Preparation of Acid-Activated Montmorillonite and Its Application

The natural Na-type montmorillonite (Na-MMT) was treated with HNO₃ to obtain acid-activated montmorillonite (acid-MMT). The materials were characterized by XRD, XRF, SEM, and N₂ adsorption–desorption at low temperature. Results indicated that the structure and textural properties of MMT were significantly changed via acid activation. Meanwhile, the potential use of acid-MMT as adsorbent for the removal of phenol from aqueous solution was evaluated. Important parameters which affected adsorption, such as contact time, pH of solution, and mass of acid-MMT had been investigated. The removal of phenol was decreased with the increase of pH value, and increased with the increase of contact time and mass of acid-MMT. The equilibrium data in aqueous solutions were well represented by the Freundlich isotherm.     

Bioaccumulation of chromium and its effects on reproduction in Neanthes arenaceodentata (polychaeta)

The levels of hexavalent chromium (Cr VI) that caused diminished reproductive ability in the polychaete Neanthes arenaceodentata were determined. Changes in numbers of offspring and time of spawning caused by Cr VI at 1 to 38 ug/litre during two generations of exposure (309 days) were measured. Time to spawning was unaffected but it was found that reductions in numbers of offsprings occurred at 16 to 38 μl/litre. Bioaccumulation of chromium was also measured and found to be proportional to exposure levels; however, a direct relationship between tissue concentration and reduced numbers of offspring could not be established.     

Effects of hexavalent and trivalent chromium on the reproduction of Neanthes arenaceodentata (polychaeta)

This study compared the very different responses of the polychaete Neanthes arenaceodentata to chronic exposure of hexavalent (Cr VI) and trivalent (Cr III) chromium. The polychaetes were exposed to sublethal concentrations of Cr VI and Cr III for periods of 440 days (three generations) and 293 days (two generations), respectively. In the Cr VI test, polychaete reproduction ceased at 100 μg litre^?1, and the number of young produced was reduced at the 12·5 to 50 μg litre^?1 levels and above. However, polychaetes that lived in Cr III during the test showed no adverse effects in 50400 μg litre^?1.     

Seasonal changes in speciation of dissolved chromium in the surface Sargasso Sea

The concentrations of Cr (III) and Cr (VI) were determined in the upper 500 m of the Sargasso Sea at different times of the year. Total Cr concentrations ranged between 2.5 and 4.5 nM, and the predominant species of Cr was the thermodynamically favoured Cr (VI). Cr (III) concentrations were greatest during periods of high biological activity, as indicated by strong correlations between the ratio of Cr (III):Cr (VI) and both bacterial biomass and primary productivity. Whilst the oxidation state varied substantially over the seasonal cycle, the upper water column inventory of Cr was relatively constant. The long residence time of Cr in the surface Sargasso Sea estimated with respect to atmospheric inputs (1410–2240 years) is indicative of the largely conservative behaviour of this element. Deep particle fluxes of Cr are similar or somewhat greater than atmospheric inputs, and this downward flux of Cr is well correlated with organic carbon fluxes from the upper Sargasso Sea. The long residence time coupled with the seasonal changes in oxidation state of Cr implies rapid seasonal recycling of Cr between redox states, with only slow removal via particles to the deep ocean at this site.     

掺杂氮、硫的石墨烯材料对磺胺类抗生素的吸附行为

水环境中抗生素污染日益严重。本研究制备了掺杂氮、硫的新型石墨烯材料(GO-NS),研究了其对磺胺类抗生素(Sulfonamides,SAs)的吸附和去除能力,并阐明吸附机制。研究发现,GO-NS对SAs的最大吸附量达100.26 mg·g^-1,吸附能力优于多层石墨烯(Multilayer graphene,MG)和还原氧化石墨烯(Reduced graphene oxide,rGO)这两种传统石墨烯材料。疏水作用和氢键作用是GO-NS吸附SAs的主要机理。相比于MG和rGO,GO-NS适用的pH范围最广,在pH=2~10范围内均具有较强的吸附效果,并且离子强度和腐殖酸(Humicacid,HA)的加入提升了GO-NS的吸附性能。此外,GO-NS仅通过短时间超声可实现有效的剥离分散,使吸附量增加。故该新型石墨烯材料GO-NS具有优越地吸附SAs的能力和广泛的环境适应性,可作为治理水环境中SAs污染的一种有效吸附剂。     

Evaluation of the chemical forms of plutonium in seawater

Thermodynamic considerations based on existing data from various laboratory studies of plutonium species in aqueous solution are used to predict the speciation of this radioactive pollutant in seawater. Oxidation-reduction data for plutonium suggest that Pu(VI) should be very dominant in seawater solution compared to Pu(IV), and that Pu(III) and Pu(V) should be absent. The disproportionation reactions and the alpha reduction mechanism are probably of no consequence to the oxidation state in seawater. However, the irreversible hydrolysis of Pu⁴⁺ and the associated formation of polymeric Pu(OH)₄ colloids are important mechanisms of speciation control and plutonium removal to sediments, by adsorption onto suspended matter. Stability constants for plutonium complexation with inorganic ligands in seawater suggest that Pu(VI) dissolved in seawater will be dominantly PuO₂CO₃OH⁻.The theoretical predictions of plutonium speciation and behaviour in seawater are compared to the only available data on plutonium speciation in seawater (Nelson and Lovett, 1978). Good agreement between the predictions and field observations was obtained, within the limitations imposed by the scarcity of data on this subject.     

溶液中褐藻胶低聚糖在活性炭上的吸附特性与机制研究

本文研究了不同pH、反应时间、温度、初始糖浓度条件下溶液中褐藻胶低聚糖(AOS)在活性炭上的吸附性能及其吸附动力学和热力学机制。结果表明,溶液pH对活性炭吸附AOS具有重要影响,随pH降低, AOS在活性炭上的吸附增强, pH=1时吸附量可达0.116 g/g。吸附反应在5 min内迅速发生, 60 min后达到吸附平衡。活性炭吸附AOS符合准二级吸附动力学过程。吸附热力学研究表明,吸附过程为自发的放热反应,吸附等温线符合Langmuir模型。综上,吸附过程为单分子层均相吸附,降低pH、低温有利于AOS在活性炭上的吸附。     

负载镧的EGDE交联壳聚糖微球对氟离子的吸附平衡与吸附动力学

采用负载镧的乙二醇二缩水甘油醚(EGDE)交联壳聚糖微球对含氟水进行吸附处理.该吸附剂的适宜工作条件为:温度30～50℃,pH值7.0,吸附时间30 min.用吸附等温线描述了F-在吸附剂上的吸附平衡,并用动力学模型研究了其吸附动力学机制.结果表明:吸附剂对F-的吸附平衡符合Langmuir吸附等温线和Freundlich吸附等温线,饱和吸附容量为25.7mg·g-1;该吸附剂对F-的吸附既包含化学吸附又包含物理吸附过程,以单分子层的化学吸附为主;吸附动力学符合拟二级动力学方程,吸附过程受化学吸附机理的控制,颗粒内扩散和液膜形成的边界层是其限速步骤.     

Adsorption of acid fuchsin onto the chitosan–montmorillonite composite

The chitosan–montmorillonite composites (CTS–MMT) were prepared by CTS in combination with Na-type montmorillonite (Na-MMT). The composites were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The effects of initial pH value of the solution, adsorbent dose, the mass ratio of CTS to Na-MMT, the adsorption temperature, and contact time on acid fuchsin (AF) removal efficiency were investigated. The results indicated that the CTS could be successfully intercalated into the interlayers of Na-MMT. With the increase in content of CTS, some of them may be distributed on the surfaces of the clay and the AF removal efficiency can reach 80.2% using CTS–MMT as adsorbent to treatment AF wastewater (the AF concentration 20?mg/L) under the condition of pH, 5; adsorbent dose, 5?g/L; the mass ratio of CTS to Na-MMT, 0.25:1; adsorption temperature, 40°C; and contact time, 90?min. Meanwhile, it was shown that the adsorption processes were better fitted by pseudo-second-order model and the Freundlich model.     

Trace element diagenesis in pyrite-rich sediments of the Achterwasser lagoon, SW Baltic Sea

The early diagenesis of trace elements (V, Cr, Co, Cu, Zn, As, Cd, Ba, U) in anoxic sediments of the Achterwasser, a shallow lagoon in the non-tidal Oder estuary in the Baltic Sea, was investigated in the context of pyrite formation. The dissolved major redox parameters show a two-tier distribution with transient signals in the occasionally re-suspended fluid mud layer (FM) and a permanently established diagenetic sequence in the sediment below. Intense microbial respiration leads to rapid depletion of O₂ within the uppermost mm of the FM. The reduction zones of Mn, Fe and sulfate overlap in the FM and in the permanently anoxic sediment section which appears to be a typical feature of estuarine sediments, under low-sulfate conditions. Degrees of pyritization (DOP) range from 50% in the FM to remarkably high values > 90% at 50 cm depth. Pyrite formation at the sediment surface is attributed to the reaction of Fe-monosulfides with intermediate sulfur species via the polysulfide pathway. By contrast, intense pyritization in the permanently anoxic sediment below is attributed to mineral growth via adsorption of aqueous Fe-sulfide complexes onto pyrite crystals which had originally formed in the surface layer.The studied trace elements show differential behavior patterns which are closely coupled to the diagenetic processes described above: (i) Zn, Cu and Cd are liberated from organic matter in the thin oxic layer of the sediment and diffuse both upwards across the sediment/water boundary and downwards to be trapped as monosulfides, (ii) V, Cr, Co and As are released during reductive dissolution of Mn- and Fe-oxyhydroxides, (iii) U removal from pore water occurs concomitantly to Fe reduction in the FM and is attributed to reduction of U(VI) to U(IV), (iv) the Ba distribution is controlled by reductive dissolution of authigenic barite in the sulfate reduction zone coupled with upward diffusion and re-precipitation. The incorporation of trace elements into pyrite is most intense for Co, Mn and As, intermediate for Cu and Cr and little to negligible for U, Zn, Cd, V and Ba. The observed trend is largely in agreement with previous studies and may be explained with differing rates for ligand exchange. Slow and fast ligand exchange and thus precipitation kinetics are also displayed by downcore increasing (Mn, Cr, Co and As) or constantly low (Zn, Cu, Cd) pore water concentrations. The downward increasing degrees of trace metal pyritization (DTMP) for Co, Cu, Zn and As are, in analogy to pyrite growth, assigned to adsorption of sulfide complexes or As oxyanions onto preexisting pyrite minerals.     

Geotechnical sealing material for coastal disposal facility for soils and wastes contaminated by radioactive cesium

Safe disposal of wastes produced due to the process of decontamination in and around Fukushima No. 1 nuclear power plant is an urgent requirement. The purpose of this study was to develop a sealing material which can be used as an engineered barrier for a final disposal facility for the soils and wastes contaminated by radioactive cesium. The analyses conducted based on 4-m-thick sealing layer revealed that the hydraulic conductivity of the sealing material needs to be kept below 5.0?×?10^?10?m/s to avoid the seepage of contaminants below the environmentally safe limits. Sealing material was developed using marine clay–bentonite mixture and the engineering characteristics were examined. The results of laboratory experiments showed that, with the addition of bentonite, the hydraulic conductivity equal to or less than 5.0?×?10^?10?m/s was achieved when the effective consolidation stress is equal to or more than 27?kPa. From the tests for adsorption properties for cesium, it was found that the sealing material showed the significant capacity of adsorption for cesium in seawater. It was concluded that the construction of waste disposal facility on the sandy seafloor is feasible using the sealing layer proposed in this study.     

Uptake and release of 51Cr(VI) and 51cr(III) by Barnacles (Balanus sp)

Barnacles (Balanus sp) were used to examine the uptake and release of chromium-51 added to sea water in two different valence states, ⁵¹Cr(VI) and ⁵¹Cr(III).Hexavalent chromium-51 (sodium chromate) forms a true ionic solution in filtered sea water and barnacles were able to accumulate chronium in soft tissues 543 times the levels found in sea water. The experiment showed that incorporated Cr(VI), is released to the water in such way that only 20%% of maximum uptake was lost by the organisms after 26 days. Addition of the hexavalent form to non filtered sea water showed that 2% of the total radioactivity was attached to the suspended particles. Here again chromium is mainly concentrated in soft tissues, showing a concentration factor of 380 related to total chromium available in aquarium (solution + suspended particles). From the total radioactivity incorporated by the organisms, 20 % was released after 56 days in the clearance experiment.Chromium, as trivalent chromic chloride, when added to sea water precipitates and is quickly removed from the water by the filter activity of the barnacles. Unlike the hexavalent form, trivalent chromium is not concentrated in soft tissues of the barnacles and is quickly released to the water through the organisms digestive system.     

Pu(V) as the stable form of oxidized plutonium in natural waters

This work presents analytical evidence supporting the proposition that Pu(V) is the sole or predominant form of oxidized plutonium in natural waters. Two independent methods, the selective adsorption of Pu(VI) by silica gel, and the somewhat less selective coprecipitation of Pu(V) with calcium carbonate, were developed to separate Pu(V) from Pu(VI). Measurements of ambient plutonium in several natural waters by these methods found only Pu(V). In laboratory tracer studies, Pu(VI) was shown to be highly unstable in dilute bicarbonate solution and in Lake Michigan water, reducing in first-order fashion to Pu(V).     

Chromium in Cascadia Basin,northeast Pacific Ocean

Water samples from a Pacific Ocean basin have been analysed for a number of forms of chromium. Total Cr, almost entirely as dissolved Cr(VI), steadily increases with depth and correlates most closely with silica data. Mid-depth regeneration of Cr is suggested by a multiple regression equation which includes Cr(total), silica and phosphate data.The release of Cr and silica from bottom sediments is apparent as the continental margin is approached. Box model transport calculations suggest that a Cr flux from the sediments on the order of 100 nmol Cr m^?2 day^?1 could be balanced by horizontal and vertical eddy diffusion coefficients of 10⁶ and 10 cm² s^?1, respectively, and by horizontal and vertical advection rates of 10^?2 and 10^?4 cm s^?1, respectively.     

酰胺醚类化合物缓蚀行为的理论研究

应用密度泛函(DFT)理论,在M062X/6-311+G(d,p)水平下对丙烯酰胺基甲基醚(AAME)和N-羟甲基丙烯酰胺(N-MAM)在真空和溶剂条件下模拟其缓蚀行为。结果表明,N-MAM与AAME分子的活性位点主要分布在N、O杂原子上,同等条件下AAME分子的缓蚀性能优于N-MAM,溶剂化效应使分子的缓蚀性能比在真空条件下得到了提高。通过分子动力学模拟,AAME在真空和溶剂条件中,在Fe(110)面的吸附能分别为486.39和789.44 kJ/mol,均大于相同条件下N-MAM的吸附能(228.85和449.84 kJ/mol),表现出更优的缓蚀效果。多个N-MAM或AAME分子可通过分子间氢键作用在Fe(110)面有序自组装铺展成膜。     

一株六价铬还原菌的分离及其用于含铬废水处理的初步研究

从济南裕兴化工厂含铬废水排放口及小清河等处的污泥中分离到一株属于假单胞菌属的杆菌。该菌在厌氧条件下以Cr(Ⅵ)作为电子受体,有机物作为电子供体,具有很强的还原铬酸盐、重铬酸盐的能力。研究了该菌的生长以及还原Cr(Ⅵ)的最适条件,并以生活污水为基质进行了实际净化含铬废水的实验,发现该菌生长迅速,还原Cr(Ⅵ)速率高,生态稳定性好,可用于含铬废水的净化。     

Chromium(VI) distributions in the Arctic and the Atlantic Oceans and a reassessment of the oceanic Cr cycle

Chromium(VI) concentrations ranging between 3.0 and 6.1 nmol l⁻¹ and 3.1 and 7.3 nmol l⁻¹ were found in the Arctic and Atlantic Oceans, respectively. The vertical profiles show modest depletion of chromium(VI) in surface waters, but poor overall correlations between Cr(VI) and nutrient profiles. Given that Cr(VI) is the dominant oxidation state of chromium in open-ocean waters, these data are combined with literature data to reassess the distribution of Cr in oceanic waters. It is concluded that while Cr shows some characteristics of both “recycled” and “accumulated” vertical profiles, it does not fall clearly within either group.     

Evidence of gas hydrate accumulation and its resource estimation in Andaman deep water basin from seismic and well log data

2D and 3D seismic reflection and well log data from Andaman deep water basin are analyzed to investigate geophysical evidence related to gas hydrate accumulation and saturation. Analysis of seismic data reveals the presence of a bottom simulating reflector (BSR) in the area showing all the characteristics of a classical BSR associated with gas hydrate accumulation. Double BSRs are also observed on some seismic sections of area (Area B) that suggest substantial changes in pressure–temperature (P–T) conditions in the past. The manifestation of changes in P–T conditions can also be marked by the varying gas hydrate stability zone thickness (200–650 m) in the area. The 3D seismic data of Area B located in the ponded fill, west of Alcock Rise has been pre-stack depth migrated. A significant velocity inversion across the BSR (1,950–1,650 m/s) has been observed on the velocity model obtained from pre-stack depth migration. The areas with low velocity of the order of 1,450 m/s below the BSR and high amplitudes indicate presence of dissociated or free gas beneath the hydrate layer. The amplitude variation with offset analysis of BSR depicts increase in amplitude with offset, a similar trend as observed for the BSR associated with the gas hydrate accumulations. The presence of gas hydrate shown by logging results from a drilled well for hydrocarbon exploration in Area B, where gas hydrate deposit was predicted from seismic evidence, validate our findings. The base of the hydrate layer derived from the resistivity and acoustic transit-time logs is in agreement with the depth of hydrate layer interpreted from the pre-stack depth migrated seismic section. The resistivity and acoustic transit-time logs indicate 30-m-thick hydrate layer at the depth interval of 1,865–1,895 m with 30 % hydrate saturation. The total hydrate bound gas in Area B is estimated to be 1.8 × 10¹⁰ m³, which is comparable (by volume) to the reserves in major conventional gas fields.     

Chromium(III) — chromium(VI) interconversions in seawater

The stable form of dissolved chromium in oxygenated seawater is Cr(VI). But Cr(III)-species are also present at an analytically significant level. It is shown that Cr(III) is oxidized only slowly by dissolved oxygen, and that manganese oxide is a strong catalyst for such oxidation. However, the low oceanic concentration of suspended MnO₂ impedes the conclusion that the former process is quantitatively less important than the latter one. The distribution of dissolved chromium among Cr(VI)- and Cr(III)-species is probably kinetically controlled.