Negatively charged carboxymethylated polyethersulfone (CMPES) and positively charged quaternized polyethersulfone (QAPES) ultrafiltration (UF) membranes were prepared by bulk chemical modification and non-solvent induced phase separation method. The effects of PES membrane interfacial electrokinetic property on the bovine serum albumin (BSA) membrane fouling behavior were studied with the aid of the membrane-modified colloidal atomic force microscopy (AFM) probe. Electrokinetic test results indicated that the streaming potential (ΔE) of QAPES membrane was not consistent with its expected IEC value, however, within the pH range of 3–10, the ζ potentials of two charged-modified PES membranes were more stable than the unmodified membrane. When pH value was 3, 4.7 or 9, the interaction behavior between charged PES membrane and BSA showed that there was significant linear correlation between the jump distance r0 of membrane-BSA adhesion force (F/R) and the ζ potential absolute value. Charged modification significantly reduced the adhesion of PES membrane-BSA, and the adhesion data was good linear correlated with the flux decline rate in BSA filtration process, especially reflected in the CMPES membrane. The above experimental facts proved that the charged membrane interfacial electric double layer structure and its electrokinetic property had strong ties with the protein membrane fouling behavior.
This paper studied the biofilm properties and corrosion behavior of sulfate reducing bacteria (SRB) on stainless steel 316L (SS316L) surface in circulating cooling water system with and without additives including hydroxy ethyl fork phosphonic acid (HEDP), dodecyl dimethyl benzyl ammonium chlotide (1227) and NaClO. Biochemical technique, electrochemical technology, X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) were used. The results show that the extracellular polymeric substance (EPS) in biofilm attached on the SS316L surface mainly contain proteins and polysaccharides, the contents are 98 ug·cm-2 and 635ug·cm-2, respectively. The polysaccharides were cut by 1227 about 80%, while 55% by NaClO. The proteins were reduced by NaClO about 53%, while only 30% by 1227. The potentiodynamic polarization shows that the corrosion potential of SS316L was enhanced from -0.495 V to -0.390 V by the chemical additives, delaying the occurrence of the corrosion. And the corrosion rate was also reduced from 5.19 × 10-3 mm·a-1 to 2.42 × 10-3 mm·a-1. But NaClO still caused pitting corrosion after sterilizing the bacteria, while 1227 can form a protective film on the surface of SS316L. Though HEDP contribute to the bacteria activity, it can enhance the breakdown potential. XPS results confirmed that 1227 can change the value of C:O in the biofilm attached on metal surface, and NaClO can eliminate the existence of amidogen. This study would provide some recommendations for the selection of chemical additives in the thermal power plant.
Annual normalized difference vegetation index (NDVI) and chlorophyll-a (Chl-a) concentration are the most important large-scale indicators of terrestrial and oceanic ecosystem net primary productivity. In this paper, the Sea-viewing Wide Field-of-view Sensor level 3 standard mapped image annual products from 1998 to 2009 are used to study the spatial–temporal characters of terrestrial NDVI and oceanic Chl-a concentration on two sides of the coastline of China by using the methods of mean value (M), coefficient of variation (CV), the slope of unary linear regression model (Slope), and the Hurst index (H). In detail, we researched and analyzed the spatial–temporal dynamics, the longitudinal zonality and latitudinal zonality, the direction, intensity, and persistency of historical changes. The results showed that: (1) spatial patterns of M and CV between NDVI and Chl-a concentration from 1998 to 2009 were very different. The dynamic variation of terrestrial NDVI was much mild, while the variation of oceanic Chl-a concentration was relatively much larger; (2) distinct longitudinal zonality was found for Chl-a concentration and NDVI due to their hypersensitivity to the distance to shoreline, and strong latitudinal zonality existed for Chl-a concentration while terrestrial NDVI had a very weak latitudinal zonality; (3) overall, the NDVI showed a slight decreasing trend while the Chl-a concentration showed a significant increasing trend in the past 12 years, and both of them exhibit strong self-similarity and long-range dependence which indicates opposite future trends between land and ocean. 相似文献
This work aimed to determine the DNA and oxidative damage on mice by mixtures of organic contaminants in wastewater-irrigated soil, in order to assess their usefulness as markers for this kind of pollution. Wastewater-irrigated soil samples in the vicinity of an industrial area in Tangshan, China were collected, and soil irrigated by underground water satisfying drinking water standards was used as control group. Organic pollutants were extracted from the soil using ultrasonic oscillation, and analyzed by gas chromatography–mass spectrometry (GC-MS). Meanwhile, DNA damage on mice was determined by the Comet assay after oral gavage with the extracts, and changes in total superoxide dismutase (T-SOD) activity, glutathione peroxidase glutathione, GSH peroxidase (GSH-PX) activity and malondialdehyde content in serum of mice were investigated. The number of categories and concentrations of organic compounds in the wastewater-irrigated soil is more than those in groundwater-irrigated soil, as identified by the GC-MS. The toxicity test of mice showed that compared with reagent control group, the activities of T-SOD and GSH-PX decreased; the tailing rate of peripheral blood lymphocyte of mice increased and was more than that of the control group. This shows that mammalian toxicity end points can be used to determine the joint toxicity of organic pollutants in soil. When there is no means to identify each and every pollutant in soil, it is feasible to evaluate the combined effects of various pollutants to determine the extent to which the soil is polluted. 相似文献
