| Bromate and perchlorate are two common oxysalt in water,they are given extensive attention because of their potential carcinogenicity and thyroid disruption.Moreover, their high solubility and low adsorption determine them threaten environment and people mainly via aquatic system Since ater has a closely bound up to life, studying on bromate and perchlorate in water is of vital importance. This research introduces the n ZVI-GAC to remove bromate and percglorate from water, by integrating the large surface area and strong reducing power of n ZVI and high adsorption ability of GAC.It not only prepares the Fe(II)-GAC material by using filtration method,but also obtains the supported n ZVI-GAC material by assisting Na NH4 reduction method based on water treatment theory and experiment.The main parameters including shapes and sizes, surface morphology, chemical composition have been measured by scanning electron microscope(SEM), X-ray powder diffraction(XRD), and infrared spectrometry(FTIR), respectively. In the single set of bromate and perchlorate cases, The effects of environmental conditions on removal of bromate and perchlorate are evaluated; Under the condition of the two-component experiment, The influence of p H value and temperature and the mutual effect between bromate and perchlorate are investigated. On the basis of the above research, The removing kinetics of bromate and perchlorate by n ZVI-GAC, reaction products and removing mechanism are analyzed in detail. The results are as follows:1. Ferrous ions and nano zero-valent iron ion have different morphological distribution effects on the surface of activated carbon α-Fe successfully load on n ZVI-GAC, the introduction of the activated charcoal can prevent the contact and oxidation between the iron nanoparticles, and increase the dispersion of nanometer zero-valent iron particles, thereby increasing the specific surface area and active site of n ZVI-GAC.2. The single set of bromate and perchlorate experiment show that n ZVI-GAC of bromate and perchlorate removal rate increased significantly compared with the Fe(Ⅱ)-GAC, and bromate was fully biodegradable by n ZVI-GAC; When the content of nano zero-valent iron on active carbon is between 0.893% and 3.633%, the more content, the quickly degradation efficiency of bromate and the better of the results.But when the nano zero-valent iron content is between 0.893% and 2.422%, the removal rate of perchlorate increases with the increase of iron content, when load iron content is 2.422%,it had the highest removal rate of 85%, when the nano zero-valent iron content is more than 1.969%, the precipitation of iron ion concentration in water increased significantly, it will cause secondary pollution to the environment. When bromate and perchlorate in different initial concentration, The maximum adsorption capacity of bromate and perchlorate is respectively 28 mg/g and 16 mg/L. The lower the initial p H value of solution, the more it is helpful to degradation of bromate; In the p H=5, perchlorate reached the highest removal rate to 86%.The coexisting ions in water inhibited bromate and perchloraten from removing by ZVI-GAC, with the increase of coexisting ions concentration, the inhibition was stronger, and the order of inhibitory effect is: PO43->CO32->NO3->Cl-.3. When the bromate and perchlorate simultaneously existence in water, the acidic conditions is beneficial to the degradation of bromate. When the temperature is 25℃, the maximum removal of bromate is 94.8%.When p H=7, perchlorate had the highest removal rate of 80%, so the neutral condition promoted the removal of perchlorate.When the temperature is 15℃, perchlorate removal rate of 60%, and when the temperature of 55℃, perchlorate had the highest removal rate of 85%, therefore, the increase of temperature helps the degradation of perchlorate.4. The removal results of bromate and perchlorate by NZVI-GAC conform to the quasi level dynamics; The removal of bromate and perchlorate including two kands of mechanism, that was adsorption and reduction. The synergy between n ZVI and GAC promoted the degradation of bromate and perchlorate, and decomposition product of bromate and perchlorate were non-toxic bromide ion and chloride ion。... |
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