Evaluation of the absorption performance of new compound absorbents for toluene under extremely high load.

Absorption is an effective way to control volatile organic compound (VOC) industrial air pollution, and the key variable in this process is the selection of suitable liquid absorbents to absorb as many organic pollutants as possible. The objective of this study was to prepare a series of high-efficiency absorbents with different proportions of vegetal oil, mineral oil, and waste engine oil, which can be used for toluene absorption. The absorption efficiency (AE), saturated absorption (SA), and effective absorption time (EAT) of various absorbents were systematically analyzed. The results showed that when the inlet concentration of toluene was 8000 mg/m3 and the inlet flow was 1 L/min, the SA capability of vegetal oil, mineral oil, and waste engine oil was 7.15, 12.43, and 18.16 mg/g, respectively. With the 4000 mg/m3 inlet concentration, the SA of the absorber which was made in the ratio of 2:3:1 was increased to 50.93 mg/g. According to the thermodynamic equilibrium and absorption results, it is proved that the influence of the composition of the absorbent on absorption is greater than viscosity. It is also to be noted that the AE of the composite absorbent can still reach more than 80% after three times of heating and air purification.

Enhancing performance evaluation and microbial community analysis of the biofilter for toluene removal by adding polyethylene glycol-600 into the nutrient solution.

Polyethylene glycol-600 (PEG-600), as a carrier for slow release of organic substances, can improve the biocompatibility of packing fillers and the construction of biofilms. The gradient experiments were established to evaluate the feasibility of adding different content of PEG-600 to the biofilter for enhancing toluene removal. In particular, the evolution trend of microbial community embedded in packing fillers was measured by 16S rRNA-based gene sequencing. Results showed that the toluene removal efficiency of biofilter with 7.5% adding content of the PEG-600 was greatly improved, and the maximum elimination capacity of 152 g/(m3·h) was obtained. The introduction of PEG-600 enhanced the tolerance ability to withstand the transient impact loading and intensified the production of extracellular polymeric substances and bonding strength of biofilms. It should be noted that the abundance of Pseudomonas and Steroidobacter at genus level increased significantly. The microbial community evolved into a co-degradation system of toluene and PEG-600.