Facile and Green Production of Cu from CuO Using Cellulose under

Article pubs.acs.org/IECR

Facile and Green Production of Cu from CuO Using Cellulose under Hydrothermal Conditions Qiuju Li,† Guodong Yao,† Xu Zeng,† Zhenzi Jing,‡ Zhibao Huo,§ and Fangming Jin*,§ †

State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, and ‡School of Materials Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China § School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China ABSTRACT: A simple and green hydrothermal process has been developed to produce Cu from CuO using cellulose as a reductant under mild hydrothermal conditions. The results showed that CuO was easily reduced to Cu in the presence of cellulose, and a complete conversion of CuO into Cu was obtained at a temperature of 250 °C with a reaction time of 1.5 h in 0.50 mol/L NaOH. At the same time, cellulose was converted into value-added chemicals, such as lactic acid and acetic acid. A reaction mechanism for the reduction of CuO to Cu with cellulose as a reductant was also proposed.

1. INTRODUCTION Sustainable development is threatened by the exhaustion of energy sources and environmental pollution that can be attributed to the rapid consumption of fossil fuels caused by human activities. It is strongly desired to develop new methods to reduce energy consumption by improving current technologies, especially those that require a large amount of energy. Copper manufacturing is a large-scale industry with high energy use and has led to serious environmental pollution. In the conventional hydrometallurgical process for producing Cu, sulfuric acid is used as a leaching agent and organic solvents are used as extractants.1,2 In addition, pyrometallurgy involves the emission of CO2, SO2, and particulate matter.3,4 Therefore, the development of a new method for producing copper in an environmentally friendly way that uses less energy is strongly desired. In recent years, the focus has been on reductive biological treatment that generally uses heterotrophic microorganisms capable of utilizing the oxidized ore as a final acceptor of electrons.5 Although this technology generates less pollution, the biological process requires a supply of organic carbon and an energy source. Hydrothermal conversion6−12 is receiving increasing attention because of the unique inherent properties of high-temperature water (HTW), including a high ion product (Kw) and a low dielectric constant, which are favorable conditions for promoting reactions without catalysts. The remarkable properties of HTW allow it to convert a wide range of biomass materials into fuels and other value-added products. More importantly, HTW is an environmentally benign solvent that is preferable to organic solvents and alternative reaction media. Hydrothermal processes have been demonstrated to be some of the most promising methods for the conversion of carbohydrate biomass into value-added products.13−15 Biomass has wide applications as a renewable source of clean energy and as a raw material for different chemical stocks.6,15−18 It has been reported13,19,20 that carbohydrates can easily be converted into lactic acid under alkaline hydrothermal conditions. The conversion of carbohydrates into lactic acid is an oxidation reaction. Therefore, metal oxides such as © 2012 American Chemical Society

CuO may be reduced to Cu under alkaline hydrothermal conditions with carbohydrate as a reductant. Our previous research21 has demonstrated that FeCl2 or Fe(OH)3 can be reduced into Fe0 using glycerin as a reductant. Cellulose is the main component of biomass, and glucose, a monosaccharide that makes up cellulose, may have a higher reductive potential than glycerin. Moreover, the reductive ability of glucose could be enhanced under hydrothermal conditions because of the unique properties of HTW. Therefore, cellulose could have great potential for the direct reduction of CuO to Cu under mild hydrothermal conditions. In this study, we investigated the conversion of CuO into Cu directly using cellulose as a reductant under alkaline hydrothermal conditions.

2. EXPERIMENTAL SECTION 2.1. Experimental Materials. Cellulose (filter paper powder, 200 mesh, Toyo RoShi Kaisha, Ltd., Japan), CuO (200 mesh, AR, Sigma), and NaOH (99%) were used without further purification. Standard solutions (1.0 N) of lactic acid, formic acid, acetic acid, pyruvic acid, and acrylic acid (98%, Alfa Aesar Co., Japan) was used for the qualitative analysis of the products in the liquid samples. 2.2. Experimental Procedure. All experiments were conducted in a Teflon-lined stainless steel batch reactor with an inner volume of 20 mL. All the experiments were carried out with 1.8 g of cellulose, 0.48 g of CuO, and water, filling the vessel to 50% of capacity. The experimental procedure has been described in detail elsewhere.21,22 Briefly, the desired amount of starting materials and 10 mL of deionized water were added into the reactor, which was subsequently sealed and placed in an oven that had been preheated to the desired temperature. After a given time, the reactor was taken out of the oven and cooled to room temperature with an electric fan. The reaction Received: Revised: Accepted: Published: 3129

September 20, 2011 November 29, 2011 January 10, 2012 January 10, 2012 dx.doi.org/10.1021/ie202151s | Ind. Eng.Chem. Res. 2012, 51, 3129−3136

Industrial & Engineering Chemistry Research

Article

Figure 1. XRD patterns of the solid samples at (a) 250 °C, 0.50 mol/L NaOH, 1.5 h; (b) 180 °C, 0.50 mol/L NaOH, 3 h; and (c) 180 °C, without NaOH, 3 h.

Figure 2. XRD patterns of the solid samples from blank experiments at 250 °C after 1.5 h. (a) Cu and NaOH (only). (b) CuO and NaOH (only).

time was defined as the time that the reactor was in the oven. The solid samples were collected, washed with distilled water and absolute ethanol several times to remove impurities, and dried in a vacuum at 40 °C for 24 h. The liquid product was also collected and filtered with a 0.22-μm filter membrane. 2.3. Product Analysis. The solid samples collected were analyzed by X-ray diffraction (XRD; Bruker D8 Advance X-ray diffractometer equipped with Cu Kα radiation) to determine the composition and phase purity. The quantitative analysis of the compositions of the products was performed using TOPAS 4.2 from Bruker AXS, USA.23,24 The particle size distribution was determined using a laser retardance technique with an EyeTech Particle Size Analyzer with a PD-10 dry powder dispersion unit. The liquid product analysis was performed using an HPLC system (Agilent 1200) equipped with a UV/vis detector.

Table 1. Distribution of Particle Size of the Purchased CuO with 200 Mesh and the Obtained Cu with Cellulose after the Reaction at 250 °C with 0.50 mol/L NaOH after 1.5 ha

purchased CuO (200 mesh) obtained Cu

av diam (μm)

D10 (μm)

D50 (μm)

D90 (μm)

6.19

2.53

5.77

10.33

2.41

0.76

1.64

5.01

a

D10, D50, and D90 mean that 10, 50, and 90% of the powder particles are smaller than this value, respectively.

3. RESULTS AND DISCUSSION 3.1. Examination of the Reduction of CuO to Cu with Cellulose. Figure 1 shows the XRD patterns of the solid samples obtained from the hydrothermal reactions at temper-

Figure 3. HPLC chromatograms of liquid samples (a) without CuO and (b) with CuO at 250 °C, 1.5 h, 0.50 mol/L NaOH. 3130

dx.doi.org/10.1021/ie202151s | Ind. Eng.Chem. Res. 2012, 51, 3129−3136


Article

atures of 250 and 180 °C with and without 0.50 mol/L NaOH. The reduction of a portion of the CuO was achieved, even at the lower temperature of 180 °C (see Figure 1b), and only a Cu peak was observed when the temperature was increased to 250 °C. These results indicate that CuO can be completely reduced to highly pure Cu at 250 °C. Comparing the XRD patterns in the presence and absence of NaOH at the temperature of 180 °C (see Figure 1b,c), it is clear that only a small quantity of Cu2O and no Cu was produced, and a large peak for cellulose was observed, which suggest that alkali was favorable for the reduction of CuO to Cu2O or Cu. Besides, to investigate whether NaOH can reduce CuO under hydrothermal conditions, the blank experiments with 6 mmol of CuO or Cu and 0.50 mol/L NaOH were conducted. As shown in Figure 2, which is the XRD patterns of the solid samples collected after the reactions, a small amount of Cu was converted into CuO and there was no reaction within CuO and NaOH after hydrothermal reactions. These results demonstrate that NaOH cannot directly reduce CuO under hydrothermal

Figure 4. Yields of Cu and Cu2O with the variation of reaction temperature at 0.50 mol/L NaOH, 2 h.

Figure 5. Yields of Cu and Cu2O with reaction time at temperatures of (A) 180 and (B) 200 °C, respectively, at 0.50 mol/L NaOH.

Figure 6. Effect of concentration of NaOH on yields of Cu and Cu2O at 0.50 mol/L NaOH, 3 h. 3131



Article

Figure 7. Proposed pathways of reduction of CuO to Cu in the presence of cellulose under alkaline hydrothermal conditions. R1, Lobry−de Bruyn− Alberda−van Ekenstein transformation (LBAE); R2, elimination of H2O; R3, benzilic acid rearrangement.

The liquid samples obtained from the hydrothermal degradation of cellulose with and without the addition of CuO were analyzed by HPLC to determine the effect of CuO on the conversion of cellulose. As illustrated in Figure 3, lactic acid, formic acid, acetic acid, pyruvic acid, and some other lowmolecular-weight carboxylic acids were detected in the absence and presence of CuO. However, in the presence of CuO, the amount of acetic acid increased from 2.0 to 4.0 g/L, the yield of formic acid decreased by 85%, and the amount of lactic acid increased slightly. The increase in the amount of acetic acid that was produced may be attributable to the oxidative decomposition of lactic acid in the presence of CuO, as discussed below. Therefore, the production of lactic acid from cellulose was promoted in the presence of CuO. Moreover, the decrease in the amount of formic acid produced may be due to further oxidative decomposition into CO2.25 3.2. Effects of Reaction Conditions on the Conversion of CuO into Cu. The effects of reaction parameters, including the reaction temperature, the reaction time, and the concentration of alkali, on the conversion of CuO into Cu were investigated to determine the optimum conditions for the conversion of CuO into Cu. The yield of Cu2O or Cu was defined as the ratio of the mass of Cu2O or Cu to the mass of the solid sample collected after the reaction. The quantitative analyses of Cu2O and Cu were performed using TOPAS 4.2 from Bruker AXS, USA. The effect of the reaction temperature was determined by varying the temperature from 180 to 250 °C after 2 h, as shown in Figure 4. The yield of Cu greatly increased with the increase in the reaction temperature. When the temperature was increased to 250 °C, the CuO was completely reduced to Cu in 1.5 h. However, at the temperature of 180 °C, the yield of Cu was only approximately 71%, even for the longer reaction time of 8 h. As shown in the XRD pattern (Figure 1b), there was unreacted cellulose remaining in the solid sample, which suggests that, at the lower temperature, not all of the cellulose took part in the reduction reaction, leading to less conversion of CuO. These results suggest that the degradation of cellulose played an important role in the reduction of CuO to Cu. Moreover, regarding the thermodynamics of the reaction,

Figure 8. XRD patterns of solid samples with lactic acid at temperature of 250 °C, 3 h, and (a) Cu = 6 mmol, pH 3.0; (b) CuO = 6 mmol, pH 3.0; (c) CuO = 6 mmol, pH 6.0; and (d) CuO = 6 mmol, pH 12.0.

conditions, which further indicate the significant role of cellulose in the reduction of CuO. These results clearly indicate that CuO can be easily reduced to Cu in the presence of cellulose at a lower temperature, such as 250 °C, and alkali significantly improved the reduction of Cu2O to Cu under hydrothermal conditions. To investigate the particle size distribution of the reduced Cu, the particle size distributions for the original CuO and the Cu obtained after the reaction at temperature of 250 °C for 1.5 h without any further processing were determined using a laser particle size analyzer. As shown in Table 1, the average particle sizes of the initial CuO and the Cu after reaction were 6.19 μm (standard deviation (SD) = 3.50 μm) and 1.46 μm (SD = 1.03 μm), respectively. The range of the Cu particle size distribution was narrower than that of CuO, indicating that the particle size of Cu obtained after the reaction was smaller and more uniform. 3132



Article

Figure 9. HPLC chromatograms of liquid samples in the presence of CuO and lactic acid with different pH values at 250 °C, 3 h.

ΔGred (the Gibbs free energy for the reduction of oxides) slowly decreases as the temperature increases.26 Therefore, the improvement in the conversion of CuO to Cu at a higher temperature, that is, above 200 °C, could be attributed to the decrease in ΔGred. As shown in Figure 5, which presents the effect of reaction time, the yield of Cu increased from approximately 61% after 2 h to approximately 93% after 4 h at 200 °C. Similarly, at the lower temperature of 180 °C, no further increase in the yield of Cu was observed after 6 h. As shown in Figures 4 and 5, a large amount of Cu2O was produced at a lower temperature after a short reaction time, which suggests that the formation of Cu from CuO is a multistep reaction that proceeds via the formation Cu2O. The first step in the reduction of CuO to Cu2O is exothermic with a calculated ΔrHm of −1306.94 kJ/mol, and the second step for reduction of Cu2O to Cu is endothermic with a calculated ΔrHm of 703.07 kJ/mol. Therefore, CuO can easily be converted into Cu2O at a lower temperature after a short reaction

time, whereas a higher temperature is needed to convert Cu2O into Cu. A series of experiments were carried out to investigate the effect of alkali by varying the concentration of NaOH from 0.0 to 1.0 mol/L. As shown in Figure 6, a higher NaOH concentration was favorable for the reduction of CuO. The yield of Cu increased greatly with the increase in the concentration of NaOH and exceeded 90% with the addition of 0.50 mol/L NaOH at a temperature of 200 °C and a reaction time of 3 h. The significant increase in the conversion of CuO with the increase in the NaOH concentration probably occurred for two reasons. First, alkalinity promoted the hydrolysis of cellulose. It has been found that, under hydrothermal conditions, NaOH can readily break the hydrogen bonds in cellulose and promote the degradation of cellulose in favor of C−C bond cleavage.27,28 Second, NaOH promoted the conversion of glucose into lactic acid due to its alkaline catalytic activity.29,30 Moreover, with respect to electrochemistry, according 3133



Article

the decomposition of cellulose. To test the latter hypothesis, gas samples were collected and examined by GC-TCD. No reducing gas, such as H2 and CO, was produced, and approximately 58% (v/v) of the gas collected was CO2. Therefore, it was reasonable to suggest that CuO was reduced by glucose formed by the hydrolysis of cellulose. Based on our previous studies on the mechanism of the formation of lactic acid from glucose or cellulose,6,20,29,30,41 a possible mechanism of hydrothermal alkaline reduction of CuO with cellulose as a reductant was developed and is presented in Figure 7. Initially, cellulose is hydrolyzed into glucose under alkaline hydrothermal conditions, and the acid−base equilibrium is reached with the production of glucose alkoxide during the second step. For the third step, the proposed retro-aldolization of D-glucose via coordination with divalent copper occurs, along with the formation of glyceraldehyde (aldoses of three carbon atoms) and the reduction elimination of Cu(II) to Cu. Next, glyceraldehyde produces lactic acid via the formation of pyruvaldehyde through the elimination of water and a benzilic acid rearrangement in step 4. As mentioned before, the increase in the amount of acetic acid produced in the presence of CuO may be attributable to the oxidation of lactic acid. To test this assumption, further experiments with lactic acid as a reductant in the presence of CuO at the temperature of 250 °C and a reaction time of 3 h were conducted under acidic, neutral, or alkaline conditions by adjusting the pH with NaOH. As shown in Figure 8, which depicts the XRD patterns of the solid samples after reactions with lactic acid as the reductant at pH 12.0, 6.0, and 3.0, at a lower pH, the peak of Cu was higher, and the peak for CuO was not detected at pH 3.0. These results indicate that acidic conditions are favorable for the reduction of CuO to Cu with lactic acid as a reductant. Figure 8 a is an XRD pattern of solid sample after the blank experiment with Cu and lactic acid, which indicated that there were no reactions with Cu and lactic acid. Figure 9 shows the HPLC chromatograms of the liquid samples produced under the same conditions. These chromatograms show that pyruvic acid and acetic acid were present in the liquid samples. Comparing the HPLC chromatograms at different pH values, the lactic acid peak was smaller, and the acetic acid peak became higher with a decrease in the pH, thereby indicating that the increases in the amounts of acetic acid could be attributed to the oxidation of lactic acid.42 These results also demonstrate that acidic conditions are favorable for the decomposition of lactic acid, perhaps because organic acids are difficult to degrade under alkaline conditions, as demonstrated by our previous research.15 A comparison of the HPLC chromatograms of the liquid samples obtained under the same conditions with and without CuO (Figure 9 C,D) reveals that

Figure 10. XRD patterns of solid samples in the presence of CuO and acetic acid at temperature of 250 °C, 3 h, and (a) pH 3.0, (b) pH 6.0, and (c) pH 12.0.

to the Pourbaix diagram, which is also called a potential/pH diagram and maps out the possible stable phases of an aqueous electrochemical system, the Eh (reduction potential) decreases as pH increases.31,32 Therefore, the increase in the reduction of CuO to Cu with the increase in the concentration of alkali may be the result of the OH− ions reducing in the Eh, thereby enhancing the reaction rate by facilitating the delivery of electrons. To maintain the safety of the experiments and the durability of the reactor, the optimum concentration of NaOH was set at 0.50 mol/L. 3.3. Proposed Mechanism of Reduction of CuO to Cu with Cellulose. It is generally known that cellulose can be hydrolyzed into oligosaccharides or glucose monomers with base or acid. This reaction can also take place in HTW even without base or acid, due to inherent acid and base catalytic roles of HTW.33,34 Therefore, under the alkaline hydrothermal conditions, cellulose may first be hydrolyzed into glucose,34,35 which subsequently is used for the reduction of CuO. Moreover, it is known that hydrogen or syngas can be produced from the hydrothermal gasification of biomass under subcritical water conditions.36−39 Therefore, there are two possible explanations for the reduction of CuO to Cu in the presence of cellulose. One explanation is that CuO is reduced by the glucose formed by the hydrolysis of cellulose. The other explanation is that CuO is reduced by a reducing gas, such as CO and H2,10,40 formed by

Figure 11. Proposed flow sheet for converting CuO into Cu. 3134



Article

(5) Zhang, W.; Cheng, C. Y. Manganese metallurgy review. Part I: Leaching of ores/secondary materials and recovery of electrolytic/ chemical manganese dioxide. Hydrometallurgy 2007, 89, 137. (6) Jin, F. M.; Enomoto, H. Rapid and highly selective conversion of biomass into value-added products in hydrothermal conditions: chemistry of acid/base-catalysed and oxidation reactions. Energy Environ. Sci. 2011, 4, 382. (7) Wu, B.; Gao, Y.; Jin, F.; Cao, J.; Du, Y.; Zhang, Y. Catalytic conversion of NaHCO3 into formic acid in mild hydrothermal conditions for CO2 utilization. Catal. Today 2009, 148, 405. (8) Jin, F.; Zhong, H.; Cao, J.; Cao, J.; Kawasaki, K.; Kishita, A.; Matsumoto, T.; Tohji, K.; Enomoto, H. Oxidation of unsaturated carboxylic acids under hydrothermal conditions. Bioresour. Technol. 2010, 101, 7624−7634. (9) Kishida, H.; Jin, F.; Yan, X.; Moriya, T.; Enomoto, H. Formation of lactic acid from glycolaldehyde by alkaline hydrothermal reaction. Carbohydr. Res. 2006, 341, 2619. (10) Takahashi, H.; Kori, T.; Onoki, T.; Tohji, K.; Yamasaki, N. Hydrothermal processing of metal based compounds and carbon dioxide for the synthesis of organic compounds. J. Mater. Sci. 2008, 43, 2487. (11) Savage, P. E. A perspective on catalysis in sub- and supercritical water. J. Supercrit. Fluids 2009, 47, 407. (12) Yuksel, A.; Sasaki, M.; Goto, M. Complete degradation of Orange G by electrolysis in sub-critical water. J. Hazard. Mater. 2011, 190, 1058. (13) Jin, F. M.; Enomoto, H. Hydrothermal Conversion of Biomass into Value-Added Products: Technology That Mimics Nature. Bioresources 2009, 4, 704. (14) Abbasi, T.; Abbasi, S. A. Biomass energy and the environmental impacts associated with its production and utilization. Renewable Sustainable Energy. Rev. 2010, 14, 919. (15) Jin, F. M.; Yun, J.; Li, G. M.; Kishita, A.; Tohji, K.; Enomoto, H. Hydrothermal conversion of carbohydrate biomass into formic acid at mild temperatures. Green Chem. 2008, 10, 612. (16) Kruse, A.; Gawlik, A. Biomass conversion in water at 330−410 °C and 30−50 MPa. Identification of key compounds for indicating different chemical reaction pathways. Ind. Eng. Chem. Res. 2003, 42, 267. (17) Jin, F.; Zhang, G.; Jin, Y.; Watanabe, Y.; Kishita, A.; Enomoto, H. A new process for producing calcium acetate from vegetable wastes for use as an environmentally friendly deicer. Bioresour. Technol. 2010, 101, 7299. (18) Jin, F. M.; Zhou, Z. Y.; Moriya, T.; Kishida, H.; Higashijima, H.; Enomoto, H. Controlling hydrothermal reaction pathways to improve acetic acid production from carbohydrate biomass. Environ. Sci. Technol. 2005, 39, 1893. (19) Jin, F. M.; Enomoto, H. Application of hydrothermal reaction to conversion of plant-origin biomasses into acetic and lactic acids. J. Mater. Sci. 2008, 43, 2463. (20) Jin, F.; Zhou, Z.; Enomoto, H.; Moriya, T.; Higashijima, H. Conversion mechanism of cellulosic biomass to lactic acid in subcritical water and acid-base catalytic effect of subcritical water. Chem. Lett. 2004, 33, 126. (21) Jin, F. M.; Gao, Y.; Jin, Y. J.; Zhang, Y. L.; Cao, J. L.; Wei, Z.; Smith, R. L. High-yield reduction of carbon dioxide into formic acid by zero-valent metal/metal oxide redox cycles. Energy Environ. Sci. 2011, 4, 881. (22) Yao, G. D.; Huo, Z. B.; Jin, F. M. Direct reduction of copper oxide into copper under hydrothermal conditions. Res. Chem. Intermed. 2011, 37, 351. (23) Rietveld, H. A profile refinement method for nuclear and magnetic structures. J. Appl. Crystallogr. 1969, 2, 65. (24) Cheary, R. W.; Coelho, A. A fundamental parameters approach to X-ray line-profile fitting. J. Appl. Crystallogr. 1992, 25, 109. (25) Yu, J.; Savage, P. E. Decomposition of formic acid under hydrothermal conditions. Ind. Eng. Chem. Res. 1998, 37, 2.

the sizes of the lactic acid and acetic acid peaks increased in the presence of CuO, indicating that the addition of CuO promoted the decomposition of lactic acid and the increased yield of acetic acid. Furthermore, a series of experiments with acetic acid (0.50 mol/L) and CuO at the temperature of 250 °C were conducted to investigate the reducing capacity of acetic acid for CuO. As shown in Figure 10, the reduction of CuO was not observed at pH 6.0 and 12.0, respectively, and a small amount of CuO was reduced to Cu2O at pH 3.0. In contrast with experiments with lactic acid, the reducing ability of acetic acid is much lower in the reduction of CuO under hydrothermal conditions. Therefore, CuO can be reduced not only by cellulose but also by the products of cellulose decomposition, such as lactic acid. At present, our results show that CuO can be reduced into Cu with cellulose as a reductant under mild conditions. Hence, a simple and green process to produce Cu from CuO could be proposed as shown in Figure 11. In this proposition, the organic acid solutions after hydrothermal reactions and separating with Cu solid could be separated and regenerated by electrodialysis and reverse osmosis.17 Work along this line is now in progress.

4. CONCLUSIONS The investigation of the reduction of CuO to Cu with cellulose as a reductant under alkaline hydrothermal conditions showed that CuO can be reduced completely to Cu in 1.5 h under mild conditions at the temperature of 250 °C in the presence of 0.50 mol/L NaOH. This process also resulted in the conversion of cellulose into value-added chemicals, such as lactic acid and acetic acid. CuO can be reduced by not only cellulose but also by the products of cellulose decomposition, such as lactic acid. These results have great significance in the development of a green process for the production of Cu with a low energy cost.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected].

■

ACKNOWLEDGMENTS

■

REFERENCES

The authors gratefully acknowledge the financial support of the National Natural Science Foundation of China (No. 21077078), the National High Technology Research and Development Program of China (No. 2009AA063903), and the Projects of International Cooperation by the Shanghai Committee of Science and Technology, China (No. 09160708100).

(1) Luo, R. Overall equilibrium diagrams for hydrometallurgical systems: copper-ammonia-water system. Hydrometallurgy 1987, 17, 177. (2) Oishi, T.; Yaguchi, M.; Koyama, K.; Tanaka, M.; Lee, J. C. Hydrometallurgical process for the recycling of copper using anodic oxidation of cuprous ammine complexes and flow-through electrolysis. Electrochim. Acta 2008, 53, 2585. (3) Dimitrijevic, M.; Kostov, A.; Tasic, V.; Milosevic, N. Influence of pyrometallurgical copper production on the environment. J. Hazard. Mater. 2009, 164, 892. (4) Moskalyk, R. R.; Alfantazi, A. M. Review of copper pyrometallurgical practice: today and tomorrow. Miner. Eng. 2003, 16, 893. 3135



Article

(26) Larcher, D.; Patrice, R. Preparation of Metallic Powders and Alloys in Polyol Media: A Thermodynamic Approach. J. Solid State Chem. 2000, 154, 405. (27) Bobleter, O. Hydrothermal Degradation of Polymers Derived from Plants. Prog. Polym. Sci. 1994, 19, 797. (28) Deng, T. Y.; Sun, J. Y.; Liu, H. C. Cellulose conversion to polyols on supported Ru catalysts in aqueous basic solution. Sci. China: Chem. 2010, 53, 1476. (29) Yan, X.; Jin, F.; Tohji, K.; Moriya, T.; Enomoto, H. Production of lactic acid from glucose by alkaline hydrothermal reaction. J. Mater. Sci. 2007, 42, 9995. (30) Yan, X.; Jin, F.; Kishita, A.; Enomoto, H.; Tohji, K. Formation of lactic acid from cellulosic biomass by alkaline hydrothermal reaction. AIP Conf. Proc. 2008, 987, 50. (31) Van der Weijden, R. D.; Mahabir, J.; Abbadi, A.; Reuter, M. A. Copper recovery from copper(II) sulfate solutions by reduction with carbohydrates. Hydrometallurgy 2002, 64, 131. (32) Joseyphus, R. J.; Kodama, D.; Matsumoto, T.; Sato, Y.; Jeyadevan, B.; Tohji, K. Role of polyol in the synthesis of Fe particles. J. Magn. Magn. Mater. 2007, 310, 2393. (33) Sakanishi, K.; Ikeyama, N.; Sakaki, T.; Shibata, M.; Miki, T. Comparison of the hydrothermal decomposition reactivities of chitin and cellulose. Ind. Eng. Chem. Res. 1999, 38, 2177. (34) Sasaki, M.; Fang, Z.; Fukushima, Y.; Adschiri, T.; Arai, K. Dissolution and hydrolysis of cellulose in subcritical and supercritical water. Ind. Eng. Chem. Res. 2000, 39, 2883. (35) Goto, M.; Obuchi, R.; Hirose, T.; Sakaki, T.; Shibata, M. Hydrothermal conversion of municipal organic waste into resources. Bioresour. Technol. 2004, 93, 279. (36) Dolan, R.; Yin, S. D.; Tan, Z. C. Effects of headspace fraction and aqueous alkalinity on subcritical hydrothermal gasification of cellulose. Int. J. Hydrogen Energy 2010, 35, 6600. (37) Muangrat, R.; Onwudili, J. A.; Williams, P. T. Alkali-promoted hydrothermal gasification of biomass food processing waste: A parametric study. Int. J. Hydrogen Energy 2010, 35, 7405. (38) Yanik, J.; Ebale, S.; Kruse, A.; Saglam, M.; Yuksel, M. Biomass gasification in supercritical water: Part 1. Effect of the nature of biomass. Fuel 2007, 86, 2410. (39) Fang, Z.; Minowa, T.; Fang, C.; Smith, J. R. L.; Inomata, H.; Kozinski, J. A. Catalytic hydrothermal gasification of cellulose and glucose. Int. J. Hydrogen Energy 2008, 33, 981. (40) Li, Y.; Xu, G.; Liu, C.; Eliasson, B.; Xue, B. Co-generation of syngas and higher hydrocarbons from CO2 and CH4 using dielectricbarrier discharge: effect of electrode materials. Energy Fuels 2001, 15, 299. (41) Yan, X. Y.; Jin, F. M.; Tohji, K.; Kishita, A.; Enomoto, H. Hydrothermal Conversion of Carbohydrate Biomass to Lactic Acid. AIChE J. 2010, 56, 2727. (42) Yuksel, A.; Sasaki, M.; Goto, M. Electrolysis Reaction Pathway for Lactic Acid in Subcritical Water. Ind. Eng. Chem. Res. 2011, 50, 728.

3136


Facile and Green Production of Cu from CuO Using Cellulose under

Recommend Documents