SUBSTITUTION CASE STUDY

Detection of traces of 2-Naphthylamine in wastewater

June 2018

Abstract

Wastewater analysis of a textile mill in Bangladesh showed the presence of 2-naphthylamine.   Direct dyes and reactive dyes based on tobias acid (CAS: 81-16-3 / EC: 201-331-5) and sulfo-tobias acid (2-naphthylamine-1,5-disulfonic acid, CAS: 117-62-4 / EC: Not reported) as the diazo component, need to be used with caution in yarn dyeing processes, as desulphonation during the coloration process can lead to the generation of 2-naphthylamine.  This can be avoided by using dyeing methods which do not enable the desulphonation process, or by using direct dyes/ reactive dyes which are not based on tobias acid or sulpho tobias acid as the diazo component if the tonal variation is acceptable.

Substituted substance

C.I Reactive Red 141 and C.I. Reactive Red 250. 

Alternative substances

Alternative dyes readily available in the market, using C.I.Reactive Red 120 (CAS No. 61951-82-4) in place of C.I Reactive Red 141, and C.I.Reactive Red 108 instead of C.I.Reactive Red 250.  

Application

  • Sector: Manufacture of textiles, wearing apparel, leather and related products. 
  • Process: Dyeing 
  • Function of substituted chemicals: Colouring agents, dyes  
  • Enterprise using the alternative: Tesco Stores Ltd (F&F Clothing), 6 Trident Place, Mosquito Way, Hatfield, Hertfordshire, AL10 9UL. www.tesco.comcr.enquiries@tesco.com 
  • State of implementation: pilot study
  • Date when alternative was implemented and in what country:  2018, Bangladesh
  • Availability of the alternative: The alternatives are readily available from many reputable suppliers. The C.I. Numbers are readily available.
  • Reliability of information: there is evidence that the solution was implemented and in use at the time of publication

Substitution description

A textile supplier based in Dhaka, Bangladesh produces various types of high quality tubular fabrics.  Its chemical management policy complies with and goes beyond EU legislation.  This supplier recognises the importance of evolving its chemical management policy in line with industry best practices and of minimizing the environmental impact of textile manufacturing processes. The company has committed to working with industry and other stakeholders to achieve the goal of zero discharge of hazardous chemicals within its textile and apparel supply chain by 2020.

With this aim, a pilot study was conducted at the supplier’s dyeing and printing mill in Bangladesh to assess current chemical usage and identify issues related to chemical management practices.  During the pilot, traces of 2-naphthylamine were detected in the mill's wastewater effluent.

By assessing the mill's chemical inventory, the source of 2-naphthylamine was attributed to the use of reactive dyes based on tobias acid (2-naphthylamine-1-sulfonic acid).  The dyes identified were C.I.Reactive Red 250, and sulpho tobias acid-based reactive dye C.I.Reactive Red 141.

The dyeing process can create conditions conducive to desulphonation, in which tobias acid present in excess in the dyestuffs can release 2-naphthylamine as a residue. There is also the potential for dyestuff to undergo reductive splitting, generating tobias acid and traces of 2-naphthylamine. 

The supplier switched to alternative dyes readily available in the market, using C.I.Reactive Red 120 (CAS No. 61951-82-4) in place of C.I Reactive Red 141, and C.I.Reactive Red 108 instead of C.I.Reactive Red 250.   After switching dyes, the wastewater from the plant was clear of 2-naphthylamine. The use of C.I.Reactive Red 286 also showed safer results.