Cmc Synchronous Modification Of Nano-iron Particle Removal In Water Perchlorate

Waste water which contains perchlorate remediation by nanoscale zero-valent iron(NZVI)has received increasing attention in recent years. However, Agglomeration of magnetic metal nanoparticles takes place, and then reduces the specific surface area, thereby diminishing particle stability and reactivity. Carboxymethyl Cellulose (CMC), a nontoxic and biodegradable stabilizer, is used in the synthesis of the nanoseale zero-valent iron as a stabilizer. It can effectively prevent agglomeration of NZVI particles, to enhance its stability, and thus effectively improve on the reduction of perchlorate in water. In the present paper is reported an efficient method of synthesizing CMC-stabilized NZVI. They were observed by TEM and XRD, and utilized ultraviolet spectrum and infrared spectrum to study their stability. The CMC stabilized NZVI particles used to reduce perchlorate. The effect of mass concentration of CMC, mass concentration of NZVI, initial concentration of perchlorate, initial pH value, reaction temperature and mass concentration of chlorion on removal efficiency was investigated. The energy of activation of the reaction of perchlorate with CMC stabilized NZVI particles was obtained. The dynamic laws for the reaction for perchlorate removal were discussed initially. At the same time, various factors to reduction system on removal efficiency was investigated in the ultrasonic environment and to determine the optimum process. The experimental result indicated: After modified NZVI, the average particle diameter is smaller than the NZVI and the particle size distribution is quite even. The intermolecular hydrogen bond of CMC and the carboxyl ion of CMC molecule have combined with iron by monodentate chelating, increased electrostatic repulsion and steric hindrance effect between the particles, enhanced the NZVI's stability. The optimal ratio of CMC: Fe is 5: 1. The removal efficiency increased with the increasing of NZVI addition dosage and reaction temperature. Low pH value could accelerate the rate of perchlorate. Relative to other factors, chlorion concentration was less affected on the efficiency of degradation. The reductive reaction of perchlorate with CMC-stabilized NZVI conforms to first order reaction dynamic law, and the apparent activation energy is 38.63kJ/mol. Under the same experimental conditions, the sequence of removal efficiency and the reaction rate constant of the four reaction systems were: ultrasonic synergistic CMC stabilized NZVI> CMC stabilized NZVI> ultrasonic synergistic NZVI> general NZVI. And ultrasonic synergistic CMC-stabilized NZVI particles's removal efficiency were respectively 1.4, 2.6 and 5.0 times as well as that at latter, the corresponding apparent rate constants are: 0.0052min^-1, 0.0015min^-1, 0.0008min^-1 and 0.0004min^-1. In the ultrasonic environment, the degradation efficiency of system and the reaction rate have been greatly enhanced, and through the orthogonal experiment, the optimum conditions of perchlorate reduction degradation was obtained。Under the ultrasonic frequency is 20kHz, the primal concentration of perchlorate fixed at 10mg/L, which was the initial pH 5.0, the content of NZVI particles 0.5g/L, reaction temperature 50℃, output power 240W, degradation time 5h. In the optical condition, degradation rate of perchlorate was 95.2 percent.