Adsorption behavior of pesticide methomyl on activated carbon in a high gravity rotating packed bed reactor

Abstract

High gravity rotating packed bed (HGRPB) reactor possesses the property of high mass transfer rate, which is expected to promote the adsorption rate for the process. In this study, HGRPB has been applied on adsorption removal of methomyl from solution, adopting the adsorbent of activated carbon F400. The influence of operating parameters of HGRPB on mass transfer such as the rotating speed (N(R)), the flow rate of solution (F(L)) and initial concentration of methomyl (C(b0)) were examined. The traditionally internal mass transfer models combined with Freundlich isotherm were used to predict the surface and effective diffusion coefficients. In addition, the results have also been compared with those obtained from the traditional basket stirred batch reactor (BBR). The results showed that the larger values of N(R) and F(L) enhanced the effective intraparticle diffusion and provided more accessible adsorption sites so as to result in lower equilibrium concentration in HGRPB system when compared to SBR system. The results of adsorption kinetics demonstrated that surface and effective diffusions were both significantly greater in HGRPB system instead of BBR system. Furthermore, the values of Bi(S) also manifested less internal mass transfer resistance in HGRPB system. The contribution ratio (R(F)) of the surface to pore diffusion mass transport showed that the larger contribution resulted from the surface diffusion in HGRPB system. Therefore, the results reasonably led to the conclusion that when the HGRPB system applied on the adsorption of methomyl on F400, the lower equilibrium concentration and faster internal mass transfer can be obtained so as to highly possess great potential to match the gradually stricter environmental standard.