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INTRODUCTION Nitrate contamination in groundwater and sur-face water has become an increasingly serious envi-ronmental problem. Anthropogenic sources such asnitrogen fertilizers, animal wastes, and septic systemsaccount for most nitrate contamination of ground-water. Nitrate itself is relatively non-toxic. However,it can be microbially reduced to nitrite, which posesseveral health threats to humans including methemo-glo-binemia, liver damage and cancers. Nitrate out-flow onto shallow cont… 相似文献
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以高压汞灯作为反应光源,以硝酸银和柠檬酸三钠(TSC)为反应试剂,以聚乙烯吡咯烷酮(PVP)为保护剂,建立了水溶液中一步光化学还原快速制备绿色纳米银溶胶的简便方法.研究了光照时间、TSC的浓度、转速等反应条件对纳米银胶的影响及纳米银胶的稳定性,采用紫外-可见分光光度法、共振散射光谱法和扫描电镜对纳米银胶进行了表征.结果表明,反应时间及TSC的浓度均会影响纳米银胶的性质,制备得到的绿色纳米银胶粒子为高分散准球形,且在室温避光条件下十分稳定.此外,实验发现,通过控制TSC的浓度可以制备得到具有不同光谱性质的绿色纳米银胶. 相似文献
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以300W汞灯为光源,纳米TiO2为光催化剂,甲基橙为目标降解物,以分光光度法测定其脱色率,以重铬酸钾法测定其COD降解率,研究了在不同溶液pH值、甲基橙初始浓度及TiO2投加量等条件下的甲基橙光催化降解效率．结果表明,甲基橙溶液脱色率和COD降解率并不一致,脱色比COD降解更容易发生;将脱色率、COD降解率等指标的变化综合考虑,才能更全面准确地判断光催化反应的效率． 相似文献
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以纳米TiO2富集分离-冷原子吸收法测定水环境中的Hg（Ⅱ）、苯基汞,考察了两种形态汞在纳米TiO2上的富集、分离行为。试验结果表明：pH值对纳米TiO2吸附Hg（Ⅱ）、苯基汞影响显著,最佳pH值分别为9.0、10;纳米TiO2对Hg（Ⅱ）、苯基汞的吸附速度快,最佳吸附时间均为12min;φ（HCl）=15%时,对Hg（Ⅱ）和苯基汞的洗脱率达90%以上。 相似文献
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An expanded granular sludge bed (EGSB) reactor inoculated with anaerobic granular sludge was started up with its COD removal performance, self-balancing of pH, biogas production rate and characteristics of the granular sludge during the start-up period being investigated. The results indicated that the EGSB reactor can be started up successfully in 27 d by increasing the organic loading rate rapidly. The removal efficiency of COD was maintained above 93% with influent COD concentration of 25 000 mg/L and OL... 相似文献
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CAI Jing ZHENG Ping MAHMOOD Qaisar ISLAM Ejazul HU Bao-lan WU Dong-lei 《浙江大学学报(A卷英文版)》2007,8(7):1149-1156
The optimal operation conditions in an anoxic sulfide oxidizing (ASO) bioreactor were investigated. The maximal removal rates for sulfide and nitrate were found to be 4.18 kg/(m3·d) and 1.73 kg/(m3·d), respectively. The volumetrical volumetric loading rates (LRs) observed through decreasing hydraulic retention time (HRT) at fixed substrate concentration are higher than those by increasing substrate concentration at fixed HRT. The sulfide oxidation in ASO reactor was partially producing both sulfate and sulfur; but the amount of sulfate produced was approximately one third that of sulfur. The process was able to tolerate high sulfide concentration, as the sulfide removal percentage always remained near 99% when influent concentration was up to 580 mg/L. It tolerated relatively lower nitrate concentration because the removal percentage dropped to 85% when influent con- centration was increased above 110 mg/L. The process can tolerate shorter HRT but careful operation is needed. Nitrate conversion was more sensitive to HRT than sulfide conversion since the process performance deteriorated abruptly when HRT was decreased from 3.12 h to 2.88 h. In order to avoid nitrite accumulation in the reactor, the influent sulfide and nitrate concentrations should be kept at 280 mg/L and 67.5 mg/L respectively. Present biotechnology is useful for removing sulfides from sewers and crude oil. 相似文献
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Cellulose is one of the mostabundantnatural pol-ymers that have received much attention in research tomodify its physical and chemical structures to improveits properties and broaden its applications. A lot ofwork[1—5]has been reported on the modification viagraft copolymerization of vinyl monomers onto cellu-lose, often using different initiator systems. Variousvinyl monomers such as methyl methacrylate[6,7], 4-vinylpyridine[8], acrylonitrile[9,10], and styrene[11]have been used for cellulos… 相似文献
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采用急性毒性实验方法,研究了不同浓度的镉离子（Cd2＋）和汞离子（Hg2＋）单一及复合染毒对田螺肝胰脏过氧化氢酶（CAT）活性的影响.结果表明：在实验剂量范围（ρCd2＋0.5～8.0mg/L,ρHg2＋0.05～0.8mg/L）,单一染毒时,低浓度的Cd2＋,Hg2＋溶液对CAT活性有诱导作用;高浓度的Cd2＋,Hg2＋溶液有抑制作用.Cd2＋,Hg2＋复合染毒时,低、中浓度的镉与汞复合染毒,对CAT活性具有诱导作用,高浓度的镉与汞复合染毒,对CAT活性具有抑制作用.表明了在不同浓度Cd2＋,Hg2＋及联合作用的胁迫下,一定时间后CAT活性出现了较为显著的变化,从而为探讨重金属Cd2＋、Hg2＋对田螺的毒理作用及根据田螺肝胰脏CAT活性的变化可作为间接检测环境的污染程度的指标. 相似文献
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研究电化学方法制备高铁酸钾,通过单因素实验确定最佳工艺条件为:电解液KOH浓度16 mol/L,电解时间为6 h,反应温度为65 ℃,阳极表观电流密度为50 A/m2,制得高铁酸钾的浓度可达5.72 mmol/L。对高铁酸钾强化电动修复技术去除土壤中的苯酚进行初探,结果表明该技术可以大幅度提高苯酚污染的修复效能,在反应120 h后,苯酚的去除率可达到90%以上,而且产生的Fe(OH)3固体无毒无害,不会对环境造成二次污染。 相似文献
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Cheng-hang Zheng Li Wang Yong-xin Zhang Wei-guo Weng Hai-tao Zhao Jin-song Zhou Xiang Gao 《浙江大学学报(A卷英文版)》2018,19(1):68-79
The co-benefit of hazardous trace elements such as mercury (Hg), arsenic (As), and selenium (Se) capture in dust removal devices of ultra-low emission coal-fired power plants was investigated. Feed fuel and ash samples collected from 15 different coal-fired power units equipped with ultra-low emission systems were characterized to determine the concentrations and distribution characteristics of trace elements. It was found that the low-low temperature electrostatic precipitator (LLT-ESP) and the electrostatic fabric filter (EFF) had greater abatement capacity for Hg than normal cold-side ESP (CS-ESP). Only 0.8%–36.1% of Hg escaped from LLT-ESP and EFF, whereas 42.1%–90.6% of Hg escaped from CS-ESP. With the employment of EFF and ESP (inlet temperature<125 °C), 72.3%–99.1% of As and 70.7%–100% of Se could be captured before the wet flue gas desulfurization (WFGD) system. The significance level of the effects on the abatement capacity for Hg, As, and Se in ESP were analyzed by the Pearson correlation analysis and grey relational analysis. The results indicated that the low inlet temperature of LLT-ESP had significant promotional effect on the simultaneous removal of Hg, As, and Se. The smaller particle size of fly ash can be conducive to the adsorption of hazardous trace elements. The inhibitory effect of sulfur content in coal was significant for the enrichment of Hg and Se in fly ash. 相似文献
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以钛酸四丁酯为钛源,硝酸银为银源,采用溶胶-凝胶法制备了掺银的纳米Ti02。用X射线衍射和透射电子显微镜对材料进行了表征,以掺银TiO2为催化剂对甲基橙进行了光催化降解实验。考查了催化剂掺银量、催化剂总用量、甲基橙溶液浓度及降解时间对甲基橙降解率的影响。结果表明,制得的样品颗粒细小均匀,3％掺银Ti02样品比表面积高达132．2m^2／g。掺银Ti02中的银钛原子摩尔比以及催化剂用量均影响光催化活性,银的掺杂量为3％时,纳米TiO2光催化活性最高,3％掺银TiO2催化剂最佳用量为0．3g/L。降解率随甲基橙初始浓度的增加而降低,随光照降解时间的增加而提高,光照20-30min之间．降解速度最快。 相似文献
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Decomposition of dimethyl sulfide （DMS） in air was investigated experimentally by using a wire-cylinder dielectric barrier discharge （DBD） reactor at room temperature and atmospheric pressure. A new type of high pulse voltage source with a thyratron switch and a Blumlein pulse-forming network （BPFN） was adopted in our experiments. The maximum power output of the pulse voltage source and the maximum peak voltage were 1 kW and 100 kV, respectively. The important parameters affecting odor decomposition, including peak voltage, pulse frequency, gas flow rate, initial concentration, and humidity, which influenced the removal efficiency, were investigated. The results showed that DMS could be treated effectively and almost a 100% removal efficiency was achieved at the conditions with an initial concentration of 832 mg/m3 and a gas flow rate of 1000 ml/min. Humidity boosts the removal efficiency and improves the energy yield （EY） greatly. The EY of 832 mg/m3 DMS was 2.87 mg/kJ when the relative humidity was above 30%. In the case of DMS removal, the ozone and nitrogen oxides were observed in the exhaust gas. The carbon and sulfur elements of DMS were mainly converted to carbon dioxide, carbon monoxide and sulfur dioxide. Moreover, sulfur was discovered in the reactor. According to the results, the optimization design for the reactor and the matching of high pulse voltage source can be reckoned. 相似文献
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本文研究处理废感光胶片中银及片基的方法,达到减少对环境污染,同时变废为宝的目的。采用稀硝酸将废感光胶片所附的银化合物溶解成银离子,达到脱银目的,用电解方法从含银溶液提取纯银。综合各种处理废感光胶片方法中,化学溶解法性最佳。试验证明10%稀硝酸处理废感光胶片在温度为70～90℃效果最佳,当硝酸银溶液银浓度为12 g/L时,电解法提银处理溶液效果最佳,处理后硝酸溶液还可以胶片脱银,达到循环利用、高效目的。 相似文献
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Removal of chromium (Ⅵ) dissolved in water by intermittent foam separation was implemented with cetyl trimethy-ammonium bromide as surfactant. The influence of various factors on removal efficiency was systematically studied. The removal efficiency has a maximum value near pH 4.0; thus, most experiments were carried out at pH 4.0. The orthogonal experiment was conducted to confirm the optimal operating parameters. The orthogonal experimental results show that when the liquid feed concentration is 10 mg/L, the pH value of feed solution is 4.00, air flow rates 0.9 L/min, surfactant dosage is 300 mg/L, the maximum removal efficiency of chromium (Ⅵ) reaches 97.80%, and condense multiple reaches 1711. The kinetic test indicates that the foam separation of chromium is a first-order process. The equivalent rate constant calculated from the slope is 0.406 4, and the equivalent rate equation is obtained. 相似文献
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Removal of chromium (VI) dissolved in water by intermittent foam separation was implemented with cetyl trimethy-ammonium bromide
as surfactant. The influence of various factors on removal efficiency was systematically studied. The removal efficiency has
a maximum value near pH 4.0; thus, most experiments were carried out at pH 4.0. The orthogonal experiment was conducted to
confirm the optimal operating parameters. The orthogonal experimental results show that when the liquid feed concentration
is 10 mg/L, the pH value of feed solution is 4.00, air flow rates 0.9 L/min, surfactant dosage is 300 mg/L, the maximum removal
efficiency of chromium (VI) reaches 97.80%, and condense multiple reaches 1 711. The kinetic test indicates that the foam
separation of chromium is a first-order process. The equivalent rate constant calculated from the slope is 0.406 4, and the
equivalent rate equation is obtained. 相似文献
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聚丙烯酰胺的合成与研究 总被引：1，自引：0，他引：1
穆志坚 《南通职业大学学报》2001,15(2):21-23
采用过硫酸钾－氮三丙酰胺引发体系，进行丙烯酰胺水溶液聚合，考察了溶液PH值，温度等工艺对产物分子量，转化率及聚合物溶解性能的影响，在PH＝8，60℃时，氨水滴加7滴时，可得到分子量为62．00E4聚丙烯酰胺及转化率为98．94％。 相似文献
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在特定缓冲底液（pH6．40）中,甲磺酸吉米沙星（Gemifloxacin mesylate,简称FACTIVE）在汞电极上可以发生还原反应,测得了还原反应的峰电位,该还原峰为典型的吸附峰;测定表明,吸附于滴汞电极上的粒子为甲磺酸吉米沙星的中性分子,通过实验测得了待测物在滴汞电极汞滴上的饱和吸附量,测得了FACTIVE分子在汞滴上吸附后所占电极面积,实验证明待测物中性分子在汞滴上的吸附符合Langmuir吸附等温式;实验表征了吸附系数,25℃时的吸附自由能,电极反应过程中转移电子数,不可逆体系动力学参量,汞滴表面反应速率常数;并通过实验给出了吸附溶出伏安法测定FACTIVE的最佳条件,方法的检出限满足常规分析的要求． 相似文献
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The characteristics of the start-up period of single-step autotrophic nitrogen removal process were investigated. The autotrophic nitrogen removal process used a sequencing batch reactor to treat wastewater of medium to low ammonia-nitrogen concentration, with dissolved oxygen （DO）, hydraulic retention time （HRT） and temperature controlled. The experimental conditions were temperature at （30±2） ℃, ammonia concentration of （60 to 120） mg/L, DO of （0.8 to 1.0） mg/L, pH from 7.8 to 8.5 and HRT of 24 h. The rates of nitrification and nitrogen removal turn out to be 77% and 40%, respectively, after a start up period going through three stages divided according to nitrite accumulation： sludge domestication, nitrifying bacteria selection and sludge adaptation, It is demonstrated that dissolved oxygen is critical to nitrite accumulation and elastic YJZH soft compound packing is superior to polyhedral hollow balls in helping the bacteria adhere to the membrane. 相似文献