| This study aimed to synthesize activated carbon (AC) supported nanoscale zero-valent iron (NZVI/AC) for solving agglomeration and low acitivty during the using process. Moreover, trihalomethans (THMs) and acrylonitrile (AN) were seleted as the target in studing the performance of NZVI/AC. In addition, the removal mechanism of THMs and AN were preliminarily studied. The mainly studies of this paper are as followed:(1) The morphologies of as-prepared AC, NZVI and NZVI/AC were characterized by scanning electron microscope (SEM) and transmission electron microscopy (TEM) observation. The surface functional group, crystal structure and chemical compositions of original and modified NZVI were characterized by using Fourier Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). BET specific surface area analyzer and inductively coupled plasma-atomic emission spectrometry (ICP-AES) were used to determine the specific surface area, pore structure and the total iron content of the particles. Results showed that the aggregation of iron nano-particles was decreased by the support of AC and the dispersion of Polyethylene glycol (PEG-4000). SEM and TEM showed uniformly dispersed NZVI particles with diameters of 30-100 nm on average and were spherical on the surface or inside the pores of AC. NZVI displayed a typical BET surface area of 25.8 m2/g and NZVI/AC had a bigger BET surface area (63.9 m2/g). Besides, both stability and reactivity of NZVI particles were increased by using AC as a support. The analysis of EDS showed that the form and content of Fe element on the surface or loaded into the pores of AC. The experimental value of Fe loadings were reasonably close to the theoretical value (10%). NZVI particles had been successfully loaded on AC from the results of XRD, FTIR and XPS. In addition, the dispersion and antioxidant ability of supported NZVI particles were enhanced.(2) NZVI/AC was applied for THMs removal in composition with AC and NZVI. Morever, we solely investigated the effects of NZVI/AC dosage, contact time (t) and initial pH (pHo) of solution on the removal efficiency. The results showed that the removal capacity and removal rate followed the order of NZVI/AC>NZVI> AC and AC>NZVI>NZVI. Additional NZVI/AC enhanced the removal efficiency and the rate, but the increased amplitude of removal efficiency of THMs was smaller when NZVI/AC addition was higher than 1.8 g/L. When the dose of NZVI/AC was 1.8 g/L and the pH was neutral, the removal efficiency was best. The experimental results demonstrated that the brominated methane was easier to treat than chlorinated methane and the removal efficiency and rate followed the order CHBr3>CHBr2Cl>CHBrCl2>CHCl3. In addition, the results also revealed an increased reaction rate with an increasing number of bromine atoms in the brominated methane. The removal efficiencies of the four THM were all over 90% and the highest removal efficiency of CHC13, CHBrCl2, CHBr2Cl and CHBr3 were 94.5%,95%,97.8% and 100%, respectively.(3) Comparative study of the effect in removing acrylonitrile (AN) was done between NZVI/AC and AC. The results suggested that NZVI/GAC had a higher removal capacity for acrylonitrile which resulted from the combined effects of adsorption by AC, reduction by Fe2+, [H] and Fe0 generated in the reaction and micro-electrolysis by the Fe0/GAC system. The adsorption onto NZVI/AC was neither very close to the pseudo-second-order model nor the pseudo-first-order model. The adsorption isotherms of NZVI/AC followed the Freundlich model with high correlation coefficients (R2> 0.998). The results from UV and FTIR indicated that C=N could be broken by NZVI/AC which was benefited from the redox between [H] and Fe2+ generated in the reaction and AN. The activity of activated sludge was determined from the changes of dissolved oxygen (DO) and Oxygen uptake rates (OUR) before and after reaction. The results showed that the biodegradability was enhanced by NZVI/AC-pre-treatment, which is associated with less toxicity for activated sludge. |
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