posted on 2024-03-01, 17:48authored byMengfei Zhang, Qingping Wang, Shangyou Liu, Yiran Li, Xing Wang, Jinyi Qin, Min Yang
Etching waste gases derived from photovoltaic cell production
are
difficult to treat at room temperature. Therefore, the use of wet
denitrification with Na2S2O5 is recommended
to overcome this issue. The presence of O2, Cl2, and metals in gases leads to the consumption of 65% of SO32– within 2 h. Although alkaline pretreatment adsorbs
most of the gases and metals, the high ceiling temperature results
in a short residence time and incomplete reaction with the lye. Therefore,
in this study, urea was added to Na2S2O5. After adding the optimum concentration of urea (0.5 mol
L–1) to a 1.0 mol L–1 SO32– solution, the anodic potential measured using
cyclic voltammetry shifted from 0.051 to −0.119 V, the electron
transfer rate k0 decreased from 4.89 ×
10–5 to 4.27 × 10–5 cm s–1, the exchange current density measured using the
polarization curve decreased from 18.37 to 13.58 A cm–2, and the reaction activation energy increased from 37 to 63 kJ mol–1. Therefore, adding urea to generate hydroxyl functional
groups can effectively block the free radical oxidation chain reaction
of SO32–, hindering its oxidization.
In summary, alkaline pretreatment and urea addition can increase the
effective reaction between SO32– and
NOx and reduce the costs. Our study provides
data to support the application of wet denitrification at room temperature.