A review on application of flocculants in wastewater treatment

Flocculation is an essential phenomenon in industrial wastewater treatment. Inorganic coagulants (salts of multivalent metals) are being commonly used due to its low cost and ease of use. However, their application is constrained with low flocculating efficiency and the presence of residue metal concentration in the treated water. Organic polymeric flocculants are widely used nowadays due to its remarkable ability to flocculate efficiently with low dosage. However, its application is associated with lack of biodegradability and dispersion of monomers residue in water that may represent a health hazard. Therefore, biopolymers based flocculants have been attracting wide interest of researchers because they have the advantages of biodegradability and environmental friendly. But, natural flocculants are needed in large dosage due to its moderate flocculating efficiency and shorter shelf life. Thus, in order to combine the best properties of both, synthetic polymers are grafted onto the backbone of natural polymers to obtain tailor-made grafted flocculants. This paper gives an overview of the development of different types of flocculants that were being investigated for treatment of industrial wastewater. Furthermore, their flocculation performance will be reviewed and the flocculation mechanism will be discussed.     

湿法消解-原子荧光光谱法同时测定地表水中的砷和汞

为提高检测效率、降低检测成本、提高检测的准确性,采用硝酸消解水样,断续流动进样,在KBH_4-酸体系中、最佳的仪器试验条件下,用原子荧光光谱法同时测定地表水中的砷和汞。实验结果表明:砷、汞检出限分别为0.109、0.0026μg/L,线性范围分别为0～40μg/L和0～2μg/L,精密度都是1.4%,加标回收率分别为93.5%～107%和96.0%～104%。表明该检测方法检出限低、干扰性小、精密度高、测定结果稳定,能够满足地表水中砷和汞同时测定要求。     

Hydroxyl, hydroperoxyl free radicals determination methods in atmosphere and troposphere

The hydroxyl radical (?OH) has a crucial function in the oxidation and removal of many atmospheric compounds that are harmful to health. Nevertheless, high reactivity, low atmospheric abundance, determination of hydroxyl, and hydroperoxyl radical's quantity is very difficult. In the atmosphere and troposphere, hydroperoxyl radicals (HO₂) are closely demanded in the chemical oxidation of the troposphere. But advances in technology have allowed researchers to improve the determination methods on the research of free radicals through some spectroscopic techniques. So far, several methods such as laser-induced fluorescence (LIF), high-performance liquid chromatography (HPLC), and chemical ionization mass spectroscopy have been identified and mostly used in determining the quantity of hydroxyl and hydroperoxyl radicals. In this systematic review, we have advised the use of scavenger as an advance for further researchers to circumvent some of these problems caused by free radicals. The primary goal of this review is to deepen our understanding of the functions of the most critical free radical (?OH, HO₂) and also understand the currently used methods to quantify them in the atmosphere and troposphere.     

Predicting the contents of BTEX and MTBE for the three types of tollbooth at a highway toll station via the direct and indirect approaches

This study was set out to assess the contents of five volatile organic compounds (VOCs), including BTEX (the acronym for benzene, toluene, ethylbenzene, and xylene) and methyl tertiary-butyl ether (MTBE), in three types of tollbooth (including the car lane/ticket-collecting, car lane/cash-collecting, and bus/truck lane tollbooths) at a highway toll station via the direct and indirect approaches. For the direct approach, VOC samples were collected from the breathing zone of booth attendants at all selected tollbooths during the three workshifts. For samples collected during the dayshift, we found VOC contents of BTEX and MTBE in both the car lane/ticket-collecting (=6.23, 21.93, 3.24, 8.56, and 5.63 ppb, respectively) and car lane/cash-collecting tollbooths (=5.98, 21.71, 3.25, 8.59, and 6.04 ppb, respectively) were quite comparable, but both were significantly higher than that in the bus/truck lane tollbooth (=3.13, 13.91, 2.05, 4.52, and 2.70 ppb, respectively). The same pattern can also be found for the other two workshifts. For the indirect approach, we conducted multivariate regression analyses to predict VOC contents for any given type of tollbooth by using the four independent variables of the vehicle flowrate, wind speed, relative humidity, and air temperature. We found that, except the vehicle flowrate, the other three factors did not have a significant effect on VOC contents in the three types of tollbooth. In addition, the magnitudes of the effect of the vehicle flowrate on VOC contents for the three types of tollbooth were: car lane/cash-collecting>bus/truck lane>car lane/ticket-collecting. All regression results yielded R²-values in the range of 0.41−0.74 indicating that the developed indirect approach was able to predict VOC contents for three types of tollbooth.     

原子吸收法测定铜检出限的测量不确定度评估

对原子吸收法测定铜检出限的测量不确定度进行分析探讨,建立了不确定度的评估方法。影响铜检出限测量不确定度的主要因素包括标准溶液不确定度;拟合曲线不确定度;检测仪器不确定度;吸光值量化误差不确定度等,提供了上述各因素的计算方法及过程。     

UPLC-MS/MS法同时测定地表水中多种有机污染物

采用超高效液相色谱-串联质谱法直接进样测定地表水中26种有机污染物,通过优化试验条件,使各目标化合物在1.00μg/L^100μg/L范围内线性良好,相关系数(r 2)>0.995,方法检出限为0.003μg/L^1.0μg/L。将该方法用于地表水样的测定,加标回收率为79.0%~120%,6次测定结果的RSD均<15%。     

地表水中痕量金属元素的原子吸收法测定

采用单缝石英管技术作为火焰原子化器的原子捕集阱,以火焰法测定地表水中Cu、Pb、Zn、Cd等痕量元素,进一步提高了石英管法的灵敏度。依上述元素的顺序,其方法的最低检出浓度分别为4.0、10.0、1.0、1.0μg·l~(-1);对不同浓度标准溶液的精密度实验,其变异系数分别为0.5％、0.6％、1.6％、0.4％;对地表水加标回收率试验结果分别为95％—106％、100％—105％、95％—109％、84％—99％。     

An embryogenic model to explain cytogenetic inconsistencies observed in chorionic villus versus fetal tissue

While the fetus and placenta have a common ancestry, chorionic villus tissue does not always reflect fetal genotype. Data are presented from 15 CVS subjects in whom cytogenetic inconsistencies were observed when comparing (1) cultured chorionic villi, (2) direct chromosome preparations of intact villi, and (3) cultured fetal tissue. Embryogenic models are presented to explain these discrepancies. Mosaicism confined to direct chromosome preparations was the most commonly observed inconsistency. This can be explained by postzygotic non-disjunction limited to cytotrophoblast. In all but one instance, the abnormal cell line was limited to the placenta, with the normal cell line reflecting fetal genotype. Analysis of direct chromosome preparations from multiple individually processed villus fragments may be helpful in recognizing mosaicism confined to the placenta. While both direct chromosome preparations and villus cultures can be misleading, the latter are more likely to reflect fetal genetic status since they are derived from the extraembryonic mesoderm.     

Admixture of maternal metaphases in first trimester direct chromosome preparations?

The autoradiographic labelling of different cell types in chorionic villi and decidual tissue was investigated after [³H]-thymidine incorporation in vitro. Although the extent of labelling was found to be lower in decidual than in villus tissue the possibility that direct chromosome preparations may contain maternal metaphases should be considered. The need for careful selection of villi for direct cytogenetic analysis was stressed.     

论对外引资中的环境管理

对外引资中的环境管理是尚未引起人们充分重视的严重问题，这一问题解决得好坏将直接影响对外引资工作的健康发展。本文论述了强化对外引资中环境管理的必要性，提出了强化管理的原则、目标以及对策。