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29 INHIBITION OF NICKEL PRECIPITATION BY ORGANIC LIGANDS Hsien-Lun Hu, Ph.D. Candidate Nikolaos P. Nikolaidis, Associate Professor Domenic Grasso, Associate Professor Environmental Engineering Program Environmental Research Institute Department of Civil and Environmental Engineering and Department of Chemical Engineering The University of Connecticut Storrs, Connecticut 06269-2037 INTRODUCTION Nickel is the most commonly used metal in the electroplating industry. The electroplating industry discharges more than 68% of the total nickel discharged from all industries in the United States.1 In 1988 alone, 9,700 tonnes of nickel were released into the environment without recovery.2 The Environmental Protection Agency (EPA) has identified nickel as a high risk industrial chemical because it poses significant risk to human health and the environment.3-4 Wastewaters from electroplating are very complex due to the composition of the plating baths. A nickel plating bath typically consists of a nickel source (nickel chloride or nickel sulfate), complexing agents to solubilize nickel ions controlling their concentration in the solution, buffering agents to maintain pH, brighteners to improve brightness of the plated metal, stabilizers (inhibitors) to prevent undesired reactions, accelerators to enhance speed of reactions, wetting agents to reduce surface tension at the metal surface, and reducing agents (only for electro- less nickel plating) to supply electrons for reduction of the nickel.56 Alkaline precipitation is the most common method of recovering nickel from wastewaters. However, organic constituents found in the wastewaters can mask or completely inhibit the precipitation of nickel. Strong lig- ands like cyanide, EDTA, and NTA or less strong ligands like triethanolamine (TEA) and di- ethonalamine (DEA) form strong nickel complexes and hinder or even prohibit the formation of nickel precipitates.7"9 These complexes inhibit crystal growth by forming fine particles that do not coagulate. Some organic ligands (hydroxyl carboxylate acids) such as tartrate and gluconate form less strong nickel complexes in the lower pH range (acidic to neutral solution) and stronger complexes in the higher pH ranges (highly alkaline solution).1011 This implies that the traditional alkaline precipitation method of treating nickel may not be feasible when these hydroxyl carboxylate acids are present in the wastewaters. Unfortunately, their effect on nickel precipitation has yet to be studied in detail. In addition, nickel precipitation is a kinetically controlled process that does not reach equilibrium within the typical detention time of the processing units (minutes to hours). Longer reaction times should be used when studying such precipitation phenomena. Although various innovative technologies for nickel recovery other than alkaline precipitation exist (such as evaporation, electrolysis, reverse osmosis, ion exchange, and electrodial- ysis), the recycling rate is still low due to the high cost of utilizing these technologies.12 This low recycling rate not only represents a significant waste of resources, but also implies the possibility for significant degradation of water quality. The objective of this study was to conduct an equilibrium study to explore the inhibition behavior of various organic ligands on nickel precipitation. This will lay the groundwork for development of technologies efficacious in the treatment of complexed nickel. The organic ligands used in this study are EDTA, triethanolamine (TEA), gluconate, and tartrate. 50th Purdue Industrial Waste Conference Proceedings, 1995. Ann Arbor Press, Inc.. Chelsea. Michigan 48118. Printed in U.S.A. 269
Object Description
Purdue Identification Number | ETRIWC199529 |
Title | Inhibition of nickel precipitation by organic ligands |
Author |
Hu, Hsien-Lun Nikolaidis, Nikolaos P. Grasso, Domenic |
Date of Original | 1995 |
Conference Title | Proceedings of the 50th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://e-archives.lib.purdue.edu/u?/engext,45474 |
Extent of Original | p. 269-280 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Date Digitized | 2009-11-24 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 269 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Transcript | 29 INHIBITION OF NICKEL PRECIPITATION BY ORGANIC LIGANDS Hsien-Lun Hu, Ph.D. Candidate Nikolaos P. Nikolaidis, Associate Professor Domenic Grasso, Associate Professor Environmental Engineering Program Environmental Research Institute Department of Civil and Environmental Engineering and Department of Chemical Engineering The University of Connecticut Storrs, Connecticut 06269-2037 INTRODUCTION Nickel is the most commonly used metal in the electroplating industry. The electroplating industry discharges more than 68% of the total nickel discharged from all industries in the United States.1 In 1988 alone, 9,700 tonnes of nickel were released into the environment without recovery.2 The Environmental Protection Agency (EPA) has identified nickel as a high risk industrial chemical because it poses significant risk to human health and the environment.3-4 Wastewaters from electroplating are very complex due to the composition of the plating baths. A nickel plating bath typically consists of a nickel source (nickel chloride or nickel sulfate), complexing agents to solubilize nickel ions controlling their concentration in the solution, buffering agents to maintain pH, brighteners to improve brightness of the plated metal, stabilizers (inhibitors) to prevent undesired reactions, accelerators to enhance speed of reactions, wetting agents to reduce surface tension at the metal surface, and reducing agents (only for electro- less nickel plating) to supply electrons for reduction of the nickel.56 Alkaline precipitation is the most common method of recovering nickel from wastewaters. However, organic constituents found in the wastewaters can mask or completely inhibit the precipitation of nickel. Strong lig- ands like cyanide, EDTA, and NTA or less strong ligands like triethanolamine (TEA) and di- ethonalamine (DEA) form strong nickel complexes and hinder or even prohibit the formation of nickel precipitates.7"9 These complexes inhibit crystal growth by forming fine particles that do not coagulate. Some organic ligands (hydroxyl carboxylate acids) such as tartrate and gluconate form less strong nickel complexes in the lower pH range (acidic to neutral solution) and stronger complexes in the higher pH ranges (highly alkaline solution).1011 This implies that the traditional alkaline precipitation method of treating nickel may not be feasible when these hydroxyl carboxylate acids are present in the wastewaters. Unfortunately, their effect on nickel precipitation has yet to be studied in detail. In addition, nickel precipitation is a kinetically controlled process that does not reach equilibrium within the typical detention time of the processing units (minutes to hours). Longer reaction times should be used when studying such precipitation phenomena. Although various innovative technologies for nickel recovery other than alkaline precipitation exist (such as evaporation, electrolysis, reverse osmosis, ion exchange, and electrodial- ysis), the recycling rate is still low due to the high cost of utilizing these technologies.12 This low recycling rate not only represents a significant waste of resources, but also implies the possibility for significant degradation of water quality. The objective of this study was to conduct an equilibrium study to explore the inhibition behavior of various organic ligands on nickel precipitation. This will lay the groundwork for development of technologies efficacious in the treatment of complexed nickel. The organic ligands used in this study are EDTA, triethanolamine (TEA), gluconate, and tartrate. 50th Purdue Industrial Waste Conference Proceedings, 1995. Ann Arbor Press, Inc.. Chelsea. Michigan 48118. Printed in U.S.A. 269 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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