| dc.description.abstract | The increased demand for cheap, biodegradable, renewable, and recyclable fibers
with good electrical, thermal, sorption, and mechanical properties positioned jute in second
place (after cotton) in the natural fiber world market. Multicellular jute fibers are recognized
by their heterogeneous chemical composition which includes α-cellulose (58-63%),
hemicelluloses (21-24%), lignin (11-12%), and some minor components (like fats, waxes,
and pectin). The non-cellulosic components (especially hemicelluloses and lignin) negatively
affect fibers’ processing leading to limited application. However, cellulose and noncellulosic components have excellent reactivity due to the presence of a high amount of
functional groups (hydroxyl, carboxylic, phenolic, aldehyde), making jute fibers suitable
candidates for a variety of chemical (such as alkali and oxidative), and physical
modifications and adjustments in their structure and properties.
This paper summarizes the investigation focused on chemical and atmospheric
pressure plasma treatments as fast and cost-effective methods for improving the jute sorption
and electro-physical properties. Alkali modifications with sodium hydroxide lead to selective
hemicellulose removal, increased the content of cellulose exposed on the fiber surface,
decreased the crystallinity index, and contributed to elementary fiber liberation.
Modifications using > 10% NaOH (so-called mercerization) change the structure of the
native cellulose I to cellulose II and increase the number of possible reactive sites. On the
other hand, the sodium chlorite modifications are used to selectively remove lignin, which is
followed by simultaneous oxidation of fiber carbonyl into the corresponding carboxyl
groups. Furthermore, periodate oxidation lead to the conversion of cellulose hydroxyl groups
on C2 and C3 atoms to aldehydes, wherein the ring cleavage occurred and 2,3-dialdehyde
cellulose was formed.
Nevertheless, the alterations of molecular-, fine, and microstructure, these chemical
modifications also homogenize jute fiber structure, and thus, provide unique sorption and
electro-physical properties. Some of the biggest benefits of the jute fibers’ alkali and
oxidative modifications are improved accessibility of the cell wall components to water
vapor, and the total water holding capacity, which lead to the increase in the moisture
sorption, water retention power, and degree of fiber swelling. The jute electro-physical properties such as dielectric loss tangent, AC specific electrical conductivity, effective
relative dielectric permeability, and volume electrical resistivity are very sensitive to fibers’
chemical composition, crystallinity, and their ability for moisture sorption. More precisely,
alkali modifications under mild conditions lead to a decrease in the volume electrical
resistivity, while the resistivity of mercerized jute is mostly dictated by the presence of
cellulose II polymorph as well as pronounced fiber liberation and fabric crimp. The overall
improved AC specific electrical conductivity of the jute fabrics with lower hemicellulose
content is the sum of three contributors: moisture sorption, crystallinity index, and
hemicellulose content. In the case of jute fabrics with lower lignin content, the moisture
sorption and crystallinity index significantly influences the AC specific electrical
conductivity only at a lower relative humidity (30% RH), while, at a higher relative humidity
(80% RH), the moisture sorption and bulk-free water have a higher influence. The obtained
increase of the effective relative dielectric permeability after the alkali and oxidative
modifications is attributed to the changes in the structural characteristics and decrease in the
content of non-cellulosic components. Having in mind that the metals are highly conductive,
one of the strategies that can be used to improve the fibers’ electro-physical properties is
their functionalization by incorporation of ions, nanoparticles, or oxides of various metals.
The incorporation of silver ions leads to a decrease in jute fabrics’ volume electrical
resistivity by 3.0-38.5 times and provided maximum bacterial reduction for E. coli and S.
aureus. Further amelioration of fibers’ electro-physical properties could be achieved by the
treatment with CuSO4 and in situ synthesis of Cu-based nanoparticles on their surfaces by
reduction. Exploitation in specific conditions that contribute to copper reduction will make
jute fabrics able to store 21-163 times more energy from an external electric field than before
the exploitation, which will extend their lifetime. The measurements of jute electro-physical
properties as a function of different internal and external factors enable the prediction of its
behavior in real application conditions, making it possible to design fabrics with desired
properties. The chemically modified jute fabrics are particularly stable to achieve good
energy accumulation in the presence of an electric field and they can be successfully used in
flexible electronics, as well as, for electrical applications such as electrostatic discharge and
fabric-based electromagnetic shielding devices, etc.
Except for the above-mentioned high-performance technologies, jute fabrics with
improved dielectric properties could be also used for some ordinary products, such as
protective clothing or textile of a specific behavior in environments sensitive to electrical
discharges and home textiles (carpet). The increased production of these ordinary, as well as
products with high performances, brings a considerable amount of waste in the form of
fabric. Recycling in the way of producing filters for wastewaters minimizes the disposal
costs of such fabrics thus contributing to “closing the loop” of their lifecycle, which is in
agreement with the circular economy concept. To move towards a circular economy and to
ensure the recycling and re-use of recycled fabrics, the jute fabrics with improved sorption
properties were evaluated as adsorbents for various heavy metal ions, and anthraquinone dye
C. I. Acid Blue 111 and Congo Red (C. I. 22120). It is worth mentioning that jute fabrics
obtained after the adsorption of Zn2+ and Cu2+-ions provided maximum bacterial reduction
for E. coli and S. aureus and can be further utilized as filters for water disinfection. After
use, these adsorbents can be burned and the metals recovered (e.g., for catalysis), while the
lignocellulosic material as abundant and low-cost waste can be used to prepare activated
carbons. properties such as dielectric loss tangent, AC specific electrical conductivity, effective
relative dielectric permeability, and volume electrical resistivity are very sensitive to fibers’
chemical composition, crystallinity, and their ability for moisture sorption. More precisely,
alkali modifications under mild conditions lead to a decrease in the volume electrical
resistivity, while the resistivity of mercerized jute is mostly dictated by the presence of
cellulose II polymorph as well as pronounced fiber liberation and fabric crimp. The overall
improved AC specific electrical conductivity of the jute fabrics with lower hemicellulose
content is the sum of three contributors: moisture sorption, crystallinity index, and
hemicellulose content. In the case of jute fabrics with lower lignin content, the moisture
sorption and crystallinity index significantly influences the AC specific electrical
conductivity only at a lower relative humidity (30% RH), while, at a higher relative humidity
(80% RH), the moisture sorption and bulk-free water have a higher influence. The obtained
increase of the effective relative dielectric permeability after the alkali and oxidative
modifications is attributed to the changes in the structural characteristics and decrease in the
content of non-cellulosic components. Having in mind that the metals are highly conductive,
one of the strategies that can be used to improve the fibers’ electro-physical properties is
their functionalization by incorporation of ions, nanoparticles, or oxides of various metals.
The incorporation of silver ions leads to a decrease in jute fabrics’ volume electrical
resistivity by 3.0-38.5 times and provided maximum bacterial reduction for E. coli and S.
aureus. Further amelioration of fibers’ electro-physical properties could be achieved by the
treatment with CuSO4 and in situ synthesis of Cu-based nanoparticles on their surfaces by
reduction. Exploitation in specific conditions that contribute to copper reduction will make
jute fabrics able to store 21-163 times more energy from an external electric field than before
the exploitation, which will extend their lifetime. The measurements of jute electro-physical
properties as a function of different internal and external factors enable the prediction of its
behavior in real application conditions, making it possible to design fabrics with desired
properties. The chemically modified jute fabrics are particularly stable to achieve good
energy accumulation in the presence of an electric field and they can be successfully used in
flexible electronics, as well as, for electrical applications such as electrostatic discharge and
fabric-based electromagnetic shielding devices, etc.
Except for the above-mentioned high-performance technologies, jute fabrics with
improved dielectric properties could be also used for some ordinary products, such as
protective clothing or textile of a specific behavior in environments sensitive to electrical
discharges and home textiles (carpet). The increased production of these ordinary, as well as
products with high performances, brings a considerable amount of waste in the form of
fabric. Recycling in the way of producing filters for wastewaters minimizes the disposal
costs of such fabrics thus contributing to “closing the loop” of their lifecycle, which is in
agreement with the circular economy concept. To move towards a circular economy and to
ensure the recycling and re-use of recycled fabrics, the jute fabrics with improved sorption
properties were evaluated as adsorbents for various heavy metal ions, and anthraquinone dye
C. I. Acid Blue 111 and Congo Red (C. I. 22120). It is worth mentioning that jute fabrics
obtained after the adsorption of Zn2+ and Cu2+-ions provided maximum bacterial reduction
for E. coli and S. aureus and can be further utilized as filters for water disinfection. After
use, these adsorbents can be burned and the metals recovered (e.g., for catalysis), while the
lignocellulosic material as abundant and low-cost waste can be used to prepare activated
carbons. Our latest investigations are focused on the preparation of jute geo-prebiotic support
for cyanobacteria growth as a novel solution for damaged land rehabilitation. More
precisely, raw jute fabric was subjected to atmospheric pressure dielectric barrier discharge
(DBD) under different conditions (power and frequency of discharge, air as working gas,
constant time of 120 s) to tailor its wettability properties which were monitored by wetting
time and capillary height measurements. Special emphasis was put on the effect of aging on
the mentioned properties. The biocrust inoculum survival and efficiency of biocrust
restoration could be improved by increasing the availability of water during the initial phase
of damaged soil rehabilitation. By tailoring geo-prebiotic polysaccharide supports’ sorption
properties, the viability of the cyanobacterial inoculum will be improved, the development of
the biocrust accelerated, and finally, the efficiency of the biocrust carpet significantly
increased. | sr |
