INTERACTION OF ACRYLONITRILE VAPORS ON A BENCH SCALE BIOFILTER TREATING STYRENE-POLLUTED WASTE GAS STREAMS

Abstract

Considering concurrent use of styrene and acrylonitrile as raw
materials in the production of synthetic resins and plastic and their
associated differences in physiochemical properties and
biodegradability, our experiments were conducted in a three-stage
downflow bench-scale biofilter to study the potential suppressive
effects of acrylonitrile on styrene removal. A Mixture of yard waste
compost and shredded plastics and activated sludge was used as bed
media. Gas phase concentration of styrene and acrylonitrile was
determined via gas chromatographic analysis. Under steady-state
conditions, maximum elimination capacity of styrene and acrylonitrile
was 44 and 120 g/m3 h, respectively. The effect of moisture was very
significant in reducing the specific adsorptive capacity (μg/g of bed
media) of styrene and acrylonitrile. The bed media with 60% moisture
content lost styrene absorption capacities by more than one order of
magnitude when compared to dry media. The existence of water increased
the absorption capacity of medium for acrylonitrile about 95%. Styrene
elimination capacity of the biofilter during co-treatment was less as
compared to pure styrene biodegradation indicating the likelihood of
inhibitory kinetics. Introduction of acrylonitrile into the air stream
reduced elimination capacity of styrene to 103 g/m3 h. The adverse
impact on removal rate of acrylonitrile due to the presence of styrene
in the gas stream was minimal. Carbon-equivalent removal for the system
amounted to about 85 g C/m3 h at empty bed retention time of 120 s.