| With the rapid development of the economy and industry, the amount of phenol is gradually increasing, and phenolic wastewater do seriously harm to the environment and human beings. More and more attention has been focused on the the treatment of organic wastewater containing phenolic compounds. Among many methods, adsorption has been recognized as one of the most used methods for removing emissions phenolic compounds from industrial wastewater, which is simple to operate and has the advantages of low energy cost and recycling useful materials.Batch agitator kettle, fixed bed and fluidized bed etc. are commonly used as adsorption equipments, in which the mass transfer process between the solid-liquid only depends on gravity to implementation, resulting in low mass transfer efficiency. With the purpose of intensifying this process and improving wastewater treatment efficiency at the same time,high gravity technology is proposed in this paper.Firstly, Langmuir model and Freundlich model were used to study the adsorption equilibrium of phenol on activated carbon. The results indicated that Freundlich model was more suitable for describing the adsorption process. In the meantime the adsorption equilibrium equation of high gravity adsorption method and traditional adsorption method were obtained. The internal diffusion model was applied in high gravity adsorption diffusion process. The result indicated that the internal diffusion was the rate-limiting step in the early period and then the adsorption process was controlled by film diffusion. The adsorption equilibrium was reached when the total adsorption rate was equal to desorption rate. In addition, the existence of the high gravity field strengthened the diffusion process and shortened the time reaching adsorption equilibrium, which result in that the mass transferbetween liquid and solid was intensified.Secondly, the influence of operating parameters on wastewater treatment efficiency were examined to determine the optimum operating conditions. In terms of the phenol removal efficiency η, the most significant influence factor was liquid flow rate F, followed by high gravity factor β, and initial concentration of phenol CPhOH was the least. Under the operational conditions, the removal efficiency of phenol η could reach 89.51%, which was 1.42 times higher than the traditional adsorption method. In terms of the phenol desorption efficiency γ,the most significant influence factor was high gravity factor β, followed by lye concentration CNaOH, and liquid flow rate F was the least. Under the operational conditions, the phenol desorption efficiency γ could reach 93.01%, which was 3.88 times higher than the traditional desorption method. The correlations of the phenol removal efficiency η and phenol desorption efficiency γ were established. The average relative errors of correlations were 4.571% and6.047% respectively.Finally, The pseudo-first-order model and the pseudo-second-order model were used to study the adsorption and desorption kinetics. The kinetics equations of high gravity adsorption method and traditional adsorption method were obtained. The effect of operating parameters on the adsorption rate constant k2-as and desorption rate constant k2-des were studied. Under the same conditions, the value of adsorption rate constant k2-as improved from 5.28×10-4 to9.02×10-4 compared with the traditional adsorption method, which was 13.66×10-4 to29.59×10-4 of k2-des. The result showed that the mass transfer between liquid and solid was intensified by high gravity.Consequently, with high gravity adsorption method, the solid-liquid mass transfer process is intensified, thereby removal rate is improved and the volume of air stripping equipment is reduced. Therefore, the high gravity adsorption method in the treatment of wastewater has great industrial application prospects. |
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