Surfactant-stabilized cyclopentane hydrate emulsions for removing tetramethylammonium hydroxide from semiconductor wastewater

Abstract

This study presents an innovative hydrate-based wastewater treatment approach specifically designed for semiconductor wastewater containing tetramethylammonium hydroxide (TMAH), utilizing cyclopentane (CP)-in-water emulsions stabilized by nonionic surfactants Span 80 and Vitamin E-TS. The stabilized emulsions significantly accelerated hydrate formation kinetics, reducing the induction time from 313.33 min to approximately 12.67 min (a 96 % decrease), thus greatly enhancing the process's energy efficiency. Structural analyses using powder X-ray diffraction (PXRD) and Raman spectroscopy confirmed that TMAH molecules at concentrations of 515 mg/L were effectively excluded from the hydrate structure, demonstrating no interference with hydrate crystalline structures or cage occupancy. Furthermore, incorporating Vitamin E-TS as an anti-agglomerant promoted the formation of porous hydrate structures, increasing TMAH removal efficiency substantially from 45.51 % to 62.96 %, though reducing water recovery from 69.74 % to 61.64 %. Subsequent post-washing procedures further increased TMAH removal efficiency to 74.88 % but decreased water recovery to 49.24 % due to partial hydrate melting. These findings underscore the importance of balancing water recovery and contaminant removal efficiency, providing essential insights for optimizing hydrate-based wastewater treatment processes, and highlighting its potential as an energy-efficient and sustainable solution for semiconductor wastewater and other industrial wastewater containing persistent organic contaminants.