Applied Energy 100 2012 187 192

7/30/2019 Applied Energy 100 2012 187 192

http://slidepdf.com/reader/full/applied-energy-100-2012-187-192 1/6

Silver recovery and chemical oxygen demand (COD) removal from waste

fixer solutions

Wei-Ting Chen a, Chin-Chi Ma b, Ming-Hsun Lee a, Yung-Chuan Chu a, Lung-Chang Tsai b, Chi-Min Shu b,⇑

a Graduate School of Engineering Science and Technology, National Yunlin University of Science and Technology (YunTech), Douliou, Yunlin 64002, Taiwanb Department of Safety, Health, and Environmental Engineering, YunTech, Douliou, Yunlin 64002, Taiwan

h i g h l i g h t s

" This study focused on the Ag recovery from waste fixer solutions by electrolysis.

" 99.55% of silver recovery was obtained with electric current of 3 A during 2.5 h.

" The purity of silver was 98.62% with electric current of 3 A.

" Higher removal efficiency of COD by employing distillation was obtained.

a r t i c l e i n f o

Article history:

Received 17 February 2012

Received in revised form 24 April 2012

Accepted 8 June 2012

Available online 12 July 2012

Keywords:Silver recovery

Waste fixer solutions

Electrolysis

Chemical oxygen demand (COD)

Distillation

a b s t r a c t

This study focused on the silver recovery from waste fixer solutions by electrolysis under different exper-

imental conditions. During an 8 h electrolysis procedure, the silver recovery efficiencies were 10.57%,

11.75%, 45.5%, 62.68%, and 83.88% for electric currents of 0.1 A, 0.3 A, 0.5 A, 0.7 A, and 0.9 A, respectively.

Thus, the most efficient recovery factor of silver was found for a current of 0.9 A. Additionally, the pH

values of the waste fixer solutions were adjusted prior to treatment by electrolysis, and the silver recov-

ery was 100% for a solution with pH 8 that underwent electrolysis for 8 h at an electric current of 0.9 A.

The recovery efficiency of silver was 88.64% for an electric current of 3 A and a duration of 3.5 h, but therecovery efficiency of silver decreased to 83.72% for an electrolytic time of 6 h. Furthermore, the recovery

efficiency of silver increased to 99.55% with a decreased electrolysis time of 2.5 h when the solution was

adjusted to pH 8 at an electric current of 3 A. These results suggest that the most suitable experimental

conditions were an electric current of 3 A, pH 8, and2.5 h of electrolysis. Thetreated waste fixer solutions

still had high concentrations of chemical oxygen demand (COD) after electrolysis. The addition of 30 mL

of sulfuric acid to 1000 mL of waste fixer solution resulted in a COD removal efficiency of 42%. Further-

more, when the waste fixer solutions were treated by distillation to remove COD, the removal efficiency

of COD was 99.3%. Although a higher COD removal efficiency was obtained by employing distillation, the

cost of the distillation treatment was more expensive.

Ó 2012 Elsevier Ltd. All rights reserved.

1. Introduction

The demand for energy is increasing because of rapid industri-

alization and societal growth. Conventional primary energy

sources, such as coal, oil, and natural gas, have limited reserves

that are not expected to last for an extended period of time. Addi-

tionally, the environmental problems associated with these con-

ventional energy sources continue to affect the global ecosystem.

To reduce fossil fuel consumption and alleviate environmental

problems, renewable energy resources are expected to play a key

role in future energy consumption [1]. There are many previous

studies of energy recovery from waste sources and materials, such

as waste heat [2,3], waste tyres [4], and waste solutions. For each

of these processes, waste energy can be recovered and reused,

and this study evaluates a recovery process to recycle silver from

waste fixer solutions.

Because of their high photosensitivity, beginning in 1837, silver

halides were employed in the photographic fixing process using

ammonium thiosulfate (ATS) and sodium thiosulfate solutions

(STSs) as fixing baths [5]. Because of the extensive usage of silver

halides, photographic manufacturing processes resulted in enor-

mous amounts of waste fixer solutions. According to the disposal

estimation of waste fixer solutions from the Environmental Protec-

tion Administration, Executive Yuan (Taiwan), approximately

36,310 tons of waste fixer solutions are generated per year from

0306-2619/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.apenergy.2012.06.026

⇑ Corresponding author. Tel.: +886 5 534 2601; fax: +886 5 531 2069.

E-mail address: [email protected] (C.-M. Shu).

Applied Energy 100 (2012) 187–192

Contents lists available at SciVerse ScienceDirect

Applied Energy

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / a p e n e r g y

http://dx.doi.org/10.1016/j.apenergy.2012.06.026

mailto:[email protected]


http://www.sciencedirect.com/science/journal/03062619

http://www.elsevier.com/locate/apenergy

http://www.elsevier.com/locate/apenergy

http://www.sciencedirect.com/science/journal/03062619


mailto:[email protected]


7/30/2019 Applied Energy 100 2012 187 192


photographic manufacturing [6]. These waste fixers contain high

levels of silver (Ag), where concentrations are typically in the range

of 5000–10,000 mg/L. Furthermore, the waste fixer solutions con-

tain substantial quantities of components that can be both toxic

and valuable depending on the quality of the raw materials [7].

Thus, for both economic and environmental reasons, it is important

to recover valuable components (such as Ag) from waste fixer

solutions. Conventional fixing of silver compounds (AgX) in photo-

graphic and medical X-ray films has been extensively used by the

photo-industry for more than two centuries. The fixing of silver

halides by thiosulfates and thiocyanates is usually rapid and does

not need any catalytic influence. Silver halides are highly soluble

in these lixiviants and are considered to be thermodynamically

stable at a slightly alkaline pH. The simplified mechanisms for

the dissolution of AgCl in thiosulfate solutions are shown in Eqs.

(1) and (2) [8].

AgClðsÞ þ 2ðNH4Þ2S2O3ðaqÞ () ðNH4Þ3½AgðS2O2ÞðaqÞ þ NH4ClðaqÞ ð1Þ

AgClðsÞ þ 2Na2S2O3ðaqÞ () Na3½AgðS2O2ÞðaqÞ þ NaClðaqÞ ð2Þ

ATS and STS are commonly used as preservatives, hardeners,

and buffers in fixing baths, which perform various functions inthe photographic fixing process [8]. This process leads to waste

fixer solutions that have high levels of silver, which can be recov-

ered using many conventional methods, including electrolysis [9],

oxygenation reduction [10,11], and sulfide precipitation [12]. The

treated waste fixer solutions contain high concentrations of chem-

ical oxygen demand (COD) after electrolysis, so it is necessary to

remove the high COD concentrations before disposing of the solu-

tions. This study evaluates the recovery of Ag from waste fixer

solutions, as well as the removal efficiency of COD from the treated

waste fixer solutions.

2. Experimental

2.1. Materials

The waste fixer solutions, which were obtained from a photo-

graphic shop (Kodak) in Douliou, Yunlin, Taiwan, did not receive

any pre-treatment, such as electrolysis [9], oxygenation, reduction

[10,11], sulfide precipitation [12], or ion exchange [13], and they

were not mixed with any other chemicals. The concentration of

Ag in the waste fixer solutions was measured by Inductively

Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) (Optima,

5100 DV) or Atomic Absorption Spectroscopy (AA) (Perkin Elmer,

5100), and the concentrations of Ag were found to be in the range

of 2700–3300 mg/L. Additionally, the waste fixer solutions con-

tained a variety of organic and inorganic materials, including as

chelating-agents such as EDTA, acetate, thiosulfate, metabisulfite,

and ammonium compounds. These materials account for the high

COD concentration of 88,654 mg/L in the solution, excluding the

concentration of Ag. EDTA and acetate were the primary cause of

the acidic pH of the waste fixer solutions, which had a pH of

6.09.

2.2. Analysis of component elements

The component elements in the waste fixer solutions were ana-

lyzed by ICP-AES or AA, whichwereused to determine the metalion

concentration in the aqueous phase and to analyze the ores. Equal

volumes (10 mL) of the aqueous and organic phases were shaken

at roomtemperature (25 ± 3 °C) for 5 min to ensurecomplete equil-

ibration. The two phases were separated, and a suitable aliquot of

the aqueous phase was assayed for the metal ion concentration.

Three tests indicated that the value of 95% extraction for the metal

ion was associated with a variation coefficient of ±3% [14].

2.3. Electrolysis procedures

Electrolysis was used to recover silver from the waste fixer solu-

tions, where the cathode plate and the anode plate were made of

stainless steel and graphite, respectively. To determine the most

suitable electrolysis efficiency, the electrolysis process was evalu-

ated over a range of settings for a variety of parameters, such as

pH, electric current, and electrolysis time.

0

10

20

30

40

50

60

70

80

90

100

0

500

1,000

1,500

2,000

2,500

3,000

3,500

0 1 2 3 4 5 6 7 8

0.1 A SIC

0.3 A SIC

0.5 A SIC

0.7 A SIC

0.9 A SIC

0.1 A SRE

0.3 A SRE

0.5 A SRE

0.7 A SRE

0.9 A SRE S i l v e r i o n c o n c e n t r a t i o n ( m g / L )

Electrolysis time (h)

R e c o v e r y e f f i c i e n c y ( % )

Fig. 1. The silver recovery from waste fixer solutions by electrolysis with lowelectric currents.

0

10

20

30

40

50

60

70

80

90

100

0

500

1,000

1,500

2,000

2,500

3,000

3,500

0 1 2 3 4 5 6 7 8

pH3 SIC

pH4 SIC

pH5 SIC

pH6 SIC

pH7 SIC

pH8 SIC

pH9 SIC

pH10 SIC

pH3 SRE

pH4 SRE

pH5 SRE

pH6 SRE

pH7 SRE

pH8 SRE

pH9 SRE

pH10 SRE


S i l v e r i o n c o n c e n t r a

t i o n ( m g / L )


Fig. 2. Silver recoveries with an electric current of 0.9 A at various pH values.

0

10

20

30

40

50

60

70

80

90

100

0

500

1,000

1,500

2,000

2,500

3,000

3,500

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

SIC

SRE



S i l v e r i o n c o n c e n t r a t i o n ( m g / L )

Fig. 3. The silver recovery with an electric current of 3 A.

188 W.-T. Chen et al./ Applied Energy 100 (2012) 187–192

7/30/2019 Applied Energy 100 2012 187 192


2.4. Removal efficiency of COD

The COD test is commonly used to indirectly measure the con-centration of organic compounds in a water sample, and it provides

a useful index of the amount of organic pollutants that are present.

Most applications of the COD test are intended to determine the

amount of organic pollutants found in a surface water (e.g., lakes

and rivers), which makes COD a useful measure of water quality.

COD is typically expressed in milligrams per liter (mg/L), which

indicates the mass of oxygen consumed per liter of solution,

although older references may express COD as parts per million

(ppm) [15]. We did not use conventional COD removal methods,

such as activated sludge processes [16], aerobic and anaerobic

treatment processes, or coagulation treatment. Instead, we used

acid leaching and distillation treatments to remove COD.

3. Results and discussion

3.1. Electrolysis of waste fixer solutions at a low electric current

To obtain the proper electric current for electrolysis, 1000 mL of

waste fixer solution was treated at a low electric current. We eval-

uated the process at different electric currents (0.1 A, 0.3 A, 0.5 A,

0.7 A, and 0.9 A), and samples were collected at hourly intervals

throughout the duration of the electrolysis procedure. Following

this procedure, we used the proper electric current to determine

the most suitable pH value for electrolysis by varying the pH of

the waste fixer solution (with set pH values of 3, 4, 5, 7, 8, 9, and

10), where the original pH of the waste fixer solution was 6.

Fig. 1 shows that the recovery of silver increases for a specificelectric current as the electrolysis time is increased. The recovery

efficiencies of silver during the 8 h electrolysis procedure at

0.1 A, 0.3 A, 0.5 A, 0.7 A, and 0.9 A were 10.57%, 11.75%, 45.50%,62.68%, and 83.88%, respectively. These results show that the most

suitable electric current is 0.9 A. We obtained the most suitable pH

value for the waste fixer solutions from the experiment shown in

Fig. 2, which used an electric current of 0.9 A for solutions at varied

pH values. The recovery efficiencies of silver at pH 3, 4, 5, 6, 7, 8, 9,

and 10 were 83.65%, 84.66%, 81.54%, 83.88%, 99.09%, 100%, 98.63%,

and 81.20%, respectively. These results show that the most suitable

pH value is pH 8. These experiments demonstrate that the most

suitable recovery efficiency of silver is 100% at 0.9 A and pH 8.

The recovery efficiency of silver at pH 9 or pH 10 was less than

the recovery efficiency at pH 8 because a portion of the metal ions

were deposited while the pH of the waste fixer solutions was ad-

justed to 9. Furthermore, the phenomenon of metal ion deposition

becomes obvious when the pH value is adjusted to pH 10. Theco-precipitation of metal ions during electrolysis resulted in a

0

10

20

30

40

50

60

70

80

90

100

0

500

1,000

1,500

2,000

2,500

3,000

3,500

0 0.5 1 1.5 2 2.5 3 3.5

SIC

S i l v e r i o

n c o n c e n t r a t i o n ( m g / L )



SRE

Fig. 4. The silver recovery with an electric current of 3 A at pH 8.

0

10

20

30

40

50

60

70

80

90

100

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

0 10 20 30 40 50 60 80 100 1 20 150 180 210 240

SIC

SRE


Electrolysis time (min)

S i l v e r i o n c o n c e n t

r a t i o n ( m g / L )

Fig. 5. The purification of silver by electrolysis with an electric current of 0.9 A.

Fig. 6. The appearance of the silver metal.

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,00090,000

100,000

0 1 2 3 4 5 C O D c o n c e n t r a t i o n ( m g

/ L )

Mass volume (%)

HCl

H2SO4

HNO 3

Fig. 7. The COD removal efficiency of waste fixer solutions with 1–5% of various

acids.

Table 1The COD removal efficiency of waste fixer solutions with 1–5% of various acids.

Acid

volume

(%)

COD concentration

after mixed with

H2SO4 (mg/L)

COD concentration

after mixed with

HNO3 (mg/L)

COD concentration

after mixed with

HCl (mg/L)

0 88,654 88,654 88,654

1 81,693 87,166 83,948

2 65,667 80,130 79,846

3 51,205 74,267 78,897

4 54,332 64,495 77,307

5 53,550 57,850 76,717

W.-T. Chen et al./ Applied Energy 100 (2012) 187–192 189

7/30/2019 Applied Energy 100 2012 187 192


decrease in the recovery efficiency of silver. Conclusively, we can

obtain the most suitable recovery efficiency of silver by employing

these suitable experimental parameters for the electrolysis

procedure.

3.2. Electrolysis of waste fixer solutions at a high electric current (3 A)

We employed a high electric current (3 A) instead of the low

electric currents previously evaluated (0.1 A, 0.3 A, 0.5 A, 0.7 A,

and 0.9 A) to lessen the electrolysis time, as shown in Figs. 3 and4. A maximum silver recovery efficiency of 88.64% was obtained

for the electrolysis procedure with a current of 3 A and a duration

of 3.5 h. The recovery efficiency did not increase with additional

electrolysis time, and the proper electrolysis time is therefore

3.5 h, as shown in Fig. 3. Fig. 4 shows that when we adjusted the

waste fixer solutions to pH 8 and then used an electric current of

3 A, the electrolysis time decreased from 3.5 h to 2.5 h, and the

recovery efficiency of silver increased from 88.64% to 99.55%. Addi-

tionally, the purity of silver was 98.31% and 98.62% for an electric

current of 0.9 A and 3 A, respectively.

3.3. The purification of silver

The silver in the waste fixer solutions formed a metal coating onthe stainless steel plate during the electrolysis procedures, and we

scraped this silver metal from the plate in order to obtain purified

silver after an additional purification procedure. The silver metal

that was scraped off of the plate was dissolved in a high concentra-

tion solution of nitric acid, and we applied an electric current of

0.9 A to obtain high purity silver via electrolysis. Fig. 5 shows that

as the electrolysis time increased, the silver concentration in the

waste fixer solution decreased and the silver recovery efficiency in-

creased. The recovery efficiency of silver reached 98.85% after 3 h

of electrolysis, but then decreased for durations of electrolysis

greater than 3 h. The reason for this decrease in recovery efficiency

is that the stainless steel plate was coated with too much silver

metal to allow for additional silver metal to coat the plate. The pur-

ity of the silver metal reached 99.9% from the purification process,and the appearance of the silver metal is shown in Fig. 6.

Fig. 8. The deposits from waste fixer solutions mixed with H2SO4.

Table 2

The COD removal efficiency of waste fixer solutions mixed with H2SO4 at an electric

current of 10 A.

Electrolysis

time (h)

Without H2SO4 With H2SO4

COD

concentration

(mg/L)

COD

recovery

efficiency

(%)

COD

concentration

(mg/L)

COD

recovery

efficiency

(%)

0 90,313 0 84,196 0

1 65,330 27.6 44,459 47.2

2 58,830 34.8 44,259 47.1

3 55,320 38.7 44,065 47.6

4 52,130 42.2 33,442 60.3

5 49,250 45.4 33,836 59.8

6 45,810 49.2 32,655 61.2

7 46,520 48.5 33,049 60.7

8 47,320 47.6 33,442 60.3

0

10

20

30

40

50

60

70

80

90

100

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

0 1 2 3 4 5 6 7 8

C O D c o n c e n t r a t i o n ( m g / L )


C O D r e m o v a l e f f i c i e n c y ( % )

COD with

H2SO4

COD RE

COD without

H2SO4

COD RE

without H2SO4

with H2SO4

Fig. 9. The COD removal efficiency of waste fixer solutions mixed with H2SO4 with

an electric current of 10 A.

-50

-40

-30

-20

-10

0

10

20

30

40

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

0 1 2 3 4 5 6

COD 5A

COD 7A

COD 8A

COD 10A

COD 15A

COD RE 5A

COD RE 7A

COD RE 8A

COD RE 10A

COD RE 15A


C O D r e m o v a l e f f i c i e n c y ( % )

C O D c o n c e n t r a t i

o n ( m g / L )

Fig. 10. The CODremoval efficiencyof waste fixer solutions mixed with H2SO4 with

various electric currents.


7/30/2019 Applied Energy 100 2012 187 192


3.4. The efficiency of COD removal

Continuous-flow activatedsludge reactorswere usedto treat the

photoprocessing wastewaters from two commonly used photopro-

cesses: Kodak Flexicolor Process C-41 (film processing) and Kodak

Ektacolor Process RA-4 (paper processing). Simulated wastewaters

were fed to laboratory-scale reactors at a loading level of 10% (v/v)

along witha syntheticbase feed. Thebiodegradationof the basefeedwas not affected by the photoprocessing wastewaters. In addition,

more than 36% of the photoeffluent-derived COD was destroyed,

primarily as a result of sulfite and thiosulfate oxidation. Therefore,

the efficiency of COD removal by the continuous-flow activated

sludge reactors was not suitable [17]. Furthermore, Lin and Yang

[18] found that photoprocessing wastewaters that were treated by

an electrochemical method resulted in a high efficiency of COD

removal (approximately95% of COD) butthat thecost of thiselectro-

chemical treatment was too expensive to use. However, we used

acid leaching anddistillation forCOD removal andfound this meth-

od to be an ideal approach to remove COD.

3.4.1. Acid leaching for COD removal

Small volumes (1–5 mL) of various inorganic acids (hydrochlo-

ric acid (HCl), nitric acid (HNO3), and sulfuric acid (H2SO4)) were

added to 100 mL of waste fixer solution in order to remove COD.

Fig. 7 and Table 1 show that the efficiency of COD removal was

the best for the H2SO4 treatment. In addition, the COD concentra-

tion decreased from 88,654 mg/L to 81,693 mg/L after being mixed

with 1 mL of H2SO4 and from 88,654 mg/L to 51,205 mg/L after

being mixed with 3 mL of H2SO4. The suitable efficiency of COD re-

moval was found to be 42.24% for the case where 3 mL of H2SO4

was used. A 1000 mL waste fixer solution that received the addi-

tion of 30 mL of H2SO4 resulted in the deposits shown in Fig. 8,

and the deposits were assessed to be thiosulfate or organic sulfide.

We separated the deposits and the waste fixer solutions beforeconducting electrolysis at an electric current of 10 A. Table 2 and

Fig. 9 show that the efficiency of COD removal froma mixture with

H2SO4 is better than the efficiency of COD removal without H2SO4

because the hydrogen ions in the mixing solutions are affected by

electrolysis. Therefore, the waste fixer solutions mixed with H2SO4

resulted in proper efficiency of COD removal. Furthermore, various

electric currents (5 A, 7 A, 8 A, 10 A, and 15 A) were applied via

electrolysis to remove COD. The proper efficiencies of COD removal

under 5 A, 7 A, 8 A, 10 A, and 15A were 26.94%, 27.12%, 35%,

32.52%, and 11.45%, respectively (see Fig. 10). Most of the waste

fixer solutions would vaporize under an applied current of 15 A,

resulting in the concentration of the organic materials present in

the waste fixer solution. This occurrence resulted in an abnormal

phenomenon, where the efficiency of COD removal did not in-crease with the increased electric currents.

3.4.2. Enhancement of concentration by distillation for COD removal

After the silver recovery processes, 1000 mL of treated waste

fixer solution was distilled and concentrated using a condenser

for COD removal, and the distillation water and waste sludge were

separated, as shown in Fig. 11. The COD concentration of the waste

fixer solutions decreased from 88,657.3 mg/L to 579.9 mg/L, and

the efficiency of COD removal was 99.3%, as shown in Table 3.

4. Conclusions

Samples of waste fixer solution (1000 mL) with a silver concen-

tration of 3000 mg/L underwent an 8 h electrolysis procedure at

low electric currents. For an electric current of 0.9 A, the silver

recovery was 83.88%, which was better than the silver recovery

for any of the other electric currents that were studied (0.1 A,

0.3 A, 0.5 A, and 0.7 A). In addition, when the solution was

adjusted to pH 8 and then underwent 8 h of electrolysis at an

electric current of 0.9 A, the silver recovery increased from

83.88% to 100%. When the electric current was increased to

3 A for a 3.5 h period, the silver recovery was 88.64%. Addition-

ally, when the solution was adjusted to pH8 and an electric cur-

rent of 3 A was applied for 2.5 h, the silver recovery reached99.55% purity. The purity of silver was found to be 98.31% and

98.62% for an electric current of 0.9 A and 3 A, respectively, not-

withstanding the recovered silver, which could obtain 99.9%

purity after being dissolved in nitric acid and undergoing elec-

trolysis. The proposed flow chart for the treatment of waste

fixer solutions is shown in Fig. 12.

The efficiency of COD removal for waste fixer solutions mixed

with H2SO4 (100 mL of waste fixer solution and 1 mL of

H2SO4) is better than the efficiency of COD removal of waste

fixer solutions mixed with other acids. The COD concentration

decreased from 88,654 mg/L to 51,205 mg/L after being mixed

with 3 mL of H2SO4. The proper efficiency of COD removal for

the 3 mL H2SO4 mixture was 42.24%.

The waste fixer solutions mixed with H2SO4 resulted in a properefficiency of COD removal. Electric currents at 5 A, 7 A, 8 A, 10 A,

and 15 A were applied during an electrolysis procedure to

remove COD, and an electric current of 8 A provided the most

suitable COD removal efficiency.

Higher COD removal efficiencies were obtained by employing

distillation, but the cost of the distillation treatment is more

expensive.

Fig. 11. The distillation water and waste sludge following distillation.

Table 3

The COD removal efficiency by distillation of the waste fixer solution.

COD concentration (mg/

L)

COD removal efficiency

(%)

Waste fixer

solution

88,657.3 0

Cooling water 579.9 99.3

W.-T. Chen et al./ Applied Energy 100 (2012) 187–192 191

7/30/2019 Applied Energy 100 2012 187 192


Acknowledgements

This study was guided by the late Professor Hung-Yuan Fang

and was carried out by his team of environmental and microbio-

logical researchers. This study could not have been accomplishedwithout his meticulous instruction and positive feedback.

References

[1] Wang J, Zhao P, Niu X, Dai Y. Parametric analysis of a new combined cooling,

heating and power system with transcritical CO2 driven by solar energy. Appl

Energ 2012;94:58–64.

[2] Chae SH, Kim SH, Yoon SG, Park S. Optimization of a waste heat utilization

network in an eco-industrial park. Appl Energ 2010;87:1978–88.

[3] Hsu GT, Huang GY, Chu HS, Yu B, Yao DJ. Experiments and simulations on low-

temperature waste heat harvesting system by thermoelectric power

generators. Appl Energ 2011;88:1291–7.

[4] Sharma VK, Fortuna F, Micarini M, Berillo M, Cornacchia G. Disposal of waste

tyres for energy recovery and safe environment. Appl Energ 2000;65:381–94.

[5] Eaton GM. The chemistry of color and black-and-white photography. New

York, USA: Morgan and Morgan, Inc., Publishers; 1965.

[6] http://waste.epa.gov.tw/prog/NewsZone/news_browse.asp?nid=1171.

[7] Othman N, Mat H, Goto M. Separation of silver from photographic wastes by

emulsion liquid membrane system. J Membrane Sci 2006;282:171–7.

[8] Adani KG, Barley RW, Pascoe RD. Silver recovery from synthetic photographic

and medical X-ray process effluents using activated carbon. Miner Eng

2005;18:1269–76.

[9] Chatelut M, Gobert E, Vittori O. Silver electrowinning from photographic fixing

solutions using zirconium cathode. Hydrometallurgy 2000;54(2–3):79–90.

[10] Han Z, Shen G, Lu W. Research on the technique of recovering Ag and

producing nanometer-size Ag powders from colorprint fixation rinsing waste

water. Precious Metals 2003;24(3):45–9 [in Chinese, with English abstract].[11] Jiang G. Recovery of silver from spent fixing bath with organic acid (Ar(OH)3

COOH). Hydrometallurgy of China 2001;20(2):88–91 [in Chinese, with English

abstract].

[12] Li G, Li YS, Gao H. Probing on the transacting methods of waste solutions in

printing and processing of color photographic materials. Inform Rec Mater

2005;6(2):27–30 [in Chinese, with English abstract].

[13] Gnusin NP, Berezina NP, Dyomina OA, Kononenko NA. Physico-chemical

principles of testing ion-exchange membranes. Elektrokhimiya (Russ J

Electrochem) 1996;32:173.

[14] Skoog DA, West DM, Holler FJ, Crouch SR, Kinsel GR. Fundamentals of

analytical chemistry. 8th ed. Belmont, California, USA: Brooks/Cole; 2003.

[15] http://en.wikipedia.org/wiki/Chemical_oxygen_demand.

[16] Pavlostathis SG, Maeng SK. Aerobic biodegradation of a silver-bearing

photoprocessing wastewater. Environ Toxicol Chem 1998;17:617–24.

[17] Pavlostathis SG, Morrison D. Response of continuous-flow activated sludge

reactors to photoprocessing wastewaters. Water Res 1994;28(2):269–76.

[18] Lin SM, Yang HM. Treatment of photographic effluents by electrochemical

method. Environ Eng Sci 1997;14(4):201–6.

Waste fixer solutions

Electrolysis(Deposition: Ag2S)

pH=6.09, Ag=2,700–3,300 mg/L,

COD=88,654 mg/L

Annealing processWaste solution after

electrolysis

Dissolved in

HNO3

Crude Ag(Purity: 98.32%)

Rising to 1,000oC,

during 3 hDistillation

(The removal efficiencyof COD: 99.3%)

Current: 3 A

Purified Ag(Purity: 99.9%)

Electrolysis

(Current: 0.9 A)

Fig. 12. The proposed flow chart for the treatment of waste fixer solutions.


http://waste.epa.gov.tw/prog/NewsZone/news_browse.asp?nid=1171

http://en.wikipedia.org/wiki/Chemical_oxygen_demand

http://en.wikipedia.org/wiki/Chemical_oxygen_demand

http://waste.epa.gov.tw/prog/NewsZone/news_browse.asp?nid=1171

Documents

Applied Energy 100 2012 187 192