Recovery of tantalum metal from used tantalum capacitor by using stream gasification
S. Katano1, ZZ.Hlaing1,2, M. Adachi1, Y.Yanagisawa1 and H. Nakagome1*
S.Uchiyama 2, K. Taniguchi3
1 Graduate School of Engineering, Chiba University, 1-33, Yayoi, Inage, Chiba, 236-8522, Japan
2 National Institute of Public Health, 2-3-6 Minami, Wako city, Saitama, 351-0197, Japan
3 Torres Environmental Systems Co.,Ltd., 1-11 -22

Aoyagi, Ichihara City, Chiba, 299-0102, Japane-mail: nakagome@tu.chiba-u.ac.jp ; Tel +81-43-290-3466 & Fax ; +81-43-290-3466

Abstract
Recovery of tantalum from used tantalum capacitor is important because the price and the quantity of production of tantalum
have not been stable, recently. However, recovery of tantalum from tantalum capacitor is difficult since the flame retardantand halogenated compound are contained in the tantalum capacitor. In this study we investigated by using steam gasification
for recovery of tantalum, stabilization of halogenated compounds and hydrogen production. At first, we investigated theoptimum conditions by using stream gasification with mixed molten carbonate for tantalum recovery rate. Secondly, we usedsodium hydroxide (NaOH) by using steam gasification for the possibility tantalum recovery rate. Mold resin can be
decomposed at low temperature, energy and short time by using stream gasification with NaOH.
Keywords: Tantalum, metal, low temperature, stream gasification, sodium hydroxide

1. Introduction
Tantalum metal is one of the rare metals and also theprice and output are not stability. And it is called “conflictmetal”, the argument involving the rights of mining has
occurred in Congo which is one of the producing
countries [1]. On the other hand, the high concentration
tantalum is contained in the tantalum capacitor used for
an electronic device. The development of recycling
technology from used tantalum capacitors is required inorder to reduce the environmental impact and the point ofview of "urban mines". In the processing method, such as
combustion and solubilization have been proposed
previously [2], but this recycling methods are difficult
because the chemical treating heavy metals or halogen
compounds, thermosetting resin harmful. Therefore, therecycling of tantalum has not been carried out. In thisstudy, we have investigated recovery of tantalum metalfrom used tantalum capacitor by using the steam
gasification technology for the recovery of tantalum,stabilization of halogenated compounds and hydrogenproduction.

2. Materials and Methods
The tantalum capacitor (size: 6.0 × 3.2 × 2.5mm, model
number: ESVC1V475M) was obtained from NEC /TOKIN
Co.,Ltd. In this experiment, the catalyst was used molten
carbonate (Na2CO3 : K2CO3 : Li2CO3 )(1:1:1) and sodiumhydroxide (NaOH). The experimental apparatus is shownin Fig. 1. The catalyst put into the reactor and heated byan electric furnace while flowing nitrogen (160ml/min)and steam (1ml/min) warmed by the heater. After heating
to the reaction temperature of 530ºC, the tantalum
capacitor (about 3g) was thrown in the reactor and thereaction time is 5~10 min.
Experiment (1); Setup of appropriate reaction conditions

Our previous study, separation of the tantalum ofsintered compact was now possible by the steam
gasification using mixed molten carbonate. Based on thisresult, we examined the suitable reaction temperature,
the recovery rate of tantalum and the reaction time byusing the mixed molten carbonate at 530 ºC for 5~10 min.
Experiment(2); Stream gasification by using NaOH
The experiment (2) was carried out based on the same
conditions obtained in the experiment (1) and, using
NaOH at 530 ºC for 5 to 10 min. Sodium hydroxide canbe expected more hydrogen production and lower costthan the molten carbonate.
Experiment(3); Cause gasification occurs at low
temperature
We investigated the reason of gasification occurs fromabout 500 ºC by using mold resin and change theamount of NaOH and nickel.In the experiment (3) was
gasified to 650 ºC under the following conditions,
1 mold resin (1.3g)○
2 mold resin +nickel (1.3g+0.1g)○
3 mold resin + NaOH (1.3g+1g)○
4 mold resin + nickel + NaOH (1.3g+0.1g+1g).
○
After the experiment, the product gas was analyzed by agas chromatograph (GC-2014ATF) made by SHIMADZU.
The residue remaining in the reactor was allowed to melt
deposits on a hot stirrer charged with distilled water andstir. The water that used bubbling and stirred wasanalyzed by ion chromatography (DX-120).

3. Results and Discussion
Figure 2(a) and 2(b) are shown the sintering compact
after the experiment by using the mixed molten
carbonate at 530 ºC for 5~10 min. In the case of 10 min,the sintering was broken while the reaction time 5 min,the tantalum was not broken and, able collect from all thesamples. This is considered that if the reaction time was

7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013

long, the carbon contained in the sintered compact isalso gasified.
Inject sample

GC2014-ATFN2Gas bag

NaOH.But the addition of Ni and NaOH could beconfirmed that the production of active hydrogen from
500ºC.We suggested that gasification happened from500 ºC in the gasification of tantalum capacitor, NaOHand nickel in the tantalum capacitor terminal are reacted
as a catalyst.

Heater

8H2O

Thermocouple
Electric heater

Gas trap

Fig.1 Experiment apparatus of stream gasification(a)530℃,5minCollect sintered compacts(b)530℃,10minproduced gas (mmol)

stream6molten carbonate

4sodium hydroxide

2Broken sintered compacts

0HH2
2CH4CH4COCOCO2
CO2

Fig.4 Effect on the product gas of steam, carbonate, andsodium hydroxide (530ºC, reaction time 5 minutes)
Fig.2 Effect of reaction time at 530ºC

Table.1 Halogen concentration of residual substance(a) Stream(b)Sodium hydroxide
Resin remained.

Collect sintered compacts

Halogen concentration of residue (ppm)
FCl
43.42
16.81
Table.2 Composition of resin before and after theexperiment
The result of ultimate analysis (wt%)
CHN
Before
15.94
1.59
0.12
After10.38
1.37
0.00
hydrogen production (mmol)

In the second experiment was carried out when only
steam gasification, the molded resin was left and could
not complete separation (Fig. 3 (a)).If sodium hydroxide
was also used,the mold resin is broken, and sinteredcompact is exposed (Fig. 3 (b)). Figure 4 shows acomparison of the effect on the product gas of steam,carbonate, and sodium hydroxide.From these result, weunderstand that the amount of hydrogen production wassignificantly increases when using NaOH. The CO andCO2 gas are produced OCN epoxy resin which have amain component of the organic matter in the molding
resin and OCN epoxy can react by the water gas shift
reaction . Table 1 show the analysis of the halogen
concentration of residue. From the results we understandthat sodium hydroxide can react on the remaining
residue and was able dehalogenation.

8Resin+Ni+NaOH

6Resin+NaOH

4Resin+Ni
2Resin
0450

500

550

600

650

Temperature (℃）

Fig.5 The amount of hydrogen generation in gasificationof mold resin
Fig.3 The sample collected after the experiment (530ºC,
reaction time 5 minutes)
Table 2 shows the ratio of the mold resin composition
before and after the experiment.Since the carbon ofmold resin before the experiment was about 16%, it wasreduced to 10% after experiments.Therefore, we wereable to confirm the gasification reaction at 530ºC. Figure
5 shows the hydrogen produced in experiment 3. Since
the amount of hydrogen is not increased under 600ºC byusing only stream gasification, we considered that theactive gasification does not occur 500ºC. When using Ni,
the amount of hydrogen is greatly increased comparedwith only water vapor from 550ºC. The gasification ofhydrogen producted was occur from 550ºC when using

4. Conclusions
The tantalum sintering compacts could collect from all
the samples by using NaOH and molten carbonate at
530 ºC for 5 min. The stream gasification was occured at
low temperature because the terminal of Ni in thecapacitor and NaOH were reacted. Therefore, we canexpect, the tantalum metal can separate and collect byusing stream gasification with NaOH.

Reference[1] IR universe,The symbol of conflict metal (2012)
http://iruniv.net/pdf/colum_20120504.pdf[2] Tohru Kamo, Scientific research for promoting
formation of a recycling society, p.4 (2010)

7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013