改性沸石吸附氨氮及电化学再生研究

研究了改性沸石对氨氮的吸附效能、动力学机制以及电化学再生效果。间歇和连续试验结果表明:沸石经改性后,能高效去除水中的氨氮,其吸附等温式更符合Langmuir模型,沸石、改性沸石的饱和吸附量分别为8.09 mg/g和13.55 mg/g,沸石的钠型改性能显著提高吸附容量约40.3%;颗粒内扩散是改性沸石吸附氨氮的控制性步骤,可以利用Vermeulen的内扩散模型进行描述;利用电化学再生吸附饱和后的沸石,再生液为NaCl溶液,阳极涂覆RuO2-Ti,再生时间为3h,可高效地再生沸石,无二次污染物排出,对环境冲击较小。

On ammonia-absorption from sewage by means of modified zeolite and its electrochemical regeneration

The paper is aimed at reporting our study of the adsorption behavior of modified zeolite to ammonia-nitrogen.For this need,we have investigated the dynamic mechanism of adsorption and its electrochemical regeneration.The results of our batch and continuous experiments show that the ammonia can be efficiently removed by the modified zeolite within 3 h with its removal efficiency being as high as 87.8%.As compared with Freundlich isotherms,whose coefficient of determination(R2) was 0.965 and 0.946,the adsorption of ammonia by natural zeolite and that by modified zeolite is well in conformity with Langmuir isotherms of R2 of 0.993 and 0.999.The results of Langmuir isotherms clearly indicate that the theoretical maximum adsorption capacity of those two adsorbents was 8.09 mg/g and 13.55 mg/g.In comparison with natural zeolite,the modified zeolite could raise the adsorption capacity by 40.3%.As for the ammonia in the sewage from the UASB reactor,the adsorption column tends to get broken within 30 h.Whereas the dynamic data were well described by Vermeulen model,the diffusion coefficient of ammonia by modified zeolite was 3.25×10-11.The results prove that the intraparticle diffusion is a restrictive factor,and the absorbed zeolite can be regenerated by electrochemical method within 3 h,with the current of 0-2 A,voltage of 0-10 V and current density of 55.3 A/m2.The anode of electrochemical reactor would be found covered by RuO2/Ti while the cathode was stainless,whose size was 172 mm×38 mm×1 mm with the distance between anode and cathode being 10 mm.The NaCl solution,at the concentration of 300 mg/L,can be used as circulating fluid.The removal efficiency by the regenerated zeolite can also be made higher and the breakthrough curve may indicate that the breakthrough point would take at 72 h.The ammonia-nitrogen can be oxidized into nitrogen with no second pollution to the environment.Besides,since the electrochemical reactor runs efficiently and flexibly,which would make it fit for regenerating zeolite absorbed by ammonia-nitrogen.Thus its results and parameters can serve as a reference to the removing ammonia-nitrogen and regeneration of modified zeolite.