两江重庆段沉积物中腐殖酸特性及其对荧蒽的吸附

从长江、嘉陵江(简称两江)重庆段的5个表层沉积物样品(JL1、JL2、YZ1、YZ2、YZ3)中提取腐殖酸,对其进行了化学组成分析和结构特性表征.结果表明,各样点的腐殖酸中元素含量比值(H/C值、O/C值、C/N值等)存在一定的差异.JL1、YZ3和YZ1样品中的腐殖酸具有较高的O/C值和H/C值,呈现明显的脂肪特性,而YZ2样品的芳香性特征相对明显;各样点腐殖酸的C/N值＞10,表明受藻类污染的潜势较低.傅里叶红外图谱结果表明,各样点腐殖酸的官能团结构组成相似度较高,均含有羧基、羟基、羰基等活性官能团,但官能团的含量存在差异.借助荧光光谱分析,进行腐殖酸对荧蒽的吸附特性试验以及吸附等温线修正Freundlich模型模拟,修正吸附系数(Kf')的大小顺序为:YZ2＞ JL2＞ YZ1＞YZ3＞ JL1,且吸附能力与腐殖酸的极性强弱、元素含量、活性官能团特征等具有一定的相关性;在连续多步解吸附试验中,相对于加标荧蒽的吸附量,各样点的解吸率为40.3％ ～74.8％.     

石灰、粉煤灰改性对盐渍土吸附石油污染物行为的影响

有效调控污染物的运移是实现污染土工程再利用的前提。考虑石油污染盐渍土的特殊性及工程利用的力学需求,优选石灰和粉煤灰为改性材料,结合静态动态试验,研究石灰和粉煤灰对滨海盐渍土中石油污染物的吸附解吸行为的影响。结果表明:单独的石灰和粉煤灰,对石油污染物的吸附率分别为26%和14%,两者联合作用时,吸附率提高到39%,在盐渍土中加入石灰和粉煤灰可有效提高对石油污染物的吸附量,加快吸附稳定速率;盐渍土、石灰+盐渍土、粉煤灰+盐渍土、石灰+粉煤灰+盐渍土对石油的吸附动力学均符合Lagergren二级动力学非线性方程,联合作用可使吸附平衡时间由400min缩短至60min;石灰、粉煤灰有利于吸附赋存于土颗粒孔隙中未被盐渍土颗粒吸附的呈自由态的石油;盐渍土、石灰+盐渍土、粉煤灰+盐渍土、石灰+粉煤灰+盐渍土对石油污染物的吸附等温线均为非线性Freundlich模式;石油被解吸的能力依次为盐渍土粉煤灰+盐渍土石灰+盐渍土石灰+粉煤灰+盐渍土,石灰+粉煤灰对石油污染物的吸附以化学吸附为主,具有不可逆性,有助于缓解环境温度的影响,增强稳定性。     

Investigation on the oxygen reduction reaction mechanism of PrBa0.5Sr0.5Co1.5Fe0.5O5+δ@La2NiO4+δ core-shell structure cathode for solid oxide fuel cells

Excellent electrochemical performance is achieved by PrBa_0.5Sr_0.5Co_1.5Fe_0.5O_5+δ@La₂NiO_4+δ (PBSCF@LN) core-shell structure cathode, LN coating's existence enhances the cathode catalytic activity by promoting the oxygen reduction reaction (ORR) surface process. Besides the LN's excellent oxygen adsorption-desorption property, roughness surface of LN coating provides more ORR active sites compared to pristine PBSCF cathode. Thorough investigation is carried out based on the PBSCF and LN oxide's oxygen diffusion mechanism and corresponding ORR process elementary steps are constructed. Combine the theoretical derivations with experimental results, rate-determining step of PBSCF and PBSCF@LN cathode can be ascertained. With LN coating's introduction, PBSCF cathode's rate-determining step transfers from surface oxygen exchange to oxygen species' crossing LN coating, reducing thickness of LN coating can further improve PBSCF@LN cathode’ performance.     

乙二酸和苯甲酸在活性炭上的脱附行为

低挥发性有机酸不仅自身污染环境而且显著促进颗粒污染物形成,对其吸脱附性能的研究有助于这类物质的控制。采用程序升温脱附(TPD)技术对乙二酸、苯甲酸在活性炭(AC)上的脱附行为进行了研究。结果表明,吸附主要发生在粗微孔(0.7~2 nm)、细微孔(<0.7 nm)中,对应TPD曲线中的吸附位Ⅰ、Ⅱ。粗微孔对乙二酸、苯甲酸的脱附活化能为101.63、112.43 kJ·mol^-1,吸附量均大于总吸附量的91%。细微孔对乙二酸、苯甲酸的脱附活化能为118.01、130.87 kJ·mol^-1,吸附量均小于总吸附量的9%。细微孔吸附强度高于粗微孔,但吸附量远低于粗微孔,因为细微孔对吸附质的迁移阻力较大,仅少量吸附质能进入细微孔中。苯甲酸在迁移中受到阻力较乙二酸大,在细微孔中吸附量更小,表现为分子筛分作用。     

石灰、粉煤灰改性对盐渍土吸附石油污染物行为的影响

有效调控污染物的运移是实现污染土工程再利用的前提。考虑石油污染盐渍土的特殊性及工程利用的力学需求,优选石灰和粉煤灰为改性材料,结合静态动态试验,研究石灰和粉煤灰对滨海盐渍土中石油污染物的吸附解吸行为的影响。结果表明：单独的石灰和粉煤灰,对石油污染物的吸附率分别为26%和14%,两者联合作用时,吸附率提高到39%,在盐渍土中加入石灰和粉煤灰可有效提高对石油污染物的吸附量,加快吸附稳定速率;盐渍土、石灰+盐渍土、粉煤灰+盐渍土、石灰+粉煤灰+盐渍土对石油的吸附动力学均符合Lagergren二级动力学非线性方程,联合作用可使吸附平衡时间由400 min缩短至60 min;石灰、粉煤灰有利于吸附赋存于土颗粒孔隙中未被盐渍土颗粒吸附的呈自由态的石油;盐渍土、石灰+盐渍土、粉煤灰+盐渍土、石灰+粉煤灰+盐渍土对石油污染物的吸附等温线均为非线性Freundlich模式;石油被解吸的能力依次为盐渍土 > 粉煤灰+盐渍土 > 石灰+盐渍土 > 石灰+粉煤灰+盐渍土,石灰+粉煤灰对石油污染物的吸附以化学吸附为主,具有不可逆性,有助于缓解环境温度的影响,增强稳定性。     

The origin of the band at 1462 cm−1 generally appearing upon desorption of pyridine from acidic solids. Steps towards a more comprehensive understanding

The pyridine adsorption-desorption method, followed by IR spectroscopy, is generally applied for acidity determination of solid catalysts. A peculiar band at 1462 cm^–1 was observed by several authors upon pyridine desorption at higher temperatures and was interpreted in various ways. A new complex between Lewis framework acid sites and pyridine is proposed and several evidences are reported.     

Hydrocarbon storage modeling for diesel oxidation catalysts

A simple hydrocarbon (HC) storage model was proposed which represents the adsorption-desorption processes in zeolites incorporated in a diesel oxidation catalyst (DOC). Using four experiments in which the HC was stepped up and the reactor run until steady state, a Langmuir isotherm was generated that was sufficient to represent the equilibrium data, and the remaining rate constant capturing the adsorption time scale was obtained by fitting. The model thus developed was validated using reactor data which was obtained by stepping the inlet HC concentration to zero after outlet reached equilibrium.A typical DOC which contained both a storage component (zeolite) and noble metal component (for oxidation) was studied using a full scale 1D reactor model which includes the storage kinetics developed here with the oxidation kinetics developed in our previous work [Sampara et al., 2008. Global kinetics for a commercial diesel oxidation catalyst with two exhaust hydrocarbons. Industrial & Engineering Chemistry Research 47, 311-322]. Simulations of a simplified warm-up process indicated that the zeolite storage component reduces the overall cold start HC emissions by at least a factor of two if the warm-up rate achieves , a range commonly observed during start-up. Modeling results also showed that the HC oxidation for these reactors commonly starts at the rear end of the reactor due to reduced CO inhibition. The rates of the individual processes during cold start were analyzed in detail and compared with the rate of inlet temperature increase provided from the exhaust.     

负载型钼基催化剂的制备及其合成甲硫醇的性能研究

本文采用等体积浸渍法制备了一系列负载型钼基催化剂,系统研究了不同K/Mo摩尔比、第二助剂和不同载体的钼基催化剂对混合气(CO/H2S/H2)制备甲硫醇性能的影响.由催化剂的活性评价可知,当K/Mo摩尔比为2.0时,催化剂具有最大的反应活性;分别添加铁、钴和镍3种过渡金属制备的催化剂对甲硫醇的选择性大小顺序为:CoNiFe;比较SBA-15和Si O2两种载体,发现K-Mo-Co/SBA-15的催化活性明显高于K-Mo-Co/Si O2,甲硫醇的选择性达到46.77%.实验分别采用N2-吸脱附、XRD和H2-TPR等手段对不同K/Mo摩尔比和负载2种不同载体的钼基催化剂进行了表征,并对催化剂的结构和性能进行了探讨.     

春季小浪底出库水氨氮含量显著变化调查研究

通过对小浪底水库从入库至出库不同水深水质进行监测,并以入库水质全年最差时段采集的水样为研究对象,模拟研究泥沙对氨氮的吸附与解吸能力,以及硝酸盐氮在小浪底水库水环境(表层水有氧水环境和深层水缺氧水环境)下转化为氨氮的情况。小浪底水库水质监测及模拟研究结果表明:春季小浪底出库水氨氮含量显著增加不是小浪底水库底泥释放氨氮所致,也不是硝酸盐氮在小浪底水库水环境转化所致,而是水库上游输入引起的。     

纳米二氧化硅/凹土复合材料的制备以及吸附性能

以硅酸钠为主要原料,用硫酸调节pH,通过液相沉淀法在凹土单晶表面原位生成纳米粒状二氧化硅,制备纳米二氧化硅/凹土复合粉体。利用XRD、TEM、TG-DTG、氮气吸附脱附曲线等方法对复合粉体进行表征。XRD表明,二氧化硅以非晶态的形式包覆在凹土表面,防止了凹土的团聚。TEM照片显示,包覆后的纳米二氧化硅粒径减小,粒度分布均匀,表面光滑。