A Novel Preparation and Vapour Phase Modification of 2D-open
Channel Bio-adsorbent for Uranium Separation
Mudasir Ahmad a, b, Jianquan Ren a,
Tao Xiua, Mehraj-ud-din Naik c,
Qiuyu Zhang a, b, Baoliang Zhang a,
d, 11Corresponding author, Northwestern Polytechnical
University, Youyi Road 127#, Xi’an (710072), China. Email:
blzhang@nwpu.edu.cn
a School of Chemistry and Chemical Engineering,
Northwestern Polytechnical University, Xian, China, 710072.
b Xian Key laboratory of Functional Organic porous
materials, Northwestern Polytechnical University, China, 710129.
c Department of Chemical Engineering, College of
Engineering, Jazan University, Jazan 45142, Kingdom of Saudi Arabia.
d Shaanxi Engineering and Research Center for
Functional Polymers on Adsorption and Separation, Sunresins New
Materials Co. Ltd., Xi’an, 710072, China.
Abstract: An economical and highly uranium extraction from
seawater remains a crucial task for energy sources and environmental
safety. Aiming for improving the mass transfer rate of uranium from
seawater, a new synthetic strategy was adopted to synthesize 2D-open
channel microporous bio-adsorbent for uranium extraction from seawater.
Herein, a vapor phase modification approach was adopted to graft
divinylbenzene(DVB), and polyacrylonitrile(AN) onto the surfaces of
microporous frameworks via a free radical polymerization method. The
post-synthetic functionalization was carried out by hydrothermal
process, where amidoxime groups are structure-directing agents to trap
uranium. Further, amidoxime groups not only enhanced hydrophilicity but
also adjusts adsorbents pKa. AO-Fc faces minimum interference of
competing ions and achieves a high uranium adsorption capacity of
8.57±0.02 and 409±1 mg/g in seawater and simulated solution. Despite its
stable structure, AO-Fc exhibits a long life span and negligible weight
loss revealed AO-Fc could be applied as a potential adsorbent for
radionuclides.
Keywords: Microporous bioadsorbent; 2D-open channel;
vapor-phase modification; uranium
Introduction
A rapid increase in energy demands has given rise to energy shortage,
nuclear energy with the advantage of low carbon emission plays an
important role in sustainable energy source1,2.
Uranium plays a key role in nuclear energy sources, therefore its
extraction is very important for continuous energy
supply3-5. However, it is estimated uranium in the
terrestrial ores is limited and at the current usage, the terrestrial
resources might be ended at the end of the current
century6. Comparatively, it is estimated that 4.5
billion tons of uranium in seawater is a thousand times higher than
terrestrial ores7-9. Therefore, a new strategy needs
to develop to extract efficient uranium from seawater to fill the energy
gap, environmental protection, and sustainable development. However, the
presence of competing ions, low uranium concentration (3.3 ppb), and
high-cost synthetic preparation hinder the development of materials for
the extraction of uranium from natural seawater10-14.
Various materials such as porous organic polymers
(POPs)15,16, covalent organic frameworks
(COFs)17-19, porous aromatic frameworks
(PAFs)3,20, metal-organic frameworks
(MOFs)21,22 and biopolymers23-25have been used for the extraction of uranium from seawater. Among all of
them, amidoxime-modified adsorbents are promising with the advantage of
high selectivity towards uranium in seawater26-29.
However, the development of most of the material is either expensive,
difficult to synthesize, poor stability and low uranium adsorption
efficiency in seawater. Recently, efforts have been devoted to
developing advanced materials via simple and facile methods from
inexpensive raw materials with ample uranium adsorption capacity.
Charcoal-based materials are highly interested due to their low cost,
porous structure, and environmentally friendly
nature1,30-32. Recently, amidoxime-modified hollow
fibers were used for uranium adsorption33. Zhou et al.
reported 1D porous adsorbent from wood waste for adsorption of
polycyclic aromatic hydrocarbons34. Liao et al.
reported pig manure-based biochar for uranium
extraction35. Wang et al. reported 1D amidoxime
modified bamboo charcoal for uranium extraction from
seawater36. Although fewer amidoxime modified
adsorbents show higher uranium adsorption capacity in natural seawater.
However, most of them suffer some drawbacks such as high cost, difficult
synthetic procedures, and systematic examination is necessary to find
the uranium adsorption mechanism. The efficient adsorption of uranium
from seawater in a sustainable way remains a major task due to the lack
of functional adsorbent.
In this work, we have implemented two ways to prepare amidoxime polymer
chain grafted charcoal adsorbent material by free radical polymerization
for uranium adsorption from seawater. (i) polymerization of AN in
presence of azobisisobutyronitrile (AIBN) and (ii) the enhancement of
polymerization using DVB as a crosslinking agent. Accordingly, a porous
polymer chain grafted adsorbent was synthesized chemically for efficient
uranium adsorption. Various batch adsorption experiments, theoretical
models, and analytical techniques were used to investigate the
adsorption characteristics and adsorption mechanism including adsorption
capacity, kinetics, and selectivity, the interaction between uranium and
chelating sites, interference due to competing ions, and investigation
of uranium recovery and adsorbent stability. The uncertainty in uranium
adsorption results due to error propagation is also reported in this
study.