Abstract: The worldwide consumption of pharmaceuticals and personal care products for healthcare
purposes has resulted in the occurrence of organic micropollutants (OMPs) in freshwater
and wastewater resources. These pollutants are not entirely removed by conventional water
and wastewater treatment plants, leading to potential human and animal health problems.
Membranes are a promising technology capable of solving this problem.
This study evaluated the ability of high-pressure driven membranes such as nanofiltration (NF) and
reverse osmosis (RO) to remove OMPs. A total of 13 compounds were selected so that a
broad range of molecular weights and octanol-water partition coefficients (log Kow) could
be studied. Three commercial thin-film-composite polyamide membranes (NF1, NF6, and
RO4) were tested. Filtration experiments were conducted using a cross-flow membrane
system at pH 6 8 and 10.
The membranes were characterized by atomic force microscopy and scanning electron microscopy that allowed a
more profound understanding of the membrane surface structures. Experimental results showed
that the permeate flux of NF6 is dependent on the pH of the feed solution. An increase in the feed pH from 6 to 10 resulted in an increase on the permeate flux from 14.5 to 24 L m-2 h-1 bar-1, which caused
a drop in the rejection of some OMPs by NF6. Nevertheless, for most OMPs, as pH
increased to 10, rejection increased for NF1 and RO4 due to electrostatic repulsion between
the negatively charged membrane surface and the ionized OMPs. It was observed that ionic
hydrophobic compounds could be highly rejected (> 95%) by NF1 and RO4.
The study indicated that the rejection of non-ionic hydrophilic and hydrophobic OMPs were rejected
effectively by RO4 (> 90%), and the rejection was mostly dominated by size exclusion and
hydrophobic interactions between the membrane and the OMPs. Furthermore, the study
revealed that the properties of the compounds, the intrinsic properties of the membrane,
and the operating conditions have a significant influence on the rejection of OMPs.
|Date of Award
- Physical Sciences and Engineering
|Ingo Pinnau (Supervisor)
- Organic micropollutants
- Membrane separation
- Reverse osmosis
- Rejection efficiency