Effects of bicarbonate and cathode potential on hydrogen production in a biocathode electrolysis cell

A biocathode with microbial catalyst in place of a noble metal was successfully developed for hydrogen evolution in a microbial electrolysis cell （MEC）. The strategy for fast biocathode cultivation was demonstrated. An exoelectrogenic reaction was initially extended with an H2-full atmosphere to enrich Ha-utilizing bacteria in a MEC bioanode. This bioanode was then inversely polarized with an applied voltage in a half-cell to enrich the hydrogen-evolving biocathode. The electrocatalytic hydrogen evolution reaction （HER） kinetics of the biocathode MEC could be enhanced by increasing the bicarbonate buffer concentration from 0.05 mol·L-1 to 0.5 mol· L-1 and/or by decreasing the cathode potential from -0.9 V to - 1.3 V vs. a saturated calomel electrode （SCE）. Within the tested potential region in this study, the HER rate of the biocathode MEC was primarily influenced by the microbial catalytic capability. In addition, increasing bicarbonate concentration enhances the electric migration rate of proton carriers. As a consequence, more mass H＋ can be released to accelerate the biocathode-catalyzed HER rate. A hydrogen production rate of 8.44 m3. m 3. d1 with a current density of 951.6 A. m-3 was obtained using the biocathode MEC under a cathode potential of - 1.3 V vs. SCE and 0.4 mol· L-1 bicarbonate. This study provided information on the optimization of hydrogen production in biocathode MEC and expanded the practical applications thereof.     

Rice seedlings under cadmium stress: effect of silicon on growth,cadmium uptake,oxidative stress,antioxidant capacity and root and leaf structures

In this study, the effect of silicon (Si) addition on cadmium (Cd) toxicity in rice seedlings was investigated. After a series of screening experiments, 50 μmol·L^?1 of Cd and 10 μ mol·L^?1 of Si were selected. Treatment of rice seedlings with Cd (50 μ mol·L^?1) resulted in significant accumulation of this metal in roots and shoots. The data revealed that accumulation of Cd resulted in oxidative stress in rice seedlings as evidenced by increased accumulation of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA; a peroxidation product of lipids). However, addition of Si (10 μ mol·L^?1) together with Cd prevented accumulation of Cd, H₂O₂ and MDA. Antioxidant capacity was decreased by Cd but enhanced by Si addition. Cd decreased the length and frequency of root hairs, stomatal frequency, and distorted leaf mesophyll cells and vascular bundles. However, addition of Si together with Cd reduced these abnormalities. The results showed that addition of exogenous Si protected rice seedlings against Cd toxicity by preventing Cd accumulation and oxidative stress (H₂O₂ and MDA accumulation) by increasing Si accumulation and antioxidant capacity, which maintained the structure and integrity of leaf and root.     

异质结型光催化剂CuO/SnO2的制备及产氢性能

光催化降解有机废水可以实现在降解污染物同时回收清洁能源.本研究采用简单沉淀法制备了CuO/SnO2系列复合光催化剂,并用XRD、TEM对其结构进行表征.分别考察了氧化铜含量和乙醇浓度对复合材料光催化产氢性能的影响.实验结果表明,通过氧化铜与二氧化锡适当比例复合能显著提高复合材料的光催化产氢性能.复合材料48.51%CuO/SnO2的产氢性能比纯二氧化锡提高了近5倍.乙醇的浓度也对复合材料的产氢性能有较大影响,最佳的乙醇浓度为2.00 mol.L-1左右.长时间光催化产氢结果表明,每降解废水中1 kg的COD可产生氢气3724 mL.另外,对复合材料光催化分解乙醇的产氢机理也进行了分析.     

饮用水中二级胺的气相色谱快速检测方法研究

以二甲胺、二乙胺、甲乙胺、吗啉和N-甲基苄胺5种二级胺代表物质为例,分别使用气相色谱-氢火焰(GC-FID)技术和气相色谱-质谱(GC-MS)技术检测饮用水中二级胺质量浓度。结果表明,使用优化的预处理方法处理后进样分析,5种代表物质的线性范围在20~2 000μg/L,相对标准偏差(RSD)≤0.46%,最低检出限在3.18~24.19μg/L。FID比MSD具有较强优势。该方法对于直链脂肪类和杂环类的二级胺都有良好的检测效果,可用于对饮用水二级胺类物质的检测。     

我国硫化氢职业中毒现状、原因与对策

分析了硫化氢的主要存在场所,对近年来硫化氢职业中毒行业事故进行汇总并分析了易发事故行业中毒原因,介绍了当前硫化氢中毒的预防措施及我国管理政策。指出硫化氢职业中毒事故的发生与国家的监管力度、企业的重视程度以及工人的自我保护意识密切相关,相关部门加大监管力度是防治硫化氢职业中毒的一个不可忽视的环节,同时应加大力度开发防治硫化氢中毒及应急处理的技术与装备。     

毒气泄漏事故应急用个体呼吸防护用品防护效果研究

本文对毒气泄漏事故应急过程中公众常用的个体呼吸防护用品的防护效果进行了研究.针对硫化氢气体,利用无机气体防护时间检测系统,测试研究了滤毒盒、简易防护口罩、毛巾等个体防护用品在不同工况下的防护性能,试验结果表明,有毒气体浓度及温湿度两种工况条件均对个体防护用品的防护时间有较大影响,滤毒盒的防护效果远好于简易防护口罩,毛巾的防护效果较差,在此基础上进一步分析了毒气泄漏事故应急过程中个体呼吸防护用品的选择策略.本研究可为建立个体防护对策的选择方法提供基础数据和参考.     

城市生活垃圾有机组分厌氧发酵产氢和甲烷

为了提高能源回收效率,采用大米、土豆、生菜、瘦肉、花生油和榕树叶作为实验原料,模拟有机垃圾中普遍存在的淀粉、膳食纤维、蛋白质、脂肪和木质纤维类成分,进行厌氧发酵产氢以及对其剩余物厌氧发酵产甲烷.结果表明.在厌氧发酵产氢阶段,整个过程没有甲烷生成,大米、土豆、生菜、瘦肉、花生油和榕树叶的氢气产率分别为125、103、35、0、5和0 mL g-1(VS),能源回收效率分别为7.9%、6.8%、1.9%、0、0.1%和0.大米、土豆和生菜的氢气浓度分别为34%～59%、41%～56%和37%～70%,整个产氢阶段没有甲烷生成.在厌氧发酵产甲烷阶段,上述原料的甲烷产率分别为232、237、148、278、866和50 mL g-1(VS),生物气中甲烷含量分别为42%～70%、57%～71%、73%～77%、59%～73%、68%～80%和54%～74%.厌氧发酵联产氢气和甲烷整个过程上述原料的能源回收效率分别为56.3%、58.4%、28.8%、39.2%、81.2%和8.8%,总COD去除率分别为72.30%、81.70%、32.63%、47.59%、97.46%和11.29%.图4表5参35     

磁赤铁矿/多羧基有机酸体系中五氯酚的异相光化学降解

自然界广泛存在的铁氧化物与多羧基有机酸在光照条件下能够由内源自身生成活性物过氧化氢,构成异相类Fenton体系降解污染物.在实验室构建了由磁赤铁矿和多羧基有机酸组成的光化学体系,研究了五氯酚在此体系中的降解和脱氯.结果表明,五氯酚在此异相光化学体系中的降解效率受波长范围、有机酸种类和氧气的显著影响.在UV-A波长范围,五氯酚具有较高的光降解效率.草酸能够显著促进五氯酚在磁赤铁矿中的异相光降解,但柠檬酸不具有此作用.氧气是体系中生成各种含氧活性物的必要条件.五氯酚在此体系中的降解遵循一级反应动力学.最佳实验条件下,五氯酚1 h的降解率可达80%以上,脱氯率可达35%以上.对体系主要活性物过氧化氧的定量研究较好的解释了体系在各种条件下的活性差异.     

Effects of nitrate concentration on biological hydrogen production by mixed cultures

The effects of nitrate on fermentative hydrogen production and soluble metabolites from mixed cultures were investigated by varying nitrate concentrations from 0 to 10 g N/L at 35°C with an initial pH of 7.0. The results showed that the substrate degradation rate, hydrogen production potential, hydrogen yield, and average hydrogen production rate initially increased with increasing nitrate concentrations from 0 to 0.1 g N/L, while they decreased with increasing nitrate concentrations from 0.1 to 10 g N/L. The maximum hydrogen production potential of 305.0 mL, maximum hydrogen yield of 313.1 mL/g glucose, and maximum average hydrogen production rate of 13.3 mL/h were obtained at a nitrate concentration of 0.1 g N/L. The soluble metabolites produced by the mixed cultures contained only ethanol and acetic acid (HAc) without propionic acid (HPr) and butyric acid (HBu). This study used the Modified Logistic model to describe the progress of cumulative hydrogen production in batch tests. A concise model was proposed to describe the effects of nitrate concentration on average hydrogen production rate.     

过渡金属负载γ-Al2O3对HCN催化水解性能的影响

为高效催化水解净化废气中的HCN,采用等体积浸渍法改性γ-Al₂O₃制备HCN水解催化剂,考察不同金属组分及其负载量对HCN催化水解效率的影响. 结果表明:不同金属对HCN的催化水解活性依次为Cu>Cr>Fe>Zn>Ni>Co,Cu/γ-Al₂O₃系催化剂中Cu的最佳负载量为15.0%,添加1.0%的Ni有助于增加该催化剂对HCN的催化水解性能. 空速为18 000 h-1时,Cu/Ni/γ-Al₂O₃型催化剂在6 h内净化效率均能保持在91%以上,尾气中ρ(NH₃)为16.6 mg/m3. 采用X线衍射(XRD)、扫描电镜与能量色谱(SEM/EDS)、N₂物理吸附(N₂-BET)对Cu/Ni/γ-Al₂O₃系催化剂表征可知,CuO是Cu/Ni/γ-Al₂O₃系催化剂的主要活性成分,与未改性γ-Al₂O₃相比,Cu、Ni改性后催化剂微孔和中孔(孔宽为1.7~15.0 nm)的孔体积有所降低,其中直径较小的中孔对HCN的催化水解起主导作用.