Study On The Removal Of Inorganic Nitrogen From Wastewater By Membrane Capacitive Deionization

For uneven state nutritional of low ammonia-nitrogen and high ammonia-nitrogen wastewater, no satisfied treatment has been found already and it often has a high cost.Methods and technologies of dislodging inorganic nitrogenous compounds from this kind of wastewater were widely concerned and studied. Membrane capacitive deionization technology with the characteristics of lower power consumption and non-pollution has been become the research hot spot in the field of desalination. As a kind of water treatment technology, it also has been appealed to most of the attentions. This paper is adopted the soft-template method to synthesize the mesoporous carbon materials and it is prepared to electrode which was characterized used for membrane capacitive deionization technology to perform experiments and to validates the feasibility of nitrogen removal. Membrane capacitive deionization treatment device is designed to study on influence factors and inorganic nitrogen removal and kinetic and thermodynamics.The preparation conditions of the mesoporous carbon electrodes are that the ratio of mesoporous carbon material, adhesive PTFE and conductive carbon black is 8:1.8:0.2. The preparation electrode with the hysteretic loop and the mesopore adsorption behavior belongs to characteristic curve of Ⅳ adsorption, its specific surface area being greater than 1000m2/g, its most probable pore size of 2.04nm beloinging to the range of mesopores and being the maximum, has better capacitance characteristics. Its specific capacitance is the maximum of 237F/g. By contrasting CDI and MCDI, we find that anion and cation exchange membrane has promote the efficiency of ammonia-nitrogen removal rate, and also renders more easier desorption. The adsorption capacity has increase from 5.46mg/g to 13.15mg/g. The optimum process parameters of the mesoporous carbon electrode performed membrane capacitive deionization for NH4CI solution, with the condition of the electrode spacing of 1mm, applied voltage of 1.2V, flow rate of 23.8mL/min and initial concentration of 1500mg/L. At the moment the ion removal rate of NH4+ and NO2- and NO3- for a pair of electrodes was 82.33%, 90.96% and 97.73% in the process of membrane capacitive deionization. The rate of removal varied with the differences of relative molecular mass and ionic hydrated radius.Kinetic studies showed that the proposed first-order kinetic equation can be well described by membrane capacitive deionization adsorption of NH4Cl, the activation energy were37.11kJ/mol. This showed that the adsorption of NH4Cl in the process of physical adsorption. Study of thermodynamics showed that adsorption isotherms can be used Langmuir adsorption isotherm model well fitted, the adsorption of membrane capacitive deionization process follows the monolayer adsorption. -20kJ/mol<AG<0, the adsorption process is physical adsorption process and the reaction of adsorption can spontaneously reach equilibrium.