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Combined Oxidative Leaching and Electrowinning Process for Mercury Recovery from Spent Fluorescent Lamps

  • Isparta University of Applied Sciences
Combined oxidative leaching and electrowinning process for mercury
recovery from spent fluorescent lamps
Cihan Ozgur
, Sezen Coskun
, Ata Akcil
, Mehmet Beyhan
, Ismail Serkan Üncü
, Gokhan Civelekoglu
Department of Environmental Engineering, Suleyman Demirel University, TR32260 Isparta, Turkey
Egirdir Vocational School, Suleyman Demirel University, TR32500 Egirdir, Isparta, Turkey
Mineral-Metal Recovery and Recycling Research Group, Mineral Processing Division, Department of Mining Engineering, Suleyman Demirel University, TR32260 Isparta, Turkey
Department of Electrical and Electronic Engineering, Suleyman Demirel University, TR32260 Isparta, Turkey
article info
Article history:
Received 30 September 2015
Revised 30 January 2016
Accepted 21 March 2016
Available online 31 March 2016
Mercury recovery
Spent fluorescent lamps
In this paper, oxidative leaching and electrowinnig processes were performed to recovery of mercury
from spent tubular fluorescent lamps. Hypochlorite was found to be effectively used for the leaching
of mercury to the solution. Mercury could be leached with an efficiency of 96% using 0.5 M/0.2 M
NaOCl/NaCl reagents at 50 °C and pH 7.5 for 2-h. Electrowinning process was conducted on the filtered
leaching solutions and over the 81% of mercury was recovered at the graphite electrode using citric acid
as a reducing agent. The optimal process conditions were observed as a 6 A current intensity, 30 g/L of
reducing agent concentration, 120 min. electrolysis time and pH of 7 at the room temperature. It was
found that current intensity and citric acid amount had positive effect for mercury reduction. Recovery
of mercury in its elemental form was confirmed by SEM/EDX. Oxidative leaching with NaOCl/NaCl
reagent was followed by electrowinning process can be effectively used for the recovery of mercury from
spent fluorescent lamps.
Ó2016 Elsevier Ltd. All rights reserved.
1. Introduction
Waste of electrical and electronic equipment commonly known
as e-waste includes various forms of all electric and electronic
apparatus which are at the end of its life. Some e-wastes such as
televisions, computer monitors and fluorescent lamps contain Hg
(mercury) (Bhutta et al., 2011; Garlapati, 2016). Due to the toxic
effect of mercury, the disposal of e-wastes together with municipal
wastes causes environmental problems in the landfill areas. Mer-
cury is essential to the operation of fluorescent lamps. Distribution
of electrical and electronic waste was determined in EU Directive
2002/96. Spent lamps were calculated 1.7% of total electrical and
electronic wastes as the 5B lighting equipment e-waste group by
European Union in 2005 (Erust et al., 2013; EU Directive
2002/96). E-waste stream is very fast growing in the modern world
(Huang et al., 2009; Behnamfard et al., 2013) and these wastes
should to be designed considering their recycle and reuse potential
(Petter et al., 2014; Sahin et al., 2015). Though the lighting industry
has achieved significant reductions in mercury content, the mer-
cury is still an important component for the working of fluorescent
lamps (NEMA, 2002; Tunsu et al., 2015). When the spent
fluorescent lamps are improperly discarded, mercury may contam-
inate soil and water resources and it can be harmful to the humans
and other organisms. Therefore, the recovery of mercury from
spent fluorescent lamps would reduce the amount of waste, thus
reducing the potential environmental risks (Durão et al., 2008;
Coskun and Civelekoglu, 2014, 2015).
Hydrometallurgy process called as leaching had been widely
applied for metal recovery from electronic wastes because of its’
flexible and energy-saving characteristics (Kinoshita et al., 2003;
Lai et al., 2008). However, acidic-leaching was usually applied to
obtain high mercury yields in the studies (Rey-Raap and
Gallardo, 2013; Tunsu et al., 2014), potential health risks and envi-
ronmental impacts of using acidic reagents should be considered.
In addition, acidic reagents used in the process caused to extraction
of other metals (e.g., Al, Mn, Cu, Zn and Cd) solution and it may lead
to reduce the efficiency of mercury leaching (Kalb et al., 1999;
Coskun and Civelekoglu, 2014, 2015). Therefore, oxidative sodium
hypochlorite (NaOCl)/sodium chloride (NaCl) was selected and
conducted as oxidative leaching solution to extract mercury as
Hg(II) complex as mercury tetra chloride, HgCl
according to Eq.
(1) (Twidwell and Thompson, 2001).
0956-053X/Ó2016 Elsevier Ltd. All rights reserved.
Corresponding author.
E-mail address: (S. Coskun).
Waste Management 57 (2016) 215–219
Contents lists available at ScienceDirect
Waste Management
journal homepage:
In order to recovery of mercury from the leaching solution, it
needs to be reduced to its elemental state (Hg
). After oxidative
leaching, mercury can be recovered as a Hg
from the leachate
by suitable separation processes such as cementation, ion
exchange, solvent extraction, biodegradation/bioreduction, hetero-
geneous photocatalysis, electrowinning and hybrid use of these
processes (Cui and Zhang, 2008; Bussi et al., 2010; Chaturabul
et al., 2015). The electrowinning technology was successfully
applied electroplating process to recover heavy metals from con-
centrated leaching solutions (Vegliò et al., 2003). This process is
attractive due to its versatility, energy efficiency, simple equip-
ment, easy operation, and low operation cost (Jüttner et al.,
2000; Meunier et al., 2006; Lai et al., 2008). However, little infor-
mation is available about recovery of mercury using electrowin-
ning from spent fluorescent lamps. The dissolved mercury in
leachate can be recovered by cathodic reduction according to Eq.
(2). On the other hand, mercury agglomerating may occur at the
electrode surfaces. This may lead to Hg
precipitation according
to Eq. (3). When the solution pH goes down below 4, Hg
formed (Hummer et al., 2006). Therefore, neutral pH (pH of 7) con-
dition was provided for electrowinning experiments in the current
In the present study, electrowinning process was applied for
convert mercury to its metallic state after oxidative (hypochlorite)
leaching of mercury from spent tubular fluorescent lamps. The
optimal process conditions for high efficiency of recovery were
2. Material and methods
2.1. Sample preparation and oxidative leaching tests
Spent fluorescent lamps were collected from hospitals, schools
and factories in the city center of Isparta, Turkey. T8 and T12 linear
(tubular) types of spent fluorescent lamps were selected for study
owing to their high rate of consumption around the world (Coskun
and Civelekoglu, 2015). These lamps also have higher mercury con-
tent than the other mercury-containing lamps such as T2, T5 and
compact fluorescent lamps (CFLs) (Hu and Cheng, 2012). Each
spent fluorescent lamp was manually dismantled under vacuum
in laboratory. The oxidative leaching experiments were conducted
on pulverized mixture samples of lamps (50–50% mixture of the T8
and T12 lamps) to simulate a realistic situation. Sample prepara-
tion method was described in detail by Coskun and Civelekoglu
To determine the initial mercury concentration of lamps, 20 g
pulverized samples were extracted with 25 mL water and 25 mL
aqua regia (HCl/HNO
, v/v - 3/1) in polypropylene flasks using a
magnetic stirrer at 200 rpm (Heidolph MR Hei-Tec 3001) at room
temperature for 18 ± 2 h. Each sample was filtered through funnels
using following the mixing stage. The initial mercury concentra-
tions were determined using atomic absorption spectrophotome-
ter (AAS) (PerkinElmer-FIMS 400, attached with flow injection
automated system). NaOCl (6–14% active chlorine, Merck
105614) and NaCl (extra pure, Merck 106400) were used as chem-
ical (oxidative) leaching reagents to extract mercury from pulver-
ized lamp samples. The leaching tests were performed in 250 mL
polypropylene flasks placed in temperature-controlled water baths
(GFL 1086) with mechanical stirrers. During the leaching tests, the
pH of the solutions was monitored using a digital pH meter (WTW
multi, 340i). The solutions were filtered (20
m, pure cellulose
filter papers), and analyzed for their mercury content to quantify
leaching efficiency. Each sample was diluted by a factor of 1:10
using nitric acid solution (pH = 2) to avoid the precipitation of met-
als and then stored at 4 °C for further analysis using AAS. Quantifi-
cation of leaching efficiency was determined by comparing initial
mercury concentration in extracted lamp sample solutions and
final mercury concentration in filtered leaching solutions. All mer-
cury analysis were based on Method 7471B (Mercury in solid or
semisolid waste-manual cold vapor technique) from USEPA’s ‘‘Test
methods for evaluating solid waste-physical/chemical method”
(SW-846) (USEPA, 1998).
2.2. Electrowinning tests
Leaching process was followed by electrowinning and oxidative
leaching solution was used as electrolyte in this process. The reac-
tion system was comprised of a 150 mL glass reactor with one gra-
phite electrode (0.5 cm diameter, 6 cm length), acting as the
cathode, one dimensionally stable anode (DSA
) (2 cm width,
5 cm length), which is made of titanium substrate with a thin layer
of iridium oxide (IrO
) acting as the anode of the electrolytic cell. A
power supply (GW Instek GPR-1820 HD) that provides electric cur-
rent (0–10 A and 0–18 V) was used to provide electric current.
While the applied current was constant (e.g., 2, 4 or 6 A), the volt-
age value was varied from 7 to 12 V between the two electrodes
during the experiments. All electrowinning tests were carried at
room temperature and pH of 7. The pH values were adjusted using
reagent grade NaOH and/or HCl solutions with different molar con-
centrations (0.2 M–0.5 M–1 M). The electrodes were connected
parallel to the power supply and the mercury was analyzed with
Citric acid (C
, Merck-818707) was added into filtered
leaching solution as a reducing agent. The effects of the current
intensity (A), citric acid amount (g/L), electrolysis time (min.) on
process yield were evaluated on basis of 2
full factorial designs
(Table 1)at25°C of temperature. The central point tests were used
to evaluate the experimental error of electrowinnig process and
therefore the SE (standard error) for the effects. The experimental
matrix was designed according to Yates Algorithm (Montgomery,
The graphite electrodes were analyzed before and after of elec-
trowinnig process by scanning electron microscope coupled with
an energy-dispersive X-ray spectrophotometer (SEM/EDX) (FEI
Quanta250 FEG) to investigate the elemental compositions.
3. Results and discussion
3.1. Leaching tests
Oxidative leaching tests were carried out to determine the opti-
mal leaching conditions in terms of simultaneous mercury extrac-
tions. Mercury could be leached by NaOCl/NaCl reagent with an
efficiency of 96% from real spent fluorescent lamps at 2-h contact
time, 50 °C of temperature, pH 7.5 and 120 rpm agitation speed
(Coskun and Civelekoglu, 2015). The addition of chloride ions
Table 1
Factors and levels investigated in electrowinning tests.
Code Factor (variable) Level
10 +1
A Current intensity (A
B Citric acid amount (g/L) 5 15 30
C Electrolysis time (min) 30 60 120
Ampère (A).
216 C. Ozgur et al. / Waste Management 57 (2016) 215–219
provided to increase the solubility of mercury through forming the
soluble and stable complex of HgCl
at neutral conditions. This
process was found to be more environmental friendly than the
acidic leaching of mercury. All leaching tests were carried out using
this combination, prior to conducting the electrowinning tests.
3.2. Electrowinning tests
Complex of HgCl
which was present in leaching solution
transferred to the elemental mercury during electrowinning pro-
cess. Electrowinning efficiencies were displayed in Fig. 1a. As seen
from this figure, recovery efficiency of factor 1 (minimum current
intensity, citric acid amount and electrolysis time) was found
lower than the central point tests. When all of these factors
increased to the average value (factor 0: A, current intensity 4 A;
B, citric acid amount 15 g/L; and C, time 60 min.), the recovery effi-
ciency also increased from a rate of 27–62% (Fig 1a). Citric acid was
used as the reductant agent for the conversion of Hg (II) to Hg (0).
Efficiency of factor A (maximum current intensity 6 A; minimum
citric acid amount 5 g/L; and minimum electrolysis time 30 min.)
and factor C (minimum current intensity 2 A; minimum citric acid
amount 5 g/L; and maximum electrolysis time 120 min.) was
measured low (Fig. 1a). However, factor B was found higher
recovery yield than the factor A and C. According to these results,
citric acid amount was more effective than current intensity and
electrolysis time in the process. In addition, AB and ABC factors
had high recovery efficiencies (about 77% and 81%, respectively).
Therefore, the recovery efficiency was increased by the increasing
current intensity and citric acid amount. The maximum
electrowinning efficiency was calculated as 81% (Fig. 1a, ABC).
Efficiency of mercury recovery was slightly increased with
maximum of all factors (current intensity: A, citric acid amount:
B and electrolysis time: C).
ANOVA method was used to evaluate the effect of the main fac-
tors on the process of electrowinning and the results were summa-
rized in Fig. 1b. F test statistics was used to evaluate factor
coefficients for significance at 95% (p = 0.05) confidence level. The
calculated SE value using central point experiment of electrowin-
ning was 6.76. The factors ‘‘C, ‘‘AC” and ‘‘ABC” were determined
to be statistically insignificant (p > 0.05) and these factors were
excluded from the figure (Fig. 1b).
It was found that current intensity (A) and citric acid amount
(B) had positive effect for mercury reduction (Fig 1b, A; +19% and
B; +28%). Furthermore, interaction effects of these variables (AB)
AB C 0
Hg(0) recovery (%)
Main and interaction effects
Effects (%)
Fig. 1. Electrowinning process mercury extraction yield (a) and extraction effects (b).
C. Ozgur et al. /Waste Management 57 (2016) 215–219 217
had positive effect to electrowinning process (+7.8%). Nanseu-Njiki
et al. (2009) observed that an increase in current intensity
also increases the rate of anode dissolution. The higher current
intensity may play a role more turbid the solution, and
consequently favors recovering. Citrate ions (Cit
) formed to a
complex with Hg
was reduced to Hg
as shown in Eq. (4)
(Kabra et al., 2004).
On the other hand, the main effect of electrolysis time (factor C)
did not significantly influence mercury reduction. Interaction
effects of citric acid amount and electrolysis time (BC) had little
negative influence (8.2%) on mercury recovery (Fig 1b). It means
there was no advantage in working at high electrolysis time
because of increasing the energy consumption and process costs
as reported in Hummer et al., 2006.
Overall the results indicated that higher mercury recovery
efficiencies could be reached with electrowinning experiments.
The optimal process conditions were observed to be 6 A current
intensity, 30 g/L of reducing agent concentration and 120 min.
electrolysis time. Similarly, Hummer et al. (2006) reported high
mercury recovery efficiency with a current intensity of 6 A, elec-
trolysis time of 240 min. at the end of electroleaching process. As
seen from the results, electrolysis time was reduced by half in
our study. While white phosphor powders of fluorescent lamps
were used as samples and NaCl was chosen as leaching solution
in aforementioned study, we used pulverized glass and phosphor
powder mixture samples of T8 and T12 lamps to simulate a more
realistic situation. Furthermore, NaOCl and NaCl mixture reagent
was used as leaching solution as distinct from Hummer et al.
3.3. Elemental composition experiments
SEM/EDX analyses of graphite electrode were obtained before
and after the electrowinning process. Fig. 2a shows a SEM/EDX
image including elemental analysis of pure graphite electrode.
According to this analysis, 100% C of total weight was measured
elemental composition of graphite electrode (Fig. 2b). After elec-
trowinning test, approximately 46.65% C, 35.61% O, 8.25% Na, 3.
26% Hg, 2.83% Mg, 2.55% Cl and 0.85% Ca was measured on graphite
electrode (Fig. 2d). Elemental mercury was detected in the SEM/
EDX image in Fig. 2c.
4. Conclusions
The oxidative leaching and electrowinning processes were
performed to recovery of mercury from spent tubular fluorescent
lamps. The experiments were conducted on pulverized mixture
samples of T8 and T12 lamp types. Mercury could be leached
with an efficiency of 96% using NaOCl/NaCl reagent. The maxi-
mum electrowinning efficiency was calculated as 81%. It was
found that current intensity and citric acid amount had positive
effect for mercury reduction. Electrolysis time did not signifi-
cantly influence the efficiency of electrowinning process. Recov-
ery of mercury in its elemental form was confirmed by SEM/
EDX. The oxidative leaching with NaOCl/NaCl reagent was fol-
lowed by electrowinning process approach appears to be techni-
cal feasibility of the mercury from spent fluorescent lamps. In
the future studies, the researchers can focus on using of different
types, materials and numbers of electrodes in the process to
improve the mercury recovery. Furthermore, the economical
evaluations should be conducted prior to each specific
The authors would like to thank to Erik Zimmerman from Per-
mascand AB for providing the DSA Anodes. This work was sup-
ported by research grants from Scientific and Technical Research
Council of Turkey (TUBITAK) (project no. 110Y264).
Fig. 2. Pure graphite electrode SEM image (a) EDX analysis (b) and graphite
electrode - Hg SEM image (c) EDX analysis (d).
218 C. Ozgur et al. / Waste Management 57 (2016) 215–219
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File (1)

... Decontaminating or recovering mercury present in the glass, phosphor powder, and end caps of spent fluorescent lamps can become a source of mercury in the environment Mercury percentage recovery depends on the wet or dry treatment methods used. Sobral et al. 4 , removed 99% of mercury from spent fluorescent lamps by electroleaching process, while a combination of electrowinnig process led to the recovery of 81% of mercury 5 . Moreover, 95% of mercury was recovered by the combination of photocatalytic process with sodium hypochlorite extraction solution 6 . ...
Full-text available
The current work presented here focuses on the remediation of mercury from water using modified low-cost materials. Modified date pits, low cost, minimal pretreatment steps and locally abundant agricultural waste materials were effectively employed as an adsorbent for remediating Hg²⁺ from aqueous media. Physical and chemical modification were developed such as thermal roasting (RDP), sulfur (SMRDP) and silane (SIMRDP) based modifications. Results showed that maximum adsorption by RDP was at pH 6, AC and both modifications was at pH 4. Furthermore, RDP has exothermic adsorption mechanism while AC, SMRDP, and SIMRDP have endothermic. All adsorbents except SIMRDP have spontaneous adsorption process. SEM analysis showed that the surface morphology of RDP was not significantly affected by different treatments while surface of AC was affected. The investigation for good adsorbents for Hg²⁺ uptake from different anthropogenic sources has been carried out by many investigators worldwide towards having a safe environment. In the current study, the highest Hg²⁺ adsorption of SMRDP was relatively high compared to other known adsorbents.
The injection of adsorbent can effectively remove Hg from syngas, in which metal oxide based adsorbent (MOBA) is a promising adsorbent as their simultaneous adsorption and oxidation properties. This review summarized the influences and mechanisms of adsorbent composition, syngas component, and reaction temperature on Hg⁰ removal by MOBA in syngas. The adsorption of Hg⁰ by CeO2-based, Fe2O3-based, CuO-based, and V2O5-based MOBA belong to physisorption, the adsorption of Hg⁰ by MnO2 and Co3O4 belong to chemisorption. The oxidation of Hg⁰ by MOBA follows Mars-Maessen mechanism. The Hg⁰ removal capacity of MOBA with different composition follows the descending sequence of V2O5 > MnO2 > Co3O4 > Fe2O3 > CuO(CeO2). H2S and HCl are beneficial to Hg⁰ removal by MOBA, but CO, H2, and H2O are harmful to Hg⁰ removal by MOBA. The influence of H2S, HCl, and CO are affected by their concentration. Both HCl and H2S can mitigate the inhibition of CO and H2 on Hg⁰ removal by MOBA. The increase of temperature can both promote and inhibit Hg⁰ removal by MOBA. In addition, the advantages and disadvantages of three main regeneration methods of thermal regeneration, non-thermal plasma regeneration, and elution regeneration were respectively summarized, especially the prominent advantages of elution regeneration method were emphasized. Finally, further works about the development of spine MOBA, the synergistic removal of Hg⁰ and H2S by MOBA, study at higher temperature range, and the application of elution regeneration method were summarized to provide some references for the application of MOBA on Hg⁰ removal in syngas.
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Abstract The investigations in this study were performed on two types of waste linear (tubular) lamps (T8 and T12), which are mostly spent in Turkey. Total average value of the mercury mass per lamp for the T8 lamps (6 mg/lamp) was calculated to be about 50% lower than that of the T12 lamps (12 mg/lamp). SEM-EDX elemental analysis showed that 52% percent of phosphor powders of waste T8 and T12 lamps was measured as calcium (Ca), while the next is 24.23% of P, 9% of F, 8% of Nb, 2% of Al, 1.3% of Cl and other elements/metals (K, Mn, Cu and Cd) by weight. The white powder comprises mainly fluorapatite and hydroxylapatite the predominant crystalline phase as was revealed by XRD analysis. ICP-OES analysis showed that some rare earth elements were determined in the T8 and T12 phosphor powders ranged between 100-1565 g/g and 325-1630 g/g, respectively. These waste lamps could be considered as an ore of secondary raw materials. In addition to hazardous metals (Cd, Hg, Pb) and valuable metals (Ce, Eu, La, Tb, Y), a range of substances such as glass, phosphorous salts and plastics can also be recovered. Such materials can be captured by the recovery systems in terms of hydrometallurgical or pyrometallurgical processes and diverted from municipal waste. The use of recycled metals in lamp production instead of virgin metals may have positive environmental impacts through reduced energy use and reduced pollution related to the mining of the virgin source in Turkey. Keywords: Material characterization; recovery; waste fluorescent lamps.
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study were performed on two types of waste linear (tubular) T8 and T12 lamps, which are mostly used in Turkey. Total average value of the mercury mass for the T8 and T12 lamps were calculated to be about 6 mg and 12 mg per lamp, respectively. SEM-EDX elemental analysis showed that approximately 52% percent of phosphor powders of waste T8 and T12 lamps was measured as calcium (Ca) by weight. ICP-OES analysis showed that some rare earth elements were traced in the T8 and T12 phosphor powders. These waste lamps could be considered as an ore of secondary raw materials. The use of recycled metals in lamp production instead of virgin metals may have positive environmental impacts through reduced energy use and reduced pollution related to the mining of the virgin source in Turkey.
Electronic waste or e-waste is one of the global rising problems in developing countries like India and developed countries. E-waste comprises material that is valuable as well as toxic and has shoddier health and environment impact. This review paper presents an overview of global ewaste stats, health concerns of e-waste components along with the waste management, recycling, legislative polices and recommendations related to e-waste. Existing and future initiatives of waste management have been addressed by explaining the developed countries initiatives towards e-waste management. The key to success in terms of e-waste management such as Extended Producer Responsibility (EPR) and Producer Responsibility Organization (PRO) initiatives have been presented in a lucid manner. E-waste arena is a platform for business initiative for energy production (hydrogen and electricity) and precise metal recovery (gold, silver and platinum) through biotechnological approaches.
Printed circuit board (PCB) is the essential part of electronic devices and has an important source of base and precious metals with high economic potential. In this study, selective leaching of gold from PCB was performed in an iodine-hydrogen peroxide (I2-H2O2) solution system. The effects of different parameters such as iodine concentrations, H2O2 concentrations and solids-% on the gold leaching dynamics were investigated. The results show that increasing solids-% has a negative influence on the gold leaching. However, gold recovery from the e-wastes in a solution containing 3% iodine, 1% H2O2 with solids-% of 15% resulted with 100% recovery among all leaching tests.
The separation of mercury(II) from petroleum-produced water from the Gulf of Thailand was carried out using a hollow fiber supported liquid membrane system (HFSLM). Optimum parameters for feed pretreatment were 0.2 M HCl, 4% (v/v) Aliquat 336 for extractant and 0.1 M thiourea for stripping solution. The best percentage obtained for extraction was 99.73% and for recovery 90.11%, respectively. The overall separation efficiency noted was 94.92% taking account of both extraction and recovery prospects. The model for this separation developed along a combined flux principle i.e. convection–diffusion–kinetic. The results showed excellent agreement with theoretical data at an average standard deviation of 1.5% and 1.8%, respectively.
With the rising popularity of fluorescent lighting, simple and efficient methods for the decontamination of discarded lamps are needed. Due to their mercury content end-of-life fluorescent lamps are classified as hazardous waste, requiring special treatment for disposal. A simple wet-based decontamination process is required, especially for streams where thermal desorption, a commonly used but energy demanding method, cannot be applied. In this study the potential of a wet-based process using iodine in potassium iodide solution was studied for the recovery of mercury from fluorescent lamp waste. The influence of the leaching agent's concentration and solid/liquid ratio on the decontamination efficiency was investigated. The leaching behaviour of mercury was studied over time, as well as its recovery from the obtained leachates by means of anion exchange, reduction, and solvent extraction. Dissolution of more than 90% of the contained mercury was achieved using 0.025/0.05M I2/KI solution at 21°C for two hours. The efficiency of the process increased with an increase in leachant concentration. 97.3±0.6% of the mercury contained was dissolved at 21°C, in two hours, using a 0.25/0.5M I2/KI solution and a solid to liquid ratio of 10% w/v. Iodine and mercury can be efficiently removed from the leachates using Dowex 1X8 anion exchange resin or reducing agents such as sodium hydrosulphite, allowing the disposal of the obtained solution as non-hazardous industrial wastewater. The extractant CyMe4BTBP showed good removal of mercury, with an extraction efficiency of 97.5±0.7% being achieved in a single stage. Better removal of mercury was achieved in a single stage using the extractants Cyanex 302 and Cyanex 923 in kerosene, respectively. Copyright © 2014 Elsevier Ltd. All rights reserved.
Current resource issues and the growing demand for metals used in advanced technologies have focused attention towards more efficient processing of end-of-life products and waste streams. Fluorescent lamp waste is a viable target for the recovery of rare earth metals (REMs); specifically cerium, europium, gadolinium, lanthanum, terbium, and yttrium. Waste originating from a discarded lamp processing facility was investigated using Scanning Electron Microscopy/Energy Dispersive Spectroscopy and X-ray Diffraction. Total dissolution experiments were carried out with aqua regia at elevated temperatures in order to estimate an average metal content and assess the recycling potential of the material.
Electronic waste has been increasing proportionally with the technology. So, nowadays, it is necessary to consider the useful life, recycling, and final disposal of these equipment. Metals, such as Au, Ag, Cu, Sn and Ni can be found in the printed circuit boards (PCB). According to this, the aims of this work is to characterize the PCBs of mobile phones with aqua regia; obtaining "reference" values of leaching, to gold and silver, with cyanide and nitric acid, respectively; and study the process of leaching of these metals in alternative leaching with sodium thiosulfate and ammonium thiosulfate. The metals were characterized by digesting the sample with aqua regia for 1 and 2h at 60°C and 80°C. The leaching of Au with a commercial reagent (cyanide) and the Ag with HNO3were made. The leaching of Au and Ag with alternative reagents: Na2S2O3, and (NH4)2S2O3 in 0.1M concentration with the addition of CuSO4, NH4OH, and H2O2, was also studied. The results show that the digestion with aqua regia was efficient to characterize the metals present in the PCBs of mobile phones. However, the best method to solubilize silver was by digesting the sample with nitric acid. The leaching process using sodium thiosulfate was more efficient when an additional concentration of 0.015 and 0.030M of the CuSO4 was added.