A novel dithiourea and its response to metal ions

Article abstract of DOI:10.1016/j.cclet.2011.09.009

The synthesis, characterization, and its response to metal ions of a novel thiourea N,N′-diethoxycarbonyl-N″,N?-(1,2-ethylidene) dithiourea was reported. The results show that this dithiourea with new structure can react with Cu²⁺ and Ni²⁺ separately, and has a best selectivity to Fe³⁺ ions. Bench-scale flotation tests were also carried out, verifying it has higher copper flotation recovery and better selectivity to sulfide ores containing Cu compared with universal collectors.

Full text of DOI:10.1016/j.cclet.2011.09.009

Available online at www.sciencedirect.com
Chinese Chemical Letters 23 (2012) 93–96
www.elsevier.com/locate/cclet
A novel dithiourea and its response to metal ions
*
Lu Yuan, Hong Zhong , Li Qing Li, Jing Jing Xiao
Key Laboratory of Resources Chemistry of Nonferrous Metals, College of Chemistry and Chemical Engineering,
Central South University, Changsha 410083, China
Received 31 May 2011
Available online 8 November 2011
Abstract
0
00 000
The synthesis, characterization, and its response to metal ions of a novel thiourea N,N -diethoxycarbonyl-N ,N -(1,2-
2+
2
ethylidene) dithiourea was reported. The results show that this dithiourea with new structure can react with Cu and Ni
+
3
+
separately, and has a best selectivity to Fe ions. Bench-scale flotation tests were also carried out, verifying it has higher copper
flotation recovery and better selectivity to sulfide ores containing Cu compared with universal collectors.
#
2011 Hong Zhong. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Diethoxycarbonyl dithiourea; Synthesis; Characterization; Response to metal ions
Thioureas are universal collectors for their excellent chelating abilities with metal ions such as Cu, Pb, Zn and Au [1].
At the moment, the thioureas applied as flotation collectors contain only one functional group, for example, alkyl
thioureas, isothioureas, N-ethoxycarbonylthioureas, andsoon[2,3]. Theutilizationof ethoxycarbonylthioureas asa new
type of collectors in flotation separation of Cu/Fe sulfide minerals was reported [4,5]. Ethoxycarbonyl thioureas show
well collecting capability to chalcopyrite, and nice selectivity to galena and pyrite compared with thiocatbamates [6].
Whereas, research about dithioureas has been rarely reported. Dithioureas exhibit stronger adsorption to metalliferous
minerals because they have two thiourea groups in every molecule. Meanwhile, their collecting capability and selectivity
can be enhanced via adjusting structures of connecting groups and substituents. Therefore, dithioureas may display
powerful collecting capability and high selectivity to nonferrous metal ores and precious metal ores when used as
flotation collectors. Diacyl-dithioureas and diesterthioureas could apply as collectors in flotation separation of sulfide
ores, the results indicated that both of them performed nice collecting capability and selectivity [7,8].
0
00 000
In this paper, N,N -diethoxycarbonyl-N ,N -(1,2-ethylidene) dithiourea was synthesized by two steps. Its response
2
+
2+
3+
to metal ions such as Cu , Ni , Fe was studied by UV–vis spectrophotometer. Bench-scale flotation tests were also
carried out.
1
. Experimental
0
00 000
The N,N -diethoxycarbonyl-N ,N -(1,2-ethylidene) dithiourea was synthesized by two steps (Scheme 1). Dissolve
0
sodium thiocyanate (8.11 g, 0.1 mol) in distilled water (20 mL), N,N -dimethylaniline (0.51 mL, 0.004 mol) was
*
Corresponding author.
E-mail address: zhonghongcsu@163.com (H. Zhong).
1001-8417/$ – see front matter # 2011 Hong Zhong. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2011.09.009

94
L. Yuan et al. / Chinese Chemical Letters 23 (2012) 93–96
O
O
S
O
O
S
N, N-dimethylaniline
1, 2-propylidene
NaSCN +
OC H5
2
S
C
N
OC H5
N
H
N
H
Cl
OC H5
2
o
2
o
C H O
N
H
3
~8 C, 4 h
20 C, 1 h
2 5
N
H
0
00 000
Scheme 1. Synthesis of N,N -diethoxycarbonyl-N ,N -(1,2-ethylidene) dithiourea.
added into the solution as catalyst. Cooled this mixture down to ꢀ1 to 5 8C, ethyl chloroformate (9.53 mL, 0.1 mol)
was dropped into the mixture slowly in 0.5 h, then put them at 3–8 8C for 4 h with constant stirring. After the reaction
nearly complete, the mixture turned into two phases, 1,2-ethylenediamine (3.34 mL, 0.05 mol) was added very slowly
into this mixture at 8–15 8C in 1 h. After that, the mixture was heated to 20 8C with reflux and stirrer until completion
(
1 h) as checked by TLC. The production was purified by recrystallization from a DMF–ethanol–distilled water
13
1
mixture (50:10:1), its structure was confirmed by elemental analysis, IR, ESI-MS, H NMR and C NMR
spectroscopy [9].
2
. Results and discussion
The dithiourea was condensed to explore its potential utility as a collecting agent for metal ions. Solutions
2+
ꢀ
5
2+
3+
(
(
4 ꢁ 10 mol/L, in methanol) of Cu , Ni , and Fe were prepared from the corresponding chloride salts. Solutions
ꢀ
5
0
00 000
4 ꢁ 10 mol/L, in methanol) of N,N -diethoxycarbonyl-N ,N -(1,2-ethylidene) dithiourea was prepared and ready
for the following experiments, too. Mixing 10 mL of one metal ion solution with 10 mL of the dithiourea solution,
sufficient oscillation and several hours of standing were required before measuring the absorbance of the supernatant
against the metal ion’s blank. As presented in Fig. 1, after added those metal ions solutions, the absorbance of solutions
2
+
2+
which added Cu and Ni were weaker. Moreover, the absorbance at 262 nm was significantly reduced in the
2
+
2+
3+
presence of Cu ions, the one which added Ni ions weakened less, the one which added Fe ions had little weaken
degree. It was indicated that this dithiourea had different selectivity towards these metal ions. The reduction of
absorbance was due to the formation of dithiourea-metal complexes, so the concentration of dithiourea in supernatants
had decreased. And it was noteworthy that the dithiourea exhibited stronger complexing ability with Cu (II) than with
Ni (II) or Fe (III). Consequently, we believe that this new form of thiourea can use in ore flotation field to collect Cu
from copper ore.
Bench-scale flotation tests were carried out. The flotation test material was refractory copper porphyry ore from the
Dexing Copper Mine of Jiangxi Province in China, and the copper bearing minerals were chalcopyrite, chalcocite,
digenite, covellite, tetrahedrite, tennantite, bornite, as well as some oxide copper minerals such as malachite and
cuprite. The main iron bearing minerals were pyrite and marcasite. The molybdenum form was molybdenite and the
gold forms were native gold and electrum. The significant amounts of non-sulfide gangue minerals were quartz,
sericite, chlorite, illite and biotite. The ore (1 kg, crushed to ꢀ2 mm during sampling) was ground to 68% passing
0
0
0
0
0
0
0
.6
.5
.4
.3
.2
.1
.0
dithiourea
dithiourea+Cu(II)
dithiourea+Ni(II)
dithiourea+Fe(III)
2
25
245
265
285
305
325
Wavelength/nm
Fig. 1. Spectra of solutions before and after the addition of metal ions.

L. Yuan et al. / Chinese Chemical Letters 23 (2012) 93–96
95
Feed
Lime
Collector
Frother
5
'
Rough concentrate
Tailing
Fig. 2. Flow sheet of flotation test.
Table 1
Results of flotation tests.
Reagent dosage (g/t)
Product
Yield (%)
9.86
Grade (%)
Cu
Recovery (%)
Cu
78.87
S
S
Butyl xanthate 50
Rough concentrate
3.48
23.23
81.42
#
2
frothing agent 20
Tailing
Feed
90.14
0.102
0.435
0.58
2.81
21.13
18.58
100.00
100.00
100.00
0
N-ethoxycarbonyl-N -propyl-thiourea 20
Rough concentrate
7.50
4.58
16.32
80.31
44.03
#
2
frothing agent 15
Tailing
Feed
92.50
0.091
0.428
1.68
2.78
19.69
55.97
100.00
100.00
100.00
0
00 000
N,N -diethoxycarbonyl-N ,N -(1,2-ethylidene) dithiourea 20
Rough concentrate
6.79
5.14
15.87
80.98
37.68
#
2
frothing agent 15
Tailing
Feed
93.21
0.088
0.431
1.91
2.86
19.02
62.32
100.00
100.00
100.00
7
4 mm in a closed steel Ø200 mm ꢁ 400 mm XMB ball mill at a pulp density of 62.5% by weight. The flotation tests
3
were performed in XFD-63 flotation cell (self-aeration) whose volume for rougher flotation was 3.0 dm , used 1 kg ore
at every turn to obtain a Cu/Fe rougher concentrate. The flotation flow sheet was described in Fig. 2. After wet
grinding, the pH of the pulp slurry was pre-adjusted to 9.0 by the addition of 1600 g/t lime, other reagents dosage and
the result of flotation test is presented in Table 1.
The result indicated that, the novel dithiourea reported in this paper could obtain higher copper flotation recovery
0
compared with butyl xanthate and N-ethoxycarbonyl-N propyl thiourea this two kinds of universal collectors, in
addition, it has better selectivity to sulfide ores containing Cu.
3
. Conclusions
In this paper, N,N -diethoxycarbonyl-N ,N -(1,2-ethylidene) dithiourea was synthesized by two steps. The
intermediate N-ethoxylcarbonyl isothiocyanate was synthesized from ethyl chloroformate and sodium thiocyanate by
0
00 000
nucleophilic substitution reaction and isomerization. Then using this intermediate with 1,2-ethylenediamine as raw
0
00 000
materials, the target product N,N -diethoxycarbonyl-N ,N -(1,2-ethylidene) dithiourea was obtained by nucleophilic
addition reaction. The structure of the prepared compound was determined by elemental analysis, infrared spectrum,
1
13
2+
2+
3+
mass spectrometry, H NMR and C NMR spectroscopy. Mix the solution of the compound with Cu , Ni , Fe ion
solution respectively, the changes of the absorbance of three compound solutions via UV–vis spectrophotometer were
2
determined. The results show that this dithiourea with new structure can react with Cu and Ni separately, and has a
+
2+
3
+
best selectivity to Fe ion. Bench-scale flotation tests were also carried out, verifying it has higher copper flotation
recovery compared with universal collectors and better selectivity to sulfide ores containing Cu.

96
L. Yuan et al. / Chinese Chemical Letters 23 (2012) 93–96
Acknowledgments
We are grateful for the financial supports from National High-Tech Research and Development Plan of China (No.
007AA06Z122), National Basic Research Program of China (No. 2007CB613602) and National Natural Science
Foundation of China (Nos. 51074183 and 50604016).
2
References
[
[
[
[
[
[
[
[
[
1] D.W. Fuerstenau, Metallic Ore Dressing Abroad 3 (2001) 2 (in Chinese).
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3] D.Z. Wang, Q. Lin, Y.R. Jiang, Molecular Design of Reagents for Mineral and Metallurgical Processing, Changsha, 1996.
4] D.R. Nagaraj, M.E. Lewellyn, S.S. Wang, XVIth International Mineral Processing Congress, 1988, p. 1225.
5] D.R. Nagaraj, C.I. Basilio, R.H. Yoon, in: Proceedings of the International Symposium on Processing of Complex Ores, 1989, p. 160.
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9] Select data of production: white powdery crystals; yield 86.39%; mp 208–209 8C. Anal. Cacld. for C10
H
18
O
4
N
4
S
2
: C, 37.27; H, 5.59; N, 17.39.
Found: C, 37.19; H, 5.45; N, 16.90. IR (film, cm ): 3181, 3035, 2980, 2934, 1721, 1543, 1040. H NMR (400 MHz, DMSO-d ): d 10.921 (s,
H), 9.901 (s, 2H), 4.106–4.159 (m, 4H, J = 7.2 Hz), 3.821–3.833 (t, 4H, J = 2.4 Hz), 1.189–1.225 (t, 6H, J = 7.2 Hz). C NMR (400 MHz,
ꢀ1
1
6
1
3
2
+
6
DMSO-d ): d 180.617 (s, 2C), 153.708 (s, 2C), 62.135 (s, 2C), 43.687 (s, 2C), 14.592 (s, 2C). ESI-MS (m/z): 346.3 ([M+Na] ).