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Comparative studies on the adsorption of gold from waste rinse water (Au 178.3 mg/L and trace Cu, Ni, Zn, Sn,
etc) of the semiconductor manufacturing industry have been reported using nonionic Amberlite XAD-7HP,
strong base Bonlite BA304, and Purolite A-500. Batch and column studies were carried out to optimize various
process parameters such as contact time, acidity of solution, and resin dose for gold adsorption from waste
rinse water and elution to get a gold-enriched solution. The results showed that Bonlite BA304 and Purolite A-
500 resins could exchange gold easily at high acidity whereas Amberlite XAD-7HP adsorbs gold effectively at
low acidity (adjusted pH=0). Purolite A-500 was found to be the most suitable resin as it adsorbed 99.6% gold
at an A/R ratio of 8.33 and a sorption capacity of 53.6 mg gold/mL resin. The mixture of acetone and
hydrochloric acid at a volumetric ratio of 9.0 could elute gold loaded on Purolite A-500 resin to yield
10,497 mg gold/L. The adsorption behavior of gold on Amberlite XAD-7HP and Bonlite BA304 followed both
the Langmuir and Freundlich isotherms. In the case of the Purolite A-500 resin, it followed suitably a Langmuir
isotherm. Kinetic data for gold adsorption on the three resins followed a second-order rate.
Comparative studies on the adsorption of gold from waste rinse water (Au 178.3 mg/L and trace Cu, Ni, Zn, Sn, etc) of the semiconductor manufacturing industry have been reported using nonionic Amberlite XAD-7HP, strong base Bonlite BA304, and Purolite A-500. Batch and column studies were carried out to optimize various process parameters such as contact time, acidity of solution, and resin dose for gold adsorption from waste rinse water and elution to get a gold-enriched solution. The results showed that Bonlite BA304 and Purolite A- 500 resins could exchange gold easily at high acidity whereas Amberlite XAD-7HP adsorbs gold effectively at low acidity (adjusted pH=0). Purolite A-500 was found to be the most suitable resin as it adsorbed 99.6% gold at an A/R ratio of 8.33 and a sorption capacity of 53.6 mg gold/mL resin. The mixture of acetone and hydrochloric acid at a volumetric ratio of 9.0 could elute gold loaded on Purolite A-500 resin to yield 10,497 mg gold/L. The adsorption behavior of gold on Amberlite XAD-7HP and Bonlite BA304 followed both the Langmuir and Freundlich isotherms. In the case of the Purolite A-500 resin, it followed suitably a Langmuir isotherm. Kinetic data for gold adsorption on the three resins followed a second-order rate.
Hydrometallurgy 105 (2010) 161–167 Contents lists available at ScienceDirect Hydrometallurgy j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / h yd r o m e t Comparative studies on the adsorption of Au(III) from waste rinse water of semiconductor industry using various resins Nghiem V. Nguyen a,b, Jinki Jeong b, Manis K. Jha c, Jae-chun Lee b,⁎, Kwadwo Osseo-Asare d,e a Resources Recycling, University of Science and Technology, Daejeon 305-350, Republic of Korea b Mineral Resources Research Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon 305-350, Republic of Korea c Metal Extraction and Forming Division, National Metallurgical Laboratory (CSIR), Jamshedpur, India d Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802, USA e Department of Energy and Mineral Engineering, Pennsylvania State University, University Park, PA 16802, USA a r t i c l e i n f o a b s t r a c t Article history: Comparative studies on the adsorption of gold from waste rinse water (Au 178.3 mg/L and trace Cu, Ni, Zn, Sn, Received 2 July 2010 etc) of the semiconductor manufacturing industry have been reported using nonionic Amberlite XAD-7HP, Received in revised form 14 July 2010 strong base Bonlite BA304, and Purolite A-500. Batch and column studies were carried out to optimize various Accepted 21 September 2010 process parameters such as contact time, acidity of solution, and resin dose for gold adsorption from waste Available online 29 September 2010 rinse water and elution to get a gold-enriched solution. The results showed that Bonlite BA304 and Purolite A- Keywords: 500 resins could exchange gold easily at high acidity whereas Amberlite XAD-7HP adsorbs gold effectively at Gold recovery low acidity (adjusted pH = 0). Purolite A-500 was found to be the most suitable resin as it adsorbed 99.6% gold Adsorption at an A/R ratio of 8.33 and a sorption capacity of 53.6 mg gold/mL resin. The mixture of acetone and Waste water hydrochloric acid at a volumetric ratio of 9.0 could elute gold loaded on Purolite A-500 resin to yield IX resins 10,497 mg gold/L. The adsorption behavior of gold on Amberlite XAD-7HP and Bonlite BA304 followed both Amberlite XAD-7HP the Langmuir and Freundlich isotherms. In the case of the Purolite A-500 resin, it followed suitably a Langmuir Purolite A-500 isotherm. Kinetic data for gold adsorption on the three resins followed a second-order rate. Bonlite BA304 © 2010 Elsevier B.V. All rights reserved. 1. Introduction In general, the concentration of gold from various solutions varies from 1 to 2000 ppm (Konishi et al., 2006). Several authors studied the Gold is an important metal used for several applications. In the recovery of gold using different techniques such as: precipitation industry the most important use of gold is for the manufacturing of (Chmielewski et al., 1997), solvent extraction with dibutyl carbitol electronic parts and devices such as cell phones, calculators, personal (DBC) (Byoung et al., 2008) or methyl isobutyl ketone (MIBK) digital assistants, and global positioning system units. Generally, solid- (Marczenko and Kowalski, 1984), adsorption and ion exchange using state electronic devices use very low voltages and currents which are activated carbon, various bio-derived adsorbents (e.g., persimmon easily interrupted by corrosion or tarnish at the connector's contact tannin gel, neem leaf broth, tannin, and fugal biomass) and ion exchange points. Gold is a highly efﬁcient conductor that can carry these low resins (Ishikawa et al., 2002; Nakajima et al., 2003; Tasdelen et al., 2009). voltage currents and remain free from corrosion. Electronic compo- Adsorption of metals using a solid resin is a proven technique for the nents such as connectors, switches, relay contacts, soldered joints, puriﬁcation and separation of metals from different aqueous solutions connecting wires, and connection strips made of gold or coated with (Nguyen et al., 2009). In comparison to other techniques, the adsorption this metal are highly reliable (Ming et al., 1999). During the processing or ion exchange technique is more suitable for the extraction of metals and manufacturing of electronic parts and devices various steps such from a relatively dilute solution as it can be highly selective, less subject as electroplating, etching, rinsing, and chemical and mechanical to sludge formation, easily regenerated, and more likely to be polishing (CMP) are required. During these processing steps waste environmentally acceptable (Jha et al., 2008a). Some strong base resins rinse water containing various valuable and precious metals is such as Purolite A-500 (Rajasingam et al., 2006), Dowex 21K and Dowex generated. Due to the presence of an appreciable amount of gold in G-55 (Zhang and Dreisinger, 2002) have been used for the adsorption of these wastes, signiﬁcant attention has been drawn to the recovery of gold due to the high capacity and fast loading rate. Nonionic Amberlite this precious metal (Ishikawa et al., 2002; Nakajima et al., 2003). XAD-7 resin was used effectively for the recovery of gold from a waste solution (Latif et al., 2003). Additionally, the resin can be eluted easily and without loss of subsequent loading capacity (Harris et al., 1990). ⁎ Corresponding author. Tel.: +82 42 868 3613; fax: +82 42 868 3415. The present work is focused on the comparative studies for the E-mail address: firstname.lastname@example.org (J. Lee). adsorption of gold from waste rinse water of the Korean 0304-386X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.hydromet.2010.09.003 162 N.V. Nguyen et al. / Hydrometallurgy 105 (2010) 161–167 Table 1 hydrochloric acid to remove any impurities and organics. Afterwards, Speciﬁcations of waste rinse water. the resins were washed several times with deionized water to remove Elements Concentration (mg/L) excess acid and dried for 12 h in an oven at 50 °C. Au 178.30 Cu 0.30 2.2. Methods Ni 0.96 Zn 0.23 The experiments for the adsorption and elution of gold using the Sn 1.30 Cl− 60,350 (1.7 M) various resins and mixture of eluents were carried out in batch and NO−3 359,600 (5.8 M) column scale. The batch experiments were carried out in a conical H+ 7500 (7.5 M) ﬂask using a shaking water bath under atmospheric conditions using Amberlite XAD-7HP, Bonlite BA304 (gel strong base resin) and Purolite A-500 (macroporous strong base resin). The theoretical loading capacity of strong base resins was determined by titrating Cl− semiconductor industry. After the gold electroplating of an electronic using Mohr's method (Helfferich, 1962). To convert the strong base device, the etching of plated material with a solution of reverse aqua resins to chloride form completely, these were contacted with an regia (HCl:HNO3 = 1:3) is performed to remove a portion of the excess of 1.0 M of HCl. The resins were washed with deionized water electroplated and the exposed seed layer of gold. Finally, water is used to remove the acid and were then dried for 12 h. The exact amount of to wash the etched material, resulting in waste rinse water containing dry resin was contacted with a known amount of 3.0% Na2SO4 solution gold(III) ion in [AuCl4]− complex with high chloride concentration. for 10 h to elute chloride ions. The eluted chloride solutions were then With the aim to select the best resin to be used in a continuous closed- titrated by AgNO3 to determine the loading capacity of the resins. The loop industrial process to recover gold generated during the total loading capacity was found to be 1.22 eq/L and 1.27 eq/L for manufacturing of electronic products, comparative studies were Bonlite BA304 and Purolite A-500, respectively. carried out using nonionic (Amberlite XAD-7HP) and strong base After the gold adsorption, the resin was separated from the resins (Bonlite BA304 and Purolite A-500). The effects of various rafﬁnate with a ﬁlter paper (Whatman no. 41). The gold adsorption process parameters viz. contact time, the acidity of the solution, and and elution experiments were also carried out in a column made of the resin dose on gold adsorption were studied using all three resins. Pyrex glass with a diameter of 10 mm and a length of 200 mm. The From the loaded resins, gold is eluted to get a gold-enriched solution ﬂow rate of the solution in the column was controlled by the using suitable elution solution. The pure gold metal could be obtained adjustment of a stopcock. The bed volume (BV) was determined by from the gold-enriched solution by electrowinning or precipitation. adding a weighed amount of resin into a 25-mL cylinder and then immersing the resin into water. After the adsorption of gold on the 2. Experimental resins, the loaded resins were eluted by a mixture of acetone and hydrochloric acid. The eluted solutions were then evaporated by 2.1. Materials heating at 60 °C to release acetone. After that the near-dried samples were added with hydrochloric acid and diluted with deionized water The original waste rinse water generated during the manufacturing before sampling and analysis. The aqueous rafﬁnate and eluate were of the semiconductor supplied by the Korean Semiconductor Company analyzed for gold content by atomic absorption spectroscopy was used for experimental purposes. The composition of waste rinse (AAnalyst 400, PerkinElmer Inc., USA). water used for experimental purposes is presented in Table 1. The waste rinse water contained the following metals: 178.30-mg/L Au, 0.30-mg/L 3. Results and discussion Cu, 0.96-mg/L Ni, 0.23-mg/L Zn, and 1.30-mg/L Sn. The acidity of the waste solution was titrated using sodium carbonate (Na2CO3), and the 3.1. Effect of contact time acid (H3O+) concentration was found to be 7500 mg/L. The Cl− anionic content in the waste solution was determined by using the Volhard The effect of contact time on the adsorption of gold by the three method of titration. Chemical reagents (sodium hydroxide, sodium resins was determined using 1 g of resin and 25 mL of the original carbonate, potassium thiocyanate, silver nitrate, acetone, and nitric and waste solution in different stoppered ﬂasks. The ﬂasks were shaken at hydrochloric acids) were of laboratory reagent grade. 140 rpm for different time intervals and at room temperature Purolite A-500 (macroporous strong base resin) was supplied by (temperature controller was ﬁtted to the shaking machine). The Purolite Company, Bonlite BA304 (gel strong base resin) by Born percentage adsorption is plotted against time in Fig. 1. For all three Chemical Company and Amberlite XAD-7HP (nonionic resin) by resins a smooth curve leading to the equilibrium adsorption of gold Rohm and Hass. The characteristic properties of all the three resins are complexes was obtained. With an increase in time from 2 to 30 min, presented in Table 2. The resins were washed with 1.0 M of gold adsorption increased from 53.6%, 84.8% and 85.5% to 64.4%, 96.3% Table 2 Characteristic properties of three resins. Properties Name of resin Amberlite XAD-7HP Bonlite BA304 Purolite A-500 Matrix Macroreticular aliphatic cross-linked polymer Polystyrene–DVB Macroporous polystyrene cross linked with DVB Type Nonionic Gel strong basic type I Macroporous strong basic type I Physical form White translucent beads White/light yellow spherical beads Faint light yellow spherical beads Functional group Nonionic R–N+ (CH3)3–X- R–N+ (CH3)3–X- Capacity, Cl− form (eq/L) 1.3 1.15 Moisture content 61%–69% 50%–60% 53%–58% Speciﬁc gravity (g/mL) 1.06–1.08 1.26 1.08 Harmonic mean size 0.56–0.71 mm 0.45–0.70 mm 0.6–0.85 mm Uniformity coefﬁcient ≤ 2.0 ≤1.6 1.7 Shipping weight (g/L) 655 660–710 670–700 N.V. Nguyen et al. / Hydrometallurgy 105 (2010) 161–167 163 Table 3 Rate constants for the pseudo ﬁrst- and second-order rates for the adsorption of gold on resins. Resin Pseudo ﬁrst order Pseudo second order k1 qe (mg/g) R2 k2 qe (mg/g) R2 Amberlite XAD-7HP 0.140 2.40 0.854 0.86 2.90 0.99 Bonlite BA304 0.094 1.98 0.835 0.67 4.34 1.00 Purolite A-500 0.098 2.52 0.920 0.78 4.33 1.00 qe from the empirical data of Amberlite XAD7-HP = 2.87 mg/g; qe from the empirical data of Purolite A-500 = 4.31 mg/g; qe from the empirical data of Bonlite BA = 4.3 mg/g. presented in Table 3. The correlation coefﬁcient R2 for the second-order rate was found greater than the ﬁrst order and the value of the rate constant of the pseudo second-order sorption k2 was also found constant. Thus, the second-order rate expression ﬁts the data most satisfactorily. 3.2. Effect of acidity Fig. 1. Effect of contact time on the adsorption of gold by the three resins (A/R ratio,25 mL/g; aq. feed, 178.3 mg/L; agitation speed, 140 rpm; temperature, 25oC). As the acid concentration in the solution is one of the vital parameters in the adsorption process, the effect of acidity on gold and 96.7% for Amberlite XAD-7HP, Bonlite BA304 and Purolite A-500 adsorption by the three resins was investigated. The waste rinse water resins, respectively. Subsequent increase in contact time had no effect used for the experiment contained very high acidic content i.e. 7.5 M. on the gold adsorption. Therefore, 30 min is a sufﬁcient contact time The pH of the waste rinse water was adjusted by the addition of NaOH. to reach the adsorption reaction equilibrium for the three resins. The results presented in Fig. 3 for the adsorption of gold using Based on the obtained results for adsorption, orders of reaction were Amberlite XAD-7HP showed that the gold adsorption increased tested. The results presented in Fig. 2 indicate that the reaction with decreasing the concentration of acid in the waste solution. followed the second-order rate. The dissociation of the gold chlorocomplex is the reason of this The pseudo second-order reaction is mostly concerned with the phenomenon, which can be expressed as amount of metal on the adsorbent's surface and the amount of metal adsorbed at equilibrium (Nguyen et al., 2009). The pseudo second- HAuCl4 ↔ AuCl4 þ H : – þ ð3Þ order rate reaction was also analyzed by ﬁtting the same data for gold adsorption and may be presented by the following equation: The adsorption of the gold complex on Amberlite XAD-7HP can be proposed in Eqs. (4) and (5) to express the interaction between dq 2 the protonated oxygen atom of the ester group C_O with gold = k2 ðqe −qÞ ð1Þ dt chlorocomplex. where k2 = rate constant of pseudo second-order sorption (g/mg min). In the adsorption of gold from the solution of high acidic con- Integrating and applying boundary conditions t = 0 and q = 0 to t = t centration, the equilibrium tends to shift toward the left side in Eq. (3); and q = qe, Eq. (1) can be written in linear form as therefore, gold is present in the aqueous solution as non-adsorbable HAuCl4 species. The adsorption percentage of gold using Amberlite t 1 1 XAD-7HP reached 92.2% at solution pH= 0 (1.0 M H3O+). It should be = + t ð2Þ q h qe noted that Amberlite XAD-7HP resin is an aliphatic ester containing the C_O group which might be degraded in a high acidic solution where h = k2 q2 is the initial sorption rate. e (Gopferich, 1996; Jung et al., 2006), causing the decrease of resin The plot of (t/q) against t for the previous equation should give a capacity and lifetime. Therefore, the waste solution was partly linear relationship from which the constants k2 and correlation coefﬁcient neutralized to an acidity of 1.0 M H3O+ by adding sodium hydroxide R2 =1. The comparative results for the ﬁrst- and second-order rates are throughout the gold adsorption experiments using Amberlite XAD-7HP. Fig. 3 indicates that the adsorption of gold by the strong base resins 16 Bonlite BA304 and Purolite A-500 is not signiﬁcantly affected by y = 0.230x + 0.0791 changes in acid concentration (1.0–7.5 M H3O+) in the solution. y = 0.3441x + 0.1379 14 2 R =1 R2= 0.999 CH3 CH3 CH3 CH3 12 CH2 C CH2 C CH2 C CH2 C y = 0.231x + 0.0683 C O C O C O C OH+ O O 10 R2 = 1 + nH + O O R O R O R R (4) O O t/qe 8 C O C O C O C O CH2 C CH2 C CH2 C CH2 C CH3 CH3 6 n CH3 CH3 n 4 Amberlite XAD-7HP CH3 CH3 Bonlite BA304 CH3 CH3 CH2 C CH2 C 2 Purolite A-500 C O C OH+ CH2 C CH2 C C O C O H + A u C l4 - O O n A u C l4 - O O + 0 0 10 20 30 40 50 60 70 R O R O R R (5) O O Time (min) C O C O C O C O CH2 C CH2 C CH2 C CH2 C CH3 CH3 n Fig. 2. Fitting of the pseudo-second-order rate for gold adsorption on the three resins. CH3 CH3 n 164 N.V. Nguyen et al. / Hydrometallurgy 105 (2010) 161–167 and Purolite A-500 resins, respectively. It is observed that the amount of gold adsorbed per unit mass increased with an increasing amount of resin and adsorption density. As reported by several researchers, increasing adsorbent doses provide a greater surface area or ion exchange sites for a ﬁxed initial solute concentration (Gode and Pehlivan, 2006; Lin and Juang, 2007). 3.4. Loading capacity Studies were carried out to determine the loading capacity of all three resins. A 1.0-g sample of each resin was contacted at room temperature with 25 mL of waste rinse water for 30 min in a conical ﬂask ﬁtted to a controlled shaker. In the case of Amberlite XAD-7HP, the pH of the waste rinse water was adjusted to zero (acidity = 1.0 M H3O+). The waste rinse water without pH adjustment was used for gold adsorption using Bonlite BA304 and Purolite A-500 resins. The repeated contacts with the same gold-loaded resin were made with Fig. 3. Effect of acidity on the adsorption of gold. (A/R ratio, 25 mL/g; time, 30 mins; aq. fresh waste rinse water until a maximum adsorption of gold was feed, 178.3 mg/L; agitation speed, 140 rpm; temperature, 25oC). achieved. In the ﬁrst stage of contact, the adsorption of gold was found to be 4.1, 4.27 and 4.25 mg gold/g resin with Amberlite XAD-7 HP, Bonlite BA304 and Purolite A-500 respectively. In the subsequent These resins (Bonlite BA304 and Purolite A-500) contain the stages of contact, the extraction of gold from the aqueous feed functional group –N(CH3)3–Cl− which is very active at low pH (high decreased, as the available site for the adsorption decreased in each acidity) (Helfferich, 1962), giving an ionized group through dissoci- subsequent contact. A cumulative adsorption at an aqueous to resin ation. The ion exchange reaction can be expressed as ratio of 25 in 15, 50 and 57 stages for Amberlite XAD-7HP, Bonlite þ − BA304 and Purolite A-500 resins was found to be 58.8 mg, 109.2 mg R–NðCH3 Þ3 –Cl þ HAuCl4 ↔ R–NðCH3 Þ3 –AuCl4 þ H þ Cl : ð6Þ and 142.8 mg gold/g resin, respectively. The plot for the loading capacity of resin for gold is presented in Fig. 5. The macroporous strong base resin Purolite A-500 has the highest loading capacity in comparison to XAD-7 HP and Bonlite BA304 resins. 3.3. Effect of resin dose 3.5. Adsorption isotherm The gold adsorption behavior of the resins Bonlite BA304 and Purolite A-500 is not signiﬁcantly affected by changes in acid con- Based on the data obtained from the above loading capacity centration (1.0–7.5 M) of the solution; therefore, the effect of resin experiments, the adsorption isotherms were plotted. The Langmuir dose on gold adsorption was investigated without pH adjustment. In and Freundlich models are well-known isotherms used to determine the case of Amberlite XAD-7HP, the maximum adsorption was found at adsorption phenomena. According to the Langmuir model the uptake pH = 0, therefore the adsorption studies were carried out by adjusting of metal ions occurs on a homogeneous surface by monolayer the waste rinse water pH = 0. In all cases the maximum contact time adsorption without any interaction between adsorbed ions. The was maintained at 30 min. A solution volume of 25 mL was used and model can be presented in linear form as follows: the resin dose was varied from 0.1 to 3.0 g (8.33–250 mL aqueous solution/g resin). The results in Fig. 4 indicate that the gold adsorption 1 1 1 1 increased with an increasing resin dose. With an increase in resin dose = × + ð7Þ q k1 qm Ce qm from 0.1 to 3.0 g, the gold adsorption increased from 51.8%, 63.4% and 62.9% to 94.3%, 98.7% and 99.6% for Amberlite XAD-7HP, Bonlite BA304 where Ce = equilibrium concentration of metal in the solution (mg/mL), q = amount of metal adsorbed on the resin at equilibrium (mg/g), Fig. 4. Effect of resin dose on the adsorption of gold. (time, 30 mins; aq. feed, 178.3 mg/ Fig. 5. Adsorption isotherm of resins for the adsorption of gold. (A/R ratio, 25 mL/g; L; agitation speed, 140 rpm; temperature, 25oC). time, 30 mins; aq. feed, 178.3 mg/L; agitation speed, 140 rpm; temperature, 25oC). N.V. Nguyen et al. / Hydrometallurgy 105 (2010) 161–167 165 0.30 Table 4 Constants and correlation coefﬁcients of the Langmuir and Freundlich isotherm for the y = 2.0507x − 0.0081 adsorption of gold using the three resins. 0.25 R2 = 0.983 Resin Langmuir isotherm Freundlich isotherm y = 3.1761x − 0.0128 0.20 2 R = 0.889 k1 qm R2 kf n R2 (mg/g) y = 1.9397x − 0.0068 Amberlite XAD-7HP 0.0040 78.12 0.889 0.524 1.044 0.927 1/qe 0.15 2 R = 0.990 Bonlite BA304 0.0039 123.40 0.983 0.352 0.860 0.980 Purolite A-500 0.0035 147.05 0.990 1.022 0.980 0.936 0.10 Amberlite XAD-7HP 0.05 Bonlite BA304 to that obtained from theoretical calculation. Therefore, the Langmuir Purolite A-500 adsorption isotherm provides a suitable representation of these 0.00 adsorption data. In the case of Amberlite XAD-7HP and Bonlite 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 BA304 resins, the correlation coefﬁcient R2 is quite similar for both of 1/Ce the isotherms. Adsorption data that follow both Langmuir and Freundlich isotherms have also been reported by several authors Fig. 6. Langmuir isotherm for the adsorption of gold by the three resins. (Jha et al., 2008b; Xiong et al., 2009). kl = equilibrium constant related to the afﬁnity of the binding sites for 3.6. Determination of breakthrough curve the metals or the Langmuir constant, and qm = the resin capacity (maximum possible amount of metallic ion adsorbed per unit mass of The tests for the determination of the breakthrough curve for gold adsorbent, mg/g). adsorption using the resins Amberlite XAD-7HP, Bonlite BA304 and The Freundlich model assumes that the uptake or adsorption of Purolite A-500 were carried out in a column. The breakthrough curve metal ions occurs on a heterogeneous surface by monolayer for the adsorption of gold takes place when the concentration of gold adsorption. The model can be described as follows: in the rafﬁnate begins to increase signiﬁcantly until it ﬁnally reaches the same concentration of gold as in the feed waste rinse water. After 1=n q = kf C e ð8Þ this point, no more adsorption takes place. The breakthrough curve is considered as the time of completion of the adsorption cycle in a 1 continuous process used for industrial applications (Kose and Ozturk, log q = log Ce + log kf ð9Þ n 2008). The resin was packed in the column (bed volume, BV = 5.0 mL). The ﬂow rate for the waste rinse water as feed solution where kf and n are Freundlich constants for adsorption capacity and was maintained at 0.88 mL/min. The ratio between concentration of adsorption intensity, respectively. Ce = equilibrium concentration of gold in the rafﬁnate and feed solution (Ce/Co) increased after 90 and metal in solution (mg/L), and q = amount of metal adsorbed on the 95 BV of waste solution passed through the columns containing the resin at equilibrium (mg/g). strong base resins Bonite BA304 and Purolite A-500. The increase in The plots ‘(1/Ce) vs. (1/q)’ and ‘log(Ce) vs. log(q)’ were examined to the ratio Ce/Co could be explained by the condition that the active sites validate the experimental data with Langmuir and Freundlich on the resin were decreased. The breakthrough curves for all three isotherms, as presented in Figs. 6 and 7, respectively. The correlation resins are presented in Fig. 8. The corresponding breakthrough coefﬁcients of the Langmuir and Freundlich isotherms for gold capacity and sorption capacity of the three resins are shown in adsorption on the three resins are presented in Table 4. For the Table 5. Among the three resins used, Purolite A-500 was found to be Purolite A-500 resin, the R2 value for the Langmuir model is much the most effective resin for the adsorption of gold from waste rinse closer to 1 compared with the Freundlich model and the maximum water as its breakthrough capacity and sorption capacity were found capacity of the resin derived from the experimental data is very close to be 16.5 mg and 53.6 mg Au/mL resin, respectively. 2.5 y = 1.022x + 0.0096 R2 = 0.936 2.0 y = 1.1674x − 0.4525 2 R = 0.980 1.5 log qe y = 0.9575x − 0.2807 R2 = 0.927 1.0 0.5 Amberlite XAD-7HP Bonlite BA304 Purolite A-500 0.0 0.0 0.5 1.0 1.5 2.0 2.5 log Ce Fig. 8. Breakthrough curves of the three resins for gold adsorption. (bed volume BV, Fig. 7. Freundlich isotherm for the adsorption of gold using the three resins. 5mL; ﬂow rate, 0.88 mL/min). 166 N.V. Nguyen et al. / Hydrometallurgy 105 (2010) 161–167 Table 5 Column performance of the three resins. Name of resin Amberlite Bonlite Purolite XAD-7HP BA304 A-500 Breakthrough capacity (mg Au/mL resin) 0.35 15.84 16.52 Sorption capacity (mg Au/mL resin) 11.90 41.17 53.60 3.7. Batch elution test The elution experiments were carried out to desorb gold from the gold-loaded resins. Varying concentration (0.5 to 3.0 M) of hydro- chloric acid was used. The ﬂasks were shaken for 30 min maximum at 140 rpm and at room temperature (via a temperature controller ﬁtted to the shaking machine). The result presented in Fig. 9 indicates that Fig. 10. Elution of gold from the loaded resin using varying mixture concentrations of hydrochloric acid is not a suitable reagent for the elution of gold as it hydrochloric acid and acetone (time, 30 mins; hydrochloric acid, 1M; agitation speed, eluted negligible amounts of gold. Harris et al., 1990 suggested the use 140 rpm; temperature, 25oC). of a mixture of acetone and diluted hydrochloric acid for gold elution from a metal-loaded resin. Rajasingam et al. (2006) used a mixture of water and dipolar aprotic solvents i.e. acetone + water, dimethylsulf- oxide + water and N-methyl-2-yrrolidone + water for the elution of gold from loaded Purolite A-500. The reason for the effective elution was due to the enhanced activity of Cl− species in dipolar aprotic solvents, which promotes the formation of metal chloro-complexes and subsequently increases the selective elution of gold from an anion exchange resin (Jayasinghe et al., 2005). Therefore, further studies on the elution of gold from the loaded resins were carried out using a mixture of acetone and 1.0 M of hydrochloric acid. The result presented in Fig. 10 indicates that the elution of gold increased with increasing acetone/acid ratio for all the three resins. With increase in acetone/acid volumetric ratio from 1.0 to 9.0, the gold elution increased from 43.3%, 13.8% and 3.3% to 98.1%, 67.8% and 85.3% for Amberlite XAD-7HP, Bonlite BA304 and Purolite A-500 resins, respectively. 3.8. Elution in column Fig. 11. Enrichment of gold using mixtures of acetone and hydrochloric acid (bed volume BV, 5mL; acetone/acid ratio, 9; ﬂow rate, 0.88 mL/min). The elution of gold from the gold-loaded resin was carried out in a column with the mixture of acetone and hydrochloric acid in column. The volumetric ratio between acetone and hydrochloric acid was 9.0 Bonlite BA304, and Purolite A-500 resins. The corresponding gold and the ﬂow rate was 0.88 mL/min. The results presented in Fig. 11 concentration in the eluted solution were 7240 mg, 6325 mg and indicate that the elution could be achieved by up to 98.9%, 68.8%, and 10,497 mg gold/L, respectively, which are 40, 35 and 59 times more in 88.6% of gold, respectively from the gold-loaded Amberlite XAD-7HP, comparison with the concentration in waste rinse water used for the experiments. Pure gold metal or salt could be obtained from the gold- enriched solution by acetone evaporation, followed by the electro- 3.0 winning of gold or gold precipitation using hydrazine. 2.5 4. Conclusions 2.0 The main goal of this study was the assessment of the performance of nonionic and strong base resins in order to recover gold from the Elution (%) Amberlite XAD-7HP Bonlite BA304 waste rinse water of semiconductor industries. The experimental 1.5 Purolie A-500 results showed that all the three resins are effective for the recovery of gold (III) from the waste solution. The strong base resins (Bonlite 1.0 BA304 and Purolite A-500) had high adsorption efﬁciency at high acidity of solution whereas the nonionic resin (Amberlite XAD-7HP) 0.5 was only effective for the adsorption of gold at low acidity. The elution efﬁciency of Purolite A-500 was higher than the Bonlite BA304 resin. The gold loaded on Amberlite XAD-7HP was easily eluted by a mixture 0.0 of acetone and hydrochloric acid. The gold was eluted from the gold- 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 loaded Purolite A-500 resin to yield a gold-enriched solution HCl concentration (M) containing 10,497 mg gold/L. The adsorption equilibria of gold on Fig. 9. Elution of gold from the loaded resin using varying concentrations of hydrochloric Amberlite XAD-7HP and Bonlite BA304 followed both the Langmuir acid (time, 30 mins; agitation speed, 140 rpm; temperature, 25oC). and Freundlich isotherms; but in the case of Purolite A-500 resin, the N.V. Nguyen et al. / Hydrometallurgy 105 (2010) 161–167 167 adsorption data were better represented by the Langmuir isotherm. Jayasinghe, N.S., Lucien, F.P., Tran, T., 2005. Ion-exchange equilibria for [Au(CN)2]–/Cl– and [Au(CN)2]–/SCN– on Purolite A500 in mixed solvents at 303 K. Ind. Eng. Chem. The kinetics of gold adsorption on the three resins was found to follow Res. 44, 7496–7504. a second-order rate. From the overall results, the Purolite A-500 resin Jha, M.K., Upadhyay, R.R., Lee, J.-C., Kumar, V., 2008a. Treatment of rayon waste efﬂuent seems promising for the recovery of gold from waste rinse water. A for the removal of Zn and Ca using Indian BSR resin. Desalination 228, 97–107. Jha, M.K., Nguyen, N.V., Lee, J.-C., Jeong, J., Yoo, J.M., 2008b. Adsorption of copper from pure gold metal or salt could be obtained from a gold-enriched the sulphate solution of low copper contents using the cationic resin Amberlite IR solution by acetone evaporation, followed by the electrowinning of 120. J. Hazard. Mater. 164, 948–953. gold or precipitation by hydrazine. Jung, J.H., Ree, M.H., Kim, H.S., 2006. Acid- and base-catalyzed hydrolyses of aliphatic polycarbonates and polyesters. Catal. Today 115, 283–287. Konishi, Y., Tsukiyama, T., Ohno, K., Saitoh, N., Nomura, T., Nagamine, S., 2006. 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