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排序方式: 共有137条查询结果,搜索用时 31 毫秒
31.
Regeneration of pure water is an important issue not only for the healthy life but also for the fine control of precise processes in various industries.One important issue in ultrahigh purified water is to reduce the amount of total organic carbon(TOC).Herein,we introduce a new approach to reduce the TOC using the surface silanized nanoparticles,in which the magnetic nanoparticles(mNPs) are silanized and then complexed with ion exchange resin(IER) beads.The Fe_3O_4 mNPs are surface modified by using high concentrated vinyltrimethoxysilane(VTMS) and then adhered on the surface of IER beads.The surface modified mNPs have a thick-shell of polysiloxane layer varying from 5 to 22 nm depending on the amount of VTMS used,which leads the significant increase of specific surface area.The IER beads embedding VTMS-silanized mNPs achieves about 7 μg/L of the TOC level in ultrapure water system,which is two orders less than 228 μg/L of the feeding water and one order less than 96 μg/L from the system using pristine IER beads.This result is mainly attributed to the polysiloxane layer forming broccoli-like surface structure and some part by the vinyl group of VTMS exposed to the amines in the water. 相似文献
32.
Excessive nitrate(NO_3~-) is among the most problematic surface water and groundwater pollutants.In this study,a type of magnetic cationic hydrogel(MCH) is employed for NO_3~-adsorption and well characterized herein.Its adsorption capacity is considerably pHdependent and achieves the optimal adsorption(maximum NO_3~--adsorption capacity is95.88±1.24 mg/g) when the pH level is 5.2-8.8.The fitting result using the homogeneous surface diffusion model indicates that the surface/film diffusion controls the adsorption rate,and NO_3~-approaches the center of MCH particles within 30 min.The diffusion coefficient(D_s) and external mass transfer coefficient(k_F) in the liquid phase are1.15 × 10~(-6) cm~2/min and 4.5 × 10~(-6) cm/min,respectively.The MCH is employed to treat surface water that contains 10 mg/L of NO_3~-,and it is found that the optimal magnetic separation time is 1.6 min.The high-efficiency mass transfer and magnetic separation of MCH during the adsorption-regeneration process favors its application in surface water treatment.Furthermore,the study of the mechanism involved reveals that both-N~+(CH_3)_3 groups and NO_3~-are convoluted in adsorption via electrostatic interactions.It is further found that ion exchange between NO_3~-and chlorine occurs. 相似文献
33.
Magnetic Fe0/Fe3O4/graphene has been successfully synthesized by a one-step reduction method and investigated in rapid degradation of dyes in this work. The material was characterized by N2 sorption–desorption, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), vibrating-sample magnetometer (VSM) measurements and X-ray photoelectron spectroscopy (XPS). The results indicated that Fe0/Fe3O4/graphene had a layered structure with Fe crystals highly dispersed in the interlayers of graphene, which could enhance the mass transfer process between Fe0/Fe3O4/graphene and pollutants. Fe0/Fe3O4/graphene exhibited ferromagnetism and could be easily separated and re-dispersed for reuse in water. Typical dyes, such as Methyl Orange, Methylene Blue and Crystal Violet, could be decolorized by Fe0/Fe3O4/graphene rapidly. After 20 min, the decolorization efficiencies of methyl orange, methylene blue and crystal violet were 94.78%, 91.60% and 89.07%, respectively. The reaction mechanism of Fe0/Fe3O4/graphene with dyes mainly included adsorption and enhanced reduction by the composite. Thus, Fe0/Fe3O4/graphene prepared by the one-step reduction method has excellent performance in removal of dyes in water. 相似文献
34.
Maghemite (ϒ-Fe2O3) nanoparticles were impregnated to nanoporous carbon obtained from tomato waste (TWNC). The prepared magnetic composite (MTWNC) was characterized and used to remove tetracycline (TC) from water and then easily be separated from the medium by a magnetic technique. The morphologies and surface chemistries of both magnetic and non-magnetic nanoporous carbons were studied by FTIR, XRD, SEM, SEM-EDX, VSM, BET surface area, proximate and elemental analysis determinations. Batch adsorption studies were carried out and the effects of pH, initial TC concentration, adsorbent dose, ionic strength and temperature were investigated. The adsorption kinetics of TC on MTWNC could be expressed well by the pseudo-second order model, and sorption isotherms were described by Langmuir equation with maximum adsorption capacity of 60.60 mg/g at pH 4 and 50 °C. Thermodynamic parameters showed that the adsorption of TC onto MTWNC was feasible, spontaneous and endothermic. Furthermore, the recyclability of the adsorbent was tested with 0.01 M NaOH solution, and the results show that the synthesized composite adsorbent could be employed repeatedly in wastewater treatment. 相似文献
35.
实验以取自浙江湖州有机微污染水作为研究对象,研究了PAC,PFS,PAFC,KAl(SO4)2及FeCl3等常用混凝剂对该有机微污染水的CODMn的去除效果,结果表明PAC为处理该有机微污染水的最佳混凝剂,最佳投加量为30 mg/L。同时还研究了加载磁粉对有机微污染水混凝处理效果的影响,结果表明加载磁粉粒径为45μm,投加量为30 mg/L时,同一原水的CODMn去除率从常规混凝的39.3%提高到45.6%,且加载磁粉后大大缩短了混凝沉淀时间,符合微污染水源的应急处理要求,最佳投放顺序为:“磁粉+PAC+PAM”。 相似文献
36.
Mehri Kaviani Moghadam Saied Mohammad Firoozabadi Mahyar Janahmadi 《The Environmentalist》2008,28(4):341-347
In spite of growing concern about the influence of magnetic fields on biological systems, the interaction between extremely
low frequency magnetic field (ELF magnetic fields) and biological structures at the cellular level remains obscure. The aim
of this study was to investigate if 50 Hz magnetic fields could have an effect on the neuronal excitability and firing responses.
Under Current-Clamp condition, exposure to 50 Hz ELF magnetic fields at 2 mT or 0.8 mT intensities resulted in an increase
in the peak amplitude of action potential and after hyperpolaization potential in a time dependent manner. Both magnetic field
intensities decreased also the firing frequency and the duration of action potential. Taken together, these data suggest that
50 Hz ELF magnetic fields at 2 mT or 0.8 mT intensities may change the electrophysiological behavior of neuronal cells and
underlying ion channel currents. 相似文献
37.
磁种-磁滤技术处理污染河水的试验研究 总被引:1,自引:0,他引:1
采用磁种-磁滤技术处理广州市两条河涌的污染水,考察了磁种投加量、混凝剂用量、磁场强度和磁滤速度对出水浊度的影响,并确定了最佳试验条件。结果表明,该工艺对TP、SS和浊度的去除效果较好,去除率分别为96.2%、92.4%和93.9%,对CODCr有一定的去除效果,去除率为68.2%,但对NH4^ -N的去除效果较差,去除率仅为25%。 相似文献
38.
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40.
D'Emilio M Chianese D Coppola R Macchiato M Ragosta M 《Environmental monitoring and assessment》2007,125(1-3):137-146
In the framework of the development of new methods for measuring and monitoring soil pollution, this paper deals with the
use of magnetic methodologies to monitor the heavy metals presence in soils. In particular it shows a procedure for collecting
magnetic susceptibility measurements in order to interpret them as proxy variable for monitoring heavy metals in soils. Magnetic
measurements are carried out using a magnetic susceptibility meter with two different probes for in situ field surveys. The
experimental procedure is divided in two parts. In the first part we carry out laboratory tests aimed to evaluate, for both
the probes, the effective investigation depth for soil, the measurement reproducibility under different conditions, and the
influence of water content. We complete this part comparing in situ measurements obtained by means of two probes with different
characteristics. In the second part we carry out tests to evaluate the relationships between heavy metal levels and magnetic
susceptibility values of soil samples. We investigate the variability of the magnetic susceptibility measurements contaminating
different soil samples with well known concentration of heavy metals. Moreover we study the correlation between magnetic susceptibility
values and metal concentrations, determined by means of AAS, in soil samples collected during a field survey. Results suggest
that a careful check of the experimental procedure play a crucial role for using magnetic susceptibility measurements for
heavy metals in situ monitoring. This is very helpful both for improving the quality of data and for making simpler data interpretation. 相似文献