Treatment of indium-tin-oxide etching wastewater and recovery of In, Mo, Sn and Cu by liquid–liquid extraction and wet chemical reduction: a laboratory scale sustainable commercial green process

Basudev Swain, Chinmayee Mishra, Hyun Seon Hong, Sung-Soo Cho
  • Green Chemistry, January 2015, Royal Society of Chemistry
  • DOI: 10.1039/c5gc01244a

What is it about?

A laboratory scale sustainable commercial green process for treatment of indium-tin-oxide (ITO) etching wastewater and total recovery of In, Mo, Sn and Cu by combination liquid-liquid extraction and wet chemical reduction has been developed. The ITO etching wastewater is a threat to the ecosystem and human health, containing significant amounts of valuable metals like In and Cu. In metal and 100nm Cu nanopowder with 5N purity has been recovered. The developed process concurrently treats the ITO etching wastewater and recovers pure metals. By the process, Mo and Sn are recovered by liquid-liquid extraction, In is recovered through liquid-liquid extraction followed by wet chemical reduction. Value added semiconductor industry grade Cu nanopowder is recovered through wet chemical reduction using ascorbic acid. After a series of treatment, the wastewater is free of pollutant, worthy to use in the same industry or disposed. The process is a sustainable, green, versatile and flexible process.

Why is it important?

(i) This paper addresses the gap between research on metal value recovery and wastewater treatment process, commercially applicable process development and fundamental research. (ii) Most of the recovery processes reported in the open literature is about a gram to sub-gram metal recovery process, but the developed process offers versatile and flexible approach for mass production capability up to kilogram scale. (iii) The developed proposed flow sheet is a clean, green and a techno-economical feasible process for commercial treatment of several tons (m3) etching wastewater per day. (iv) The proposed process could completely recover the In with 99.999 % (5N) purity, quantitatively recover Mo and Sn with at least 99 % purity and value added Cu nanopowder with 99.999 % (5N) purity. (v) Wastewater after treatment is heavy metal free and can be disposed or reused in the same ITO etching process. (vi) Regeneration and reuse of all the organic extractant, use of non-hazardous inexpensive chemical in the process, and recovery of industrially valuable metals eventually, make the process an economical clean and green process.

Perspectives

Dr Basudev Swain (Author)
Institute for Advanced Engineering (IAE)

• A clean and green, economical wastewater treatment process developed for the treatment of ITO etching industry wastewater through liquid-liquid extraction and wet chemical reduction. • By the developed process simultaneously the valuable industrial (high pure) metals like In, Cu can be recovered to enter mainstream material flow. After values recovery and treatment, the wastewater is heavy metal free (mostly chloride free) can be disposed of or reused in the same ITO etching process. • All the organic extractant can be regenerated and reused; no hazardous chemical used for process makes the process a clean and green economical process. The use of cheaper commercial extractant and chemicals for expensive metal recovery, justifies the economical, and sustainability of the process. Regeneration and reuse of extractant, justifies the environmentally friendly and green chemistry aspect of the process. • As the process is a versatile and flexible process, can be used in small, medium and mega-scale industrial wastewater treatment where ITO etching wastewater is a concern. • The process developed can be used for batch wise treatment process or continuous treatment process. By the process, industrial wastewater disposal limit imposed by WHO can be achieved. • The developed process is a valorisation process, which convert waste to wealth in true sense.

The following have contributed to this page: Dr Basudev Swain