Correlation between physico-chemical properties of RO composite membranes and separation performance on high salinity water

• Main Authors: Ling Yung Hung, 洪鈴詠
• Other Authors: S. J. Lue
• Format: Others
• Online Access: http://ndltd.ncl.edu.tw/handle/90887429504954146416

碩士 === 長庚大學 === 化工與材料工程研究所 === 98 === The global water resources have been diminishing reduce, the industrial sewage wastewater is retreated utilized again. This issue has attracted much in the past decades, especially in the area suffering from water shortage. Therefore many countries are developing water conservation and recycle protocols. The objective of this work was to investigate the salt removal efficiency from high salinity wastewater using reverse osmosis (RO) process in order to permeate water recover. Two commercial composite membranes were characterized by using attenuated total reflectance-Fourier transform infrared spectrometry ( ATR-FTIR)、x-ray photoelectron spectroscopy (XPS)、field-emission scanning electron microscopy (FE-SEM) and Variable mono-energy slow positron beam (VMSPB) of annihilation radiation. The ATR-FTIR spectra revealed characteristic amideⅠ、amideⅡ and aromatic(amide) peaks. Un-crosslinked -COOH functional groups were observed in addition to the reacted -CONH groups. XPS spectra indicated that AK membrane had higher O/N ratio and contained more groups. Scanning election micrograms showed that thickness was higher than AG membrane. This high membrane resistance also produced less permeate flux. The higher R parameter was obtained for the AK membrane using the Doppler-broadened Energy Spectrum (DBES) spectrogram. This is associated with bigger hole. Then a spiral-wound module using AG membrane was investigated on salt removal efficiency from high salinity wastewater. The permeate flux increased from 1.0×10-5 to 3.1×10-5 m3 m-2 s-1 at a pressure increase from 980 to 1960 kPa on 1% NaCl feed solution. The salt rejection was increased from 93 to 97% under the same operating condition. The salt concentration was reduced to 350-700 ppm from 1-2% NaCl solutions at an operating pressure of 1960 kPa. The water recovery was increased with insignificant change in salt rejection at an elevated temperature. The water and the salt the mass transfer models were also established in terms of the feed salinity, the operating pressure and the temperature. Water transported through the RO membrane under the pressure gradient as the driving force. Salt diffused through the membrane according to a solution-diffusion mechanism. Overall the RO is an effective process to purify wastewater containing high salt concentration.