铁酸锰纳米材料的制备及其对直接黑38的类芬顿催化降解研究

通过水热法制备了类芬顿(Fenton)催化剂铁酸锰(Mn Fe2O4)纳米粒子。通过X射线衍射仪(XRD)、扫描电镜(SEM)和X射线光电子能谱仪(XPS)对材料进行了表征。研究了此类Fenton法对难降解偶氮染料直接黑38(DB-38)的降解效果,并对反应动力学及材料的稳定性进行了研究。分析了可能产生的活性物质和降解产物,推测了降解的机制和路径。结果表明,直接黑38(20mg/L)可以被快速、有效的降解,5min后可达到90%的降解率和62%的总有机碳(TOC)去除率。降解过程为一级反应动力学,速率常数为0.36 min-1。羟基自由基(·OH)是最主要的活性基团,偶氮键被·OH攻击后,中间产物逐渐分解,成为更易挥发的小分子物质。研究表明Mn Fe2O4是一种有效的类Fenton试剂,在废水处理中有广阔的应用前景。     

4种有机农药在水中的光降解对比研究

为了解不同化学结构有机农药的光降解规律,以汞灯、氙灯为光源,在实验室中同时测定四种有机农药阿特拉津、异丙隆、灭草隆以及2,4-D丁酯,研究其在水体中的光解特性。结果表明,4种农药的光降解均符合一级降解动力学(r~20.9)。直接光解途径下,降解速率在两种光源下均遵循MNATZ2,4-DIPU(汞灯下半衰期7, 22, 4, 14 min,氙灯下半衰期16, 239, 8, 39 h);间接光解途径下,四种有机农药中IPU更容易受硝酸根诱导而加速降解(k_(indirect)/k_(direct)=8),ATZ降解速率几乎没有变化(k_(indirect)/k_(direct)=1),光解速率遵循MN2,4-DIPUATZ。从有机农药母体分子结构出发,提出芳环上取代基不同与光解机理对不同种农药光解动力学的影响。     

多氯联苯光化学降解研究的最新进展

综述了近10年以来多氯联苯(PCBs)在有机相、表面活性剂中的直接光化学降解行为,以及PCBs在水相中的光敏化反应和光催化反应等间接光化学降解行为。从光解动力学、光解途径、光解机理以及光解产物等几方面阐述了PCBs的光化学行为,光催化降解有机污染物是一种很有发展前景的有机污染物治理技术。     

有机农药对土壤的污染及生物修复技术研究

农药的大量使用污染了大气、水体及生态系统。有机农药以直接施用、拌种、喷撒、随降水落入等方式进入土壤。农药在土壤中会以吸附、扩散稀释和降解等几种方式发生转化,并改变土壤结构、对土壤中生物的生存及酶的活性产生影响。生物修复技术可以通过动植物、微生物及根际环境对农药污染的降解来治理土壤中的农药,是治理农药污染的一种推荐方法。     

降解菌DNEH-S1的室内模拟试验

农业生产中广泛使用的农药、地膜、化肥等农用化学品,造成多种有机物对土壤的复合污染。当有害物质过多,超过土壤的自净能力,就会引起土壤的组成、结构和功能发生变化,微生物活动受到抑制,有害物质或其分解产物在土壤中逐渐积累,并间接危害人体健康。邻苯二甲酸酯(PAEs)是一类环境内分泌物质,作为农用塑料地膜中的增塑剂被大量使用,易从塑料地膜中释放而造成土壤污染。我国农田土壤普遍存在农药、PAEs等有机物复合污染,生物降解是削减土壤中有机污染物的重要途径。试验研究了降解菌DNEH-S1在土壤中对DEHP降解特性及土壤中养分的动态变化,探讨了典型有机物复合污染土壤生物降解技术的可行性。     

农药水环境化学行为研究进展

农药在水中的环境化学行为包括农药的光化学降解、水化学降解和农药对水生生物的毒性。结合国内外在农药水环境化学行为的研究进展,讨论了农药在水中的直接光解和间接光解行为;农药水化学降解的机理以及pH、温度对农药水化学降解的影响,并以藻类、鱼类等为例阐述了农药对水生动植物及水生生物群落的毒性。     

基于UV/PMS工艺降解水中高效氟吡甲禾灵研究

针对普通方法难以降解水中农药废水的问题,运用紫外(UV)/过氧硫酸氢钾(PMS)系统降解高效氟吡甲禾灵,探讨溶液中反应污染物的初始浓度、氧化剂PMS添加量、腐殖酸浓度、初始pH值和常见无机阴离子等的影响因素。结果显示:UV通过催化PMS产生氧化性很强的活性自由基(·SO_4~-、·OH),能有效降解水中高效氟吡甲禾灵,降解反应符合拟一级动力学模型(R~20.98),反应污染物的初始浓度与降解速率呈负相关;氧化剂PMS添加量与降解速率呈正相关。添加的腐殖酸浓度越高,抑制降解反应的作用越明显,中性和弱碱条件下降解效果较好。当pH=7.41时,具有最大去除率(56.82%);少量的HCO_3~-对降解高效氟吡甲禾灵具有促进作用,高浓度则会抑制降解。在c(HCO_3~-)=10mmol/L时最大,Cl~-会抑制其降解;添加乙醇和叔丁醇淬灭剂,kobs均大量减小,UV/PMS的活性氧化物主要是·SO_4~-。     

农药在人体中的变化(二)

三、水解代谢水解代谢是农药在生物体内的代谢中研究得最多的,也是发生得最多和最普遍的一类代谢反应。水解酶的种类很多,其中关系最大的有五大类,分为二个系列:A—酯酶和B—酯酶。它们的主要区别为,前者水解有机磷酸酯类农药,而后者到则受     

纳米二氧化钛粉体的制备及对染料脱色的研究

以钛酸四丁酯为原料,采用溶胶-凝胶法、水热沉淀法、水解法制备了纳米二氧化钛粉体。经XRD对三种方法制得粉体进行了表征,讨论了三种方法的优缺点。以水解法制得二氧化钛粉对六种染料进行了脱色研究,结果表明其有良好的光催化脱色性能。     

应用聚丙烯酰胺的环境与生态行为研究

聚丙烯酰胺(PAM)在油田中的大量使用,其环境和生态行为及降解产物对环境的潜在危害,都亟待去研究。本文分析论述了其物理、化学性质及化学降解、机械降解、热降解、生物降解性,及影响其在土壤中的被吸附的因素和生态毒理学研究,提出有待进一步研究的课题为:PAM在油藏条件下的降解机理和降解速度;PAM及其衍生物在环境中的存在形式及其迁移转化的方式,在生物体内的存在形式及其在生物圈内的迁移转化等。     

零价纳米铁在修复受污染地下水中的最新进展

本文针对零价纳米铁(nZVI)在修复受污染地下水中存在的易于团聚、迁移性低及易于老化等问题,详细介绍了近年在这些问题研究上的最新进展,包括材料的改性,改性材料对污染物降解的效果及研究中不同因素的影响等。并就nZVI对难降解复杂有机污染物的降解进行了总结,在此基础上展望了nZVI对一类新兴污染物,药品和个人护理用品(PPCPs)的降解。     

Heterogeneous photocatalysed degradation of two selected pesticide derivatives, triclopyr and daminozid in aqueous suspensions of titanium dioxide

Heterogeneous photocatalysed degradation of two selected pesticide derivatives, triclopyr (1) and daminozid (2), has been investigated in aqueous suspensions of titanium dioxide by monitoring the change in substrate concentration employing the UV Spectroscopic analysis technique and depletion of Total Organic Carbon (TOC) content as a function of irradiation time. The degradation kinetics were studied under different conditions such as reaction pH, substrate and catalyst concentration, different types of TiO2 and in the presence of electron acceptors such as hydrogen peroxide (H2O2), potassium bromate (KBrO3) and ammonium persulphate (NH4)2S2O8 in addition to molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts. The pesticide derivative triclopyr (1) was found to degrade faster as compared to daminozid (2). An attempt was also made to identify the intermediate products formed during the photooxidation process using GC/MS analysis. Probable pathways for the formation of products have been proposed.     

Effects of ionic strength, temperature, and pH on degradation of selected antibiotics

Aqueous degradation rates, which include hydrolysis and epimerization, for chlortetracycline (CTC), oxytetracycline (OTC), tetracycline (TET), lincomycin (LNC), sulfachlorpyridazine (SCP), sulfadimethoxine (SDM), sulfathiazole (STZ), trimethoprim (TRM), and tylosin A (TYL) were studied as a function of ionic strength (0.0015, 0.050, or 0.084 mg/L as Na(2)HPO(4)), temperature (7, 22, and 35 degrees C), and pH (2, 5, 7, 9, and 11). Multiple linear regression revealed that ionic strength did not significantly affect (alpha = 0.05) degradation rates for all compounds, but temperature and pH affected rates for CTC, OTC, and TET significantly (alpha = 0.05). Degradation also was observed for TYL at pH 2 and 11. No significant degradation was observed for LNC, SCP, SDM, STZ, TRM, and TYL (pH 5, 7, and 9) under study conditions. Pseudo first-order rate constants, half-lives, and Arrhenius coefficients were calculated where appropriate. In general, hydrolysis rates for CTC, OTC, and TET increased as pH and temperature increased following Arrhenius relationships. Known degradation products were used to confirm that degradation had occurred, but these products were not quantified. Half-lives ranged from less than 6 h up to 9.7 wk for the tetracyclines and for TYL (pH 2 and 11), but no degradation of LIN, the sulfonamides, or TRM was observed during the study period. These results indicate that tetracyclines and TYL at pH 2 and 11 are prone to pH-mediated transformation and hydrolysis in some cases, but not the sulfonamides, LIN nor TRM are inclined to degrade under study conditions. This indicates that with the exception of CTC, OTC, and TET, pH-mediated reactions such as hydrolysis and epimerization are not likely removal mechanisms in surface water, anaerobic swine lagoons, wastewater, and ground water.     

Effect of combined application of methyl isothiocyanate and chloropicrin on their transformation

Combining several soil fumigants to increase the broad spectrum of pest control is a common fumigation practice in current production agriculture. In this study, we investigated the effect of combined application of chloropicrin and methyl isothiocyanate (MITC) on their transformations and persistence in the environment. In aqueous solution, no direct reaction between MITC and chloropicrin occurred and relatively slow rates of hydrolysis of these compounds were observed in aquatic environments free of suspended solids. The transformation of chloropicrin, however, was accelerated in aqueous solution with MITC because of a reduction reaction with bisulfide (HS(-)), which is a by-product of MITC hydrolysis. In soil, when fumigants were applied simultaneously, the degradation of MITC was suppressed under the bi-fumigant application due to the inhibition of soil microbial activity and a possible abiotic competition with chloropicrin for a limited number of reaction sites on the surface of soil particles. However, the degradation rate of chloropicrin was significantly enhanced in the bi-fumigant soil system, which was primarily attributed to the reaction of chloropicrin and HS(-). Two sequential application approaches were developed to investigate the feasibility of the combined application of metam sodium (parent compound of MITC) and chloropicrin in soil and assess their potential effects on environmental fate. For both application sequences, the degradation of chloropicrin was accelerated and that of MITC, as a major breakdown product of metam sodium, was inhibited in soil.     

光催化还原法处理含cr（Ⅵ）废水的研究

采用自制TiO2作为光催化剂,利用光催化-混凝联合处理含Cr（Ⅵ）废水,研究了废水的pH值、催化剂用量、反应时间、有机物和混凝剂种类对含Cr（Ⅵ）废水中Cr（Ⅵ）去除率的影响。结果表明,在添加EDTA,pH值为1,紫外灯120min左右,二氧化钛加入量为0．4g,采用FeCl3和PAM作为混凝剂时,Cr（Ⅵ）的去除效率最好。     

稀土水杨醛Salphen希夫碱配合物的合成与表征

利用N,N’-双（水杨醛）缩邻苯二胺配体（L）与稀土金属离子合成了稀土水杨醛Salphen希夫碱配合物{[M（NO3）2]·2H2O;M=La,Nd,Sm},并利用红外光谱（IR）、紫外-可见光谱（UV）、元素分析、摩尔电导率和差热热重（TG—DTA）对配合物的结构做了表征。结果表明,配合物中稀土金属离子M（Ⅲ）的配位数为6,同时还有2个NO3-和配位中心配位。     

油污土壤的生物处理技术及其影响因素分析

生物处理技术可以用于转化和去除土壤中的石油类污染物,微生物对油污土壤产生降解作用,其降解的最终产物是CO2和水,不产生二次污染。重点分析了影响微生物降解的主要因素,包括pH值、温度、湿度、供氧情况、营养素、表面活性剂加入量、油污染强度,论述了各种影响因素的调整和控制方法。     

风化煤腐植酸增效尿素红外光谱分析

采用碱性混合活化剂处理风化煤,研制腐植酸添加剂,按不同比例添加到尿素熔融液中,采用模拟喷浆造粒的方法,制备3类增效尿素。通过风化煤与添加剂、尿素与增效尿素红外光谱特征对比发现：风化煤经过活化后,碳单键数量降低,碳链缩短,活性腐植酸HA类提取物出现活性官能团,FR类除单键数量减少和碳链缩短外,生成部分胺、酰胺结构;增效剂与尿素在反应过程中,出现了三键和累积双键破坏、稳定性复合物形成、碳链缩短、双键结构增加等变化,但不同类型增效剂对产品红外光谱特征影响存在差异。     

树脂纳米零价铁催化过硫酸钠降解甲基橙的研究

采用树脂负载零价纳米铁（NZVI-resin）作为铁源,活化过硫酸钠,产生硫酸根自由基氧化降解偶氮染料甲基橙。考察了温度、NZVI-resin加入量、pH值及过硫酸钠的浓度等因素对甲基橙降解率的影响,并对其降解动力学规律作了初步探讨。结果表明：降解反应遵循准一级反应动力学,在pH=3.0、Fe0=0.2 g.L-1、Na2S2O8=1.33 g.L-1的条件下,30 mg.L-1的甲基橙溶液降解率为99.7%。