Role of surface functionality in the adsorption of anionic dyes on modified polymeric sorbents

While synthetic polymeric sorbents effectively treat dye wastewaters by adsorption, the underlying mechanisms remain to be understood. This work determined the adsorption of an anionic dye by three polymers differing significantly in surface functionality. Surface functional groups of polymers were indicated in FTIR spectra and quantified by the Boehm titration. In reference to the commercial sorbent XAD-4 with a low degree of functionality, the laboratory synthesized NG-8 had primarily acidic functional groups, whereas its aminated product MN-8 had mainly basic amino groups. Electrophoresis determined the points of zero charge of 4.18, 3.23, and 4.51 for XAD-4, NG-8, and MN-8, respectively. The adsorption of Reactive Black 5 dye (RB5) by all the sorbents on a unit surface area basis increased with decreasing pH. At the same low pH (4.40), the adsorption by NG-8 was similar to that by XAD-4, indicating little influence of protonated (neutral) surface functional groups. In contrast, the adsorption by NG-8 at pH 6.05 was 75% lower than that by XAD-4, resulting apparently from the strong electrostatic repulsion between RB5 and deprotonated (negative) groups. Amination substantially enhanced RB5 adsorption by eliminating acidic groups and creating a positive charge on the surface of MN-8. The adsorptive enhancement was also achieved in the presence of CaCl2, due presumably to the neutralization of negative surface charge by Ca2+ and the RB5-Ca2+ pairing. These results manifest the important role of surface functionality in the adsorption of dyes by synthetic polymers.     

Growth and photosynthetic responses of the bloom-forming cyanobacterium Microcystis aeruginosa to elevated levels of cadmium

Effects of cadmium (Cd) on the growth and photosynthesis of the bloom-forming cyanobacterium Microcystis aeruginosa Kütz 854 were investigated. The growth was markedly inhibited when it was treated with 4 microM Cd. However, the biomass production was almost not influenced after a prolonged exposure at Cd concentrations < or = 2 microM. Chlorophyll content was more sensitive to Cd toxicity than phycobiliproteins at 0.5 microM Cd. However, the decrease of phycobiliproteins was larger than chlorophyll at the highest Cd concentration. A significant increase of F(v)/F(m) value was observed at Cd concentrations < or = 2 microM. On the other hand, when cells were treated with 4 microM Cd, F(v)/F(m) was significantly increased after 12 h of treatment but decreased after 48 h. The true photosynthesis was decreased with the increase of Cd concentration at 2 h. However, we noticed a recovery when the treatment was prolonged. After 48 h of exposure at the highest Cd concentration, photosynthetic oxygen evolution was markedly inhibited but dark respiration increased by 67%. Cellular Cd contents were augmented with the increase of Cd concentration. To our knowledge, we have demonstrated for the first time that the inhibitory site of Cd in M. aeruginosa is not located at the PSII or PSI level, but is probably situated on the ferredoxin/NADP(+)-oxidoreductase enzyme at the terminal of whole electron transport chain. We noticed also an increase of PSI activity, which is probably linked to the enhancement of cyclic electron transport around PSI. We can conclude that the increase of cyclic electron transport and dark respiration activities, and the decrease of phycobiliproteins might be adaptive mechanisms of M. aeruginosa 854 under high Cd conditions.     

Environmental contamination of mercury from Hg-mining areas in Wuchuan, northeastern Guizhou, China

Total Hg and methyl-Hg were evaluated in mine wastes, soils, water, and vegetations from the Wuchuan Hg-mining areas, Guizhou, China. Mine wastes contain high total Hg concentrations, ranging from 79 to 710 microg g(-1), and methyl-Hg from 0.32 to 3.9 ng g(-1). Total Hg in soil samples range from 0.33 to 320 microg g(-1) and methyl-Hg from 0.69 to 20 ng g(-1). Vegetations present a high average total Hg concentration of 260 ng g(-1), which greatly exceeds the maximum Hg concentration of 20 ng g(-1) recommended by the Chinese National Standard Agency for food sources. The rice samples contain elevated methyl-Hg concentrations, ranging from 4.2 to 18 ng g(-1). Stream water collected from Hg-mining areas is also contaminated, containing Hg as high as 360 ng l(-1), and methyl-Hg reaches up to 5.7 ng l(-1). Data indicate heavy Hg-contaminations and significant conversion of methyl-Hg in the study areas.     

隧道火灾危险性评估研究

某公路隧道全长4km,没有设置针对通风的辅助通道,不符合规范要求,需要对火灾危险性和危害性进行定性或定量的分析评估.本文利用性能化设计方法分析该隧道在设定火灾场景下烟气流动过程以及人员疏散情况.分析结果表明,人员安全疏散时间均小于可用的安全疏散时间,当前的防火系统、疏散设施的设置能够满足不同工况下人员安全疏散的要求.     

邯钢焦化厂1#～4#焦炉烟尘治理

介绍了邯钢焦化厂1^#～4^#焦炉采用布袋式除尘的烟尘治理方案,装煤和出焦除尘工艺流程及部分改进措施。     

微囊藻毒素-LR对鸡肝脏的氧化损伤影响

蓝藻虽然能产生有毒的生物毒素,但是也含有较高的蛋白质。为探索蓝藻饲料化利用的可能性,本文通过腹腔注射的方式研究了微囊藻毒素-LR(MC-LR)对崇仁麻鸡的半数致死剂量(LD_(50))及其对肝脏的氧化损伤。实验设计了4个剂量组(对照组、5、10和20μg·kg~(-1)MC-LR),并在1、3、12、24和48 h检测了谷胱甘肽(GSH)含量以及谷胱甘肽S-转移酶(GST)、谷胱甘肽过氧化物酶(GPX)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性变化。结果表明,MC-LR对崇仁麻鸡的LD_(50)值为34.67μg·kg~(-1)体重(bw),95%的置信限为33.51～35.83μg·kg~(-1)bw。在MC-LR的作用下,鸡肝出现了氧化应激现象。3个染毒组鸡肝中GSH含量呈现先下降而后上升恢复至正常水平的趋势,GST酶活力表现为先上升而后下降至正常值的趋势,这说明GSH和GST共同参与了鸡肝中MC-LR的解毒;鸡肝中GPX酶活性在前3小时先保持不变(除了1 h的高剂量组),随即显著上升,这说明GPX和GSH共同参与了鸡肝中过量活性氧自由基(ROS)的清除,GPX可以作为监测MC-LR引起鸡毒性作用的生物标志物。CAT酶活力表现为先显著下降(P<0.05)而后快速上升至正常值的趋势,SOD酶在整个实验期间几乎保持稳定,这可能与SOD酶活性较高所致。     

Influence of low molecular weight anionic ligands on the sorption of heavy metals by soil constituents: a review

Environmental Chemistry Letters - The sorption of heavy metals by soil constituents reduces the absorption of these pollutants by crops and vegetables, and thus limit food contamination. Low...     

Interactive effects of single,binary and trinary trace metals (lead,zinc and copper) on the physiological responses of Kandelia obovata seedlings

Environmental Geochemistry and Health - Heavy metals are considered important environmental contaminants, and their mixture toxicity on plants has complex mutual interactions. The interactive...     

五爪金龙凋落叶腐解物的化感潜力研究

采用莴苣种子为受体,测试了五爪金龙凋落叶早期腐解物的化感作用,并与其鲜叶及凋落叶的化感潜力进行了比较分析。结果如下:凋落叶40d的腐解物、鲜叶及凋落叶的水提取液均具有较强的化感潜力,并表现出低促高抑的浓度效应,在FW0.1g﹒mL-1高质量浓度下的综合化感抑制强度为凋落叶未能加土壤的腐解物>鲜叶>凋落叶加土壤的腐解物>凋落叶,而在FW0.005g﹒mL-1低质量浓度下的综合化感促进作用是凋落叶>鲜叶>凋落叶加土壤的腐解物>凋落叶未加土壤的腐解物。鲜叶的抑制强度较凋落叶的大,表明叶片在衰老过程中抑制作用减弱。凋落叶未加土壤仅在空气微生物作用下的腐解物抑制作用最强,促进作用最小,而加入土壤后在土壤微生物作用下的腐解物的抑制作用却有所减弱,抑制强度介于鲜叶和凋落叶的之间,促进作用却小于鲜叶和凋落叶,说明凋落叶腐解过程中微生物的参与对化感作用产生了复杂的影响。