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Bidirectional Water‐Stream Behavior on a Multifunctional Membrane for Simultaneous Energy Generation and Water Purification

Advanced Materials

December 2022
35(7)

DOI:10.1002/adma.202209076

Authors:

Ji-Soo Jang

Korea Institute of Science and Technology

Hamin Shin

ETH Zurich

Jihan Kim

Lawrence Berkeley National Laboratory

Show all 5 authorsHide

Hydro‐electric nanogenerators have been previously proposed to recycle various water resources (e.g., sea water, ground water, sweat, or rain) and polluted water. However, as the conventional hydro‐electric nanogenerator only utilizes water resources, it cannot provide a fundamental solution for water recycling. In this study, we propose a water purification membrane that can simultaneously generate electricity during the purification process (Electricity generation and purification membrane, EPM) for water recycling. As polluted water passes through the EPM, the water is purified in the perpendicular direction, while electricity is simultaneously produced in the horizontal direction by the movement of ions. Notably, EPM exhibited high energy generation performances (maximum power 16.44 μW and energy 15.16 mJ) by the streaming effect of water‐streaming carbon nanotubes (CNT) and ion‐permselective effect of poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). Moreover, by using poly(acrylic acid)/carboxymethyl cellulose (PAA/CMC) binder to EPM, we substantially improved the energy generation performance and long‐term stability and provided outstanding mechanical stability, regardless of the acidity of the water source (pH 1–10). More importantly, EPM exhibited the water purification characteristics of >90% rejection of sub‐10 nm pollutants and potentiality of angstrom level cation rejection, with simultaneous and continuous energy generation. Overall, this study proposed an efficient EPM model, which can be potentially used as a next‐generation renewable energy generation approach, thus laying the foundation for effective utilization of polluted water resources. This article is protected by copyright. All rights reserved

Concept of EPM operation and surface characteristics. a) Schematic illustration for EPM operation. Asymmetric wetting of water on EPM induces energy generation (cross flow), while vertical water flow on EPM results in the water purification. b) Water stability: digital images of EPM with binder and w/o binder, c,d) contact angle analysis of EPM with binder (c) and EPM w/o binder (d), e) in situ contact angle profile for various EPM samples having different material components.

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CNTs effect in EPM operation for energy generation. a) The open‐circuit voltage (Voc) and short‐circuit current (Isc) profile measured over time by operating the two types of EPMs (PEDOT:PSS‐based EPM and PEDOT:PSS/CNTs EPM) using 10 µL of DI water. b) Energy generation characteristics of PEDOT:PSS‐based EPM and PEDOT:PSS/CNTs EPM, c) Molecular dynamics (MD) snapshots at different times of simulation. The comparison of H2O (blue) molecule kinetics on CNTs and PEDOT:PSS. d) Average mean square displacement (MSD) of H2O molecule on CNTs and PEDOT:PSS from our MD simulations. e) The open‐circuit voltage (Voc), short‐circuit current (Isc), and power generation profile of EPM depending on amount of CNTs contents.

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Binder effect in EPM operation for energy generation. a) The open‐circuit voltage (Voc) profile measured over time by operating the two types of EPMs (binder‐free EPM and binder‐loaded EPM) using 10 µL of DI water. b) The short‐circuit current (Isc) profile measured over time by operating the two types of EPMs (binder‐free EPM and binder‐loaded EPM) using 10 µL of DI water. c,d) The open‐circuit voltage (Voc) and short‐circuit current (Isc) profile of binder‐loaded EPM (c) and binder‐free EPM (d) using 10 µL of DI water and 0.2 m NaCl aqueous solution. e) Normalized power and energy generation behavior on binder‐free EPM and binder‐loaded EPM with DI water and 0.2 m NaCl solution. f) Normalized short‐circuit current (Isc) profile on binder‐free EPM and binder‐loaded EPM depending on the pH level. g) MD simulation snapshots at different times of simulation when deprotonation of PAA was occurred with DI water. h) Long‐term energy generation property: measured open‐circuit voltage (Voc) by dropping 10 µL of DI water on binder‐loaded EPM.

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Water purification characteristics and bifunctional properties of EPM. a) Schematic illustration of EPM operation principle. The half of EPM was exposed to ambient air while another half part of EPM was loaded in a hand‐made cell system, and continuous water pumping to the EPM‐loaded cell was conducted by a gear pump (Cole‐Parmer Instrument Company) at a flow velocity of 1 L min⁻¹. b) PEO rejection by EPM on UF and NF support. The dashed line exhibits 90% rejection, which is conventionally defined as the MWCO. c) Single salt (0.1 m of Na2SO4, MgSO4, CaCl2) and PFOA rejection of EPM on NF support. Measurements were carried out under the following conditions: hydraulic pressure of 3.45 bar (50 psi). d) The open‐circuit voltage (Voc) profile of UF‐based EPM measured on hand‐made cell for simultaneous energy generation and water purification. e) Power generation and rejection characteristics of EPM by dropping various types of liquid sources (e.g., Tryan blue, and PFOA).

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Bidirectional Water-Stream Behavior on a Multifunctional

Membrane for Simultaneous Energy Generation and Water

Puriﬁcation

Ji-Soo Jang,* Yunsung Lim, Hamin Shin, Jihan Kim, and Tae Gwang Yun*

J.-S. Jang

Electronic Materials Research Center

Korea Institute of Science and Technology (KIST)

Seoul , Republic of Korea

E-mail: wkdwltn@kist.re.kr

Y. Lim, J. Kim

Department of Chemical and Biomolecular Engineering

Korea Advanced Institute of Science and Technology (KAIST)

 Daehak-ro, Yuseong-gu, Daejeon , Korea

H. Shin

Department of Materials Science and Engineering

Korea Advanced Institute of Science and Technology (KAIST)

 Daehak-ro, Yuseong-gu, Daejeon , Korea

T. G. Yun

Department of Materials Science and Engineering

Myongji University

Yongin, Gyeonggi , Republic of Korea

E-mail: ytk@mju.ac.kr

The ORCID identiﬁcation number(s) for the author(s) of this article

can be found under https://doi.org/./adma..

DOI: 10.1002/adma.202209076

1. Introduction

Water is an invaluable and essential

resource for sustainable life and well-being

of human.[] However, the unprecedently

rapid population growth and indiscrimi-

nate industrial revolutions have trig-

gered severe water contamination, thus,

causing global water scarcity.[] Hydroelec-

tric nanogenerator that produce electrical

energy based on various water resources

(e.g., sea water, ground water, sweat, or

rain) has been recently proposed as an

ecient method for recycling polluted

water.[] Moreover, given its eco-friend-

liness and ubiquity, hydroelectric nano-

generator technology has gained notable

attention from scholars in renewable

energy research. This system is designed

based on a conductive–porous membrane

with ion permselectivity to ameliorate

the energy generation performance by

utilizing ions and impurities in solution.

For instance, Yun et al.[] have developed

conductive carbon materials (e.g., carbon

black) cotton membrane-based hydroelec-

tric nanogenerator (transpiration-driven

electrokinetic power generator, TEPG)

for utilizing various water resources. TEPG with high surface

area accommodates spontaneous physical adsorption (∆G<)

of water molecules on the surface to reduce surface energy.

This induces the formation of a double layer between the water

molecules (protons) and the surface of the conductive materials

(electrons), which triggers a dierence between wet and dry

regions based on the asymmetrical wetting of the membrane.

The electrons ﬁrst migrate from the wet region to the external

circuit and subsequently migrate to the dry region. The water

ﬂow maintains the wetness of the wet region, thus sustaining

the potential dierence and ultimately inducing a continuous

ﬂow of electrons to the external circuit. Although a hydroelec-

tric nanogenerator can re-utilize water resources, such as sea-

water, polluted water, and rain for energy generation, it is not a

fundamental solution for producing clean water.

To alleviate this challenge, thermal or ﬁltration-based water

puriﬁcation technology has been previously suggested as a

potential solution for water recycling. In thermally based water

puriﬁcation processes, the enthalpy of water vaporization (∆Hvap)

must be alleviated, while ﬁltration-based water puriﬁcation

Hydroelectric nanogenerators have been previously proposed to recycle

various water resources and polluted water. However, as conventional hydro-

electric nanogenerators only utilize water resources, they cannot provide a

fundamental solution for water recycling. In this study, a water puriﬁcation

membrane is proposed that can simultaneously generate electricity during

the puriﬁcation process (electricity generation and puriﬁcation membrane

(EPM)) for water recycling. As polluted water passes through the EPM, the

water is puriﬁed in the perpendicular direction, while electricity is simultane-

ously produced in the horizontal direction by the movement of ions. Notably,

the EPM exhibits high energy generation performance (maximum power

16.44µW and energy 15.16mJ) by the streaming eect of water-streaming

carbon nanotubes (CNTs). Moreover, by using a poly(acrylic acid)/carboxym-

ethyl cellulose (PAA/CMC) binder to EPM, the energy-generation performance

and long-term stability are substantially improved and outstanding mechan-

ical stability is provided, regardless of the acidity of the water source (pH

1–10). More importantly, the EPM exhibits the water puriﬁcation characteris-

tics of >90% rejection of sub-10nm pollutants and potentiality of ångstrom

level cation rejection, with simultaneous and continuous energy generation.

Overall, this study proposes an ecient EPM model, which can be potentially

used as a next-generation renewable energy generation approach, thus laying

the foundation for eective utilization of polluted water resources.

ReseaRch aRticle

Adv. Mater. 2023, 35, 

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Dec 2020

Emerging organic contaminants (EOCs) discharged from wastewater effluents into drinking water resources are of growing concern for human health and the environment. In this study, we demonstrate the fabrication and application of polyelectrolyte multilayer (PEM) nanofiltration (NF) membranes with tailored selectivity for effective removal of EOCs from saline wastewaters. The PEM NF membranes were prepared via layer-by-layer (LbL) assembly of a cationic polymer, i.e., poly(diallyl dimethylammonium chloride), and anionic polymer, i.e., poly(sodium styrenesulfonate). Extensive surface characterization verifies that the fabricated PEM membranes have different pore sizes and surface charge properties depending on the LbL deposition cycle. We evaluated the performance of the PEM NF membranes for the rejection of different salts as well as the retention of representative EOCs, including perfluoroalkyl substances (perfluorooctanoic acid and perfluorooctanesulfonic acid) and antibiotics (amoxicillin trihydrate and tetracycline hydrochloride). Importantly, the PEM NF membrane coated with four bilayers showed as high as 90% EOC retention, comparable to the widely used commercial NF270 membrane, while allowing high passage of salt, including scale-forming divalent cations (<20% rejections of NaCl and CaCl2). This tailored selectivity of the four-bilayer PEM membrane enables high water flux and reduced inorganic (gypsum) scaling potential compared to the NF270 membrane during treatment of EOC-contaminated wastewaters.

Relating Selectivity and Separation Performance of Lamellar Two-Dimensional Molybdenum Disulfide (MoS2) Membranes to Nanosheet Stacking Behavior

Article

Jun 2020

Bidirectional Water‐Stream Behavior on a Multifunctional Membrane for Simultaneous Energy Generation and Water Purification

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