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56 CYANIDE DESTRUCTION BY CATALYTIC OXIDATION Yi-shen Chen, Engineer Chung-guang You, Engineer Shanghai Environmental Science Research Institute Shanghai 200233, China Wei-chi Ying, Scientist Occidental Chemical Corporation Occidental Chemical Technology Center Grand Island, New York 14072 INTRODUCTION Cyanide-containing wastewaters are mostly highly toxic industrial effluents from gold refining, electroplating of metals, chemical manufacturing, iron and steel industry and other sources. Alkaline chlorination is the most common oxidative treatment technique for destruction of cyanide; however, it has many disadvantages-high chemical costs, chloride ion contamination of the treated stream, and potential formation of cyanogen chloride.' A variety of other chemical oxidation methods, employing electrolysis,2 chlorine dioxide,3 Caro's acid,4 ozone,5 and hydrogen peroxide6 have been reported, but they all suffer from high chemical cost, incomplete treatment, and/or formation of undesirable residues. Oxidation of cyanide by molecular oxygen in air is thermodynamically possible; 2 CN" + 02 = 2 CNO" which may be further oxidized: 2 CNO" + 1.5 02 + H20 = N2 + 2 C02 + 2 OH" or hydrolyzed: C02 + NH4+ + H20 Unless catalyzed, however, the reaction rate is very slow. Activated carbon and cupric ions are known to be effective catalysts for air oxidation of cyanide.7,8 Calgon developed a pressure oxidation process employing cupric ion-catalyzed oxidation of cyanide in an activated carbon adsorber. In addition to the requirement of expensive pressure vessels, the process did not achieve destruction of complexed cyanide.9 The Inco's S02/air cyanide removal process, with both cupric ion and S02 or sulfite for promoting the oxidation reactions, did achieve destruction of complexed cyanide, but it would have a high energy cost due to its inefficient aeration method employing air bubbling.10 We have combined the enhanced oxidation achieved with additions of cupric ion and sulfite with trickling bed technology in developing a more efficient, lower cost treatment process for destruction of cyanides present in industrial wastewater." Both free and complexed cyanide species are destroyed quickly in the process which is now being practiced for full-scale treatment of cyanide-containing wastewaters in China. This paper presents the excellent results of carbon adsorption-cupric ion/sulfite promoted air oxidation of free and complexed cyanide species, which were present in actual chemical plant effluents, in laboratory bench-scale and onsite pilot-scale activated carbon adsorbers. EXPERIMENTAL SECTION Adsorption Isotherm Experiments Experimental runs were first conducted to determine the adsorptive capacity of activated carbon for free cyanide (NaCN) and copper cyanide complex (Na2Cu(CH)4). Cylindrical carbon (Shanghai Activated Carbon Plant, No. 20, 3 mm diameter x 4 mm) was pulverized, and then a prescribed 46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118. Printed in U.S.A. 539
Object Description
Purdue Identification Number | ETRIWC199156 |
Title | Cyanide destruction by catalytic oxidation |
Author |
Chen, Yi-Shen You, Chung-Guang Ying, Wei-Chi |
Date of Original | 1991 |
Conference Title | Proceedings of the 46th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://e-archives.lib.purdue.edu/u?/engext,42649 |
Extent of Original | p. 539-546 |
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 539 |
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 | 56 CYANIDE DESTRUCTION BY CATALYTIC OXIDATION Yi-shen Chen, Engineer Chung-guang You, Engineer Shanghai Environmental Science Research Institute Shanghai 200233, China Wei-chi Ying, Scientist Occidental Chemical Corporation Occidental Chemical Technology Center Grand Island, New York 14072 INTRODUCTION Cyanide-containing wastewaters are mostly highly toxic industrial effluents from gold refining, electroplating of metals, chemical manufacturing, iron and steel industry and other sources. Alkaline chlorination is the most common oxidative treatment technique for destruction of cyanide; however, it has many disadvantages-high chemical costs, chloride ion contamination of the treated stream, and potential formation of cyanogen chloride.' A variety of other chemical oxidation methods, employing electrolysis,2 chlorine dioxide,3 Caro's acid,4 ozone,5 and hydrogen peroxide6 have been reported, but they all suffer from high chemical cost, incomplete treatment, and/or formation of undesirable residues. Oxidation of cyanide by molecular oxygen in air is thermodynamically possible; 2 CN" + 02 = 2 CNO" which may be further oxidized: 2 CNO" + 1.5 02 + H20 = N2 + 2 C02 + 2 OH" or hydrolyzed: C02 + NH4+ + H20 Unless catalyzed, however, the reaction rate is very slow. Activated carbon and cupric ions are known to be effective catalysts for air oxidation of cyanide.7,8 Calgon developed a pressure oxidation process employing cupric ion-catalyzed oxidation of cyanide in an activated carbon adsorber. In addition to the requirement of expensive pressure vessels, the process did not achieve destruction of complexed cyanide.9 The Inco's S02/air cyanide removal process, with both cupric ion and S02 or sulfite for promoting the oxidation reactions, did achieve destruction of complexed cyanide, but it would have a high energy cost due to its inefficient aeration method employing air bubbling.10 We have combined the enhanced oxidation achieved with additions of cupric ion and sulfite with trickling bed technology in developing a more efficient, lower cost treatment process for destruction of cyanides present in industrial wastewater." Both free and complexed cyanide species are destroyed quickly in the process which is now being practiced for full-scale treatment of cyanide-containing wastewaters in China. This paper presents the excellent results of carbon adsorption-cupric ion/sulfite promoted air oxidation of free and complexed cyanide species, which were present in actual chemical plant effluents, in laboratory bench-scale and onsite pilot-scale activated carbon adsorbers. EXPERIMENTAL SECTION Adsorption Isotherm Experiments Experimental runs were first conducted to determine the adsorptive capacity of activated carbon for free cyanide (NaCN) and copper cyanide complex (Na2Cu(CH)4). Cylindrical carbon (Shanghai Activated Carbon Plant, No. 20, 3 mm diameter x 4 mm) was pulverized, and then a prescribed 46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118. Printed in U.S.A. 539 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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