Preparation of Activated Boron Nitride and Its Adsorption Characteristics for Zn, Cu, and Cd in Flue Gas

Developing non-carbon-based adsorbents is essential for
removing
heavy metals from post-incineration flue gas. In this study, a new
high-temperature-resistant adsorbent-activated boron nitride (BN)
was prepared using precursors combined with a high-temperature activation
method. The adsorption characteristics of BN for Zn, Cu, and Cd in
simulated flue gas and sludge incineration flue gas were investigated
using gas-phase heavy metal adsorption experiments. The results showed
that BN prepared at 1350 °C for 4 h had defect structures, abundant
pores, functional groups, and a high specific surface area of 658
m2/g. The adsorption capacity of BN in simulated flue gases
decreases with increasing adsorption temperature, whereas it is always
higher than that of activated carbon (AC). The total adsorption capacities
for Zn, Cu, and Cd were the highest at 50 °C with 48.3 mg/g.
BN had strong adsorption selectivity for Zn, with a maximum adsorption
capacity of 54.45 mg/g, and its adsorption process occurred mainly
on the surface. Cu and Cd inhibited Zn adsorption, leading to a decrease
in the Zn adsorption capacity. In sludge incineration flue gas, BN
can quickly reach adsorption equilibrium. The BN had a synergistic
disposal capacity for heavy metals and fine particulate matter. The
maximum adsorption capacity was reduced compared to the simulated
flue gas adsorption capacity, which was 5.1 mg/g. However, BN still
exhibited a strong adsorption selectivity for Zn, and its adsorption
capacity was always greater than that of AC. The rich functional groups
and high specific surface area enable BN to physically and chemically
double-adsorb heavy metals.