Novel Al-doped carbon nanotubes with adsorption and coagulation promotion for organic pollutant removal

Al-doped carbon nanotubes (Al-doped CNTs) were prepared as a multifunctional integrated material of adsorbent and coagulant aid for organic pollutant removal from aqueous solution. It was observed that aluminum species were dispersed homogeneously on the surface of CNTs, and mainly anchored onto defect structures of the CNTs. The introduction of aluminium efficiently improved adsorption ability for methyl orange (MO) onto the CNTs, and maximum adsorption capacity calculated from the Langmuir isotherm model can reach 69.7 mg/g. The MO adsorption kinetics can be better described by the pseudo-second-order and pore diffusion kinetic models, and the diffusion of MO anions into pores of the Al-doped CNT adsorbent should be the rate-determining step. Thermodynamic analyses indicated that the adsorption of MO onto Al-CNTs-2.0 was endothermic and spontaneous. Moreover, adsorption capacity for MO on the Al-doped CNTs was evidently dependent on the CNT dose, solution pH and adsorbent dose. From the perspective of low-cost and multifunctional, suspension obtained during the Al-doped CNT adsorbent preparation, was tested as coagulant to remove humic acid (HA). A significant observation is that the suspension exhibited an excellent coagulation performance for HA, because abundant aluminous polymer and Al-doped CNTs existed in the suspension.     

Adsorption–desorption behavior of atrazine on agricultural soils in China

Adsorption and desorption are important processes that affect atrazine transport,transformation,and bioavailability in soils.In this study,the adsorption–desorption characteristics of atrazine in three soils(laterite,paddy soil and alluvial soil) were evaluated using the batch equilibrium method.The results showed that the kinetics of atrazine in soils was completed in two steps:a"fast" adsorption and a "slow" adsorption and could be well described by pseudo-second-order model.In addition,the adsorption equilibrium isotherms were nonlinear and were well fitted by Freundlich and Langmuir models.It was found that the adsorption data on laterite,and paddy soil were better fitted by the Freundlich model;as for alluvial soil,the Langmuir model described it better.The maximum atrazine sorption capacities ranked as follows:paddy soil alluvial soil laterite.Results of thermodynamic calculations indicated that atrazine adsorption on three tested soils was spontaneous and endothermic.The desorption data showed that negative hysteresis occurred.Furthermore,lower solution pH value was conducive to the adsorption of atrazine in soils.The atrazine adsorption in these three tested soils was controlled by physical adsorption,including partition and surface adsorption.At lower equilibrium concentration,the atrazine adsorption process in soils was dominated by surface adsorption;while with the increase of equilibrium concentration,partition was predominant.     

Effects of plant diversity on greenhouse gas emissions in microcosms simulating vertical constructed wetlands with high ammonium loading

Wastewater with relatively high nitrogen concentrations is a major source of nitrous oxide (N₂O) and methane (CH₄) emissions and exerts multiple stresses on the environment. Studies have shown that plant diversity plays an important role in ecosystem functioning. However, the effects of plant species diversity on CH₄ and N₂O emissions under high ammonium (NH₄⁺-N) loading rates remain unclear. In this study, a microcosm experiment simulating vertical constructed wetlands supplied with high NH₄⁺-N water levels was established. The treatments included four species richness levels (1, 2, 3, 4) and 15 species compositions. There was no significant relationship between species richness and N₂O emissions. However, N₂O emissions were significantly reduced by specific plant species composition. Notably, the communities with the presence of Rumex japonicus L. reduced N₂O emissions by 62% compared to communities without this species. This reduction in N₂O emissions may have been a result of decreased N concentrations and increased plant biomass. CH₄ emissions did not respond to plant species richness or species identity. Overall, plant species identity surpassed species richness in lowering N₂O emissions from constructed wetlands with high NH₄⁺-N water. The results also suggest that communities with R. japonicus could achieve higher N removal and lower greenhouse gas emissions than other wetland species.     

Coupled relationships among anammox, denitrification, and dissimilatory nitrate reduction to ammonium along salinity gradients in a Chinese estuarine wetland

Salinization in estuarine wetlands significantly alters the balance between their nitrogen (N) removal and retention abilities but these processes have not yet been characterized effectively. In the present study, the potential rates of sediment denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) were mapped using N isotope tracing methods along salinity gradients across the Yellow River Delta wetland (YRDW) in China. The contribution of anammox to total dissimilatory N transformations in YRDW was merely 6.8%, whereas denitrification and DNRA contributed 52.3% and 40.9%, respectively. The potential rate of denitrification (5.82 μmol/kg/h) decreased significantly along salinity gradients and markedly exceeded DNRA potential rate (2.7 μmol/kg/h) in fresh wetlands, but was lower than that of DNRA in oligohaline wetlands (3.06 and 3.18 μmol/kg/h, respectively). Moreover, a significantly positive relationship between salinity and DNRA/denitrification was obeserved, indicating that increased salinity may favor DNRA over denitrification. Furthermore, total sulfur (TS) content and ratio of total organic carbon to total nitrogen (C/N) increased with the salinity gradient and showed evident positive relationships with the DNRA/denitrification ratio. In this study, we proved that increased salinization resulted in the dominance of DNRA over denitrification, possible through the addition of S and alteration of the C/N in estuarine wetlands, leading to increased N retention in estuarine wetlands during salinization, which would enhance the eutrophication potential within wetlands and in downstream ecosystems.     

泗县数字石英摆倾斜仪异常与地震关系初析

本文概述了泗县地震台数字石英摆倾斜仪的工作原理,用已记录到的震例,初步分析研究了不同方向、不同区域发生的中强地震、在震前,所出现的异常波对该套仪器的不同影响,对研究未来郯庐断裂带附近的中强地震,具有一定的现实意义。     

我国电子废弃物回收处理现状及建议

电子产业的迅速发展,电子电气产品更新速率急剧攀升,随之来的就是电子废弃物的与日俱增.目前中国已成为继美国之后的世界第二大电子垃圾生产国,每年生产超过230万吨电子垃圾.且电子废弃物回收处理现状不乐观,大部分废弃电子电气产品被走街串巷的个体户回收后简单地拆解掉,污染了空气、水和土壤,也给人类健康带来一定威胁.面对当前出现的问题,本文在研究参考国外电子废弃物回收处理经验的基础上给出几点建议,探索如何妥善回收和处理电子废弃物.     

新型环保塑料制品CT的应用前景

解决白色垃圾污染问题的根本在于推广应用新型环保塑料制品。CT塑料制品的生产、使用和最终处理过程都符合环保要求，是的一次性食品仪器容器替代品。     

无缝紫铜管冷弯开裂的原因分析

在废品分析的基础上，通过一系列工艺试验表明无缝紫铜管冷弯开裂分为韧性和脆性2种，热处理温度及预先冷变形量不当是造成冷弯开裂的主要原因。     

基于罚函数法和Backofen模型的刚粘塑性有限元列式推导

讨论了刚粘塑性有限元法，对其基于罚函数法和Backofen模型的求解列式进行了详细的推导。     

Recycling of valuable chemicals through the catalytic decomposition of phenol tar in cumene process

The base catalyst LZ-2, which was the mixture of CaO and Na–NaOH/Al₂O₃·3H₂O, was chosen for the decomposition of phenol tar to generate valuable chemicals. The selectivity of LZ-2 for dimethyl phenyl carbinol, α-methyl styrene dimer and cumenyl phenol was 100%, 100% and 98%, respectively. Under the optimum operating conditions of catalyst 2.5 wt%, operating temperature 603.15 K and decomposition time 3.5 h, decomposition ratios of cumenyl phenol and dimethyl phenyl carbinol were 98.7% and 99.97%, respectively. In addition, the experimental repeatability demonstrated that the total yield of valuable chemicals still reached 90.1% after the catalyst being used five times. Mass and energy balance indicated that the catalytic decomposition was a high potential for the recycling of chemicals from phenol tar.