掺杂负载型纳米TiO2降解橙黄G的光催化活性及其动力学研究

采用溶胶-凝胶法和浸渍-焙烧法制备了掺杂Sn(Ⅳ)的TiO2/AC光催化剂,以偶氮染料橙黄G为目标降解物,对光催化反应条件进行了优化.结果表明:利用Sn(Ⅳ)掺杂量为2.5 at.%的TiO2/AC光催化剂,在进水浓度50 mg/L,催化剂的用量12.5 g/L,pH值2.0,H2O21.5 mL/L,主波长为365 nm的300W高压汞灯光照条件下,反应60 min,橙黄G的光催化去除率可达99.1%.该反应符合Langmuir-Hinshelwood动力学方程,其速控步为吸附反应.共存阴离子SO42-和H2PO4-,对橙黄G的光催化降解反应均有一定的抑制作用.     

Remediation of Cu and As contaminated water and soil utilizing biochar supported layered double hydroxide: Mechanisms and soil environment altering

Preparing materials for simultaneous remediation of anionic and cationic heavy metals contamination has always been the focus of research. Herein a biochar supported FeMnMg layered double hydroxide (LDH) composites (LB) for simultaneous remediation of copper and arsenic contamination in water and soil has been assembled by a facile co-precipitation approach. Both adsorption isotherm and kinetics studies of heavy metals removal by LB were applied to look into the adsorption performance of adsorbents in water. Moreover, the adsorption mechanisms of Cu and As by LB were investigated, showing that Cu in aqueous solution was removed by the isomorphic substitution, precipitation and electrostatic adsorption while As was removed by complexation. In addition, the availability of Cu and As in the soil incubation experiments was reduced by 35.54%–63.00% and 8.39%–29.04%, respectively by using LB. Meanwhile, the addition of LB increased the activities of urease and sucrase by 93.78%–374.35% and 84.35%–520.04%, respectively, of which 1% of the dosage was the best. A phenomenon was found that the richness and structure of microbial community became vigorous within 1% dosage of LB, which indirectly enhanced the passivation and stabilization of heavy metals. These results indicated that the soil environment was significantly improved by LB. This research demonstrates that LB would be an imaginably forceful material for the remediation of anionic and cationic heavy metals in contaminated water and soil.     

3种人工湿地基质对邻苯二甲酸二丁酯的吸附特性

通过湿地基质对邻苯二甲酸二丁酯（DBP）的吸附动力学和等温吸附实验,对比天然土壤、沸石、陶粒对DBP的吸附特性,作为人工湿地处理含DBP废水的理论依据。结果表明,DBP浓度在30~1 000 μg·L-1时,Freundlich比Langmuir模型更好地模拟出各湿地基质对DBP的吸附特征。3种基质对DBP的饱和吸附量大小：土壤（0.065 5 mg·g-1）> 沸石（0.016 4 mg·g-1）> 陶粒（0.013 7 mg·g-1）。3种基质对DBP的缓冲能力大小依次为土壤 > 陶粒 > 沸石,即当人工湿地进水的DBP浓度变化较大时,土壤可以很好地维持出水水质,土壤很适合作为处理含DBP废水的人工湿地基质。DBP浓度为600 μg·L-1时,双常数模型能很好地拟合3种基质对DBP的吸附动力学特征。     

强电离放电脱除NO的化学反应动力学模拟

强电离放电脱除NO是集化学、物理学和环境工程学为一体的交叉学科,其脱除过程本质上是等离子体中进行的一系列微观过程,难以通过实验进行直接研究。故通过建立强电离放电脱除模拟烟气中NO的化学模型并运用MATLAB对其进行数值模拟以探讨NO的去除机理。数值模拟结果表明,在800 μs内产生大量·O和·OH,而仅产生少量·N,由此可知NO的去除主要是通过与·O和·OH的氧化反应生成HNO3实现的,在脱除过程中NO先被氧化成NO2,再进一步被转化成HNO3。同时,通过实验验证了所建立模型的合理性。实验结果表明：随着NO初始浓度的增加,NO脱除效率逐渐下降;随着含氧量的增加,NO脱除效率显著增大。     

Chemical reactions of uranium in ground water at a mill tailings site

We studied soil and ground water samples from the tailings disposal site near Tuba City, AZ, located on Navajo sandstone, in terms of uranium adsorption and precipitation. The uranium concentration is up to 1 mg/l, 20 times the maximum concentration for ground water protection in the United States. The concentration of bicarbonate (HCO₃⁻) in the ground water increased from ≤7×10⁻⁴ M, the background concentration, to 7×10⁻³ M. Negatively charged uranium carbonate complexes prevail at high carbonate concentrations and uranium is not adsorbed on the negatively charged mineral surfaces. Leaching experiments using contaminated and uncontaminated sandstone and 1 N HCl show that adsorption of uranium from the ground water is negligible. Batch adsorption experiments with the sandstone and ground water at 16°C, the in situ ground water temperature, show that uranium is not adsorbed, in agreement with the results of the leaching experiments. Adsorption of uranium at 16°C is observed when the contaminated ground water is diluted with carbonate-free water. The observed increase in pH from 6.7 to 7.3 after dilution is too small to affect adsorption of uranium on the sandstone. Storage of undiluted ground water to 24°C, the temperature in the laboratory, causes coprecipitation of uranium with aragonite and calcite. Our study provides knowledge of the on-site uranium chemistry that can be used to select the optimum ground water remediation strategy. We discuss our results in terms of ground water remediation strategies such as pump and treat, in situ bioremediation, steam injection, and natural flushing.     

Boron removal from produced water using electrocoagulation

Produced water is the largest wastestream of oil and gas exploration but its chemical composition hinders its beneficial use. Effective treatment and reuse of produced water can mitigate scarcity of fresh water, especially in arid areas. Presence of inorganic compounds such as boron in produced water renders its beneficial use difficult. In this study, boron removal from produced water was investigated. Synthetic wastewater was prepared simulating the range of boron concentrations in produced water. Four operating parameters pH (3–11), charge loading (1200–3600 Ah/m³), contact time (15–90 min) and concentration (10–30 mg/L) were selected and their optimum conditions investigated. The obtained optimum conditions were applied to treat real produced water. Residual boron concentration of 0.3 mg/L was obtained from initial boron concentration of 15 mg/L in real produced water at optimum conditions of pH 7, charge loading 2400 Ah/m³ and contact time 90 min. Boron adsorption could be represented by Langmuir and Freundlich isotherm models. Electrocoagulation can be used for the effective removal of boron from produced water.     

土壤氮素矿化模型研究进展

土壤氮素矿化研究对从农田生态系统氮素平衡到全球变化和环境问题均具有重要意义。土壤氮素矿化模型的研究方面．目前主要还是以简单功能模型模拟和预测氮素矿化量为主,以双组分一阶动力学模型和一阶-零阶混和动力学模型拟合效果较好;对机理模型的研究还处于探索阶段。从目前的研究看,土壤氮素矿化模型研究应当集中在建立机理模型以阐明主要生态系统的氮素矿化过程。     

污泥基生物炭吸附重金属Cd的动力学和热力学

炭化是污泥资资源化利用的重要途径。研究了污泥基生物炭对Cd的吸附过程,探讨了污泥基生物炭吸附重金属Cd的动力学和热力学特征。结果显示污泥基生物炭对Cd的吸附符合准二级动力学方程。Freundlich方程能较好的模拟吸附等温线。随着温度增加,吸附呈现逐渐增强趋势。吸附热力学结果显示35℃时吸附并非自发进行,随着温度增加,吸附转为吸热并自发进行。污泥基生物炭对Cd的吸附主要以化学吸附为主,同时存在多种机制共同作用。研究结果表明污泥基生物炭有作为重金属Cd污染废水修复剂的潜力。     

Biodegradation modelling of a dissolved gasoline plume applying independent laboratory and field parameters

Biodegradation of organic contaminants in groundwater is a microscale process which is often observed on scales of 100s of metres or larger. Unfortunately, there are no known equivalent parameters for characterizing the biodegradation process at the macroscale as there are, for example, in the case of hydrodynamic dispersion. Zero- and first-order degradation rates estimated at the laboratory scale by model fitting generally overpredict the rate of biodegradation when applied to the field scale because limited electron acceptor availability and microbial growth are not considered. On the other hand, field-estimated zero- and first-order rates are often not suitable for predicting plume development because they may oversimplify or neglect several key field scale processes, phenomena and characteristics. This study uses the numerical model BIO3D to link the laboratory and field scales by applying laboratory-derived Monod kinetic degradation parameters to simulate a dissolved gasoline field experiment at the Canadian Forces Base (CFB) Borden. All input parameters were derived from independent laboratory and field measurements or taken from the literature a priori to the simulations. The simulated results match the experimental results reasonably well without model calibration. A sensitivity analysis on the most uncertain input parameters showed only a minor influence on the simulation results. Furthermore, it is shown that the flow field, the amount of electron acceptor (oxygen) available, and the Monod kinetic parameters have a significant influence on the simulated results. It is concluded that laboratory-derived Monod kinetic parameters can adequately describe field scale degradation, provided all controlling factors are incorporated in the field scale model. These factors include advective–dispersive transport of multiple contaminants and electron acceptors and large-scale spatial heterogeneities.     

MgAl型层状化合物对六价铬的吸附性能

尿素-水热法制备层状双金属氢氧化物MgAl-LDH,系统考察了焙烧温度、pH值、初始Cr（VI）浓度、吸附时间和吸附温度对样品的吸附性能的影响。并对其吸附热力学、动力学和吸附机理进行研究。采用傅里叶红外光谱（FT-IR）对吸附Cr（VI）前后的MgAl-LDH进行表征。MgAl-LDH的最佳吸附条件为pH=2.5,吸附过程符合Langmuir等温模型,最大吸附容量为105.15 mg·g-1,其对Cr（VI）的吸附为放热过程,并遵守准二级动力学模型,化学吸附为主导。MgAl-LDH对Cr（VI）的吸附主要在酸性条件下进行,吸附机理主要为静电作用和离子交换：在酸性条件下,MgAl-LDH表面带正电荷,并通过静电作用吸附Cr（VI）阴离子,同时MgAl-LDH的层间CO32-和NO3-与溶液中的Cr（VI）阴离子进行离子交换。