Direct recovery of copper nanoparticles from leach pad drainage by surfactant-assisted cementation with iron powder

Accepted Manuscript Title: Direct recovery of copper nanoparticles from leach pad drainage by surfactant-assisted cementation with iron powder Authors: Giuseppe Granata, Uuganzaya Tsendorj, Wenying Liu, Chiharu Tokoro PII: DOI: Article Number:

S0927-7757(19)30708-3 https://doi.org/10.1016/j.colsurfa.2019.123719 123719

Reference:

COLSUA 123719

To appear in:

Colloids and Surfaces A: Physicochem. Eng. Aspects

Received date: Revised date: Accepted date:

23 June 2019 19 July 2019 25 July 2019

Please cite this article as: Granata G, Tsendorj U, Liu W, Tokoro C, Direct recovery of copper nanoparticles from leach pad drainage by surfactant-assisted cementation with iron powder, Colloids and Surfaces A: Physicochemical and Engineering Aspects (2019), https://doi.org/10.1016/j.colsurfa.2019.123719 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Direct recovery of copper nanoparticles from leach pad drainage by surfactant-assisted cementation with iron powder

Giuseppe Granataa*, Uuganzaya Tsendorjb, Wenying Liuc, Chiharu Tokoroa

b

: Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, 169-8555 Tokyo.

IP T

a

: School of Creative Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, 169-8555

c

SC R

Tokyo

: Department of Materials Engineering, University of British Columbia, 309-6350 Stores Road, Vancouver, BC V6T 1Z4, Canada

U

*

N

Corresponding author

A

*: [email protected]

M

*: [email protected]

A

CC E

PT

ED

Graphical abstract

1

Abstract Copper nanoparticles were directly recovered from a leach pad drainage by surfactant-assisted cementation with iron powder. Factorial experimental designs were implemented to assess the influence of polyvinylpyrrolidone (PVP), sodium dodecyl sulfate (SDS) and temperature on cementation kinetics and copper particle size. Analysis of variance (ANOVA) was performed to quantify the effect of the

IP T

investigated factors. Copper(II) was selectively reduced to metal copper by Fe powder, while Mn, Fe, Cd and Zn ions were left in solution. The cementation proceeded under enthalpic driving force and could be

SC R

described by a pseudo-second-order kinetic model. Without the surfactants, the activation energy of cementation was 22.7 kJ/mol and the cemented product aggregated into micro-clusters ranging from 1 to

U

15 µm in size, depending on the temperature. The cementation with PVP at above 311 K was controlled

N

by physical adsorption of PVP on Fe powder and exhibited an activation energy of about 10 kJ/mol. The

A

average size of copper particles obtained using 4 mM PVP at 348 K was 280 nm. Adding SDS was

M

associated with a dramatic increase in the activation energy to about 45 kJ/mol, and with the formation of nanoparticles. Using 0.2 M SDS at 348 K enabled the recovery of Cu of about 99% purity with an

ED

average particle size less than 100 nm. All results suggested that capping by SDS and PVP inhibited the cementation kinetics but provided the templating ability required to form nanoparticles.

A

CC E

PT

Keywords: cementation, copper nanoparticles, recovery, kinetics, ANOVA

2

1.

Introduction Given the imbalance between copper supply and demand [1], the development of efficient and

sustainable technologies to recover copper from industrial waste streams is highly anticipated [2]. Copper can be conveniently recovered from different kinds of industrial by-products [3] and e-waste [4]. In

IP T

addition, wastewater and drainages generated in the mining and metal industry could also represent viable sources of recoverable copper. Recovering copper from these sources could be both economically and environmentally advantageous.

SC R

The scientific literature describes many different methods to remove copper ions from solution [5]. The adsorption onto innovative nanomaterials based on functionalized carbon nanotubes [6], double-layer

U

hydroxides [7], graphene oxide [8], or nature-inspired nanocomposite substrates [9,10] appears to be the

N

most recent research trend. However, the adoption of new technologies is often hindered by the relatively

A

high concentrations of cupric ions and other possible interfering ions in real mining waste streams, the

M

high cost of innovative materials, and the tendency to re-use as much as possible all liquid streams within the same processes.

ED

The hydrometallurgical practice offers more robust methods to recover copper from simple aqueous solutions and industrial wastewaters [11]. Among them, cementation is simple and

PT

environmentally sustainable [12]. Cementation is a heterogeneous redox reaction between a metal ion in

CC E

solution and a more electropositive solid metal [13]. The reaction has been used for many years in hydrometallurgical engineering to reduce and precipitate noble metals like gold and silver [14,15]. However, due to the relatively high standard redox potential of the redox couple Cu2+/Cu (E° = 0.34 V),

A

cementation is ideal to recover copper as well. The reaction could be conveniently performed by adding low-cost metals such as iron [16], zinc [17], aluminium [18] and even a mixture of them [19]. Nevertheless, given the large availability of low-cost iron scraps, the use of iron as cementing agent for copper has always attracted more attention. The cementation between copper and iron can be described through the simplified equation (1): 3

Cu2+ + Fe0 → Cu0 + Fe2+

(1)

The reaction has been extensively investigated under different configurations involving the use of iron as powder [16], grid [20], shots [21], spheres [22] and rotating cylinders [23]. Despite many studies on this process, most of them investigated cementation as downstream operation in hydrometallurgy and focused on performances and kinetics, whereas aspects concerning the

IP T

characteristics of the copper product were not considered. Conversely, the quality of produced copper is very important, all the more as cementation has been recently indicated as a suitable method to produce

SC R

nano-structured copper [24,25]. Copper nanoparticles (CuNPs) are well-known to have enhanced properties compared to their micro-sized counterparts [26]. The increased surface area and

U

thermal/electrical conductivity, along with a reduced melting point, enable CuNPs to be conveniently used

N

for many industrial applications, such as catalysis [27], inkjet printing technology [28], and low pressure

A

bonding for powder modules [29–31].

M

In this work, we studied the direct recovery of CuNPs from a leach pad drainage by surfactantassisted cementation with iron powder. Two different surfactants, namely, polyvinylpyrrolidone (PVP)

ED

and sodium dodecyl sulfate (SDS), were tested to control the particle size of copper particles. We performed two factorial experiments to investigate the effect of surfactants and temperature on the copper

PT

particle size distribution. Unlike previous studies where low concentrations of surfactants were tested with the sole purpose of altering the interface properties, in this study we used surfactants as templating agents

CC E

to limit crystal growth and/or aggregation of copper. The experimental results obtained from factorial designs were analyzed by analysis of variance (ANOVA) to identify and quantify the significant effects of

A

the investigated factors. To elucidate the cementation mechanism and the factors controlling particle size, we studied the cementation kinetics and thermodynamics by assessing activation energy, enthalpy, entropy and free energy of activation.

2.

Material and methods

4

2.1 Leach pad drainage The source of copper targeted in this work was a leach pad drainage generated from a low grade copper ore at the Erdenet Mine in Mongolia. Accounting for 22.3 million tons of ore processed per year, the Erdenet Mine is considered as the largest copper mine in Asia and the fourth in the world. At the

IP T

Erdenet Mine, the leach pad drainage is generated seasonally from the ore stockpiles due to the excess of precipitations. The concentrations of metals in the targeted drainage were as follows: 6 g/L Cu, 2.6 g/L Fe, 1.1 g/L Mn, 0.05 g/L Zn, and 0.05 g/L Cd. Given the presence of pyrite and chalcopyrite in the ore, these

SC R

metals are dissolved as sulfates in acidic environment (pH 3). Despite the relatively high concentration of potentially recoverable metals (e.g. copper), this liquid stream has so far been considered as an effluent

U

and discarded.

A

N

2.2 Materials

M

All experiments were performed using synthetic sulfate solutions that resembled the real drainage. All chemicals used in this study were of analytical grade supplied by Wako Pure Chemical Industries

ED

(Japan). These chemicals included copper sulfate (CuSO4·5H2O), iron sulfate (FeSO4·7H2O), manganese sulfate (MnSO4), zinc sulfate (ZnSO4), cadmium sulfate (CdSO4), polyvinilpyrrolidone (PVP, K-30),

PT

sodium dodecyl sulfate (SDS), and sulfuric acid (96% H2SO4) The iron used for cementation was a 99.9%

CC E

purity powder with an average particle size of 45 µm.

2.3 Cementation

A

The cementation tests were carried out upon adjustment of the pH of the synthetic solutions from 3.0 to 1.5 to prevent oxidation and precipitation of ferrous iron. In each experiment, the as-received iron powder was added to 100 mL of the synthetic drainage solution at the stoichiometric Fe to Cu ratio of 1:1. The reaction was allowed to proceed for 30 minutes in a reactor open to atmosphere with mechanical stirring at controlled temperature. Liquid samples were taken at 0.5, 1, 1.5, 2, 3, 5, 10, 20, and 30 minutes 5

to determine the residual concentration of metals in solution. In the surfactant-assisted cementation tests, PVP or SDS were added and completely dissolved in the synthetic drainage solution before adding Fe powder. The experiments within the factorial designs were carried out at three levels of PVP concentration (0, 2, and 4 mM), three levels of SDS concentration (0, 0.2 and 0.4 M), and three levels of

IP T

temperature (298, 323, and 348 K).

2.4 Analysis and particle size distribution

SC R

The concentrations of dissolved metals in the liquid samples were determined by inductively coupled plasma optical emission spectrometry (ICP-OES, Agilent 5100, Agilent Technologies, Japan)

U

upon filtration by 20 µm cellulose filters and dilution. The cemented copper was collected by

N

centrifugation (11000 rpm, 5 min), washed with ethanol and ultrapure water, dried and stored for analysis.

A

Field-emission scanning electron microscopy (Hitachi S-4500SFE-SEM) was used to assess particle size

M

distribution and morphology. The phase composition of the cemented product was determined using an xray diffractometer (Rigaku RINT UtimaIII X-ray diffactometer) with Co Ka radiation (k = 1.789 Å)

ED

operated at 40 kV and 20 mA. The purity of the cemented copper was determined by digestion in 5 M HNO3 at 348 K, followed by ICP-OES analysis.

PT

The size of the CuNPs was estimated through image analysis using Inkscape and ImageJ free

CC E

software, as explained elsewhere [32–34]. For each replicate, at least 200 particles were measured to create representative samples of each population. ANOVA was used to estimate the effects of the investigated factors on the particle size of the

A

cemented product, with particle size represented as P60 diameter (particle diameter corresponding to 60% of the passing fraction). All tests were performed with statistical significance equal to 95%, i.e. =0.05 [35,36]. According to ANOVA, the observed variability of the P60 (yijk) can be described by a statistical model assuming the additive effect of each single factor (τi and βj), their interaction ((τ β)ij), and random experimental errors (ijk) on a constant value (µ): 6

yijk= µ + τi+ βj +(τ β)ij +ijk

(2)

where the subscript i indicates the levels of the first factor (i.e. temperature), the subscript j indicates the levels of the second factor (i.e. surfactant), and k indicates the kth replicate in the ijth treatment. The significant effects associated with the change of variables were determined based on the mean squares of

Results and discussion

SC R

3.

IP T

both principal factors and interactions [37].

3.1 Cu recovery: kinetics and thermodynamics

Fig. 1 shows the changes in the concentration of various dissolved metals in the course of

U

cementation without surfactants at different temperatures. Without surfactants, the highest copper

N

recovery was obtained at 323 K (Fig. 1b). The low recovery observed at 298 K (Fig. 1a) was due to a

A

slower kinetics (discussed later) that limited the recovery within 30 minutes. The low recovery observed

M

at 348 K (Fig. 1d) could be explained by the re-oxidation of copper by the Fe3+ [38] ions generated from

ED

the oxidation of ferrous ions, as shown in Eq. (3) and (4): (3)

Cu + 2Fe3+ → Cu2+ + 2Fe2+

(4)

PT

4Fe2+ + O2 + 4H+ → 4Fe3+ + 2H2O

As a confirmation, the concentration of copper in solution started increasing again after 15 minutes, while

CC E

iron was still being oxidized and dissolved. In general, Cd, Mn and Zn remained dissolved in water under all investigated conditions, thus confirming the suitability of cementation to selectively recover copper from the targeted drainage. These metals could be easily removed from wastewater by adsorption [39],

A

chemical precipitation as hydroxides [40] or sulphides [41], or reduced with generation of H2 [42]. Given the suitability of the chosen method to selectively recover copper, we investigated the effect

of surfactants on cementation kinetics and quality of the obtained copper product. Cementation was often modeled as a (pseudo)first order reaction [16,20,22,23,25,43]. However, since we used equimolar amounts of Cu2+ and Fe, the kinetic study was performed by fitting the 7

experimental data with the linear expression of second order reaction model [44]. According to the model, if the experimental conversion of copper (X) plotted as

𝑋 (1−𝑋)

against time aligns through a straight line,

the reaction follows a second order kinetics and the slope of the line is the apparent rate constant k. The kinetic fitting for the cementation without surfactants is shown in Fig. 2 while the ones with SDS and PVP

IP T

are shown in Fig. 3 and 4, respectively. Kinetic fitting parameters and copper recovery are listed in Table 1.

The straight lines in Fig. 2 confirmed the suitability of the second order reaction model to describe

SC R

the kinetics of cementation without surfactants with equimolar amounts of Cu2+ and Fe. The rate constants without surfactants increased from 0.0417 to 0.1574 s-1 (Table 1) with increasing temperature.

U

The temperature played a key role also in the increase of the rate constants in the presence of surfactants.

N

The addition of SDS and PVP, led to a significant decrease in the rate constants, irrespective of the

A

surfactant concentration (Fig. 3), with the rate constants in the presence of PVP being always higher than

M

those observed in the presence of SDS at the same temperature.

temperatures as in equation (5):

ED

For a better analysis of this evidence, we determined the inhibition coefficient (I) at different

(5)

PT

k − k" I(%) = ( ) × 100 k

CC E

where k is the rate constant of cementation without surfactant at and k” is the one with SDS or PVP. The inhibition trend with temperature is shown in Fig. 5. In the presence of SDS, the inhibition exhibited a substantially monotonic trend with temperature: an increase in temperature led to a decrease in the

A

inhibition coefficient. Given the intrinsic mass-transport nature of the cementation reaction [18,19,45], this trend could be explained by the decrease in the surfactant solution viscosity at higher temperature [23,46]. The inhibition coefficient in the presence of PVP did not show any monotonic trend: it decreased by increasing the temperature from 298 to 311 K, but then increased from 311 to 348 K. The initial decrease might look surprising as a faster reaction might be expected when the solution viscosity

8

decreases. A reasonable explanation for this observed decrease is based on the polymeric nature of PVP. As a polymer with lactam groups and alkyl chains, PVP can coordinate Cu2+ and adsorb metal atoms [47,48]. By increasing the temperature from 298 to 323 K, PVP changes conformation from coil to globular [49]. As a consequence of the uncoiling, more lactams groups and alkyl chains would be available for coordinating Cu2+ and for adsorbing on metal particles. These increased interactions

IP T

enhanced the kinetic inhibition as the contact between reactants could be realized only by mass transport through the PVP layer.

SC R

Based on rate constants (k) obtained at different temperatures, we determined the activation energy of the cementation process from the linearized Arrhenius equation (6): 𝐸𝑎 1 𝑅𝑇

(6)

U

𝑙𝑛𝑘 = 𝑙𝑛𝐴 −

N

where R is the gas constant (8.314 J·K-1·mol−1), Ea is the activation energy (J·mol−1), and A is the

A

frequency factor (s-1). The Arrhenius plot is shown in Fig. 6. The activation energy of cementation

M

without surfactants was 22.7 kJ/mol, which is in agreement with previous studies [21,45,46]. Activation energies of this magnitude were reported as supporting evidence for diffusion-controlled reactions [17].

ED

Adding SDS resulted in a dramatic increase in the activation energy to about 45 kJ/mol. A similar

PT

value of activation energy was described by Pal et al. (2014) as evidence of a reaction controlled by the diffusion of ions through the solid product (Cu) layer [25]. The increase in the activation energy due to

CC E

addition of SDS had been reported in previous investigations [23]. However, in the present study SDS was used for not only altering the interface properties but also as a templating agent, at significantly higher concentrations. The concentrations chosen in this work were higher than the critical micellar

A

concentration (CMC) and in stoichiometric excess to Cu2+. Under these conditions, SDS self-assembles into spherical or rodlike micelles that can promote metal reduction around the spatially confined hydrophilic volume of its polar heads [50]. In addition, SDS can coordinate Cu2+ with two dodecyl sulfate groups [37]. As a consequence, the alkyl chains surrounding the metal ion would hinder the diffusion of reactants by steric effects, thereby affecting the kinetics [51]. 9

In the presence of PVP, it was not possible to fit the Arrhenius plot with just one straight line. In the temperature range 311-348 K, the activation energy in the presence of PVP was approximately 10 kJ/mol, lower than that for the temperature range 298-311 K. This analysis serves as further evidence for the different behaviour of PVP in the two temperature ranges. The lower value of the activation energy between 311 and 348 K suggests that the cementation with PVP was controlled by a purely physical

IP T

phenomenon (e.g. mass transport of reactants through the PVP layer). This evidence is in agreement with the previous consideration about the higher inhibition coefficient at higher temperatures. Increasing the

SC R

temperature would result in the uncoiling of the polymer, which in turn would produce more enhanced interactions between PVP, Cu2+ and Fe. As a consequence, the contact between Fe particles and Cu2+

U

could be realized only by mass transport through the dense polymer layer surrounding Cu2+ and Fe. We

N

refrain from providing particular considerations about the activation energy in the low temperature range.

A

However, the increased energy barrier would be in agreement with less pronounced coordination and

M

adsorption.

The obtained activation energies were used to calculate the enthalpy of activation (∆H*), entropy of

∆H ∗ = Ea − RT

(7)

∆S ∗ BTe = lnA − ln R h

(8)

∆G∗ = ∆H ∗ − T∆S ∗

(9)

CC E

PT

ED

activation (∆S*) and free energy of activation (∆G*) based on equations (7)-(9):

where B is the Boltzmann constant (1.38064852 · 10−23 J·K−1), h is the Planck constant (6.62607004 · 10−34 J · s) and e is 2.7183. The activation parameters are listed in Table 2.

A

The negative values of ∆S* are a clear indication that cementation proceeded with an increase in the

degree of order, both in the presence or absence of surfactants. The compensation theory [52] proposed a relationship between ΔH* and ∆S* as in equation (10): ∆H ∗ = 𝑇𝛽 ∆S ∗ − ∆G∗

(10)

10

Accordingly, a plot of ΔH* vs ∆S* should be linear and the slope is the isokinetic temperature (Tβ), defined as the temperature at which all plotted reactions proceed with the same speed. Based on the model, if the isokinetic temperature is lower than the experimental temperature at which the ΔH* and ∆S* were obtained, the reaction proceeds under entropic driving force. Conversely, if the isokinetic temperature is higher, the reaction proceeds under enthalpic driving force.

IP T

The isokinetic relationships of cementation exhibited a good linearity at both 298 K and 323 K (Fig. 7). The isokinetic temperatures calculated at these temperatures were 323 K and 345 K, respectively. This

SC R

result revealed that cementation proceeded under enthalpic driving force for all investigated conditions. The significantly lower values of ∆H* obtained using PVP in the temperature range 311-348 K (Table 2)

U

suggested that the mechanism was controlled by a purely physical phenomenon, most likely physical

N

adsorption. This result further confirmed that PVP exhibited a temperature-dependent behaviour

3.2 Characterization of cemented product

M

A

associated with its polymer nature (e.g. coiling/uncoiling).

ED

Results of particle characterization are summarized in Table 3. Without using surfactants, the cemented product was single phase face-centered cubic (FCC) copper crystals under all investigated

PT

temperatures (Fig. 8). Conversely, the XRD patterns of the products obtained at 298 K with 0.2 M SDS

CC E

and 4 mM PVP exhibited the peaks of α-iron as well (Fig. 9). The presence of residual iron at low temperature could be attributed to incomplete reactions due to slower kinetics. Accordingly, the copper grade of the products cemented at 298 K was generally the lowest (Table 3). The copper grade was

A

instead higher at 323 and 348 K, reaching 99% depending on the specific operating conditions (Table 3). Although the copper grade was about 98-99%, the concentrations of Fe, Mn, Zn and Cd in the cemented copper were always below the detection limit of the ICP-OES used in the present study. This result confirmed the suitability of cementation to recover copper from the targeted aqueous source.

11

The FE-SEM micrographs of the copper cemented with SDS and PVP are shown in Fig. 10 and 11, respectively. The particle size distribution curves determined from the FE-SEM micrographs are shown in Fig. 12. The FE-SEM micrographs and size distribution curves of copper particles obtained without surfactants are provided as supplementary information (Fig. S1-S2). The average P60 diameter of the particles without surfactants ranged from 16 µm at 298 K to about 1.2 µm at 348 K. Temperature

IP T

exhibited a key role in modulating the particle size of the final copper product. This observation could be reasonably explained in terms of cementation reaction kinetics. A faster reaction generated a larger

SC R

number of copper nuclei within the same time range. Therefore, individual nuclei would grow to a lesser extent and the resulting particles would be smaller. In spite of this evident decrease in the particle size,

U

copper particles aggregated into micro-clusters upon crystallization.

Adding SDS produced a dramatic decrease in the particle size to a nanoscale range. This means that

A

N

SDS successfully coordinated Cu2+ with its dodecyl sulfate group and prevented crystal growth and/or

M

aggregation through the steric effect exerted by its alkyl chains. The average P60 diameter of particles obtained with SDS was generally the largest at 298 K and the smallest at 348 K. Interestingly, the CuNPs

ED

obtained using SDS at 348 K exhibited P60 less than100 nm. Similar effects were observed in the factorial design with PVP. Both temperature and surfactant

PT

played key roles in modulating particle size. Although in the nanoscale range, the CuNPs obtained with PVP were larger than those obtained with SDS. Using PVP, the smallest particles were obtained by dosing

CC E

4 mM of surfactant at 348 K, and exhibited an average P60 diameter of 280 nm. As for morphology, whereas the CuNPs obtained with SDS were spherical, more irregular spheres

A

and elongated aggregates were obtained with PVP. The increased anisotropy might be a consequence of the adsorption of PVP on Fe, which might have slightly orientated the crystal growth.

3.3 Effect of temperature and surfactants: ANOVA results

12

ANOVA was performed to assess quantitatively the significance of the obtained results and to quantify the effect of each factor on the observed particle size. The results denoted that the main effects of the three factors under investigation were significant at the 99% confidence level. The observed variability associated with these factors was significantly larger than that associated with random errors. In other words, the decrease in the P60 diameter observed by increasing each factor from the low to the

IP T

high level was statistically significant.

The replicated factorial design with SDS at different temperatures indicated that temperature had a

SC R

significant negative effect on the P60 diameter (Fcal>Ftab as reported in Table S1 in supplementary material). Estimate of the effect associated with temperature (defined as the difference between mean size

U

at high level and mean size at low level of the factor) was -4458 nm in the range 298-323 K and -764 nm

N

in the range 323-348 K (black bars in Fig. 13). This means that increasing temperature from 298 to 323 K

A

in the presence of SDS resulted in a decrease in the P60 diameter of the particles of 4458 nm. Similarly,

M

an increase from 323 to 348 K led to a decrease in the P60 diameter of 764 nm. The effect of SDS was also significant, especially in the range 0-0.2 M. The addition of 0.2 M SDS was associated with the most

ED

pronounced effect, namely -6668 nm.

In the factorial design with PVP (white bars in Fig. 13), both temperature and PVP exhibited

PT

significant effects (Fcal>Ftab as reported in Table S2 in supplementary material). The effect of temperature was found to be -4920 nm in the range 298-323 K and -1165 nm in the range 323-348 K

CC E

(white bars in Fig. 13). The effect of the addition of 4 mM PVP was of the same magnitude (-6544 nm). The general effect of using SDS or PVP as surfactants was also assessed by performing a t-test on

A

the differences of all mean values obtained in the different conditions. The t-test confirmed with 95% confidence that the copper particles obtained by using SDS were smaller than those produced using PVP under the same conditions. The mean value of P60 obtained with SDS was 232 nm as opposed to 809 nm with PVP. Accordingly, changing the surfactant from SDS to PVP had a significant positive effect of 2029 nm on P60 diameter (grey bar in Fig. 13).

13

Although PVP has often been described as a surfactant for keeping the size of metal nanoparticles within the nanoscale range [53], the smallest P60 observed with CuNPs in this work was 280 nm. The templating ability of PVP arises from the repulsive forces between its hydrophobic carbon chains (steric hindrance effect) when the lactam group coordinates the metal ion and/or the alkyl chain adsorbs on forming metal particles. Therefore, the lower templating ability of PVP observed in our experiments can

IP T

be explained considering the unwanted consumption of PVP for the adsorption on Fe particles, as also suggested by the low values of ΔH*. In other words, part of PVP coordinated Cu2+ but a significant part of

SC R

must have adsorbed on Fe particles. As a consequence, the reaction kinetics was hindered and the templating ability was partially lost.

U

ANOVA highlighted the significant effect of the interaction of both surfactants with temperature

N

(the ANOVA graphs showing the interaction can be found in supplementary material, Fig. S3-S4). This

A

means that particles obtained when all factors were at high level (high surfactant concentration, high

M

temperature) were even smaller than when just one factor was at the high level. Clearly, both PVP and SDS had higher templating capability at higher temperatures.

ED

The effects of temperature, SDS and PVP concentrations and their interactions on P60 diameter can be represented by the simple linear model in Eq. (11):

PT

P60(nm) = a1 ∙ [SDS] + a2 ∙ T + a3 ∙ [PVP] + a4 ∙ [SDS] ∙ T + a5 ∙ [PVP] ∙ T

(11)

where the parameters of the model a1, a2 and a3, a4 and a5 were obtained by linear regression as: a1 = 1396

CC E

L · mol-1, a2 = 66 K-1, a3 = 461 L · mmol-1, a4 = - 213 L × mol-1 · K-1 and a5 = - 25 L × mol-1 · K-1.

A

Conclusions

Copper nanoparticles (CuNPs) were directly recovered from a leach pad drainage by surfactant-

assisted cementation with iron powder. Copper ions could be quantitatively reduced and precipitated as metallic copper while Cd, Mn and Zn ions were left in solution with the dissolved iron and could be later precipitated and disposed as a sludge. Both surfactants tested, polyvinylpyrrolidone (PVP) and sodium

14

dodecyl sulfate (SDS), showed inhibition effects on the cementation kinetics and, possibly produced a change in the reaction mechanism. A dramatic decrease in the size of the final copper products to nanoscale was observed in the presence of surfactants. Specifically, SDS showed the best templating ability as the CuNPs produced with 0.2 or 0.4 M SDS at 348 K were smaller than 100 nm. The use of PVP with Fe powder as cementing agent is not recommended as PVP can lose templating ability due to the

IP T

unwanted physical adsorption on Fe particles.

At the targeted mine, copper is almost entirely produced as cathode via leaching-solvent extraction-

SC R

electrowinning. Nevertheless, the relatively low amount of leach pad drainage produced seasonally could be valorized by producing CuNPs through the method developed in this study. The quality of the obtained

U

material, the fast kinetics, and the possibility to use iron scraps as cementing agent could allow for slightly

A

material such as CuNPs by an inexpensive operation.

N

diversifying the production activity. All the more as the method would enable to obtain a high added value

M

In this view, although we applied the cementation to a specific copper source, the developed method

ED

could represent a more general technology to produce CuNPs in hydrometallurgical processes.

Acknowledgements

PT

Part of this work was supported by the grant-in-aid from Mitsubishi Material Corporation (MMC, Japan). This work was also partially financially by the Waseda University Zaiken program research grant.

CC E

Part of this work was also performed as a component of the activities of the Research Institute of the

A

Sustainable Future Society, Waseda Research Institute for Science and Engineering, Waseda University.

References [1]

H.R. Watling, Chalcopyrite hydrometallurgy at atmospheric pressure: 2. Review of acidic chloride process options, Hydrometallurgy. 146 (2014) 96–110. doi:10.1016/j.hydromet.2014.03.013.

[2]

C. Klauber, A critical review of the surface chemistry of acidic ferric sulphate dissolution of

15

chalcopyrite with regards to hindered dissolution, Int. J. Miner. Process. 86 (2007) 1–17. doi:10.1016/j.minpro.2007.09.003. [3]

U.U. Jadhav, H. Hocheng, A review of recovery of metals from industrial waste Industrial management and organisation, J. Achiev. Mater. Manuf. Eng. 54 (2012) 159–167. Y. Xu, L. Liu, Current status and future perspective of recycling copper by hydrometallurgy from waste printed circuit boards, Procedia Environ. Sci. 31 (2016) 162–170. doi:10.1016/J.PROENV.2016.02.022.

V. Krstić, T. Urošević, B. Pešovski, A review on adsorbents for treatment of water and

SC R

[5]

IP T

[4]

wastewaters containing copper ions, Chem. Eng. Sci. 192 (2018) 273–287.

X. Zhang, Q. Huang, M. Liu, J. Tian, G. Zeng, Z. Li, K. Wang, Q. Zhang, Q. Wan, F. Deng, Y.

N

[6]

U

doi:10.1016/j.ces.2018.07.022.

A

Wei, Preparation of amine functionalized carbon nanotubes via a bioinspired strategy and their

doi:10.1016/j.apsusc.2015.03.081.

Q. Huang, J. Zhao, M. Liu, J. Chen, X. Zhu, T. Wu, J. Tian, Y. Wen, X. Zhang, Y. Wei,

ED

[7]

M

application in Cu 2+ removal, Appl. Surf. Sci. 343 (2015) 19–27.

Preparation of polyethylene polyamine@tannic acid encapsulated MgAl-layered double hydroxide

PT

for the efficient removal of copper (II) ions from aqueous solution, J. Taiwan Inst. Chem. Eng. 82 (2018) 92–101. doi:10.1016/j.jtice.2017.10.019. Y. Liu, H. Huang, D. Gan, L. Guo, M. Liu, J. Chen, F. Deng, N. Zhou, X. Zhang, Y. Wei, A facile

CC E

[8]

strategy for preparation of magnetic graphene oxide composites and their potential for

A

environmental adsorption, Ceram. Int. 44 (2018) 18571–18577. doi:10.1016/j.ceramint.2018.07.081.

[9]

Q. Huang, J. Zhao, M. Liu, Y. Li, J. Ruan, Q. Li, J. Tian, X. Zhu, X. Zhang, Y. Wei, Synthesis of polyacrylamide immobilized molybdenum disulfide (MoS2@PDA@PAM) composites via musselinspired chemistry and surface-initiated atom transfer radical polymerization for removal of copper

16

(II) ions, J. Taiwan Inst. Chem. Eng. 86 (2018) 174–184. doi:10.1016/j.jtice.2017.12.027. [10] G. Zeng, X. Liu, M. Liu, Q. Huang, D. Xu, Q. Wan, H. Huang, F. Deng, X. Zhang, Y. Wei, Facile preparation of carbon nanotubes based carboxymethyl chitosan nanocomposites through combination of mussel inspired chemistry and Michael addition reaction: Characterization and improved Cu2+ removal capability, J. Taiwan Inst. Chem. Eng. 68 (2016) 446–454.

IP T

doi:10.1016/j.jtice.2016.09.008.

[11] C. Ayora, F. Macías, E. Torres, A. Lozano, S. Carrero, J.M. Nieto, R. Pérez-López, A. Fernández-

SC R

Martínez, H. Castillo-Michel, Recovery of rare earth elements and yttrium from passive-

remediation systems of acid mine drainage, Environ. Sci. Technol. 50 (2016) 8255–8262.

U

doi:10.1021/acs.est.6b02084.

N

[12] L. Makhloufi, B. Saidani, H. Hammache, Removal of lead ions from acidic aqueous solutions by cementation on iron, Water Res. 34 (2000) 2517–2524. doi:10.1016/S0043-1354(99)00405-4.

M

A

[13] T.N. Lung, The history of copper cementation on iron - the world’s first h y d r o m e t a l l u r g i c a l process from medieval china, Hydrometallurgy. 17 (1986) 113–129.

ED

[14] W. Barzyk, A. Kowal, A. Pomianowski, Noble metal (Ag, Au) cementation on non-stoichiometric cuprous sulphide grains, Colloids Surfaces A Physicochem. Eng. Asp. 208 (2002) 321–335.

PT

[15] A.R. Despić, D.M. Dražić, D. Šepa, Kinetics of cementation of noble metals on nickel, Electrochim. Acta. 11 (1966) 507–515. doi:10.1016/0013-4686(66)80027-0.

CC E

[16] Y. Ku, C.H. Chen, Kinetic study of copper deposition on iron by cementation reaction, Sep. Sci. Technol. 27 (1992) 1259–1275. doi:10.1080/01496399208019424.

A

[17] N. Demirkiran, A. Ekmekyapar, A. Künkül, A. Baysar, A kinetic study of copper cementation with zinc in aqueous solutions, Int. J. Miner. Process. 82 (2007) 80–85. doi:10.1016/j.minpro.2006.10.005. [18] B. Dönmez, F. Sevim, H. Saraç, Kinetic study of the cementation of copper from sulphate solutions onto a rotating aluminum disc, Hydrometallurgy. 53 (1999) 145–154. doi:10.1016/S0304-

17

386X(99)00042-0. [19] F. Gros, S. Baup, M. Aurousseau, Copper cementation on zinc and iron mixtures: Part 1: Results on rotating disc electrode, Hydrometallurgy. 106 (2011) 119–126. doi:10.1016/j.hydromet.2010.12.011.

reactor using two-level factorial design, Arab. J. Chem. 3 (2010) 187–190. doi:10.1016/j.arabjc.2010.04.009.

IP T

[20] I. Yahiaoui, F. Aissani-Benissad, Experimental design for copper cementation process in fixed bed

SC R

[21] F. Gros, S. Baup, M. Aurousseau, Intensified recovery of copper in solution: Cementation onto iron in fixed or fluidized bed under electromagnetic field, Chem. Eng. Process. Process Intensif. 47

U

(2008) 295–302. doi:10.1016/j.cep.2007.01.002.

N

[22] A. Dib, L. Makhloufi, Cementation treatment of copper in wastewater: Mass transfer in a fixed bed

A

of iron spheres, Chem. Eng. Process. Process Intensif. 43 (2004) 1265–1273.

M

doi:10.1016/j.cep.2003.12.006.

[23] M. El-Batouti, Removal of copper metal by cementation using a rotating iron cylinder, J. Colloid

ED

Interface Sci. 283 (2005) 123–129. doi:10.1016/j.jcis.2004.08.185. [24] R.A. Crane, D.J. Sapsford, Selective formation of copper nanoparticles from acid mine drainage

PT

using nanoscale zerovalent iron particles, J. Hazard. Mater. 347 (2018) 252–265. doi:10.1016/j.jhazmat.2017.12.014.

CC E

[25] P. Pal, M. Nazim, B.K. Dutta, A. Alshoaibi, P. Pal, M. Nazim, B.K. Dutta, A. Alshoaibi, Copper deposition and formation of nano-particles, Sep. Sci. Technol. 49 (2017) 2728–2733.

A

doi:10.1080/01496395.2014.937498. [26] R. Mittu, Synthesis, characterization of copper nanoparticles -A review, Int. Adv. Res. J. Sci. Eng. Technol. 3 (2016) 37–40. doi:10.17148/IARJSET.2016.3508. [27] M.B. Gawande, A. Goswami, F.X. Felpin, T. Asefa, X. Huang, R. Silva, X. Zou, R. Zboril, R.S. Varma, Cu and Cu-based nanoparticles: Synthesis and applications in catalysis, Chem. Rev. 116

18

(2016) 3722–3811. doi:10.1021/acs.chemrev.5b00482. [28] P. Calvert, Inkjet printing for materials and devices, Chem. Mater. 13 (2001) 3299–3305. doi:10.1021/cm0101632. [29] Y. Jianfeng, Z. Guisheng, H. Anming, Y.N. Zhou, Preparation of PVP coated Cu NPs and the application for low-temperature bonding, J. Mater. Chem. 21 (2011) 15981–15986.

IP T

doi:10.1039/c1jm12108a.

[30] J.-W. Yoon, J.-H. Back, J.-W. Yoon, J.-H. Back, Effect of sintering conditions on the mechanical

SC R

strength of Cu-sintered joints for high-power applications, Materials (Basel). 11 (2018) 2105. doi:10.3390/ma11112105.

U

[31] Y. Kobayashi, T. Maeda, Y. Yasuda, T. Morita, Metal-metal bonding using silver/copper

N

nanoparticles, Appl. Nanosci. 6 (2016) 883–893. doi:10.1007/s13204-015-0489-4.

A

[32] G. Granata, T. Yamaoka, F. Pagnanelli, A. Fuwa, Study of the synthesis of copper nanoparticles:

M

the role of capping and kinetic towards control of particle size and stability, J. Nanoparticle Res. 18 (2016). doi:10.1007/s11051-016-3438-6.

ED

[33] F. Pagnanelli, G. Granata, E. Moscardini, L. Toro, Synthesis of MnCO3 nanoparticles by microemulsions: Statistical evaluation of the effects of operating conditions on particle size

PT

distribution, J. Nanoparticle Res. 15 (2013). doi:10.1007/s11051-013-1887-8. [34] G. Granata, F. Pagnanelli, D. Nishio-Hamane, T. Sasaki, Effect of surfactant/water ratio and

CC E

reagents’ concentration on size distribution of manganese carbonate nanoparticles synthesized by microemulsion mediated route, Appl. Surf. Sci. 331 (2015) 463–471.

A

doi:10.1016/j.apsusc.2015.01.101. [35] G. Granata, F. Pagnanelli, E. Moscardini, Z. Takacova, T. Havlik, L. Toro, Simultaneous recycling of nickel metal hydride, lithium ion and primary lithium batteries: Accomplishment of European Guidelines by optimizing mechanical pre-treatment and solvent extraction operations, J. Power Sources. 212 (2012) 205–211. doi:10.1016/j.jpowsour.2012.04.016.

19

[36] G. Granata, A. Miura, W. Liu, F. Pagnanelli, C. Tokoro, Iodide-assisted leaching of chalcopyrite in acidic ferric sulfate media, Hydrometallurgy. 186 (2019) 244–251. doi:10.1016/J.HYDROMET.2019.04.019. [37] G. Granata, T. Yamaoka, F. Pagnanelli, A. Fuwa, Study of the synthesis of copper nanoparticles: the role of capping and kinetic towards control of particle size and stability, J. Nanoparticle Res. 18

IP T

(2016) 133–145. doi:10.1007/s11051-016-3438-6.

[38] R. Jhajharia, D. Jain, A. Sengar, A. Goyal, P.R. Soni, Synthesis of copper powder by mechanically

SC R

activated cementation, Powder Technol. 301 (2016) 10–15. doi:10.1016/j.powtec.2016.05.031. [39] D. Mohan, S. Chander, Removal and recovery of metal ions from acid mine drainage using

U

lignite—A low cost sorbent, J. Hazard. Mater. 137 (2006) 1545–1553.

N

doi:10.1016/j.jhazmat.2006.04.053.

A

[40] Q. Chen, Z. Luo, C. Hills, G. Xue, M. Tyrer, Precipitation of heavy metals from wastewater using

M

simulated flue gas: Sequent additions of fly ash, lime and carbon dioxide, Water Res. 43 (2009) 2605–2614. doi:10.1016/j.watres.2009.03.007.

ED

[41] E. Sahinkaya, M. Gungor, A. Bayrakdar, Z. Yucesoy, S. Uyanik, Separate recovery of copper and zinc from acid mine drainage using biogenic sulfide, J. Hazard. Mater. 171 (2009) 901–906.

PT

doi:10.1016/J.JHAZMAT.2009.06.089.

[42] H. Luo, G. Liu, R. Zhang, Y. Bai, S. Fu, Y. Hou, Heavy metal recovery combined with H2

CC E

production from artificial acid mine drainage using the microbial electrolysis cell, J. Hazard. Mater. 270 (2014) 153–159. doi:10.1016/j.jhazmat.2014.01.050.

A

[43] M. Karavasteva, The effect of certain surfactants on the cementation of cobalt from zinc sulphate solutions by suspended zinc particles in the presence of copper or antimony, Can. Metall. Q. 40 (2001) 4433–1879. doi:10.1179/000844301794388416doi.org/10.1179/000844301794388416. [44] O. Levenspiel, Chemical reaction engineering, Third Edition, John Wiley & Sons, New York, 1999. doi:10.1021/ie990488g.

20

[45] F. Gros, S. Baup, M. Aurousseau, Copper cementation on zinc and iron mixtures: Part 2: Fluidized bed configuration, Hydrometallurgy. 106 (2011) 127–133. doi:10.1016/j.hydromet.2010.12.012. [46] A.A. Taha, S.A.H. Abd El-Ghani, Effect of surfactants on the cementation of cadmium, J. Colloid Interface Sci. 280 (2004) 9–17. doi:10.1016/j.jcis.2004.07.023. [47] A. Mirzaei, K. Janghorban, B. Hashemi, M. Bonyani, S.G. Leonardi, G. Neri, Characterization and

IP T

optical studies of PVP-capped silver nanoparticles, J. Nanostructure Chem. 7 (2017) 37–46. doi:10.1007/s40097-016-0212-3.

SC R

[48] P.S. Mdluli, N.M. Sosibo, P.N. Mashazi, T. Nyokong, R.T. Tshikhudo, A. Skepu, E. Van Der

Lingen, Selective adsorption of PVP on the surface of silver nanoparticles: A molecular dynamics

U

study, J. Mol. Struct. 1004 (2011) 131–137. doi:10.1016/j.molstruc.2011.07.049.

N

[49] A. EL Aferni, M. Guettari, T. Tajouri, Effect of polymer conformation on polymer-surfactant

A

interaction in salt-free water, Colloid Polym. Sci. 294 (2016) 1097–1106. doi:10.1007/s00396-016-

M

3869-8.

[50] A.R. Tao, S. Habas, P. Yang, Shape control of colloidal metal nanocrystals, Small. 4 (2008) 310–

ED

325. doi:10.1002/smll.200701295.

[51] B.L. Cushing, V.L. Kolesnichenko, C.J. O’Connor, Recent advances in the liquid-phase syntheses

PT

of inorganic nanoparticles, Chem. Rev. 104 (2004) 3893–3946. doi:10.1021/cr030027b. [52] J.E. Leffler, E. Grunwald, Rate and Equilibria of Organic Reactions, Wiley, New York, New York,

CC E

1989.

[53] K.M. Koczkur, S. Mourdikoudis, L. Polavarapu, S.E. Skrabalak, Polyvinylpyrrolidone (PVP) in

A

nanoparticle synthesis, Dalt. Trans. 44 (2015) 17883–17905. doi:10.1039/C5DT02964C.

21

Figure Caption Fig. 1. Concentrations of metals during cementation at 298 K (a), 311 K (b) 323 K (c) and 348 K (d). Fig. 2. Second order kinetic fitting for cementation without surfactants. Fig. 3. Second order kinetic fitting for cementation with SDS 0.2 M (a) and 0.4 M (b).

Fig. 5. Inhibition trends for cementation with SDS and PVP. Fig. 6. Activation energy of cementation with and without surfactants.

IP T

Fig. 4. Second order kinetic fitting for cementation with PVP 2 mM (a) and 4 mM (b).

SC R

Fig. 7. Isokinetic relationship for cementation with and without surfactants at different temperatures. Fig. 8. XRD patterns of cementation products obtained without surfactants

U

Fig. 9. XRD patterns of cementation products obtained with 0.2 M SDS (a), 0.4 M SDS (b), 2 mM PVP

N

(c), and 4 mM PVP (d).

A

Fig. 10. FE-SEM micrographs of copper cemented with 0.2 M SDS at 298 K (a), 323 K (c) and 348 K (e)

M

and with 0.4 M SDS at 298 K (b), 323 K (d) and 348 K (f). Fig. 11. FE-SEM micrographs of copper cemented with 2 mM PVP at 298 K (a), 323 K (c) and 348 K (e)

ED

and with 4 mM PVP at 298 K (b), 323 K (d) and 348 K (f). Fig. 12. Particle size distribution of copper cemented with SDS and PVP.

PT

Fig. 13. Estimates of significant effects of the factorial designs with SDS (black bars), PVP (white bars)

A

CC E

and surfactant change (grey bar)

22

3

6

Zn, Cd concentration (g/L)

IP T

SC R 0.20 0.15 0.10

0.05

(d)

0 24 27 30 9 12 15 18 21 0 3 6 0.00 9 12 15 18 21 24 27 30 0 3 6 9time 12 (min) 15 18 21 24 27 30 time (min) time (min) Cu Fe Mn Cd Zn

0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00

Zn, Cd concentration (g/L)

2

9 12 15 18 21 24 27 30 time (min)

Zn, Cd concentration (g/L)

4

10 9 8 7 6 5 4 3 2 1 0

6

U

6

0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00

N

8

(c)

3

0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00

A

CC E

PT

ED

0

10

(b)

0

A

10 9 8 7 6 5 4 3 2 1 0

10 9 8 7 6 5 4 3 2 1 0

9 12 15 18 21 24 27 30 time (min)

Cu, Fe, Mn concentration (g/L)

6

Zn, Cd concentration (g/L)

3

M

Cu, Fe, Mn concentration (g/L)

0

0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00

Cu, Fe, Mn concentration (g/L)

(a)

Zn, Cd concentration (g/L)

10 9 8 7 6 5 4 3 2 1 0

Cu, Fe, Mn concentration (g/L)

Cu, Fe, Mn concentration (g/L)

Fig. 1.

23

Fig. 2. 25 298 K 311 K 323 K 15

348 K

10

IP T

X/(1-X)

20

0 30

60 time (sec)

90

120

A

CC E

PT

ED

M

A

N

U

0

SC R

5

24

Fig. 3.

9

(a)

8 6

IP T

X/(1-X)

7 5 4 2 1 0

30

60 time (sec)

8 25 20 6 15 10 4 5 0 2 0 0

ED

M

X/(1-X)

X/(1-X)

(b)

A

10

30

PT

0

298 K

30

60

90

60 time (sec)

311 K

120 90

323 K

150 120

348 K

time (sec)

A

CC E

120

N

12

90

U

0

SC R

3

25

Fig. 4. 14

(a)

12

X/(1-X)

10 8 6

IP T

4 2 0 30

60 time (sec)

90

12

(b)

U

10

X/(1-X)

8

30 0

M

A

N

25 20 6 15 10 4 5 0 2 0 0

60

30

ED

X/(1-X)

120

SC R

0

60 time (sec)

311 K

120 90

323 K

150 120

348 K

time (sec)

A

CC E

PT

298 K

90

26

Fig. 5. 100

Inhibition (%)Inhibition (%)

80

IP T

60 100 40 80

0 40 298

318 328 338 348 temperature (K) SDS 0.2 M SDS 0.4 M PVP 2 mM PVP 4 mM

0

25

U

308

20

35

45 55 65 temperature ( C)

75

A

N

Fig. 6.

SC R

20 60

M

-1.6 -2.1

ED

-2.6

lnk

-3.1

-3.6

PT

-4.1

-4.6

-5.6 0.0028

0.003 1/T (103

0.0032 K-1)

0.0034

A

CC E

-5.1

SDS 0.2 M SDS 0.4 M PVP 2 mM PVP 4 mM NO SURFACTANT

27

Fig. 7. 60 50

SDS 0.2 M SDS 0.4 M

40

323 K

SDS 0.2 M SDS 0.4 M

30 20

NOS NOS

PVP 2 mM

10 PVP 4 mM

0 125

150

175 200 225 -ΔS* (J/mol)

275

Cu

M

A

N

U

Fig. 8.

250

SC R

100

IP T

ΔH* (kJ/mol)

298 K

PVP 2 mM PVP 4 mM

348 K

ED

323 K

PT

298 K

20

30

40

50 60 70 2θ (deg)

80

90 100 110

A

CC E

10

28

A ED

PT

CC E

IP T

SC R

U

N

A

M

Fig. 9.

29

Fig. 10.

(b)

(c)

(d)

(e)

(f)

A

CC E

PT

ED

M

A

N

U

SC R

IP T

(a)

30

(d)

(e)

(f)

SC R

(c)

U

(b)

A

CC E

PT

ED

M

A

N

(a)

IP T

Fig. 11.

31

Fig. 12. 100

IP T

80 60 SDS 0.4 M - 298 K

SC R

SDS 0.4 M - 323 K SDS 0.4 M - 348 K

20

SDS 0.2 M - 298 K SDS 0.2 M - 323 K

0 100

U

SDS 0.2 M - 348 K PVP 4 mM - 298 K PVP 4 mM - 323 K

80

PVP 4 mM - 348 K

N

Passing fraction (%)

40

PVP 2 mM - 298 K

60

A

PVP 2 mM - 323 K PVP 2 mM - 348 K

M

40

ED

20 0

100

1000 Particle diameter (nm)

A

CC E

PT

10

32

A ED

PT

CC E 0

-2000

IP T

-4000

-6000

-8000

SC R

U

N

A

M

significant effect (nm)

Fig. 13.

4000

2000

33

Surfactant

Temperature (K)

Max Cu recovery (%)

k (sec-1)

R2

298

91 ± 13

0.0417

0.9624

311

94 ± 10

0.0709

0.9457

323

100 ± 1

0.1060

0.8753

348

93 ± 6.0

0.1574

0.9598

298

90 ± 1

0.0060

0.9826

85.6

311

91 ± 13

0.0091

0.9953

87.2

323

94 ± 8

0.0208

0.9607

80.4

348

95 ± 4

0.0869

0.9689

44.8

298

83 ± 6

0.0055

0.9787

86.8

311

88 ± 4

0.0165

0.9755

76.7

323

99 ± 1

U

Table 1. Experimental conditions and results: Cu recovery and kinetic parameters I (%)

0.0296

0.9835

72.1

348

87 ± 7

0.0753

0.9790

52.2

298

91 ± 13

0.0238

0.9745

42.9

98 ± 2

0.0547

0.9770

22.9

98 ± 3

0.0650

0.9788

38.7

348

97 ± 3

0.0952

0.9811

39.5

298

95 ± 6

0.0196

0.9411

53.0

311

98 ± 1

0.0449

0.9475

36.7

323

99 ± 2

0.0587

0.9227

44.6

348

98 ± 2

0.0794

0.9664

49.6

-

311 PVP 2 mM

N

A

A

CC E

PVP 4 mM

PT

ED

323

M

SDS 0.4 M

SC R

SDS 0.2 M

IP T

None

34

-∆S* (J×K-1×mol-1)

∆G* (kJ×mol-1)

20.2

202.7

84.7

20.1

203.0

323

20.0

203.3

348

19.8

204.0

298

45.0

137.8

85.8

138.2

88.3

138.5

90.6

139.1

95.4

41.6

147.2

86.1

41.5

147.6

88.6

41.4

147.9

91.0

41.2

148.5

95.8

46.0

118.8

81.4

45.9

119.1

82.9

10.9

243.5

87.7

10.8

243.8

85.9

10.6

244.4

95.7

46.7

87.9

46.6

121.1 121.4

11.0

247.2

97.1

10.9

247.5

87.9

10.7

248.1

90.9

Ea (kJ×mol-1)

298 311

None

22.7

311 SDS 0.2 M

44.9 47.5 44.8

348

44.6

N

323

311 323 348

44.1

M

SDS 0.4 M

ED

298 311

48.5

311

PT

PVP 2 mM

323

13.5

CC E

75

A

298 311

49.1

311 323 348

A

298

PVP 4 mM

SC R

∆H* (kJ×mol-1)

Temperature (K)

U

Surfactant

IP T

Table 2. Activation parameters of cementation

13.6

87.8 90.6 96.5

90.9

35

SDS 0.4 M

PVP 2 mM

P60 diameter (nm)

298

Cu

98.1

16400 ± 604

323

Cu

98.5

3338 ± 317

348

Cu

98.8

1247 ± 417

298

Cu, Fe

96.7

547 ± 252

323

Cu

99.2

246 ± 72

348

Cu

99.3

97 ± 27

298

Cu

98.9

254 ± 82

323

Cu

99.0

152 ± 69

348

Cu

98.8

97 ± 8

298

Cu, Fe

87.2

2302 ± 387

323

Cu

99.1

826 ± 97

99.2

465 ± 110

Cu, Fe

90.2

646 ± 120

Cu

98.2

335 ± 87

Cu

98.5

281 ± 64

298 323

ED

PVP 4 mM

Cu

M

348

A

CC E

PT

348

IP T

Cu grade (%)

SC R

SDS 0.2 M

Product phase composition

U

None

Temperature (K)

N

Surfactant

A

Table 3. Experimental conditions and results: purity and particle size

36