Vanadium and molybdenum concentrations in particulate from Palermo (Italy): analytical methods using voltammetry

The main purpose of this work was to develop a reliable method for the determination of vanadium (V) and molybdenum (Mo) in atmosphere particles or aerosols because they can not be readily measured using conventional techniques. For this research, 30 particulate samples were collected from five different stations located at Palermo, Italy. We used the catalytic adsorptive stripping voltammetry and differential pulsed voltammetry to measure V and Mo in atmospheric particulate, respectively. The represented method includes advantages of high sensitivity, high selectivity, simplicity, reproducibility, speed and low costs. The quantification limits for V and Mo are, respectively, 0.57 and 0.80 ng·m⁻³. The precision, expressed as relative standard deviation (RSD %), was about 2% for both metals. The mean recoveries of added V and Mo were about 99.5% and ranged from 97% to 101%. Vanadium concentrations in particulate samples collected in Palermo area ranged from 0.57 to 7.7 ng·m⁻³, while Mo concentrations were in the range 0.8–51 ng·m⁻³. In many cases the concentrations of two elements in the particulate samples fall below the detection limits. The mean concentrations for V and Mo in particulate samples, collected in Palermo area, were respectively 3.1 and 5.9 ng·m⁻³.     

SCR钒基催化剂吸附氨和水的密度泛函研究

利用密度泛函理论和原子簇模型,对NH3和H2O分子在选择性催化还原(SCR)脱硝催化剂表面不同吸附位上的吸附进行了研究.结果表明:NH3能吸附在V2O5表面的Lewis和Bronsted酸位,但在后者吸附位上更稳定.当V2O5以多聚物结构存在时,NH3能与O(1)H生成稳定的NH4 ,该物质在SCR反应中起着关键作用,吸附能为-128 kJ·mol-1;同时水也可与该吸附位形成稳定构型,吸附能为-97 kJ·mol-1.在V2O5表面,水与NH3的吸附能相当,两者发生竞争吸附,从而在一定程度上对SCR脱硝反应产生抑制作用.     

以工业级TiO2为载体负载不同助催化剂V2O5基脱氮催化剂的性能

在工业级TiO2载体上,通过浸渍法负载V2O5,WO3和MoO3等活性物质,制备不同V2O5基的烟气脱氮催化剂．在固定床反应器中测试DeNOx活性,研究不同的助催化剂(WO3和MoO3)对该类型催化剂DeNOx活性的影响,结果表明,在三元催化剂中,V2O5是主活性物质,MoO3和WO3是助催化剂,此外,V2O5-MoO3／TiO2的脱氮效率高于V2O5-WO3／TiO2,但N2O的生成量较大。     

改进催化光度法测定水中的微量钒

采用改进催化光度法测定微量钒,即利用微量钒催化溴酸钾氧化甲基紫溶液褪色实现快速测定水中的微量钒。在50mL容量瓶中,在pH为1.6的硫酸加入量0.90mL、0.0100mol/L的溴酸钾溶液加入量4.50mL、2.5×10-4mol/L的甲基紫溶液加入量5.00mL的条件下,聚乙二醇-200作活化剂时,在92℃恒温反应12min,加钒和不加钒溶液的吸光度之差与钒质量浓度呈线性关系。该法的测定波长为580nm,检出限为5.2×10-8g/L,最大相对标准偏差为4.3%,回收率为95.8%~104.0%。该法可用于湖水、化工厂排水中微量钒的直接测定。     

闽江河口芦苇与短叶茳芏空间扩展对湿地植物钒生物富集的影响

选择闽江河口鳝鱼滩芦苇与短叶茳芏空间扩展前的芦苇湿地、短叶茳芏湿地以及二者空间扩展过程中的交错带湿地为研究对象，探讨了空间扩展过程中不同湿地植被的钒（V）生物富集特征及其主要影响因素.结果表明，空间扩展影响下不同湿地土壤的V含量在0~40 cm土层均表现为芦苇湿地 > 交错带湿地 > 短叶茳芏湿地；芦苇湿地和交错带湿地土壤的V含量垂直变化特征较为一致，并均于40~50 cm土层出现较高值.芦苇与短叶茳芏的空间扩展整体增加了交错带湿地土壤的V含量，其均值相比短叶茳芏湿地增加了8.69%，而相比芦苇湿地仅增加0.21%.空间扩展主要通过改变湿地土壤的颗粒组成、EC以及植物的生物量、株高和密度来影响土壤的V含量分布.芦苇与短叶茳芏的V生物富集特征呈相反变化，这与二者竞争过程中植被生态特征改变以及其对V的竞争利用方式有关.此外，不同湿地植被均以根的V富集能力最强，且交错带短叶茳芏的V生物富集能力要高于交错带芦苇，这与二者在竞争生境中对V的吸收利用与转运的差异有关，交错带短叶茳芏可用于未来受V污染湿地修复的备选物种.研究发现，芦苇与短叶茳芏为应对空间扩展过程中的竞争可能采取不同的V富集策略，前者通过将富集到根中的V优先转运至光合器官（叶）的方式来保持相对竞争优势，而后者通过将富集到根中的V大量转移到地上主体（茎）的方式来抗衡来自芦苇的竞争.     

Effect of competing solutes on arsenic(V) adsorption using iron and aluminum oxides

The study focused on the effect of several typical competing solutes on removal of arsenic with Fe2O3 and Al2O3. The test results indicate that chloride, nitrate and sulfate did not have detectable effects, and that selenium(IV) (Se(IV)) and vanadium(V) (V(V)) show slight effects on the adsorption of As(V) with Fe2O3. The results also showed that adsorption of As(V) on Al2O3 was not affected by chloride and nitrate anions, but slightly by Se(IV) and V(V) ions. Unlike the adsorption of As(V) with Fe2O3, that with Fe2O3 was affected by the presence of sulfate in water solutions. Both phosphate and silica have significant adverse effects on the adsorption of As(V) adsorption with Fe2O3 and Al2O3. Compared to the other tested anions, phosphate anion was found to be the most prominent solute affecting the As(V) adsorption with Fe2O3 and Al2O3. In general, Fe2O3 has a better performance than Al2O3 in removal of As(V) within a water environment where multi competing solutes are present.     

基于改进支持向量机的石煤提钒行业清洁生产评价研究

采用遗传算法(GA)对支持向量机(SVM)进行改进,并将其应用于石煤提钒行业清洁生产评价.在系统研究石煤提钒工艺类型的基础上,根据前期已建立的石煤提钒行业清洁生产评价指标体系,提出GA改进SVM的应用思路,通过对3种工艺类型企业的现场数据采集,形成训练和测试样本,并利用GA算法确定出各类参数(惩罚参数C和核函数参数g),分别为强酸浸工艺C=2.1049,g=5.2184;弱酸浸工艺C=0.0035286,g=1.9947;水浸工艺C=0.39587,g=1.4105.GA-SVM模型测试结果表明,分类精度达到100%.通过与其他评价方法对比表明,训练好的GA-SVM方法针对小样本数据在分类精度和可操作性上都较其他方法有明显优势,实现了对石煤提钒行业清洁生产水平的定量评价.     

废SCR脱硝催化剂中钨和钒的浸出实验研究

废SCR脱硝催化剂中钨和钒的浸出是实现其回收的关键.采用碳酸钠混合焙烧-稀硫酸浸出法,对废SCR脱硝催化剂中金属钨和钒的浸出实验进行了研究,考察了焙烧温度t_1(℃)、焙烧时间t_2(h)、硫酸浓度c(v/v)、液固比w、浸出温度t_3(℃)、浸出时间t_4(h)、Na_2CO_3与催化剂的质量比m(Na_2CO_3)/m(催化剂)等因素对钨和钒浸出率的影响.结果表明,在t_1为800℃、t_2为3 h、c为2%、w为8:1、t_3为80℃、t_4为4 h、m(Na2CO3)/m(催化剂)为1.2的反应条件下,废SCR脱硝催化剂中钨和钒的浸出率可分别高达99.08%、98.49%,为后续钨和钒的高效提取与回收提供了有利的条件.     

Effect of competing solutes on arsenic（Ⅴ） adsorption using iron and aluminum oxides

The study focused on the effect of several typical competing solutes on removal of arsenic with Fe_2O_3 and AL_2O_3.The test results indicate that chloride,nitrate and sulfate did not have detectable effects,and that selenium(Ⅳ)(Se(Ⅳ))and vanadium(Ⅴ)(V(Ⅴ)) showed slight effects on the adsorption of As(Ⅴ)with Fe_2O_3.The results also showed that adsorption of As(Ⅴ)on AL_2O_3 was not affected by chloride and nitrate anions,but slightly by Se(Ⅳ)and V(Ⅴ)ions.Unlike the adsorption of As(Ⅴ)with Fe_2O_3,that with Fe_2O_3 was affected by the presence of sulfate in water solutions.Both phosphate and silica have significant adverse effects on the adsorption of As(Ⅴ)adsorption with Fe_2O_3 and Al_2O_3.Compared to the other tested anions,phosphate anion was found to be the most prominent solute affecting the As(Ⅴ)adsorption with Fe_2O_3 and Al_2O_3.In general,Fe_2O_3 has a better performance than Al_2O_3 in removal of As(Ⅴ)within a water environment where multi competing solutes are present.