Recovery and Recycle of Indigo from Wash Water in Denim Manufacturing
Project Title: Recovery and Recycle of Indigo from Wash Water in Denim Manufacturing
Continuation Project? No
Research Team Leader J. Nolan Etters Phone706-542-4892
Team Leader’s Email netters@fcs.uga.edu
Team Leader’s Institution The University of Georgia
Industry Partner Contacts
Mr. Ned Lindsey, Avondale Mills, Inc. (256-249-1200)Monroe, Georgia(Headquarters)
Mr. Donald Henderson, Mount Vernon Mills, Inc.(706-734-2311)Trion, Georgia
Proposed Research Team:
Researcher Name and Institution Phone
J. Nolan Etters, UGA 706-542-4892
Warren S. Perkins, UGA 706-542-4885
George Baughman 706-542-4883
Requested Funds:
College or University $$ Requested
The University of Georgia $73,575
Total TIP-PFFP Funds Requested for FY2003 $73,575
Executive Summary
This project proposes to demonstrate the recovery and reuse of indigo from wash water at the indigo dye range using a novel precipitation technique. Recovery of indigo is attractive from economic as well as environmental viewpoints. Color in effluents from dyeing of yarn with indigo is already a serious and costly problem for some denim manufacturers in Georgia. Furthermore, Georgia denim manufacturers should expect stricter limits on color level in wastewater in the future. At its typical concentration of 0.20 g/L in wash water, the value of indigo is approximately $8.33/1000 gallons of wash water. Therefore, the potential exists for saving $360,000 worth of indigo per year in a typical dye house. Additionally, the avoided cost of color removal at wastewater treatment plants may be worth as much as $500,000 to $1,000,000 per year if recovery and reuse of indigo were implemented.
Virtually all of the indigo in wash water from the indigo dye range can be recovered using a new method developed by researchers at the University of Georgia. The process uses a polyvalent metal salt such as ferric chloride to coagulate indigo particles and concentrate the indigo to around 10 g/L, a concentration sufficient for recycle of indigo to the dye applicator boxes in the indigo dye range.
The indigo recovery process described herein was discovered during the latter stages of an earlier TIP-PFFP project, “Chemical Conservation in Denim Manufacturing.” Using the new method, indigo was recovered from wash water obtained from an indigo dye range at Avondale Mills. The color and fastness properties of cotton samples dyed in the laboratory using the recovered indigo were identical to those dyed with virgin indigo.
The principal of the indigo recovery process was shown in the previous work. Many details of implementation of the process must be worked out on laboratory and pilot plant scale. By the end of this project, the team expects to demonstrate the indigo recovery process on a commercial scale and perform an economic analysis of the indigo recovery technology.
Explanation of Work Proposed
Description of Critical Industry Problem
This project proposes to demonstrate the recovery and reuse of indigo from wash water at the indigo dye range using a novel precipitation technique. The proposed research addresses two of the Textile/apparel-related research needs identified in the TIP-PFFP FY2003 Call for Program Proposals.
First, recovery and recycle of indigo would provide environmental benefits by greatly lowering the level of color in effluents. Color in effluents from dyeing of yarn with indigo is already a serious and costly problem for some denim manufacturers in Georgia. Furthermore, Georgia denim manufacturers should expect stricter limits on color level in wastewater in the future. Usually, color in wastewater is removed during wastewater treatment by addition of costly
polymers. One site in Georgia uses a costly ozonation process to destroy color in effluent from a denim manufacturing plant.
Secondly, this project proposes to develop and demonstrate new technology for recovery and reuse of a process chemical, specifically indigo. Recovery of indigo is attractive from economic as well as environmental viewpoints. Indigo currently costs approximately $1.00 per pound of 20% active product. At its typical concentration of 0.20 g/L in wash water, the value of indigo is approximately $8.33/1000 gallons of wash water, or $360,000 per year for a typical dye house using 124,000 gallons per day of wash water.
Virtually all of the indigo in wash water from the indigo dye range can be recovered using a new method developed by researchers at the University of Georgia. The process uses precipitation by a polyvalent metal salt such as ferric chloride to coagulate indigo particles and concentrate the indigo to around 10 g/L, a concentration sufficient for recycle of indigo to the dye applicator boxes in the indigo dye range.
Measurable objectives for FY 2003
The objective for FY2003 is to demonstrate the indigo recovery process on a pilot plant scale and design a system to demonstrate the process on a commercial scale in subsequent year(s).
Previous TIP-PFFP research
The indigo recovery process described herein was discovered during the latter stages of an earlier TIP-PFFP project, “Chemical Conservation in Denim Manufacturing.” Using the new method, indigo was recovered from wash water obtained from an indigo dye range at Avondale Mills. The color and fastness properties of cotton samples dyed in the laboratory using the recovered indigo were identical to those dyed with virgin indigo.
The principal of the indigo recovery process was shown in the previous work. Many details of implementation of the process must be worked out on laboratory and pilot plant scale. By the end of this project, the team expects to demonstrate the indigo recovery process on a commercial scale and perform an economic analysis of the indigo recovery technology.
Other related work
One denim manufacturer in the United States (Cone Mills) currently recovers indigo using membrane processes. Other denim manufacturers have concluded that recovery of indigo using membrane processes is not economical for their plants (private communication). Capital investment costs and operating costs for the new indigo recovery process based on precipitation have not been determined. However, capital costs and operating costs are expected to be dramatically lower than those for ultrafiltration, the only method currently available for recovery and recycle of indigo.
A process for adsorption of indigo particles on precipitated metal salts was patented and assigned to Canton Textile Mills, Inc. in 1977. In that process indigo was recovered but was contaminated by the insoluble metal salt. To the best of our knowledge, that process was never implemented commercially and intellectual property protection afforded by the patent has expired. In the new process that is the subject of this proposal, the indigo is simply coagulated by a soluble metal salt. The process recovers indigo with only minimal contamination of indigo by the coagulating agent.
Industry partner’s involvement
During the first year, the industry partner will participate in planning the pilot plant demonstration and possibly perform trials on its own pilot plant dyeing equipment. Assuming that the pilot scale studies during the first year are successful, the industry partner will provide a site for commercial scale demonstration of the indigo recovery process. The industry partner(s) would take a lead role in conducting the commercial demonstration.
Description of Technical Approach
Work plan
Wash water will be obtained from the indigo dye range at the industrial partner’s plant. Laboratory experiments will be performed to determine the best coagulating agent to use for recovery of indigo. We know from earlier research that ferric chloride will work satisfactorily. However, other agents may work better or be more economical. Optimum temperature, pH, and chemical concentrations for the indigo recovery will be determined.
We will also obtain wash water from dyeings containing sulfur dyes to see if the process can be used to recover sulfur dyes, as well as indigo. We know from previous work that indigo can be recovered and recycled. No work has been done to determine if sulfur dyes can be recovered using the process.
Design work will be done on a commercial scale recovery process. Equipment will be sized based on volume flows and dwell time requirements in the recovery system. Capital and operating costs will be estimated based on the system designed in this aspect of the project.
The pilot plant demonstrations will be conducted using the University of Georgia’s pilot scale indigo dye range. The industrial partner will provide wash water from its indigo dye range for the pilot plant demonstration. The industrial partner will also supply yarn and other supplies required for the pilot plant demonstrations.
A method for determining concentration of indigo in water must be developed to facilitate shade control using recycled indigo. Development of a method to determine concentration of recovered indigo is included in this project. Light absorption (spectrophotometric), chromatographic, and gravimetric methods will be considered.
The industrial partner will be involved in all stages of the pilot plant demonstration for the purpose of preparing for the commercial demonstration planned for the second (or possibly third) year of the project. As a result of this participation by the industrial partner, knowledge and technology will be transferred directly to the industrial user. Additionally, the traditional technology transfer modes including presentations at technical meetings and project reports will be used.
Project Team
Professor George Baughman will lead analytical activities required in the project. Professor Baughman is an expert in analytical methods. Baughman is widely known for his research on dyes and heavy metals in the environment.
Professor Warren Perkins and Dr. Etters will coordinate all project activities. Professor Perkins has over 30 years experience in directing and coordinating research programs. Perkins will directly supervise laboratory work in required to optimize the indigo recovery process.
Dr. Nolan Etters will assist with the pilot plant demonstrations. Dr. Etters has over 30 years experience in textile chemistry and dyeing and is a widely known expert in the area of indigo and its application.
Mr. Ned Lindsay of Avondale and Mr. Don Henderson will be the industrial partner contacts. They will coordinate all participation of the industrial partner in the project. The research team will conduct planning sessions with both industrial partners. The actual site for a plant demonstration of the indigo recovery method will be selected during the first year.
Schedule (FY2003)
Months 1-3 Test various agents for coagulation of indigo and select one agent to optimize for use in the project.
Months 3-9 Prepare the pilot scale dye range for the studies. Recover indigo for the pilot scale trials. Conduct studies on recovery of sulfur dyes.
Months 2-10 Develop method(s) for determination of concentration of recovered indigo.
Months 6-12 Prepare design for commercial scale recovery system. Perform economic analysis for indigo recovery process. Select site for industrial demonstration.
Project Summary:
Researchers at The University of Georgia are attempting to develop a commercially feasible, economical method by which indigo may be recovered from the wastewater of denim yarn dye ranges and reused. The project, one of several funded by Georgia’s Traditional Industries Program, promises to have substantial economic and environmental impact. When fully implemented, it is expected that the recovery process will save about $360,000 worth of indigo per year in a typical dye house. In addition, the avoided cost of color removal at wastewater treatment plants may be worth as much as $500,000 per year.
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Recovery and Recycle...
