Excessive
emissions of gaseous pollutants such as SO2, NO
x
, heavy metals (Hg, As, etc.), H2S, VOCs,
etc. have triggered a series of environmental pollution
incidents. Sulfate radical (SO4•–)-based advanced oxidation technologies (AOTs) are one of the most
promising gaseous pollutants removal technologies because they can
not only produce active free radicals with strong oxidation ability
to simultaneously degrade most of gaseous pollutants, but also their
reaction processes are environmentally friendly. However, so far,
the special review focusing on gaseous pollutants removal using SO4•–-based AOTs is not reported. This
review reports the latest advances in removal of gaseous pollutants
(e.g., SO2, NO
x
, Hg, As, H2S, and VOCs) using SO4•–-based AOTs. The performance, mechanism, active species identification
and advantages/disadvantages of these removal technologies using SO4•–-based AOTs are reviewed. The existing
challenges and further research suggestions are also commented. Results
show that SO4•–-based AOTs possess
good development potential in gaseous pollutant control field due
to simple reagent transportation and storage, low product post-treatment
requirements and strong degradation ability of refractory pollutants.
Each SO4•–-based AOT possesses
its own advantages and disadvantages in terms of removal performance,
cost, reliability, and product post-treatment. Low free radical yield,
poor removal capacity, unclear removal mechanism/contribution of active
species, unreliable technology and high cost are still the main problems
in this field. The combined use of multiactivation technologies is
one of the promising strategies to overcome these defects since it
may make up for the shortcomings of independent technology. In order
to improve free radical yield and pollutant removal capacity, enhancement
of mass transfer and optimization design of reactor are critical issues.
Comprehensive consideration of catalytic materials, removal chemistry,
mass transfer and reactor is the promising route to solve these problems.
In order to clarify removal mechanism, it is essential to select suitable
free radical sacrificial agents, probes and spin trapping agents,
which possess high selectivity for target specie, high solubility
in water, and little effect on activity of catalyst itself and mass
transfer/diffusion parameters. In order to further reduce investment
and operating costs, it is necessary to carry out the related studies
on simultaneous removal of more gaseous pollutants.