Visible-light-driven heterostructured g-C3N4/Bi-TiO2 floating photocatalyst with enhanced charge carrier separation for photocatalytic inactivation of Microcystis aeruginosa

• Bi doping in TiO₂ enhanced the separation of photo-generated electron-hole. • The performance of photocatalytic degradation of MC-LR was improved. • Coexisting substances have no influence on algal removal performance. • The key reactive oxygen species were h⁺ and ^•OH in the photocatalytic process. The increase in occurrence and severity of cyanobacteria blooms is causing increasing concern; moreover, human and animal health is affected by the toxic effects of Microcystin-LR released into the water. In this paper, a floating photocatalyst for the photocatalytic inactivation of the harmful algae Microcystis aeruginosa (M. aeruginosa) was prepared using a simple sol-gel method, i.e., coating g-C₃N₄ coupled with Bi-doped TiO₂ on Al₂O₃-modified expanded perlite (CBTA for short). The impact of different molar ratios of Bi/Ti on CBTA was considered. The results indicated that Bi doping in TiO₂ inhibited photogenerated electron-hole pair recombination. With 6 h of visible light illumination, 75.9% of M. aeruginosa (initial concentration= 2.7 × 10⁶ cells/L) and 83.7% of Microcystin-LR (initial concentration= 100 μg/L) could be removed with the addition of 2 g/L CBTA-1% (i.e., Bi/Ti molar ratio= 1%). The key reactive oxygen species (ROSs) in the photocatalytic inactivation process are h⁺ and ^•OH. The induction of the Bi⁴⁺/Bi³⁺ species by the incorporation of Bi could narrow the bandgap of TiO₂, trap electrons, and enhance the stability of CBTA-1% in the solutions with coexisting environmental substances.     

Enhanced nitrification in integrated floating fixed-film activated sludge (IFFAS) system using novel clinoptilolite composite carrier

Novel carriers with favorable electrophilicity and hydrophilicity were prepared. Novel carriers had the capability of nitrification-enhancing. NH₄⁺-N removal efficiency of IFFAS process rose up to 20% with novel carriers. Nitrosomonadales and Nitrospirales were identified as the functional nitrifiers. The population of Nitrospirales increased by 4.51%. The integrated floating fixed-film activated sludge (IFFAS) process is an ideal preference for nitrification attributing to the longer sludge age for nitrifiers. However, as the core of this process, conventional carriers made of polymer materials usually exhibit negative charge and hydrophobicity on the surface, which is unbeneficial to nitrifying biofilm formation. In this study, novel clinoptilolite composite carriers with favorable hydrophilicity, positive charge and nitrification-enhancing capability were made and implemented in IFFAS system. In comparison with conventional carriers, the novel clinoptilolite composite carriers displayed positive charges on the surface (11.7±1.1 mV, pH 7.0) with increased hydrophilicity (surface contact angle dropped to 76.7°). The novel-carriers-based reactors achieved significantly better NH₄⁺-N removal efficiency at different influent concentrations, dissolved oxygen (DO) levels and shock loads (NH₄⁺-N removal efficiency rose up to 20% comparing with the control reactors filled with polyethylene (PE) carriers or activated sludge). High-throughput sequencing (HTS) results indicated the novel clinoptilolite composite carriers provided favorable niche for more types of bacteria, especially for Nitrosomonadales and Nitrospirales (the functional nitrifiers in the system). The population of Nitrospirales increased by 4.51% by using novel clinoptilolite composite carriers comparing with using PE carriers, which ensured enhanced nitrification process. This study was expected to provide a practical option for enhancing wastewater nitrification performance with the novel clinoptilolite composite carrier.     

不同填料类型污染源水生物预处理的比较

中国南方水质性缺水地区污染广泛采用生物预处理工艺净化污染水源,微生物载体以固定式填料和流化型填料为主.为考察2种类型填料的运行效能和微型生物多样性,以长江三角洲地区的污染源水为例,利用现场生产性试验和连续流中试研究了半软性弹性立体填料和悬浮填料的主要污染物去除效能、填料的积泥和冲洗、微型动物的生长和分布规律.研究结果表明,夏秋季相同源水水质和运行参数等条件下,悬浮填料和弹性填料对NH3-N的平均去除率分别为80%和65%左右, CODMn的去除率分别为18%和16%左右;悬浮填料上的微型动物种类和数量均低于固定式弹性立体填料,且少见群居性微型动物.生产性装置运行结果表明,源水水质相对较差的条件下,悬浮填料对NH3-N和CODMn的去除率分别比弹性填料高5%~10%;悬浮填料没有出现群居性微型动物大量生长现象,无需定期反冲洗;固定式弹性填料的某些区域出现苔藓虫等群居性微型动物大量生长现象,且积泥严重,需定期反冲洗,甚至使用高压水枪强制冲洗.流化型悬浮填料更有利于污染源水生物预处理工程应用.     

常用高分子装饰材料的燃烧特性

利用先进的锥型量热计研究了五种常用的高分子装饰材料在暴露于不同辐射热通量条件下的燃烧性能,以及用氧指数测定仪测量了这些材料的氧指数,并将这两种方法的实验结果进行了对比。     

Impacts of mussel dredging on sediment phosphorus dynamics in a eutrophic Danish fjord

Effects of mussel dredging on sediment metabolism (oxygen uptake and sulfate reduction rates) and phosphorus dynamics (flux across sediment-water interface and sequential extraction) were examined in Limfjorden (Denmark) during spring (May) and summer (August). Sediment samples were taken during mussel dredging and in addition an experimental simulation of the dredging was performed to investigate short-term changes in phosphorus (P) dynamics. Iron-bound P was reduced by up to 2/3 in the surface layer in the dredging track (from 31 to 8?mmol?P?m^?2), whereas the dissolved P-pools and less reactive particulate pools were not affected by dredging. Sediment oxygen consumption was enhanced immediately after dredging, but returned to the initial level after 4 days (20–40?mmol?m^?2?d^?1). The enhanced consumption was attributed to reoxidation of reduced compounds released during dredging. Sulfate reduction rates were high in the area (13–15?mmol?m^?2?d^?1) and sulfides competed with P for oxidized iron resulting in low iron-bound pools in the area (<4% of total P pools). Sulfate reduction rates were stimulated by the resuspension of sediments, especially in August, where a subsurface maximum was found, possibly due to a mixing of labile organic matter into these layers. In contrast sulfate reduction rates were reduced in the dredging track due to removal of labile organic matter from the surface layers. The loss of P during dredging was to some extent counteracted by regeneration of iron-bound P pools in the surface layers. The release of P due to mussel dredging was estimated to be in the same order of magnitude as the annual loading from the catchments and point sources to Limfjorden.     

氧气瓶爆炸事故性质认定及原因分析

在事故现场勘查的基础上,通过材料成分、力学性能、金相组织与断口、碎片附着物以及充装气体成分等检测和试验,结合爆炸能量的理论估算,对一起氧气瓶爆炸事故的性质和原因进行了系统分析。结果表明：瓶体存在的脱碳、微裂纹及局部腐蚀凹坑这些类裂纹缺陷在爆炸产生的巨大载荷下诱发了气瓶的开裂及扩展,其宏观断口表现为韧脆交替的快速断裂特征。依据碎片抛射距离估算的气瓶实际爆炸能量远大于其发生物理爆炸所产生的能量,气瓶爆炸属于化学爆炸。气瓶内存在的碳烃类油脂有机物以及瓶阀关闭时产生的摩擦热或静电火花是氧气瓶发生化学爆炸的直接原因。     

浅谈顶吹氧气转炉炼钢湿法除尘的脱硫功能

立足鞍钢生产实际,肯定了氧气转炉炼钢湿法除尘的降温功能与作用、除尘功能与作用,揭示了氧气转炉炼钢湿法除尘装置在碱性洗涤溶液(pH=12.0～13.5)作用下的潜在脱硫功能与作用(脱硫率99.56%),为“分体组合”选型湿法“降温除尘脱硫”设备处理高温含硫气体提供了科学依据。     

华北稳定塘氧平衡的研究

溶解氧(DO)是氧化塘内有机物降解的主要动力,本文介绍了华北稳定塘中的妤氧塘和强化塘进行污水妤氧处理所需氧的来源主要是浮游藻类光合放氧。在春季和秋季藻类产的氧可占水体溶解氧总来源的80％左右,氧的消耗是以“水呼吸”耗氧为主,“泥呼吸”耗氧为次。从氧平衡的角度阐述了各塘有机物降解与藻类产氧、生物耗氧的关系。      

复合絮凝剂Al2(SO4)3+PAM处理生活污水中CODCr和浊度的实验研究

研究絮凝剂硫酸铝Al2(SO4)3与助凝剂聚丙烯酰胺(PAM)联合处理生活污水的效果。研究表明:Al2(SO4)3与PAM联用比单独用Al2(SO4)3处理生活污水效果更好;Al2(SO4)3 PAM对生活污水CODCr和浊度具有良好的去除能力;当投加1:1的50mg/L的Al2(SO4)3 0.5mg/L的PAM,调节水体pH=7时,处理效果最理想,CODCr去除率可达95.8%,浊度去除率可达97.5%。为复合絮凝剂Al2(SO4)3 PAM处理生活污水的应用提供了有价值的参考依据。     

Cr3+离子掺杂对负载TiO2薄膜光催化活性的影响

以钛酸丁酯和CrCl3·6H2O为原料,采用溶胶-凝胶法在钛片、玻璃、釉面瓷砖、陶瓷、不锈钢和铝片六种载体上制备了Cr3 掺杂TiO2薄膜。讨论了不同Cr3 掺杂浓度下,不同载体表面上制备的TiO2薄膜对甲基橙脱色率的影响。试验结果表明:Cr3 对TiO2薄膜的掺杂效果与载体的类型密切相关,并且不同载体其Cr3 掺杂的最佳浓度也不同。Cr3 掺杂后,TiO2薄膜光催化活性提高最大的是釉面瓷砖,其次是玻璃、钛片、铝片、陶瓷,最差的是负载不锈钢。