Effect of Fouled and Non-fouled membranes on Flux and the Rejection of Pharmaceuticals and Personal Care Products
Date Issued
2010
Date
2010
Author(s)
Chang, Yu-Cheng
Abstract
Membrane or pressure-driven processes are used to remove contaminants such as dissolved solids, nature organic matter, inorganic ions, and some other hazardous compounds from water. This research investigated the effects of solute and membrane characteristics on the rejection and flux decline at various pH levels, transmembrane pressure, cross-flow velocity, and at foulant. Filtration was conducted with a cross-flow module using membrane (NF270 and NTR7450) in plate form. The concentration of effluent and membrane properties were determined using instruments such as HPLC, TOC, SEM, and AFM. The optimal operation conditions of NF filtration processes were determined using the response surface method (RSM).
There are positive correlations between rejection of target compounds and the MWCO of membrane. The rejection by NF270 was always higher than that by NTR7450 which indicated that size exclusion could be the removal mechanism of the three target compounds. At high pH, both sulfamethoxazole and triclosan are negatively charged, which implies that electrostatic exclusion could be the removal mechanism.
Standard blocking was not the main fouling mechanism for both membranes, which indicated that the molecular size of foulant in the feed solution might be larger than that of the membrane pore. Membrane fouling could be brought by the a combination of several fouling mechanisms, i.e, complete blocking, intermediate blocking, and gel layer formation.
In the presence of humic acid and calcium ions, the rejection of acetaminophen by both NF270 and NTR7450 membranes was increased whereas opposite results were observed for sulfamethoxazole. The rejection of ticlosan decreased with operation time prior to 6 hrs which could be attributed to adsorption.
The fouling layer may modify the surface properties of membrane which leads to different degrees of performance. The difference in the rejection of the three target compounds brought by distinct removal mechanisms can be attributed to their respective physic-chemical properties.
The optimum operating condition determined by the RSM was found to be at TMP of 100 psi, cross-flow velocity of 0.32 m/s, and pH 10.0. Under the best operating condition the performance was: 98.5% of rejection and 5.6% of flux decline.
Subjects
Nanofiltration (NF270 and NTR7450)
PPCP (Acetaminophen, Sulfamethoxazole, Triclosan)
Removal mechanisms
Responds surface methods (RSM)
Type
thesis
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