Separation of gold(III) ions by 1,8-diaminonaphthalene-formaldehyde chelating polymer

Hydrometallurgy 134–135 (2013) 87–95

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Separation of gold(III) ions by 1,8-diaminonaphthalene-formaldehyde chelating polymer Ümit Can Erim a, Mustafa Gülfen b,⁎, Ali Osman Aydın b a b

İstanbul Medipol University, School of Pharmacy, Department of Analytical Chemistry, Fatih 34083, İstanbul, Turkey Sakarya University, Faculty of Arts and Sciences, Department of Chemistry, Esentepe 54187, Sakarya, Turkey

a r t i c l e

i n f o

Article history: Received 29 July 2012 Received in revised form 27 January 2013 Accepted 13 February 2013 Available online 18 February 2013 Keywords: Gold(III) ions 1,8-Diaminonephthalene-formaldehyde Chelating polymer Adsorption Separation

a b s t r a c t In the present work, a new 1,8-diaminonaphthalene-formaldehyde (1,8-DAN-F) polymer was synthesized by the reaction of 1,8-DAN with formaldehyde solution. The structure of 1,8-DAN-F polymer was characterized by elemental analysis, FT-IR spectroscopy and thermal analysis. In order to prepare a useful adsorbent, 1,8-DAN-F polymer was blended at the ratio of 25% with polyvinylchloride (PVC) using THF solvent. 1,8-DAN-F/PVC polymer blend was used in selective separation and recovery of Au(III) ions from Fe(III), Cu(II) and Ni(II) ions. The effects of pH and the initial concentration of Au(III) ions on the adsorption were examined by the batch technique. The optimum pH level was found to be 1 for the Au(III) adsorption. Furthermore, the adsorption data were applied to the Langmuir and Freundlich isotherms. It was found that the adsorption data fitted well to the Langmuir isotherm. The maximum Au(III) adsorption capacity (qmax) of the polymer blend was 119.0 mg·g−1. The adsorption kinetics indicated that the Au(III) adsorption proceeds according to the pseudo-second-order model. Also, the separation of Au(III) ions from Fe(III), Cu(II) and Ni(II) ions was examined by the column technique. The column studies showed that Au(III) ions can be separated and concentrated from the base metal ions. © 2013 Elsevier B.V. All rights reserved.

1. Introduction Gold is one of the precious metals and it is used widely in various areas such as art, jewelry, electronic manufacturing, dentistry and currency. It is has a special economic interest compared with other metals. Therefore, the analysis, separation, enrichment or preconcentration of gold ions is important in recycling or prior to producing metallic gold (Fırlak et al., 2012; Goodman, 2002; Syed, 2012). Chelating resins or polymers with functional groups play a vital role in the adsorption of gold ions. Chelating polymers having N and S donor atoms are preferred in the adsorption of gold ions, because of the selectivity according to Hard–Soft Acid–Base (HSAB) principle introduced by Pearson (1968). Thiourea/urea–formaldehyde (Ertan and Gülfen, 2009; Ni et al., 2001), melamine–formaldehyde–thiourea (Aydın et al., 2008), bisthiourea–formaldehyde (Atia, 2005), chitosan derivatives (Arrascue et al., 2003; Ramesh et al., 2008; Wan et al., 1999), polyamines (Belfer and Binman, 1996; Harris et al., 1992),

⁎ Corresponding author at: Department of Chemistry, Faculty of Arts & Sciences, Sakarya University, TR-54187, Sakarya, Turkey. Tel.: + 90 264 2956051; fax: + 90 264 2955950. E-mail address: [email protected] (M. Gülfen). 0304-386X/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.hydromet.2013.02.005

fibers with amine functional group (Lu et al., 1994), chelating resins with o-phenylenediamine, amine and thiol (Abd El-Ghaffar, et al., 2009; Donia et al., 2005), and polyaniline (Nabid et al., 2011) are some examples of the chelating polymers including N and/or S donor atoms for Au(III) ions. In this study, the separation and concentration of Au(III) ions were examined using a new chelating polymer, 1,8-diaminonaphthaleneformaldehyde (poly(1,8-DAN-F)), which was synthesized from 1,8diaminonaphthalene (1,8-DAN) and formaldehyde. In the synthesis of 1,8-DAN-F polymer, it was aimed that primary aromatic amine groups will remain open as a functional coordinating group to adsorb Au(III) ions. In the literature, poly(1,8-diaminonaphthalene) poly(1,8-DAN) has been synthesized by some researchers using chemical or electrochemical oxidation methods (Nasalska and Skompska, 2003). However, poly(1,8-DAN) includes less primary amine groups since the amine groups during the polymerization of 1,8-DAN are bound to methylene group. The polymerization of 1,8-DAN with formaldehyde may be resulted in a polymer yield with primary aromatic amine as functional adsorptive group. Therefore, the polymerization of 1,8-DAN with formaldehyde was selected in this study. In the present work, 1-8,DAN-F polymer was synthesized and it was blended at the ratio of 25% (w/w) with PVC to provide a useful adsorbent. This prepared polymer blend has free primary and

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Table 1 Elemental analysis of 1,8-DAN-F polymer (w/w). C% (RSD%) (experimental)

N% (RSD%) (experimental)

H%, (RSD%) (experimental)

Cl% (theoretical)

O% (theoretical)

57.65 (0.46)

10.23 (0.81)

5.76 (0.17)

25.94

3.42

neighbor amine groups to absorb Au(III) ions and it was used in the adsorption, separation and preconcentration of Au(III) ions using the batch and column techniques. 2. Experimental procedure 2.1. Materials 1,8-Diaminonaphthalene (99.5%) and formaldehyde (37% aqueous solution, d=1.09 g·cm−3) used in the synthesis of the polymer were purchased from Merck Co. (Darmstadt, Germany). Metallic gold (Nadir Metal Refining Co., Turkey) was dissolved in aqua regia (HNO3/HCl, 1:3 v/v) and this stock solution was used as the source of Au(III) ions. All the other chemicals obtained from Merck Co. (Darmstadt, Germany) were analytical grade and used as received. 2.2. Synthesis of 1,8-DAN-formaldehyde polymer Poly(aniline-formaldehyde) polymer is known well and it can be synthesized by the binding of methylene (\CH2−) to the ortho position of aniline in HCl solution. So, poly(aniline-formaldehyde) includes primary aromatic amines (Ho et al., 2005; Kishore and Santhanalakshmi, 1983; Koner et al., 2008; Kumar et al., 1993, 2009). Similarly, 1,8-DAN-F polymer was synthesized by the polymerization of 1,8-DAN with formaldehyde in the presence of HCl acid. The synthesis was done at the molar ratio of 1/1. 2.16 g (0.02 mol) of 1,8-DAN was first dissolved by stirring for 12 h in 500 mL 1 M HCl solution in a beaker. Then 1.47 mL of formaldehyde solution (0.02 mol formaldehyde) was quickly poured into

the mixture. A brown-black the polymer began to precipitate after 5 min. The polymerization reaction was carried out for 40 min at the temperature of 15 °C. The precipitate was filtered, washed with distilled water and dried in a vacuum oven at 55 °C for 24 h. The dried sample was characterized by elemental analysis, FT-IR spectroscopy and thermogravimetric analysis. 2.3. Polymer blending To obtain a useful adsorbent, 25% 1,8-DAN-F polymer and 75% PVC were blended by kneading together with THF solvent. This polyblend adsorbent (1,8-DAN-F/PVC) was dried again to evaporate THF solvent. The all adsorption studies were performed with 25% 1,8-DAN-F polymer in 75% PVC. 2.4. Characterization of 1,8-DAN-F polymer The synthesized 1,8-DAN-F polymer was characterized by determining C, H and N elemental content using Truspec Model Leco Elemental analyzer (Leco Corp. Michigan, USA). It estimated the composition of the polymer content. The FTIR spectra of 1,8-DAN monomer and 1,8DAN-F polymer were obtained with a resolution of 0.02 cm−1 in the wavenumber range of 500–4000 cm−1 on a Shimadzu-IR Prestige-21 model FTIR spectrophotometer (Shimazu Corp. Japan) with equipped ATR. The structure of the polymer was suggested according to the obtained FTIR results. The thermogravimetric analysis of the 1,8-DAN-F polymer was performed with a Du Pont Instrument TGA951 thermogravimetric analyzer under air atmosphere. 2.5. Au(III) adsorption studies The adsorption studies of Au(III) ions on the 1,8-DAN-F blended in PVC were done using batch and column techniques. The effects of acidity, contact time and adsorption isotherms were examined by

Fig. 1. FTIR spectra of 1,8-DAN monomer and 1,8-DAN-F polymer.

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batch technique. In the column technique, the adsorption, elution, separation and preconcentration of Au(III) ions were studied. 2.5.1. Effect of acidity To determine the optimum acidity and contact time in the adsorption of Au(III) ions, the experimental studies were carried out at 1, 2 and 3 M HCl concentrations and pH = 1–7 for 192 h. Studying the adsorption in strong basic media was avoided due to the precipitation of metal hydroxides. 0.3 g of the blended polymer was placed in a beaker containing 100 mL of Au(III) ions at the concentration of 200 mg·L−1. Two milliliters of the solution was taken at different time intervals and the concentrations of Au(III) ions were determined. The adsorbed quantities of Au(III) ions on the polymer, qe (mg·g−1) were calculated with the following equation (Eq. (1)). qe ¼

ðC 0 −C ÞV w

ð1Þ

In this equation, C0 and C are the initial and final concentrations (mg·L−1) of Au(III) ions in solution, respectively, V is the solution volume (L) and w is the weight (g) of the polymeric adsorbent. Moreover, pH change during the adsorption was examined using the Au(III) solutions at pH= 3 and 5. 2.5.2. Adsorption isotherms The Langmuir and Freundlich isotherms were used to examine the adsorption behaviors of Au(III) ions on the polymeric adsorbent. The linearized forms of The Langmuir (Eq. (2)) and Freundlich (Eq. (3)) equations are expressed as follows: Ce C 1 ¼ e þ qe q max q max K L ln qe ¼ ln K F þ

1 lnC e n

ð2Þ

ð3Þ

where qe (mg·g−1) is the adsorption capacity, Ce (mg·L−1) is the equilibrium concentration of Au(III) ions, qmax (mg·g−1) is the maximum adsorption capacity, KL is the Langmuir adsorption constant, n is the Freundlich constant, and KF is the binding energy constant reflecting the affinity of the adsorbents to metal ions (Gezer et al., 2011; Gubbuk et al., 2009; Kırcı et al., 2009; Muslu and Gülfen, 2011; Unlu and Ersoz, 2006). The experiments for the adsorption isotherms were performed by placing 0.3 g portions of the adsorbent in a series of flasks containing 100 mL of Au(III) solution at the concentrations of 50, 100, 150, 200, 250 and 300 mg·L−1. The adsorption experiments were done at pH=1

89

which is the optimum pH. The concentrations of Au(III) ions in the samples taken at different time intervals up to 120 min were determined. The experiments were applied to the Langmuir and Freundlich isotherms. 2.5.3. Adsorption kinetics The adsorption kinetics was examined using the obtained adsorption data. Pseudo-first-order and pseudo-second-order equations were used in the kinetic calculations. 2.5.3.1. Pseudo-first-order equation. The pseudo-first-order equation (Lagergren's equation) describes adsorption in solid–liquid systems based on the sorption capacity. A simple kinetic analysis of adsorption is the pseudo-first-order equation in the form (Ho and McKay, 1998, 2000) dqt ¼ k1 ðqe −qt Þ dt

ð4Þ

where k1 (min−1) is the rate constant of pseudo-first-order adsorption, qe (mg·g−1) is the amount of metal ion sorbed at equilibrium, and qt (mg·g−1) is the amount of metal ion on the surface of the sorbent at any time t (min). By applying the boundary condition qe =0 at t = 0, Eq. (4) becomes ln ðqe −qt Þ ¼ ln qe −k1 t:

ð5Þ

2.5.3.2. Pseudo-second-order equation. In addition, a pseudo-second-order equation may be tested on the experimental data. The kinetic rate equation is dqt 2 ¼ k2 ðqe −qt Þ dt

ð6Þ

where k2 (g·mg − 1·min − 1) is the rate constant of pseudo-secondorder adsorption, taking into account the initial sorption rate, v0 (mg·g − 1·min − 1) (Ho and McKay, 1998, 2000). v0 ¼ k2 qe

2

ð7Þ

Eq. (6) can be rearranged to obtain t 1 1 ¼ þ t: qt v0 qe

ð8Þ

The values of v0 and qe can be determined experimentally by plotting t/qt versus t and then k2 can be calculated from Eq. (7).

Fig. 2. Suggested structure of 1,8-DAN-F polymer.

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Fig. 3. Effect of acidity on Au(III) adsorption.

2.5.4. Column studies The separation and concentration of Au(III) ions from Cu(II), Fe(III) and Ni(II) base metal ions were studied by column technique. The column system mainly consists of a peristaltic pump and a glass column which has the length of 15 cm and inner diameter of 0.8 cm. A 1.2 g portion of the blended polymer was packed into the column (Bed volume: 0.92 mL), and the bottom of the column was plugged with glass wool. The feed solution including Au(III), Cu(II), Fe(III) and Ni(II) ions was prepared at 150 mg/L concentrations and pH=1. The solution was passed through the column at the flow rate of 0.5 mL·min−1. Each 10 mL of the effluent solution was collected separately and the concentrations of the metal ions were determined by FAAS. Thereafter, the column was washed through carefully by flowing distilled water. The polymer loaded by Au(III) ions together with the base metal impurities was subjected to elution using 1 M thiourea solution acidified with 1 M HCl. Au(III) and the other metal ions in the collected effluent solutions were also analyzed by FAAS.

2.5.5. Preconcentration factor In order to obtain a high preconcentration factor, Au(III) ions in the large sample volume have been quantitatively adsorbed and then desorbed by using small stripping volumes. The effect of sample volume on Au(III) sorption was studied by passing the solutions containing 4 μg of Au(III) ions in 50, 100, 200, 400, 600 and 1000 mL water. Au(III) was quantitatively retained in all cases. The adsorbed Au(III) on the polymeric adsorbent was eluted out by 10 mL of 1 M thiourea + 1 M HCl mixed solution.

2.6. Metal ion analyses The analyses of Au(III), Cu(II), Fe(III) and Ni(II) ions before or after the adsorption were performed using a Shimadzu AA-6701 model flame atomic absorption spectrophotometer (FAAS) (Japan). The measurements of Au(III), Cu(II), Fe(III) and Ni(II) ions were carried

Fig. 4. pH change during Au(III) adsorption.

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91

Fig. 5. Adsorption isotherms.

3. Results and discussion

for benzene ring at 638–810 cm −1 also changed. These results show a new substitution to benzene ring by forming secondary amine. It suggested a structure for 1,8-DAN-F polymer and it was given in Fig. 2 (Li et al., 2004; Patys et al., 1997; Sayyah et al., 2009).

3.1. Characterization of 1,8-DAN-F polymer

3.2. Au(III) adsorption studies

Elemental analysis of the synthesized 1,8-DAN-F polymer was performed by CHN analyzer. The obtained results are given in Table 1. C, H and N contents were found nearly the ratios in 1,8-DAN monomer. 1,8-DAN-F polymer has amine groups as chelating functionality. In addition, possible chloride content bound to protonated amines (>NH2+Cl−) was estimated as 25.94% because of the synthesis in HCl solution and oxygen content was 3.42%. Thermogravimetric analysis showed that 1,8-DAN-F polymer was stable up to 190 °C. The dissolution of the polymer in 3 M HCl, 0.1 M NaOH and 0.1 M HNO3 solution was tested and it was seen that the polymer did not dissolved in these solution. The FITR spectra of 1,8-DAN monomer and 1,8-DAN-F polymer were recorded and they are given in Fig. 1. As can be seen from the FTIR spectra, it was found that the primary amine peaks at 3298– 3414 cm −1 change to the secondary amine peaks. The C–H peaks

Au(III) adsorption studies were performed by batch and column techniques. In the batch technique, the effect of acidity, adsorption isotherms, and adsorption capacity were examined. Then separation, recovery and preconcentration of Au(III) ions were studied by column technique.

out with a hallow cathode lamp (Koto, Japan) at wavelengths of 244.8, 324.8, 248.3 and 232.0 nm, respectively, using an air-acetylene flame.

3.2.1. Effect of acidity The effect of acidity of initial solution on the adsorption of Au(III) was examined at the pH = 1–7 and 1–3 M HCl concentrations in this section and the results were shown in Fig. 3. As can be seen from the experimental results, it was found that high adsorption capacities were obtained in the pH range of 1–3. It was seen that higher HCl concentrations than 1 M and higher pH values than 3 decreased slightly the quantity of Au(III) ions. The decrease at high HCl concentrations can be explained with competitive adsorption of H + ions. On the

Fig. 6. The Langmuir isotherm.

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Fig. 7. The Freundlich isotherm.

other hand, the decrease above pH=3 is due to the deprotonation of polymeric amines (R-NH2) (Birinci et al., 2009; Ertan and Gülfen, 2009). In acidic solutions (below pH=5), AuCl4−, Au(OH)Cl3−, Au(OH)2Cl2−, Au(OH)3, AuCl3, AuOHCl2 and Au(OH)2Cl may be present in the solution. At the around of pH=1 and 0.1 M HCl concetration, the predominant complex ion of Au(III) species is AuCl4− (Arrascue et al., 2003). In general, the results showed that Au(III) adsorption will be studied in the wide range of acidic conditions. For the later adsorption studies, the optimum pH was selected as pH=1. In addition, pH change during Au(III) adsorption was examined and the results were given in Fig. 4. It was seen that pH was decreased after the adsorption started. This is due to the exchange of protons bounded to amine sites with Au(III) ions. The adsorption of Au(III) onto the polymer including primary and secondary amines can be explained with ionic interaction (Eq. (9)) and chelation (Eq. (10)) mechanisms. These mechanisms confirm the proton release. It is possible that both ionic interaction and chelation mechanisms could occur, consecutively (Çelik et al., 2010; Ertan and Gülfen, 2009; Guibal, 2004). þ

−

R−NH3 Cl þ AuCl4

−

þ

¼ R−NH3 AuCl4

−

−

þ Cl

ðIonic interactionÞ ð9Þ

R−NH3 þ AuCl4 − ¼ R−ðH2 ÞN…AuCl3 þ Hþ þ Cl−

ð10Þ

ðChelationÞ

3.2.2. Adsorption isotherms To investigate the adsorption behaviors, the Au(III) solutions at various initial concentrations between 50 and 300 mg·L −1 ions were shaken with the polymeric adsorbent for 120 h. The obtained results are given in Fig. 5. It was found that the adsorption was equilibrated on the contact time of 100 h and later. The saturated adsorption capacity was about 90 mg·L −1. To understand the adsorption behaviors better, the Langmuir (Eq. (2)) and Freundlich (Eq. (3)) equations were employed to fit

Table 2 The Langmuir and Freundlich coefficients. The Langmuir isotherm

The Freundlich isotherm

qmax (mg·g−1)

b (L·mg−1)

R2

KF (mg·g−1)

n

R2

119.0

0.01764

0.9698

6.70

1.92

0.9644

the experimental data. The Langmuir model assumes that an adsorption occurs on a homogeneous surface by monolayer adsorption without any interaction between adsorbed ions. The Freundlich model assumes that the adsorption occurs on a heterogeneous surface by monolayer adsorption (Gubbuk et al., 2009; Unlu and Ersoz, 2006). The experimental adsorption data obtained from the studies at various initial concentrations of Au(III) ions were applied to both the Langmuir and Freundlich equations and the results are given in Figs. 5 and 6, respectively. In addition, the coefficients for the Langmuir and Freundlich equations were calculated from Figs. 6 and 7, and the results are given in Table 2. According to the calculations of the adsorption isotherms, it was found that the Langmuir isotherm was a better fitting model than that of Freundlich. This situation showed that a homogeneous and monolayer adsorption occurred. Moreover Au(III) adsorption capacity of 1,8-DAN-F blended polymer was calculated as 119.0 mg·g−1 from the Langmuir isotherm graph. 3.2.3. Adsorption kinetics To evaluate the kinetics of Au(III) adsorption process, the pseudofirst-order and pseudo-second-order models were tested using the experimental adsorption data. The pseudo-first-order equation (Lagergren's equation) describes adsorption in solid–liquid systems based on the sorption capacity of solids. The pseudo-second-order rate expression shows chemisorption kinetics from liquid solutions. The kinetic parameters in both the pseudo-first-order and the pseudo-second-order rate expressions were calculated from Au(III) adsorption data and the results are given in Table 3. It was found that the pseudo second-order equation gave a better fit to the sorption process than the pseudo-first-order

Table 3 Kinetic parameters in Au(III) adsorption. C0 (mg·L−1)

50 100 150 200 250 300

First order

Second order

k1 (min−1)

R2

v0

k2 (g·mg−1·min−1)

qe (mg·g−1)

R2

0.0437 0.0503 0.0512 0.0556 0.0524 0.0563

0.9117 0.9045 0.9494 0.9583 0.8993 0.9098

0.03729 0.00744 0.00311 0.00265 0.00163 0.00139

0.00106 0.00104 0.00102 0.00091 0.00082 0.00076

29.33 50.51 68.03 74.63 90.91 98.04

0.8050 0.9253 0.9524 0.9505 0.9621 0.9615

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Table 4 Comparative data for Au(III) adsorption. Adsorbent

Functional group

Au(III) adsorption capacity mg·g−1

Kinetics (min)

References

Resin Chitosan Chitosan Polymer Biosorbent Resin Resin Hydrogel Chelating resin Polymer

Triisobutyl phosphine sulfide Amine and carboxyl groups Glisin modified Bisthiourea–formaldehyde Fungi (Fomitopsis carnea) Melamine–thiourea–formaldehyde Thiourea–formaldehdye Thiol-ene hydrogels Amine-thio-mercaptane groups 1,8-Diaminonaphtalene–formaldehyde/PVC

31–513 30.95 169.98 285 100 48 29.7 45.19 443 119

10,000 30–40 100 600 18,000 10 10 120 180 6000

(Sanchez et al., 2001) (Wan et al., 1999) (Ramesh et al., 2008) (Atia, 2005) (Khoo and Ting, 2001) (Aydın, et al., 2008) (Ertan and Gülfen, 2009) (Fırlak et al., 2012) (Donia, et al., 2005) In this study

equation. The adsorption kinetic parameters indicated that Au(III) adsorption proceeds according to the pseudo-second-order model. It can be concluded that Au(III) adsorption is governed by chemisorption process. A comparison of 1,8-DAN-F blended polymeric adsorbent with the some adsorbents studied by different researchers is given in Table 4. It can be seen that the adsorption capacity of the adsorbent used in this study is reasonable for Au(III) adsorption. 3.2.4. Column studies The adsorption and separation of Au(III) ions from Cu(II), Fe(III) and Ni(II) base metal ions were also examined by column technique. The obtained breakthrough curves for the metal ions are given in Fig. 8 and elution curves are in Fig. 9. Au(III) ions may be found along with Cu(II), Fe(III) and Ni (II) base metal ions in a waste, recycling or leaching solution. Therefore, Cu(II), Fe(III) and Ni(II) ions are important for a competitive adsorption with Au(III). According to the competitive adsorption/elution results of Au(III) ions together with base metal ions, the column studies showed that Au(III) ions could be concentrated from 150 mg·L − 1 to 950 mg·L − 1, while the base metal ions were diluted from 150 mg·L − 1 to 38 mg·L − 1 for one adsorption–elution cycle. More adsorption–elution cycles will purify and concentrate more Au(III) solution from the base metal ions. 3.2.5. Preconcentration factor In order to determine the maximum applicable sample volume and maximum reachable enrichment factor, the effect of sample volume on the recovery of Au(III) was studied. For this purpose, 50, 100,

200, 400, 600 and 1000 mL volumes of model solutions containing 4 μg Au(III) were passed through the column under the optimum experimental conditions. The results are given in Fig. 10. The recovery for Au(III) was quantitative for volumes of 50–200 mL. Over 200 mL of sample volume for 4 microgram, the recovery value was under 80%. For an elution volume of 10 mL, a preconcentration factor of 20 was achieved. Moreover, quality control chart applied the results of recoveries up to 200 mL volume at the 95% confidence level (CL). The mean of the recoveries was 96.33%± 1.96*σ (n= 3). Upper control limit (UCL) was 109.4%; lower control limit was 83.3% and standard deviation (σ) was 6.66 (n= 3). 4. Conclusions A new polymer form of 1,8-DAN with formaldehyde was synthesized and blended with PVC. This blended chelating polymer was used in the adsorption, separation and preconcentration of Au(III) ions from Cu(II), Fe(III) and Ni(II) base metal ions. The maximum adsorption for Au(III) ions was obtained at pH= 1. The experimental data fitted well to the Langmuir isotherm model. The adsorption capacity of the blended polymeric adsorbent was found as 119.0 mg·g−1. It was estimated that the mechanisms in the Au(III) adsorption on the 1,8DAN-F polymer were electrostatic interaction and chelation mechanisms as consecutive. The adsorption kinetic parameters indicated that Au(III) adsorption proceeds according to the pseudo-secondorder model. The adsorption–desorption cycle results demonstrated that the Au(III) ions could be concentrated while the base metal ions were diluted. The preconcentration factor up to 200 mL volume was 20. It was concluded that 1,8-DAN-F chelating polymer blend can be

Fig. 8. Column adsorption curves of Au(III) Fe(III), Cu(II) and Ni(II) ions (Bed volume (BV): 0.92 mL).

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Fig. 9. Column elution curves of Au(III) Fe(III), Cu(II) and Ni(II) ions (Bed volume (BV): 0.92 mL).

Fig. 10. Effect of sample volume on the recovery of Au(III) ions.

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