Leaching Effects of Metal from Electroplating Sludge under ... - CORE

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ScienceDirect Procedia Environmental Sciences 31 (2016) 361 – 365

The Tenth International Conference on Waste Management and Technology (ICWMT)

Leaching effects of metal from electroplating sludge under phosphate participation in hydrochloric acid medium Ruijing Sua,*, Bo Lianga, Jie Guana a

School of Environmental and Material Engineering, Shanghai Second Polytechnic University, Shanghai 201209, China.

Abstract In recent years, with the rapid development of the electroplating industry, electroplating sludge has reached much attention. Electroplating sludge contains heavy metals such as nickel, copper, cadmium and chromium. To avoid releasing metal into the environment, removal of heavy metals from the electroplating industry is highly desired. In this study, effects of leaching metal from electroplating sludge under phosphate participation in hydrochloric acid medium were measured. The effects of the amount of hydrochloric acid, phosphoric acid concentration, temperature, and liquid to solid ratio along with leaching time were investigated and measured using inductively coupled plasma-atomic emission spectrometry (ICP-AES). Using the optimized conditions of 1.5 mol/L hydrochloric and phosphoric acid concentration, liquid to solid ration 10:1 and temperature 40 oC, actual electroplating sludge was treated. The leaching rate of copper was measured as high as to 80.6% under optimal conditions. © by Elsevier B.V This is an open access article under the CC BY-NC-ND license © 2016 2015Published The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of Tsinghua University/ Basel Convention Regional Centre for Asia and the Pacific. Peer-review under responsibility of Tsinghua University/ Basel Convention Regional Centre for Asia and the Pacific Keywords: Electroplating sludge; hydrochloric acid medium; liquid-solid ratio; metal leaching;

1. Introduction Industry which apply electroplating generate electroplating sludge (EPS) with heavy metals, such as nickel, copper, cadmium, iron and chromium, whose concentration is well above permitted levels and detrimental to the health of living organisms1. It was because of the inability of these metals to biodegrade and their tendency to accumulate in the tissues of organisms when exposed in the environment. And there are increasing amounts of EPS produced as

* Corresponding author. Tel.: +86 21 20590300; fax: +86 21 50217725. E-mail address: [email protected]

1878-0296 © 2016 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of Tsinghua University/ Basel Convention Regional Centre for Asia and the Pacific doi:10.1016/j.proenv.2016.02.048

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Ruijing Su et al. / Procedia Environmental Sciences 31 (2016) 361 – 365

heavy-metal wastes, for example, China yearly generates more than 100,000 tons which is featured by high enrichment of metals (Ni, Cu, Zn, Fe and Cr etc) as well as organics (surfactants etc) 2,3. In the meantime, however, if the heavy metals from EPS can be effectively removed, both the filtered sludge and heavy metals have a great possibility of being directly reused. Currently, EPS are disposed mainly by landfilling and brick-making 4,5, both would cause potential pollutions to the ecoenvironment. Hence, removal of heavy metals from EPS prior to its discharge into environment is highly desired 6,7. Traditionally, conventional treatment techniques, such as electrolysis8, ion exchange9, 10, membrane separation 11 and microbiological methods12-14, have been employed to remove heavy metals from EPS. But the most common method to recover metals from electroplating sludge is the acid-base extraction procedure3. In this study, effects of leaching metal from electroplating sludge under phosphate participation in hydrochloric acid medium were measured. The effects of the amount of hydrochloric acid, phosphoric acid concentration, temperature, and liquid to solid ratio along with leaching time were investigated and measured using inductively coupled plasma-atomic emission spectrometry (ICP-AES). 2. Experimental 2.1. Materials All solvents used such as H2SO4ǃHCLǃH3PO4 were AR grade and supplied by Sinopharm Chemical Reagent Co., Ltd, Shanghai, China. All aqueous solutions were prepared with distilled water without further purification. Electroplating sludge (EPS) was obtained from a Shanghai electroplating plant. Moisture of EPS were measured in an air-drying oven at 105ć and found 69.45%. Heavy metals concentrations of sludge oxidized solution were determined by inductively coupled plasma emission spectrometer (A-6300, Thermo, USA). Water bath shaker (DF-101S water bath), was from KESHENG Instrument Co., Ltd.,Shanghai, China. 2.2. Experiments The EPS were mixed, dried in a Desktop multi-function lyophilizer, grinded to fine powders before use. Then measurable dried EPS powder were under the conditions that one changed of the variables and others keep still such as liquid-to-solid ratio, temperature and different acid for leaching 4 hours. After that, to measure the concentrations of the heavy metals in the leaching solution, the dried sludge samples were placed into 100 mL beaker. Next, 10 mL sulphuric acid (98%) was added and the sample was digested nearly dry on the electric hot plate at a low temperature. The samples were transferred into 100 mL bottles with deionized water and stored at 4 oC for further analyses of the heavy metals: aluminium (wavelengths 167.0), copper (wavelengths 324.7) and iron (wavelengths 238.2) with the use of an inductively coupled plasma atomic emission spectrometry (ICP-AES) (Prodigy, Leeman, USA). Three different samples of the same sludge were prepared for the analyses. 3. Results and discussion 3.1. Effect of hydrochloric acid on leaching rate The experiments were under 25oC and liquid to solid ratio 3:1, at series of HCl solution were 0.25, 0.5, 0.75, 1,1.5, 2 mol/L for investigating the effect of HCl on metal leaching rate from the sludge. From the results showed in Fig. 1, it can be seen that with the increase of HCl concentration, the metal leaching rate were rapidly go up. When the concentration of HCl was 1.5mol/L, the metal leaching rates were up to highest for all metals measured. After that, when the concentrations of HCl were raise continually, the leaching rate were decrease sharply. On the basis of the mechanism of leaching, the reaction will consume amount theory acid, in order to keep the reaction kinetics of balance at the same time, it should be control excessive acid in the reaction. But the leaching reaction is still under the influence of coexisting ions in the solution of synergy mechanism, such as the addition of excess acid for more than 2mol/L, and did not improve the electroplating sludge increased concentration of heavy


metal copper, aluminium and iron. If acid leaching too much too much, can appear even a lot of bubble wrap sludge, unfavourable to leach acid and good contact with the sludge particles, lower leaching rate.

Fig.1 Effect of hydrochloric acid on leaching rate

3.2. Effect of phosphate on leaching rate The experiments were also under 25oC and liquid to solid ratio 3:1, at series of H 3PO4 solution were 0.25, 0.5, 0.75, 1,1.5, 2 mol/L for investigating the effect of H3PO4 on metal leaching rate from the sludge. From the results showed in Fig. 2, it can be seen that with the increase of H3PO4 concentration, the metal leaching rate were rapidly go up. When the concentration of H3PO4 was 1.5mol/L, the metal leaching rates were up to highest for all metals measured. After that, when the concentrations of H3PO4 were raise continually, the leaching rate were changed to be steady. It can be also seen that, phosphate is more efficient for Cu than the other metals.

Fig.2 Effect of phosphate on leaching rate

3.3. Effect of temperature on leaching rate Leaching rate can be raise by raising the temperature because it can shorten the time to arrival in reaction balance. Fig.3 showed under the control of liquid-to-solid ratio 3:1 and the mixed solution 1.5mol/L, the temperature effect on leaching rate of metals.

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The figure shows that as temperatures rise, the leaching rate of metal also gradually increases, when the temperature reaches 40 to 50 oC, the leaching rate of metal tends to be stable, to peak. However, as the temperature rise to 60 oC, the leaching rates of Cu and Al have appeared different degree of reduced. Observe the leaching system can also be found that the leaching solution in the bubbles, the bubbles will influence of acid leaching with electroplating sludge particles contact with penetration, thereby affect the leaching reaction process and leaching rate.

Fig.3 Effect of temperature on leaching rate

3.4. Effect of liquid-to-solid ratio on leaching rate Liquid-to-solid ratio refers to the specific value of EPS material and the acid solution that involved; its important technical and economic parameters of leaching process. Under the premise of the certain leaching acid concentration, big liquid-solid ratio can reduce the viscosity of slurry electroplating sludge and the valuable metal ion concentration, improve transfer speed between solid and liquid phase, which can potentially improve the leaching rate. But the big liquid-solid ratio will lead to the waste acid leaching, affect the economic benefits of industrial scale application. Fig. 4 showed the effect of different liquid-to-solid ratio on metal leaching under the condition of 1.5mol/L of mixture acid and 40oC. It can be seen that with liquid-to-solid ratio increase gradually from 3:1 to 10:1, metal leaching rate of Al, Cu and Fe showed a trend of rising. Generally speaking, the smaller the particle size of electroplating sludge, the higher leaching rate of heavy metal copper. Control liquid-to-solid ratio of 10:1, mixed acid concentration 1.5 mol/L, leaching rate of Cu from EPS was 80.6%.

Fig.4 Effect of liquid-to-solid ratio on leaching rate


4. Conclusions (1) Leaching Cu by hydrometallurgy from EPS has good effect comparaed to Al and Fe. Under 1.5mol/L acid concentration, liquid-to-solid ratio of 10:1and 40oC, the leaching rate of Cu has reached as high as 80.6%. (2) The mixed acid solution of hydrochloric acid and phosphoric can efficient extract valuable metals, such as Cu and Fe from EPS, the leaching process is simple and provides the basis of recycling use and safe disposal for dangerous solid waste. (3) The test for different liquid-to-solid on the leaching of Cu and Al showed that under the condition of liquidto-solid 10:1 the leaching rate up to highest but continue to increase the ratio has no efficient work on leaching rate of metals. (4) When the temperatures were reached to 40oC it was efficient leaching for Cu and Al metals, after that, when the temperature exceed 50oC, the leaching solution prone to bubbles so that affect the leaching reaction process and rate. Acknowledgements This study was financed by the financial support provided by Young Universities Teachers Training Scheme of Shanghai (ZZegd14014), Cultivate discipline fund of Shanghai Second Polytechnic University (XXKPY1303) and Innovation Foundation of Shanghai Second Polytechnic University for New Faculty Member (EGD13XQD19). References 1. Herrera SL, Hoyos DA, Palacio LA, Pizarro JL, Aguado R. Synthesis of Industrial Waste Based Metal Catalysts for Oxidative Dehydrogenation of Propane. IND ENG CHEM RES 2013; 52:7341-7349. 2. Tian Y, Zhang J, Zuo W, Chen L, Cui Y, Tan T. Nitrogen conversion in relation to NH3 and HCN during microwave pyrolysis of sewage sludge. Environ. Sci. Technol 2013; 47:3498-3505. 3. Li C, Xie F, Ma Y, Cai T, Li H, Huang Z, Yuan G. Multiple heavy metals extraction and recovery from hazardous electroplating sludge waste via ultrasonically enhanced two-stage acid leaching. J. Hazard. Mater 2010;178: 823-833. 4. Mansfeldt T, Dohrmann R. Chemical and mineralogical characterization of blast-furnace sludge from an abandoned landfill. Environ. Sci. Technol 2004; 38:5977-5984. 5. Jordan MM, Almendro-Candel MB, Romero M, Rincon J.M. Application of sewage sludge in the manufacturing of ceramic tile bodies. Appl. Clay. Sci 2005;30: 219-224. 6. Bouranene S, Fievet P, Szymczyk A, Samar MEH, Vidonne A. Influence of operating conditions on the rejection of cobalt and lead ions in aqueous solutions by a nanofiltration polyamide membrane. J. Membr. Sci 2008; 325: 150−157. 7. Sajidu SMI, Persson I, Masamba WRL, Henry EMT. Mechanisms of heavy metal sorption on alkaline clays from Tundulu in Malawi as determined by EXAFS. J. Hazard. Mater 2008; 158:401−409. 8. Veglio F, Quaresima R, Fornari P, Ubaldini S. Recovery of valuable metals from electronic and galvanic industrial wastes by leaching and electrowinning. Waste Manag 2003;23 :245-252. 9. Villiers de PGR, Deventer Van JSJ, Lorenzen L. The extraction of species from slurries of insoluble solids with ion-exchange resins. Miner. Eng 1995; 8:1309–1316. 10. Parkpian P, Leong ST, Laortanakul P, Poonpolwatanaporn P. Environmental applicability of chitosan and zeolite for amending sewage sludge, J. Environ.Sci. Health Part A: Toxic/Hazard. Subst. Environ. Eng 2002; 37: 1855-1870. 11. Chaudry MA, Ahmad S, Malik MT. Supported liquid membrane technique applicability for removal of chromium from tannery wastes. Waste Manag 1997; 17:211-218. 12. Chen SY, Lin JG. Effect of substrate concentration on bioleaching of metal contaminated sediment. J. Hazard. Mater 2001; 82: 77-89. 13. Shanableh A, Omar M. Bio-acidification and leaching of metals, nitrogen, and phosphorus from soil and sludge mixtures. Soil Sediment Contam 2003; 12:565-589. 14. Ryu HW, Moon HS, Lee EY, Cho KS, Choi H. Leaching characteristics of heavy metals from sewage sludge by Acidithiobacillus thiooxidans MET. J. Environ.Qual 2003; 32:751-759.

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