Determination of toxic elements in waters and sediments from River Subin in the Ashanti Region of Ghana

Waters and sediments of Subin River, which flows through the industrial and commercial areas of Kumasi in the Ashanti region of Ghana, were geochemically investigated to ascertain heavy metal pollution levels due to anthropogenic activities. The study shows preoccupying pollution levels that constitute a threat to public and ecological systems. The waters of Subin River are neutral to slightly basic, inferred from pH values of 6.89–7.65). Electric conductivity (EC) of the waters ranges from 822 to 1,821 μs/cm and the range of total dissolved solids (TDS) is from 409 to 913 mg/l. Toxic elements contents of sediments and waters from 10 sites along the river were analysed by instrumental neutron activation analysis (INAA), and Al, As, Cd, Cr, Cu and Zn were determined. The concentrations of Al, As, Cd, Cr, Cu and Zn in the waters range between 4.02–15.18, 0.007–0.16, 0.002–0.05, 0.001–0.019, 1.32–7.04 and 4.28–10.2 mg/l, respectively. The contamination factors (CF) computed for the elements indicate that with the exception of sampling site S10, the sediments are polluted with Cd. Chromium contamination in the sediments is observed at S6 and S7, where the CF values were 1.39 and 1.52, respectively. The pollution load indices (PLI) were low (<1) and ranged from 0.14 to 0.75, suggesting that the overall sediment column of the river is not polluted.     

苯蒸气在有机膨润土上的吸附动力学

本文研究了苯蒸气在溴化十六烷基三甲基胺（CTMAB）系列单阳离子有机膨润土上的吸附动力学过程。结果表明，苯蒸气在有机膨润土上的吸附符合一级动力学方程，即：r＝KvCo；在12h内，吸附反应均可达到平衡，吸附速率常数（Kv）与温度（T）成正相关，吸附反应的活化能在9．50－17．92kJ.mol^-1之间。     

磷酸活化植物基活性炭对水溶液中铅的吸附

以棉秆与互花米草为原料,采用磷酸活化法制备了低成本的植物基活性炭,通过静态实验研究了其对重金属铅的吸附性能。结果表明,在活化温度为500℃、活化时间为2 h条件下,制备的棉秆和互花米草活性炭比表面积为1 570m2/g和856 m2/g,含氧酸官能团含量分别为1.43 mmol/g和1.27 mmol/g。在25℃下,两种活性炭对重金属铅的Langmuir最大吸附量分别为119 mg/g和111 mg/g,吸附最佳pH为4.3,吸附平衡符合Freundlich方程,离子交换在吸附过程中发挥了重要作用。     

Development and Validation of the Total HUman Model for Safety (THUMS) Toward Further Understanding of Occupant Injury Mechanisms in Precrash and During Crash

Objective: Active safety devices such as automatic emergency brake (AEB) and precrash seat belt have the potential to accomplish further reduction in the number of the fatalities due to automotive accidents. However, their effectiveness should be investigated by more accurate estimations of their interaction with human bodies. Computational human body models are suitable for investigation, especially considering muscular tone effects on occupant motions and injury outcomes. However, the conventional modeling approaches such as multibody models and detailed finite element (FE) models have advantages and disadvantages in computational costs and injury predictions considering muscular tone effects. The objective of this study is to develop and validate a human body FE model with whole body muscles, which can be used for the detailed investigation of interaction between human bodies and vehicular structures including some safety devices precrash and during a crash with relatively low computational costs.

Methods: In this study, we developed a human body FE model called THUMS (Total HUman Model for Safety) with a body size of 50th percentile adult male (AM50) and a sitting posture. The model has anatomical structures of bones, ligaments, muscles, brain, and internal organs. The total number of elements is 281,260, which would realize relatively low computational costs. Deformable material models were assigned to all body parts. The muscle–tendon complexes were modeled by truss elements with Hill-type muscle material and seat belt elements with tension-only material. The THUMS was validated against 35 series of cadaver or volunteer test data on frontal, lateral, and rear impacts. Model validations for 15 series of cadaver test data associated with frontal impacts are presented in this article. The THUMS with a vehicle sled model was applied to investigate effects of muscle activations on occupant kinematics and injury outcomes in specific frontal impact situations with AEB.

Results and Conclusions: In the validations using 5 series of cadaver test data, force–time curves predicted by the THUMS were quantitatively evaluated using correlation and analysis (CORA), which showed good or acceptable agreement with cadaver test data in most cases. The investigation of muscular effects showed that muscle activation levels and timing had significant effects on occupant kinematics and injury outcomes. Although further studies on accident injury reconstruction are needed, the THUMS has the potential for predictions of occupant kinematics and injury outcomes considering muscular tone effects with relatively low computational costs.     

Rapid and simple spectrophotometric determination of persulfate in water by microwave assisted decolorization of Methylene Blue

A rapid and simple method for determination of persulfate in aqueous solution was developed. The method is based on the rapid reaction of persulfate with Methylene Blue(MB) via domestic microwave activation, which can promote the activation of persulfate and decolorize MB quickly. The depletion of MB at 644 nm(the maximum absorption wavelength of MB) is in proportion to the increasing concentration of persulfate in aqueous solution. Linear calibration curve was obtained in the range 0–1.5 mmol/L, with a limit of detection of 0.0028 mmol/L. The reaction time is rapid(within 60 sec), which is much shorter than that used for conventional methods. Compared with existing analytical methods, it need not any additives, especially colorful Fe2+, and need not any pretreatment for samples, such as p H adjustment.     

不同磁黄铁矿自养反硝化脱氮除磷作用

氮磷排放标准日趋严格,开发高效廉价脱氮除磷材料已成为研究热点.采用黄铁矿与赤铁矿在管式炉中氮气气氛下600 ℃煅烧,得到硫化赤铁矿形成的磁黄铁矿、黄铁矿热分解形成的磁黄铁矿,构建磁黄铁矿-方解石体系处理含氮磷模拟废水,对比不同方式制备的磁黄铁矿、天然磁黄铁矿、黄铁矿、硫磺脱氮除磷性能,考察不同磁黄铁矿晶体结构和结晶度差异及其对脱氮除磷影响,探究不同体系中矿物结构和微生物群落变化.结果表明：黄铁矿热分解产物以六方磁黄铁矿为主;硫化赤铁矿产物以低结晶度的单斜磁黄铁矿为主,因而表现出优异的脱氮除磷活性,氮磷去除率分别为99.8%和96.8%.铁硫化物与微生物反应产物的XRD、SEM和FE-TEM分析结果表明,微生物能有效利用磁黄铁矿进行脱氮,磷酸盐主要以FePO₄形式被去除.群落分析结果表明铁硫化物脱氮除磷体系中的主要功能菌属为Thiobacillus和 Sulfurimonas,结晶度低的单斜磁黄铁矿更有利于Thiobacillus定向富集.     

Hydrothermal-treated Pt/Al2O3 as an excellent catalyst for toluene total oxidation

The preparation of highly active supported noble metal catalysts with a low noble metal loading has always been the ultimate goal of researchers working on catalysis. Hydrothermally treated Pt/Al₂O₃ (Pt/Al₂O₃-H) exhibits better catalytic activity than that (Pt/Al₂O₃-C) treated via the conventional calcination approach. At the high space velocity of 100,000 mL/(g∙hr), the temperature that correspond to 50% toluene conversion (T₅₀) of Pt/Al₂O₃-H is 115°C lower than that of Pt/Al₂O₃-C, and the turnover frequency (TOF) value can reach 0.0756 sec⁻¹. The mechanism by which the hydrothermal approach enhances Pt/Al₂O₃ activity has been investigated. The structure associated with the high catalytic activity of Pt nanoparticles (NPs) can be retained via hydrothermal treatment. Furthermore, the support is transformed to AlO(OH) with numerous surface hydroxyl groups, which in turn can facilitate the adsorption of toluene. And the synergistic effects of Pt NPs and AlO(OH) increases the contents of Pt in oxidation state and active oxygen, which are beneficial for toluene oxidation.     

Phenol degradation in waters with high iodide level by layered double hydroxide-peroxodisulfate: Pathways and products

Recently, layered double hydroxide-peroxodisulfate (LDH-PDS) as an advanced oxidation system can effectively remove organics by the pathway of free radical. However, little has been known if there is a potential risk regarding the formation of high toxic iodine byproducts through another pathway when LDH-PDS is used in high iodide waters at coastal areas. Therefore, this study investigated phenol degradation pathways and transformation products to evaluate both removal mechanism and potential risk by LDH-PDS in high iodide waters. The results showed that in LDH-PDS system, with the degradation of PDS, phenol degraded till below detection limit in 1 hr in the presence of iodide, while PDS and phenol were hardly degraded in the absence of iodide, indicating iodide accelerated the transformation of PDS and the degradation of phenol. What is more, it reached the highest phenol removal efficiency under the condition of 100 mg/L LDH, 0.1 mmol/L PDS and 1.0 mmol/L iodide. In LDH-PDS system, iodide was rapidly oxidized by the highly active interlayer PDS, resulting in the formation of reactive iodine including hypoiodic acid, iodine and triiodide instead of free radicals, which contributed rapid degradation of phenol. However, unfortunately toxic iodophenols were detected. Specifically, 2-iodophenol and 4-iodophenol were formed firstly, afterwards 2,4-diiodophenol and 2,6-diiodophenol were produced, and finally iodophenols and diiodophenols gradually decreased and 2,4,6-Triiodophenol were produced. These results indicated that LDH-PDS should avoid to use in high iodide waters to prevent toxic iodine byproduct formation although iodide can accelerate phenol degradation.     

KOH活化小麦秸秆生物炭对废水中四环素的高效去除

活化是提高生物炭吸附性能的重要手段.以小麦秸秆为研究对象,KOH为活化剂,制备KOH活化生物炭（K-BC）,同时制备原状生物炭（BC）作为对照.对生物炭进行比表面积和孔径、元素分析、XPS、FTIR、Raman、XRD和pH_pzc等表征,考察KOH活化对生物炭理化性质的影响,并探究生物炭对水体中四环素的吸附性能和机制.结果表明,KOH活化之后生物炭的比表面积和孔体积可达996.4 m²·g^-1和0.45 cm³·g^-1.KOH活化会制造更多的碳结构缺陷,影响生物炭的官能团和表面电性.拟二级动力学和Langmuir模型可以较好地拟合生物炭吸附四环素的过程.环境温度升高能提高生物炭对四环素的吸附量.K-BC吸附四环素是自发、吸热和无序度增加的过程.K-BC对四环素的最大吸附量理论可达到491.19 mg·g^-1（实验温度为45℃）.结合吸附后生物炭的Raman、FTIR和XPS表征,发现孔隙填充和π-π作用是K-BC吸附四环素的主要机制,氢键和络合作用也发挥重要作用.此外,K-BC还具有良好的循环使用性能.综上所述,KOH活化小麦秸秆生物炭是有效和可行的,可用于废水中四环素的去除.     

Phenol depletion by thermally activated peroxydisulfate at 70°C

The ability of thermal activated peroxydisulfate (PS) of mineralizing phenol at 70 °C from contaminated waters is investigated. Phenol in concentrations of 10⁻⁴ to 5 × 10⁻⁴ M is quantitatively depleted by 5 × 10⁻³ to 10⁻² M activated PS in 15 min of reaction. However, mineralization of the organic carbon is not observed. Instead, an insoluble phenol polymer-type product is formed. A reaction mechanism including the formation of phenoxyl radicals and validated by computer simulations is proposed. High molecular weight phenolic products are formed by phenoxyl radical H-abstraction reactions. This is not the case for the room temperature degradation of phenol by sulfate radicals where sulfate addition to the aromatic ring mainly leads to the generation of hydroxycyclohexadienyl radicals leading to hydroxybenzenes and oxidized open chain products. Therefore, a change in the reaction mechanism is observed with increasing temperature, and thermal activation of PS at 70 °C does not lead to the mineralization of phenol. Thus PS activation at 70 °C may be considered a potential method to reduce the load of phenol in polluted waters by polymerization.