Sulfur
dioxide (SO2) is the main component of air pollution.
Recently, sodium lactate (NaLa) aqueous solution (aq) was demonstrated
as a highly efficient, renewable, and stable absorbent for SO2 absorption from flue gas. However, sulfuric acid (H2SO4) accumulated during long-term SO2 absorption
and desorption cycles. To remove H2SO4 from
NaLa (aq) efficiently, a method based on the common-ion effect was
proposed in this work. The results indicated that the residual concentration
of sulfate anion (SO4
2–) decreased with
decreasing the water content. Residual SO2 in NaLa (aq)
did not influence the removal of H2SO4. After
the removal, the content of residual SO4
2– was 0.47 wt % and the removal rate of H2SO4 was 95.6%, with a water content of 34 wt % at 20 °C. In comparison
to other reported methods, our method to remove H2SO4 in absorbents did not introduce other ions and block the
absorption tower. It was noted that the evaporation of water to decrease
the water content was combined with the regeneration of NaLa (aq),
without any extra evaporation energy. NaLa (aq) was not changed during
the removal process. Moreover, the SO2 absorption capacity
in H2SO4-removed NaLa (aq) was comparable to
the capacity of virgin NaLa (aq), and no obvious change could be found
after 5 cycles of H2SO4 removal. The mechanism
of removing H2SO4 from NaLa (aq) studied with
Fourier transform infrared spectroscopy indicated that H2SO4 was removed in the form of Na2SO4 without crystal water as a result of the common-ion effect. Furthermore,
a new process for SO2 absorption with H2SO4 removal from NaLa (aq) was proposed.