Anawat Sungpet

Performance evaluation of nanofiltration membranes for treatment of effluents containing reactive dye and salt

Abstract The main purpose of this work is to investigate the preliminary performance of nanofiltration membranes for treatment of effluents containing salt and reactive dye. The membranes, designated as ES20, NTR-729HF, and LES90, were kindly supplied by the Nitto Denko Corporation. ES20 and LES90 are negatively charged membranes. NTR-729HF, a substituted poly(vinyl alcohol) membrane, is neutral. Regardless of the feeds, LES90 provided the highest permeate fluxes, while ES20 gave the lowest flux. ES20 and LES90 membranes achieved the higher salt rejection than NTR-729HF. LES90, however, suffered a great loss in the salt rejection as the concentration of NaCl increased. The dye rejections of ES20 and LES90 are sufficient for the reuse of the permeate. The neutral NTR-729HF membrane exhibited lower dye retention than the charged membranes. For the feed containing salt and dye, the superposition of trans-membrane osmotic pressure and concentration polarization resulted in substantial flux decline. Nevertheless, with the presence of dye in the feed, the charged membranes were able to retain more salt. It was likely that a highly concentrated layer formed by the accumulation of dye near the membrane surface attributed to the higher salt rejection. An increase in the feed temperature contributed to a slight increase in the LES90 flux while the salt and dye rejections remained almost unchanged.

Treatment of effluents from textile-rinsing operations by thermally stable nanofiltration membranes

Abstract Thermally stable nanofiltration membranes were used to recover hot water from rinsing effluents from acid and reactive dyeing operations. Two types of flat-sheet membranes, MPF-34 (MWCO 200) and MPF-36 (MWCO 1000), were tested at 60°C and 10 bar. Experiments carried out with the made-up feeds containing acid dye and acetic acid showed that both membranes were able to retain more than 99% of dye. MPF-36 suffered from substantial flux decline due to the dye and acid in the feeds but still provided higher fluxes than MPF-34. Furthermore, reactive dye rejection of MPF-36 was acceptable, ranging from 97 to 99.5%, while the fluxes, 105–140 1/m 2 .h, were exceptionally high. MPF-36 was then further tested with the wastewater from industrial processes. The membrane could recover hot water by removing more than 98% of acid dye and 90% of reactive dyes. Despite severe fouling by acid dye, the membrane was still able to provide 40–50 1/m 2 .h of permeate fluxes. For the reactive dye rinsing effluents, remarkably high fluxes of 120–1501/m2.h were obtained. Chemical cleaning of the used membrane with 0.2% wt. HNO 3 and subsequently 0.5% wt. NaOH recovered 80–100% of the flux.

Reactive polymer membranes for ethylene/ethane separation

Abstract Olefin/paraffin separations by distillation are highly energy intensive. Facilitated transport, or reactive membranes have long been investigated as an alternative and/or complementary separation technology to conventional distillation. However, stability problems associated with facilitated transport membranes have been the primary obstacle in the development of commercial FT processes. In this paper, we report the development of a polymer membrane containing silver(I) ion that facilitates the transport of ethylene in the absence of solvent. Blends of ionically conductive and electrically conductive polymers were found to have the appropriate electronic environment to allow reaction of silver(I) ion and ethylene. The results for the ethylene/ethane separation were obtained with composite membranes of silver(I)-form Nafion ® and 2 wt% poly(pyrrole). Permeation measurements were performed with ethylene/ethane mixtures at total feed pressures ranging from 760 to 1900 mmHg and at temperatures of 40°C to 70°C. Pure gas permeability measurements were obtained at a total feed pressure of 1900 mmHg and temperatures of 30°C and 40°C. Ethylene/ethane separation factors with the silver(I)-form Nafion-poly(pyrrole) composite membranes increased from 8 to 15 as temperature decreased. Ethylene permeabilities increased from 0.2 to 1 Barrer over the temperature range of 30°C to 70°C. An ethylene/ethane mixed gas permeability ratio of about 2 was observed with non-reactive proton-form Nafion-poly(pyrrole) composite membranes. Ethylene permeation measurements as a function of membrane thickness suggested that the facilitated transport of ethylene approached the reaction-limited regime at membrane thickness of 5 μm. The complexation between ethylene molecules and silver(I) ions in Nafion-poly(pyrrole) composite membrane was observed with FTIR spectroscopy.

Effects of Carrier Mobility on Carrier Saturation Phenomenon in Facilitated Transport Membranes

Permeation experiments of ethylene were performed to investigate the effect of carrier mobility on carrier saturation in a facilitated transport membrane. Poly(vinyl alcohol)-based membranes containing either Na+-ions or Ag+-ions were used to prepare mobile-carrier and fixed-carrier membranes. For the membranes containing 0.49 M Ag+-ions, the fluxes obtained from the mobile-carrier membrane were higher than those obtained from the fixed-carrier membrane. It was also observed that the fixed-carrier membrane was more susceptible to the carrier saturation than the mobile-carrier membrane. However, the effect of carrier mobility on permeation flux and carrier saturation was not noticed as the carrier concentration was increased.