Behavior of VOCs competitive adsorption with water vapor in a slit-shaped phosphoric acid mesoporous activated carbon model

Abstract

Pistachio shells were activated with H3PO4, and mesoporous activated carbon (AC) was pyrolyzed and prepared at high temperature. The impacts of phosphoric acid concentrations on the structure, physicochemical properties, and VOC adsorption performance of ACs were investigated. The results indicated that the specific surface area, average pore size, and surface P content of 20% phosphoric acid AC reached 1031.8 m2·g−1, 4.16 nm, and 3.87%, respectively. With increasing phosphoric acid concentration, the microporosity and graphitization of the ACs decreased, and the average pore size and P content of the ACs increased. The adsorption performance of PSAC-1P and PSAC-2P for VOCs in high-humidity exhaust gas was the most favorable. grand canonical Monte Carlo (GCMC) calculations revealed that at a relative humidity of 80%, water molecules and VOCs were adsorbed on the graphite-structured carbon surface in turn. The larger the pore size, the easier it was for water molecules to aggregate, and the adsorption sites were occupied by water molecules. P-functional groups effectively inhibited water molecular clusters from forming water clusters, benefitting from the mesopore adsorption of VOCs in competition with water vapor. The findings provide significant support for the effective adsorption treatment of VOCs in high-humidity exhaust gas.