further transferred as Intermediate to the special treatment unit, typically used in production units of Cadmium metal (EC 231-152-8) or Cadmium compounds. In case of transport to other premises, the Intermediate will be loaded in ADR-regulated big-bags or containers (barrels, small containers, bulk containers, silo-trucks, ...). The ‘Cadmium-cake’ is optionally blended with other Cadmium-containing primary or secondary materials The mixture is continuously or semi-continuously fed: => In hydrometallurgical uses, to leaching tanks (closed loop of acidic solution, mostly sulphate) used in the production of (Intermediate) Cadmium salt => In pyrometallurgical uses, to furnaces, i.e. ISA, Blast furnace, ISF ... used in the smelting and extraction of Cadmium metal (EC 231-152-8)
Conclusion	Insoluble cadmium-containing residue resulting from the precipitation of cadmium bearing solutions, further used for the production of cadmium metal and cadmium compounds.

Classification

The boundary composition of Leach residues, cadmium cake is detailed here below.

Elemental composition - boundary:

Core	min (% w/w)	max (% w/w)	Typical (% w/w)
Cd	30	90	56.4
Zn	1	35	9.7
Cu	1	80	1.86
Pb	0.1	65	0.14
Ni	0	10	0.15
Mn	0.1	2	0.19
S	0	10	5.57
Co	0	10	0.001
Sb	0	5	0.001
Tl	0	1	0.001
As	0	1	0

Mineralogical composition - boundary:

Core	min (% w/w)	max (% w/w)	Typical (% w/w)
Cd(OH)2	30.32	90.96	57
Zn(OH)2	1.52	40.25	11.15
Cd	4.5	13.5	8.46
CdSO4	0	13.91	7.75
ZnSO4	0	12.57	3.44
Cu(OH)2	1.3	99.9	2.43
Zn	0.1	3.5	0.97
Cu	0.1	3.5	0.97
MnO	0.13	2.58	0.25
NiO	0	12.73	0.19
Pb(OH)2	0.12	75.67	0.16
Sb2O3	0	5	0.001
Co2O3	0	14.07	0.001
Tl2O3	0	1.12	0.001
As2O3	0	1	0

4. Classification

The classification is always based on the worst case. For the Leach residues, cadmium cake, this corresponds to:
Acute toxicity - oral	Acute Oral 3
Acute toxicity - inhalation	Acute inhal. 1
Skin corrosion / irritation	Skin irrit. 2
Serious eye damage / eye irritation	Eye damage 1
Skin sensitisation	Skin sens. 1A
Respiratory sensitisation	Resp. sens. 1B
Germ cell mutagenicity	Muta. 1B
Carcinogenicity	Carc. 1A
Reproductive toxicity	Repr. 1A
Specific target organ toxicity - repeated (STOT-RE)	STOT rep 1
Hazardous to the aquatic environment (acute / short-term)	Aquatic Acute 1
Hazardous to the aquatic environment (long-term)	Aquatic Chronic 1