(635c) A Simple, Reactive Approach to Mitigate Fouling and Concentration Polarization in Reverse Osmosis Systems

A Simple, Reactive Approach
to Mitigate Fouling and Concentration Polarization in Reverse Osmosis systems

Rajarshi Guha^a, Boya Xiong^b_,
Michael Geitner,^a
Tevin Moore^a,
Darrell Velegol^a, Manish Kumar^a

^aDepartment of Chemical Engineering, The Pennsylvania State
University, University Park, PA 16802, United States

^bDepartment of Civil and Environmental Engineering, The Pennsylvania State
University, University Park, PA 16802, United States

                        
                                              Abstract

Fouling of high pressure membranes is a
recalcitratnt problem, particularly in reverse osmosis (RO) and nanofiltration
(NF) systems. Colloidal, organic and biological fouling are the most commonly
encountered challenges in industrial desalination and wastewater treatment
processes and there is no convenient way to clean the membrane without
interrupting operation or resorting to expensive fouling mitigation
infrastructure. Therefore, significant energy savings can be achieved by real
time fouling elimination and concentration polarization mitigation. Although
several important technological improvements were achieved in membrane design
and fouling control in past few years, for example-  TiO₂ embedded composite
antifouling membranes, photothermal nanoheater membranes or carbon nanotube containing
composite electrolytic membranes, which are promising in reducing different
types of fouling. However, all the reported methodologies suffer from requiring
extensive new infrastructure, lack of scalability and most importantly,
efficiency without loss in productivity.

Here, we have demonstrated a simple scalable approach
of coating RO/ NF membrane with bioinspired adhesive
polymer polydopamine and copper oxide nanoparticles,
which decomposed H₂O₂ (0.006% - 0.024%) to oxygen bubbles
and thereby, swept foulants away from the surface and
at the same time reduced concentration polarization by enhancing mass transfer
co-efficient. The polydopamine layer embedded the
nanoparticles and acted as the reactive catalytic surface. Additionally, polydopamine layer helped to protect the underlying
polyamide layer from hydroxyl radicals by acting as free radical scavenger.
Such composite membrane eliminated flux decline with colloidal foulants in repeated runs and even increased the flux level
beyond the baseline value with organic humic acid foulants. Enhanced catalytic activity of humic acids in presence of H₂O₂ and
reduction of concentration polarization were found to be responsible for such
flux enhancements. Embedded copper oxide nanoparticles also retarded E. Coli attachment to the membrane
surface in stirred cell experiments. On the other hand, such composite membrane
was found to eliminate concentration polarization upon H₂O₂
addition by bubble induced mixing. Therefore, such scalable facile approach
holds promise to mitigate fouling in industrial membrane systems, reduce
concentration polarization and thereby, saving considerable energy.