2. A.D.. Bas et al. / Hydrometallurgy 121–124 (2012) 22–27 23
further treatment by ion exchange or metallic replacement to
generate environmentally acceptable effluents (i.e. b5 mg/L Ag)
(KODAK, 1999a; Yazici et al., 2011). Metallic replacement based on
the use of more active metals such as Fe, Al, Zn and Cu than silver is an
effective method for the recovery of silver (Aktas, 2008; Bober et al.,
2006; Kırmızıkan et al., 2006). However, it introduces metal
impurities (e.g. Fe2+, Al3+, Zn2+, Cu2+) to the effluent and silver
sludge produced is not pure and needs costly refinement processes
(KODAK, 1999a). Several chemicals including sodium sulphide
(Na2S), sodium dithionate (Na2S2O4), potassium borohydride
(KBH4) and 2,4,6-trimercapto-s-triazine (TMT; C3N3S3
3−) have been
used as precipitating agents to recover silver from waste photo-processing
solutions (Blais et al., 2008; KODAK, 1999b; Rivera et al.,
2007; Yazici et al., 2011; Zhouxiang et al., 2008). Silver can be readily
recovered from the waste solutions by sulphide precipitation leading
to the effluent silver levels as low as 0.1–1 mg/L. However, careful
control of precipitation process and sulphide dosing are essential to
prevent the release of noxious hydrogen sulphide gas (H2S) (KODAK,
1999a). Despite its relatively high cost and fineness of precipitates
with potential filtering problems, TMT appears to be a promising
agent for the recovery of silver since it is effective with a low labour
cost, easy control of operation and relatively low toxicity (Bober et al.,
2006; Yazici et al., 2011).
Hydrogen peroxide with oxidising and reducing properties under
suitable conditions is often regarded as a green chemical with no
hazardous by products since it decomposes only into oxygen and water
(Eq. (3)) (FMC, 2002; Yazıcı and Deveci, 2010). Reduction of silver ion
to metal by hydrogen peroxide appears to be thermodynamically
feasible (Eq. (4)). Furthermore, inorganic compounds e.g. thiosulphate
and sulphite, and organic compounds e.g. formaldehyde and hydroqui-none,
which are abundantly present in the photoprocessing effluents
(Yazici et al., 2011), can be readily destroyed by hydrogen peroxide (e.g.
Eqs. (5), (6)) (Jones, 1999; US Peroxide, 2011). These environmental
and technical attributesmake hydrogen peroxide a potential alternative
for the treatment of photoprocessing effluents.
H2O2→H2O þ 1=2O2ðgÞ ð3Þ
2Agþ þ H2O2→2Ag0 þ2 Hþ þ O2 g ð Þ ΔG293 ð ¼ −20:3 kJ=molÞ ð4Þ
2S2O3
2− þ H2O2 þ 2 Hþ→S4O6
2−
þ 2H2O ΔG293
ð ¼ −342:7 kJ=mol; pH 4–8Þ ð5Þ
S2O3
2− þ 4H2O2 þ 2OH−→SO4
2−
þ 5H2O ΔG293 ð ¼ −1307 kJ=mol; > pH 8Þ: ð6Þ
In this study, the treatment of X-ray film processing effluents by
hydrogen peroxide to recover silver was investigated. Effect of
concentration of hydrogen peroxide (5.8–51.6 g/L H2O2) and pH
(4.2–7.0) on the rate and extent of the recovery of silver were studied
within a full factorial design (42). Furthermore, the influence of the
addition of ethylene glycol on silver recoverywas also examined. Silver
precipitates were characterised by chemical analysis, SEM–EDS and
XRD to identify the nature of precipitates and provide an insight into the
precipitation process.
2. Experimental
2.1. Effluent sample and reagents
A sample of X-ray film processing effluent obtained from Farabi
Hospital (Karadeniz Technical University, Trabzon, Turkey) was used in
this study. The effluent sample was characterised to contain 1.1 g/L Ag,
17 g/L SO4
2− and 113 g/L S2O3
2− at pH 4.2. Reagent grade sodium
hydroxide (NaOH) and hydrogen peroxide (H2O2, 35% w/w) were used
to prepare test solutions using deionised-distilled water. Ethylene
glycol (C2H6O2, ≥99%) was also tested to stabilise hydrogen peroxide.
2.2. Precipitation tests and analytical methods
In the current study, the experiments were designed by using a
full factorial design (42) (Montgomery, 2001) to investigate the
effects of concentration of hydrogen peroxide (5.8–51.6 g/L H2O2)
and pH (4.2–7) on the recovery of silver. The range of concentration
of hydrogen peroxide was determined by the preliminary tests and
theoretical calculations based on silver and thiosulphate content of
the effluent sample. Factors and their levels are shown in Table 1.
Furthermore, the addition of ethylene glycol (0.5–10 mL) on the
recovery of silver was also investigated at pH 4.2 and 22.4 g/L H2O2.
Precipitation tests were carried out in 50-mL Erlenmeyer flasks. pH
of the waste solution was, if required, adjusted using 4 M NaOH before
the addition of hydrogen peroxide (35% w/w). The flasks were then
placed on a reciprocal shaker operating at 140 min−1. Due to the
exothermic nature of the reactions, hydrogen peroxide was added at a
predetermined rate of 0.5 mL per 1.5 min unless otherwise stated. Over
the reaction period, 5-mL aliquotswere removed at preset intervals and
filtered through 0.45 μm cellulose nitrate filters. These samples were
then used for the analysis of residual silver (Ag) and sulphate (SO4
2−).
Silver was analysed using an atomic absorption spectrophotometer
2−) of the
(AAS; PerkinElmer AAnalyst 400). Thiosulphate content (S2O3
effluent was determined by iodometric titration (Jeffery et al., 1989)
while sulphate (SO4
2−) in samples was monitored colorimetrically using
a filter photometer (Palintest 5000) at a wavelength of 520 nm. Due to
the interference by the intermediate sulphur compounds and the res-idual
H2O2 the concentration of thiosulphate was not monitored over the
reaction period. The statistical analysis of the experimental data based on
ANOVA was performed using Minitab statistical software (2004).
2.3. Characterisation of silver precipitates
A waste solution with a high silver content (4.5 g/L) was used to
obtain sufficient amount of precipitate for chemical and mineralogical
analysis. Precipitates were collected via filtration (0.45 μm, cellulose
nitrate filter) and washed twice with deionised-distilled water prior to
drying at 105 °C for 6 h. Dried precipitates were fixed on conductive
carbon tabs and examined under a Scanning ElectronMicroscope (SEM)
(Zeiss EVO LS10) coupled with an Energy Dispersive Spectrometry
(EDS) unit. X-ray diffraction (XRD) analyses of the precipitates were
carried out using a Rikagu D/max-IIIC X-ray diffractometer, operating
with Cu–Kα1 radiation source (λ=1.54059 Å) at 40 kV and 30 mA. The
sample was scanned over a 2θ range of 5–80° with a 0.005° step size.
Chemical analysis of the precipitate sample was also undertaken by hot
aqua-regia digestion followed by the spectrophotometric finish.
3. Results and discussion
3.1. Kinetics of silver precipitation
Kinetics of precipitation of silver by hydrogen peroxide (34 g/L)
was initially determined from the as-received photoprocessing waste
solution (pH 4.2). Fig. 1 illustrates that it is a fast reaction as the
Table 1
Factors and their levels adopted for the experimental design.
Parameters Levels
1 2 3 4
(A) H2O2 (g/L) 5.8 22.4 37.6 51.6
(B) pH 4.2a 5 6 7
a Original pH of the solution (no addition of NaOH).
3. 24 A.D.. Bas et al. / Hydrometallurgy 121–124 (2012) 22–27
precipitation of 77% Ag already occurred within 5 min under these
conditions. Silver recovery remained at these levels over an extended
period of 60 min. with the indication of the completion of the
reaction. Formation of sulphate through the oxidation of thiosulphate
was also monitored (Fig. 1). A substantial increase in the sulphate
concentration from 17.4 g/L to 71.1 g/L was recorded over the
reaction period of 60 min. This suggests that hydrogen peroxide is
mainly consumed via the oxidation of thiosulphate present in the
waste solution. During the treatment, pH tended to increase with a
final pH of 5.22, which is consistent with Eq. (5) (Jones, 1999).
Preliminary tests indicated that the reactions involved in the
hydrogen peroxide treatment of the waste solution are highly
exothermic in nature (e.g. ΔH293=−74.1 kcal/mol for Eq. (5)) with
the generation of copious amount of heat. Decomposition rate of
hydrogen peroxide was reported to increase rapidly with increasing
temperature (Yazıcı and Deveci, 2010) resulting in excessively high
consumption of hydrogen peroxide. Therefore, the tests were per-formed
to monitor the evolution of temperature at different rates of
addition of hydrogen peroxide (Fig. 2). It can be deduced fromFig. 2 that
dosing of hydrogen peroxide is required to control the temperature.
Accordingly, an addition rate of 0.5 mL H2O2 per 1.5 min was selected
for the precipitation tests.
3.2. Effect of concentration of hydrogen peroxide and pH
A full factorial design approachwas adopted to evaluate the effect of
initial concentration of hydrogen peroxide (5.8–51.6 g/L H2O2) and pH
(4.2–7) on the precipitation of silver. The results are presented in
Table 2. Recovery of silver was found to depend strongly on the
concentration of H2O2. High silver recoveries (≥95%) were achieved at
H2O2 concentrations of≥37.6 g/L,which is considerably higher than the
stoichiometric requirement for the recovery of silver (Eq. (4)) appar-ently
due to the concurrent oxidation of thiosulphate. An increase in pH
was observed to improve the precipitation of silver, which was evident
particularly at low concentrations of H2O2 (Table 2). To illustrate, the
recovery of silver was enhanced by 34% with increasing the initial pH
from4.2 to 7 at a H2O2 of 5.8 g/Lwhile the corresponding increase in the
silver recovery was 21% and only b2% at 22.4 and ≥37.6 g/L H2O2,
respectively. pH was noted to deviate from the initially set values
towards neutral/alkaline region (Table 2).
The formation of sulphate due to the oxidation of thiosulphate
was also monitored during the precipitation tests (Fig. 3). The
concentration of sulphate in solution was determined to depend
essentially on the concentration of H2O2 with no marked effect of pH.
The oxidation of thiosulphate into sulphate (Eqs. (5), (7)–(9)) was
reported to proceed through the formation of intermediates such as
tetrathionate (S4O6
2−) (Eq. (5)), trithionate (S3O6
2−) (Eq. (7)) and
2−) (Eq. (8)) (Solvay Interax, 2001). Although
sulphite (SO3
tetrathionate is the primary reaction product at low concentrations
of H2O2, the formation of the intermediates and sulphate increases
with increasing the concentration of H2O2 (Fig. 3). The presence of
metals catalyses the conversion of thiosulphate by hydrogen peroxide
into sulphate (Jones, 1999; US peroxide, 2011).
S4O2−
6
þ 3H2O2→S3O2−
6
þ SO2−
4
þ 2H2O þ2 Hþ ð7Þ
S3O6
2− þ H2O2 þ H2O→3SO3
2− þ 4 Hþ ð8Þ
SO2−
3 þ H2O2→SO2−
4 þ H2O: ð9Þ
Statistical assessment of the results was carried out by the analysis
of variance (ANOVA) (Table 3). P values were determined for the
parameters tested. The P value shows the probability that the test
statistic will take on a value that is at least as extreme as the observed
value of the statistic when the null hypothesis (H0) holds true
(Montgomery, 2001). In this respect, the calculated P values (Table 3)
confirmed that the effect of concentration of H2O2 in the range tested
was statistically highly significant even at 99.9% (α=0.001) confi-dence
level while pH was not a significant factor under these
conditions. Statistical analysis of the data also indicated that the
contributions of H2O2 concentration and pH to the response i.e. silver
Fig. 1. Kinetics of the precipitation of silver from waste X-ray solutions (34 g/L H2O2,
pH 4.2).
Fig. 2. Temperature profiles at different rates of H2O2 addition (volume of waste
solution: 50 mL).
Table 2
Recovery of silver from the waste solution under different conditions of pH and
hydrogen peroxide concentration (addition rate: 0.5 mL H2O2 per 1.5 min; precipita-tion
time: 45 min).
Exp. no. H2O2 (g/L) pH Ag recovery (%) Final pH
1 5.8 4.2a 22.7 5.56
2 5.8 5 35.2 7.77
3 5.8 6 53.4 8.30
4 5.8 7 79.1 8.28
5 22.4 4.2a 63.4 7.08
6 22.4 5 71.5 7.73
7 22.4 6 75.4 7.92
8 22.4 7 84.5 8.20
9 37.6 4.2a 94.5 7.00
10 37.6 5 95.9 7.64
11 37.6 6 96.1 7.87
12 37.6 7 96.5 8.04
13 51.6 4.2a 100 5.22
14 51.6 5 99.9 6.15
15 51.6 6 99.0 6.52
16 51.6 7 99.6 8.27
a Original pH of the solution. No addition of NaOH.
4. A.D.. Bas et al. / Hydrometallurgy 121–124 (2012) 22–27 25
recovery were 77.3% and 10.1%, respectively (Table 3). Contribution
values also reflect the relative importance of each parameter tested.
Fig. 4 illustrates the main effects plots based on the mean values
for the concentration of H2O2 and pH showing the silver recovery at
each level of these factors as if they are independent. This plot
confirms the positive effect of increasing the concentration of H2O2
and pH in the range tested. The surface plot of silver recovery (%)
versus the levels of H2O2 concentration and pH was also presented in
Fig. 5 to depict the interaction effects of these parameters on the
response. Accordingly, the effect of pH on the precipitation of silver
was discernible only at low levels (1 and 2) of H2O2 (i.e. 5.8–22.4 g/L)
while the most significant enhancement in the recovery of silver was
achieved by increasing H2O2 concentration from 5.8 g/L to 37.6 g/L at
all levels of pH tested.
Despite its great potential with technical and environmental
benefits, the utilisation of hydrogen peroxide in the treatment of
waste photographic solutions has appeared to receive limited interest
with no detailed data being available. Rabah et al. (1989) investigated
the acid and alkaline treatment of spent colour-photography solutions
to obtain a silver sludge followed by its thermal treatment (at 980 °C) to
produce silver metal. They also tested the addition of H2O2 (74 mL of
30% H2O2 by volume per litre of waste solution) in a single experiment
and did not provide data for silver recovery (though it was assumed to
be 89% in their cost analysis). Based on the yield of silver sludge, these
investigators also provided a cost analysis and claimed that the acid
treatment by a mixture of sulphuric and nitric acids wasmore effective
than H2O2 and alkaline treatments. However, it appeared that they did
not consider the factors such as neutralisation of the acidic effluents and
the formation of hazardousNOx gases in the acid treatment. In an earlier
patent, Daignault et al. (1982) proposed the treatment of waste
photographic solutions with a mixture of peroxide and ozone to
destroy the complexing agents (EDTA, NTA and thiosulphate) thereby
recovering/removing the heavy metals present. They also demonstrat-ed
that 91% of silver could be recovered with the addition of 10–20%
H2O2 (using 70% H2O2 solution) by volume of the waste solution at pH
4.5 followed by increasing pH to 9.5 by the addition of NaOH. They also
showed that further treatment of the effluents with ozone and then
Na2S were required to achieve high levels (≥98%) of recovery/removal
of Ag, Cd, Fe and Pb.
3.3. Effect of addition of ethylene glycol
Hydrogen peroxide is relatively an expensive reagent and has
inherently low stability in that its catalytic decomposition occurs in the
Fig. 3. Initial and final concentrations of sulphate in solution at different concentrations
of hydrogen peroxide (as the mean of data obtained at different pHs tested with error
bars showing±standard deviation).
Table 3
Results of analysis of variance (ANOVA) for the effect of hydrogen peroxide
concentration and pH.
Source of
Degree of
Sum of
Mean
F value P value Contribution
deviation
freedom
squares
squares
(%)
(A) H2O2 (g/L) 3 6971.8 2323.9 18.41 0.000 77.3
(B) pH 3 907.1 302.4 2.39 0.136 10.1
Residual error 9 1136.2 126.2 12.6
Total 15 9015.1 100
Fig. 4. Effect of concentration of hydrogen peroxide (a) and pH (b) at four levels.
Fig. 5. Surface plot of silver recovery as a function of levels of H2O2 concentration and pH.
5. 26 A.D.. Bas et al. / Hydrometallurgy 121–124 (2012) 22–27
presence of metal ions and solids, and at high temperatures and pHs
(Yazıcı and Deveci, 2010). The severe detraction to hydrogen peroxide
treatment is therefore its high consumption. Rabah et al. (1989) found
that H2O2 treatment had the highest reagent cost compared with acid
and alkaline treatments. In this study, the effect of the addition of
ethylene glycol was examined to reduce the consumption of hydrogen
peroxide per silver recovery. Fig. 6 illustrates a 1.3 to 18.7%
improvement in the recovery of silver with increasing the addition of
ethylene glycol from 0.5 to 10mL. This improvement in the silver
recovery can be attributed to the stabilising effect of ethylene glycol on
hydrogen peroxide apparently mitigating its decomposition during the
precipitation process. Mahajan et al. (2007) also reported the stabilising
effect of ethylene glycol for hydrogen peroxide during the leaching of
chalcopyrite at elevated temperatures. They demonstrated that the
addition of ethylene glycol significantly slowed down the decomposi-tion
of hydrogen peroxide i.e. the complete loss of H2O2 even after 2 h
compared with only 25% loss (after 4 h) in the presence of 8 mL/L
ethylene glycol.
3.4. Characterisation of silver precipitates
Chemical and mineralogical characterisations of silver precipitates
were performed to provide an insight into the precipitation process.
Silver content of the precipitate was determined to be 65.1%. SEM
studies showed that the silver precipitate, which was finely grained,
was composed of silver and sulphur as the elemental phases present
(Fig. 7). Fig. 7 also illustrates a typical EDS profile where the chemical
composition of the precipitate was determined to be 86.5% Ag and
13.5% S, which is analogous to silver sulphide (Ag2S; 87.1% Ag). X-ray
diffraction pattern of the precipitate sample confirmed the presence
of silver sulphide, metallic silver and elemental sulphur with the
former being the most abundant silver phase (Fig. 8). These findings
suggest that silver is precipitated from the waste solution mainly in
the form of silver sulphide (Ag2S). A chemical simulation and reaction
software (HSC Chemistry, 2011) with extensive thermochemical data
base was exploited to identify the thermodynamically feasible
reactions (Eqs. (10)–(14)) for the precipitation of silver from such a
waste solution.
ð Þ3−
2Ag S2O3
2
þ H2O2 þ 2 Hþ→2Ag0 þ 2S4O2−
6
þ 2H2O ðΔG293 ¼ −96:2 kcal=molÞ ð10Þ
ð Þ
6Ag S2O3
2
3− þ 13H2O2 þ6 Hþ→3Ag2S þ 5S4O6
2− þ SO4
2−
þ 16H2O þ 6O2 ΔG293 ð ¼ −492:8 kcal=molÞ ð11Þ
ð Þ
4Ag S2O3
2
3− þ 4H2O2 þ4 Hþ→2Ag2S þ S4O6
2− þ 3SO4
2−
þ 7 S0 þ 6H2O þ 4O2 ΔG293 ð ¼ −48:4 kcal=molÞ ð12Þ
6S2O3
2− þ 6H2O2→S2− þ 2S4O6
2− þ 3SO4
2− þ 6H2O
ΔG293 ð ¼ −415:0 kcal=molÞ
ð13Þ
ð Þ
2Ag S2O3
2
3− þ S2−→Ag2S þ 4S2O3
2−
ΔG293 ð ¼ −43:8 kcal=molÞ:
ð14Þ
Rabah et al. (1989) proposed that the oxidising reagents e.g. HNO3
under acidic conditions attack thiosulphate leading to the formation
of sulphate, elemental sulphur or polysulphates. Furthermore, these
investigators mooted that, in addition to these sulphur species,
hydrogen sulphide may also form during the acid and peroxide
treatment, and reacts with the liberated silver to yield insoluble silver
sulphide. This was consistent with their XRD analysis of the silver
sludge in which silver sulphide (Ag2S) and halide (AgBr) are the main
phases identified. It may be relevant to note that, in the current study,
the treatment of the silver precipitate by hot concentrated nitric acid
resulted in a fine residue, which was also examined under SEM–EDS
and determined to be AgCl (not shown). Silver halides (e.g. AgCl and
Fig. 6. Effect of the addition of ethylene glycol on the recovery of Ag from the as-received
waste solution (pH 4.2) at a H2O2 concentration of 22.4 g/L.
20
15
10
5
0
S
S
Ag
Ag
2 4 6
Fig. 7. SEM image of the silver precipitate with EDS profile indicating the presence of silver sulphide.
6. A.D.. Bas et al. / Hydrometallurgy 121–124 (2012) 22–27 27
AgBr) would form provided that thiosulphate was extensively
decomposed at sufficiently high concentrations of hydrogen peroxide.
The reagent cost based on the data (i.e. 37.6 g/L H2O2, 95% Ag
recovery) obtained in the current studywas estimated to be ~$63/m3 of
the effluent corresponding to ~$61/kg of silver recovered at an effluent
concentration of 1.1 g/L Ag and a H2O2 (50%w/w) price of $911/m3. It is
pertinent to note that the effluent sample used in the current study is
relatively lean in silver content and the reagent costwill be considerably
reduced with an increase in the silver content of the effluent. In the
current study, ethylene glycol was used as a stabiliser to mitigate the
catalytic decomposition of H2O2 and an improvement in the recovery of
silver at the same level of H2O2 was achieved. However, this
improvement will not compromise its use due to its addition at high
concentrations (i.e. 20% v/v), which prohibitively increases (e.g. by up
to 8-fold) the reagent costs for the treatment process. Further treatment
of the silver precipitate obtained in the peroxide process is also required
to produce metallic silver. In this regard, Rabah et al. (1989) proposed
the thermal treatment of the silver sludge containing silver as sulphide
and halide at 980 °C to yield metallic silver with a purity of 99.8%.
4. Conclusions
This study has demonstrated the treatment of the waste X-ray film
processing solutions by hydrogen peroxide for the recovery of silver.
Kinetics tests have shown that the precipitation of silver from the
waste solution is a rapid process, but, highly exothermic in character
with the generation of large amount of heat presumably due to the
side reactions i.e. the concomitant oxidation of thiosulphate. Dosed
addition of hydrogen peroxide was found to be required to control
the temperature. A full factorial design (42) for the factors, H2O2
concentration and pH was developed for the experiments. The
concentration of hydrogen peroxide (5.8–51.6 g/L H2O2) was identi-fied
to be the most significant parameter affecting the extent of silver
recovery as verified by the statistical analysis of data. Increasing pH
(4.2–7) appeared to improve the recovery of silver discernibly at low
levels of H2O2. The addition of ethylene glycol (0.5–10 mL) was
shown to enhance the silver recovery apparently due to its stabilising
effect on hydrogen peroxide. Characterisation studies have revealed
that silver is precipitated as fine grains predominantly in the form of
silver sulphide. It can be inferred from this study that hydrogen
peroxide as a green chemical is potentially a suitable reagent for the
treatment of X-ray photoprocessing effluents allowing the recovery of
silver as well as the removal of thiosulphate and possibly other
constituents present.
Acknowledgement
The authors would like to express their sincere thanks and
appreciations to the Research Foundation of Karadeniz Technical
University for the financial support (Project no: 2006.112.008.1) and
to Mr. Fatih Erdemir (Dept. of Metallurgical & Materials Eng., KTU) for
SEM–EDS analysis.
References
Aktas, S., 2008. Silver recovery from silver-rich photographic processing solutions by
copper. Can. Metall. Q. 47 (1), 37–43.
Baş, D., 2009. Recovery of silver from waste X-ray film solutions by precipitation. BSc
Thesis, Karadeniz Technical University, Trabzon, Turkey, 54 p. (in Turkish).
Blais, J.F., Djedidi, Z., Cheikh, R.B., Tyagi, R.D., Mercier, G., 2008. Metals precipitation from
effluents: review. Pract. Period.Hazard. ToxicRadioact.WasteManage. 12 (3),135–149.
Bober, T.W., Vacco, D., Dagon, T.J., Fowler, H.E., 2006. Treatment of photographic
wastes. In: Wang, L.K., Hung, Y.-T., Lo, H.H., Yapijakis, C. (Eds.), Hazardous
Industrial Waste Treatment. CRC Press, pp. 361–408.
Butterman,W.C., Hilliard, H.E., 2005. Silver. U.S. Geological Survey (USGS), Reston, Virginia.
HSC Chemistry, 2011. Chemical Reaction and Equilibrium Software, v. 7.18. Outotec
Research Oy.
Daignault, L.G: Schiller, E.E., 1982. Removal of complexed heavy metals from waste
effluents, United States Patent, Patent no: 4332687.
FMC, 2002. Hydrogen peroxide technical bulletin. FMC Corporation, Pennsylvania. 30 pp.
GMSF, 2011. World Silver Survey: A Summary of the Report. The Silver Institute. 11 pp.
Jeffery, G., Bassett, J., Mendham, J., Denney, R., 1989. Vogel's Textbook of Quantitative
Chemical Analysis, fifth ed. John Wiley & Sons Inc., New York.
Jones, C.W., 1999. Applications of hydrogen peroxide and derivatives. RSC Clean
Technology Monographs. The Royal Society of Chemistry, Cambridge, UK. 282 pp.
Kırmızıkan, E., Güldan, G., Yazıcı, E.Y., Alp, İ., Deveci, H., Duran, C., Celep, O., 2006.
Recovery of silver from waste photographic solutions by cementation. In: Demir, C.,
Yilmaz, A.O. (Eds.), Doğu Karadeniz Bölgesi Maden Kaynaklarının Değerlendirilmesi
Sempozyumu, 14–16 Sept., Trabzon, Turkey, pp. 309–311 (in Turkish).
KODAK, 1996. The Regulation of Silver in Photographic Processing Facilities. Publication
no: J-214 Eastman Kodak Company. Available at: http://www.kodak.com (Retrieval
date: July 2003).
KODAK, 1999a. Recovering Silver from Photographic Processing Solutions. Publication
no: J-215 Eastman Kodak Company. Available at: http://www.kodak.com (Retrieval
date: July 2003).
KODAK, 1999b. The Technology of Silver Recovery for Photographic Processing Facilities.
Publication no: J-212 Eastman Kodak Company. Available at: http://www.kodak.com
(Retrieval date: July 2003).
Mahajan, V., Misra, M., Zhong, K., Fuerstenau, M.C., 2007. Enhanced leaching of copper
from chalcopyrite in hydrogen peroxide–glycol system. Miner. Eng. 20 (7), 670–674.
Minitab, 2004. Statistical software. Evaluation Version 14.12.0. Minitab Inc., USA.
Montgomery, D.C., 2001. Design and Analysis of Experiments, fifth ed. John Wiley &
Sons Inc., New York.
Nakiboğlu, N., Toscalı, D., Nişli, G., 2003. A novel silver recovery method from waste
photographic films with NaOH stripping. Turk. J. Chem. 27, 127–133.
US Peroxide, 2011. Reduced sulfur compound treatment with hydrogen peroxide
Avaliable at: www.h2o2.com (Retrival date: Oct. 2011).
Rabah, M.A., El Barawy, K.A., Aly, F.H., 1989. Silver recovery from spent colour-photography
solutions. Int. J. Miner. Process. 26, 17–27.
Rivera, A., Roca, M., Cruells, F., Patiño, E. Salinas, 2007. Study of silver precipitation in
thiosulfate solutions using sodium dithionite. Application to an industrial effluent.
Hydrometallurgy 89, 89–98.
Solvay Interax, 2001. Hydrogen peroxide for controlling reduced sulfur compounds
Available at: http://www.solvayinterox.com.au/MSDS/Contolling%20reduced%20suphur%
20species.pdf (Retrieval date: July 2011).
USEPA, 1991. Guides to Pollution Prevention—The Photo-processing Industry. EPA/
625/7-91/012. United States Environmental Protection Agency, Office of Research
and Development, Washington.
Yazıcı, E.Y., Deveci, H., 2010. Factors affecting decomposition of hydrogen peroxide. XII.
International Mineral Processing Symposium (IMPS), 6–8 October, Kapadokya,
Turkey, pp. 609–616.
Yazici, E.Y., Deveci, H., Yazici, R., 2011. Recovery of silver from X-ray film processing
effluents using trimercapto-s-triazine (TMT). Sep. Sci. Technol. 46 (14), 2231–2238.
Zhouxiang, H., Jianying, W., Ma, Z., Jifan, H., 2008. A method to recover silver from
waste X-ray films with spent fixing bath. Hydrometallurgy 92 (3–4), 148–151.
Fig. 8. XRD pattern of the silver precipitate showing the presence of metallic silver,
silver sulphide and elemental sulphur.
