Adsorption characteristics of 2,4-dichlorophenoxyacetic acid and 2,4-dinitrophenol in a fixed bed adsorber

The influence of temperature and initial pH of aqueous solution on adsorption has been discussed in detail using the Sips equation. Single-component adsorption equilibria of 2,4-D and 2,4-DNP dissolved in water have been measured for three kinds of GACs (F400, SLS103, and WWL). For 2,4-D, the magnitude of adsorption capacity was in the order of F400>SLS103>WWL, and that for 2,4-DNP was SLS103>F400>WWL. These results may come from the effects of the pore size distribution, surface area, surface properties, and difference in adsorption affinity. Kinetic parameters were measured in a batch adsorber to analyze the adsorption rates of 2,4-D and 2,4-DNP. The internal diffusion coefficients were determined by comparing the experimental concentration curves with those predicted from surface diffusion model (SDM) and pore diffusion model (PDM). The linear driving force approximation (LDFA) model was used to simulate isothermal adsorption behavior in a fixed bed adsorber and successfully simulated experimental adsorption breakthrough behavior under various operation conditions. Efficiency of desorption for 2,4-D and 2,4-DNP was about 80% using distilled water at pH of 6.