电凝聚法处理含重金属综合废水的试验研究

本试验采用自行设计的电凝聚污水处理装置,对含重金属污染物的综合废水进行处理,废水处理能力为1m3/h。结果显示:电凝聚法处理后的出水水质达到污水综合排放标准,对铜、锌、铬等重金属的平均去除率在94%以上,乳化油的平均去除率在99%以上,COD的平均去除率在92%以上;试验装置对进水的流量负荷具有较好的耐冲击性;经济分析结果为,电耗和运行费用分别为1.1kw.h/m3和0.65元/m3。     

Graphitic carbon nitride-based photocatalysts in the applications of environmental catalysis

Semiconductor photocatalytic technology has shown great prospects in converting solar energy into chemical energy to mitigate energy crisis and solve environmental pollution problems. The key issue is the development of high-efficiency photocatalysts. Various strategies in the state-of-the-art advancements, such as heterostructure construction, heteroatom doping, metal/single atom loading, and defect engineering, have been presented for the graphitic carbon nitride (g-C₃N₄)-based nanocomposite catalysts to design their surface chemical environments and internal electronic structures to make them more suitable for different photocatalytic applications. In this review, nanoarchitecture design, synthesis methods, photochemical properties, potential photocatalytic applications, and related reaction mechanisms of the modified high-efficiency carbon nitride-based photocatalysts were briefly summarized. The superior photocatalytic performance was identified to be associated with the enhanced visible-light response, fast photoinduced electron-hole separation, efficient charge migration, and increased unsaturated active sites. Moreover, the further advance of the visible-light harvesting and solar-to-energy conversions are proposed.     

Metallic contaminant profiles in sediment cores from Lake Valencia,Venezuela

Total extractable concentrations of AI, Fe, Mn, Pb, Cu, Zn, Hg and organic carbon (C_org) were determined along four sediment cores from Lake Valencia. In one selected core, the percentage labile fractions were determined in order to establish anthropic enrichment factors, the depth reached by the contaminants and their mobilities. The distribution patterns of concentration versus depth reflect the original concentrations of the settling sediments. Only Mn seems to show diagenetic cycling. No enrichment of Fe and Mn occurs in the upper part of the cores, in spite of good water circulation and aeration of bottom lake waters during five months of the year. This immobility can be attributed to the high pH of water (7.6 – 8.9). Pb, Zn, Cu and Hg are enriched in the upper part of the cores, probably reflecting the input of contaminants. These elements show enrichment factors of up to 3.0. Background concentrations of the studied metals are reached below a depth of 30 cm.     

Simultaneous oxidation of Mn(II) and As(III) on cupric oxide (CuO) promotes As(III) removal at circumneutral pH

Oxidation of Mn(II) or As(III) by molecular oxygen is slow at pH < 9, while they can be catalytically oxidized in the presence of oxide minerals and then removed from contaminated water. However, the reaction mechanisms on simultaneous oxidation of Mn(II) and As(III) on oxide mineral surface and their accompanied removal efficiency remain unclear. This study compared Mn(II) oxidation on four common metal oxides (γ-Al₂O₃, CuO, α-Fe₂O₃ and ZnO) and investigated the simultaneous oxidation and removal of Mn(II) and As(III) through batch experiments and spectroscopic analyses. Among the tested oxides, CuO and α-Fe₂O₃ possess greater catalytic activity toward Mn(II) oxidation. Oxidation and removal kinetics of Mn(II) and As(III) on CuO indicate that O₂ is the terminal electron acceptor for Mn(II) and As(III) oxidation on CuO, and Mn(II) acts as an electron shuttle to promote As(III) oxidation and removal. The main oxidized product of Mn(II) on CuO is high-valent MnO_x species. This newly formed Mn(III) or Mn(IV) phases promote As(III) oxidation on CuO at circumneutral pH 8 and is reduced to Mn(II), which may be then released into solution. This study provides new insights into metal oxide-catalyzed oxidation of pollutants Mn(II) and As(III) and suggests that CuO should be considered as an efficient material to remediate Mn(II) and As(III) contamination.     

A case study on artificial intelligence based cleaner production evaluation system for surface treatment facilities

The metal finishing industry is water intensive. Surveys of South African metal finishing companies indicate that water consumption is as high as 400 L/m² of metal surface treated, whilst best available practice can achieve less than 10 L/m². The industry uses hazardous chemicals such as chrome VI, cadmium, nickel and cyanide. If consumption of these chemicals can be optimized, quantities of heavy metals released into the environment will be reduced. In some cases where cleaner production techniques were applied by local companies, heavy metals have been completely eliminated from effluents discharged to municipal sewers, which represent a significant benefit to the urban environment. This benefit was accompanied by significant reduction in the use of chemicals, with a concomitant cost saving and competitive advantage to the companies concerned.A Danish environmental aid initiative promoted cleaner production in the South African metal finishing industry. Local consultants were trained by Danish experts in this field. The general methodology was to conduct an audit of the chemical, water, human resource and environment aspects of the company and compare it to best available practice. Once the review was completed, a detailed feasibility was performed on systems and equipment required to reduce chemical consumption, water consumption, human resources and environmental impact. Applied to a number of South African companies, these methods have typically achieved reductions of the order of 90% in water use and 50–60% in the use of chemicals.There were difficulties in applying the Danish methodology to South African metal finishing companies, as it makes use of quantitative indices derived from the process operations. The companies are often small and technically unsophisticated, and do not have ready access to the process data that are needed. An alternate system is required to simplify the evaluation and optimization process. This paper proposes a case study on a fuzzy-logic operator based evaluation system that outputs the cleaner production status of the company. The model is compared to an established cleaner production tool.     

金属塑性变形有限元模拟中的约束处理算法

此文提出了适用于金属体积成形过程有限元模拟的约束处理算法.该算法分为三部分.首先,将整个变形域上的节点分为潜在接触节点和非接触节点,分别建在立以节点位移为变量的子系统刚度方程.然后,以潜在接触节点的子系统为对象,确定每个节点与模具的接触状态,对实际接触摸具节点施加位移约束和摩擦条件,并求解耦合了位移约束和摩擦条件的刚度方程.第三,将上述求解的位移结果回代到非接触节点的子系统中,得到剩余节点的位移值.因此,整个系统的位移场以及应变、应力分布亦可确定.该算法的优点在于,将大系统分解为小系统分开求解,使每次求解的变量数目减少,从而可以处理较大规模的工程问题;只对含接触节点的子系统施行坐标变换、约束处理等,提高了有限元计算的效率;将位移约束、摩擦条件直接耦合到子系统中求解,当N—R迭代收剑时,力平衡条件与几何约束条件同时得到满足,从而保证了各控制方程之间的相容性,有利于提高迭代收敛速度和计算稳定性.     

Response of antioxidants in sunflower (Helianthus annuus L.) grown on different amendments of tannery sludge: its metal accumulation potential

The interaction of metals present in tannery waste and their tolerance in the plants of sunflower (Helianthus annuus L.) was studied in the present paper under field conditions. Effects of 100% tannery sludge and various amendments of tannery sludge (10%, 25%, 35%, 50%, 75%) along with one set of control were studied on the physiological and biochemical parameters of the plant along with their metal accumulation potential after 30, 60 and 90 d after sowing. The plants of H. annuus were found effective in the accumulation of metals (Cr, Fe, Zn and Mn) in roots, shoots and leaves, however, the level of toxic metal, Cr was found below detection limit in the seeds of the plant. The oil was extracted from the seeds of the plant and the level of oil content was increased up to 35% tannery sludge as compared to control followed by decrease at higher tannery sludge ratio. An increase in the chlorophyll, protein, cysteine, non-protein thiol and sugar contents was observed at the lower amendment of tannery sludge at initial exposure periods followed by decrease than their respective controls. Malondialdehyde content in the roots and leaves was increased beyond 50% sludge amendments at all the exposure periods as compared to control. However, proline and ascorbic acid contents of the roots and leaves of the plant increased at all the exposure periods and sludge amendments, compared to their respective controls.     

Changes in water quality after addition of sea salts to fresh water: implications during toxicity testing

Sea salts (seven brands from six commercially-available sources) were dissolved in water to develop 30 g/l solutions, and selected water quality characteristics were then monitored for 96 h. One or more water quality characteristics changed significantly during the 96 h period in six of the reconstituted sea salts. Measured characteristics of sea water diluted to 30 g/l demonstrated no changes during the observation period. The sea salts from different sources also demonstrated differences in absolute concentrations of some characteristics measured. Application of the Biotic Ligand Model to predict copper toxicity to the bivalve Mytilus edulis in solutions of the salts tested yielded 96-h median-lethal concentrations that ranged from 2 to 13 μg/l. Since water quality affects toxicity of many environmental pollutants, the source of the sea salt and equilibration time should be considered when planning toxicity tests.     

Photodegradation of new amino acid derivatives suitable for chelating agents in pulp bleaching applications

The purpose of this study was to evaluate photodegradabilities of the following new low-nitrogen chelating agents: N-bis[(carboxymethoxy)ethyl]glycine (compound 1), N-bis[(1,2-dicarboxyethoxy)ethyl]glycine (compound 2) and N-bis[(1,2-dicarboxyethoxy)ethyl]aspartic acid (compound 3). At first photodegradation of these chelating agents as uncomplexed Na-compound 1–3 and Cu(II) complexes were tested, both in lake and distilled water, by exposing them to near-UV region radiation at the range of 315–400 nm. Uncomplexed Na-compounds 2 and 3 were selected to sunlight exposure experiments carried out in lake and distilled water. Compound 3 was also tested in sunlight as Cu and Ca complexes in both solutions. Photodegradation of Na₆-compound 3 in distilled water was studied by exposing it to radiation at the wavelength of 253.7 nm. Photodegradation products were analysed by means of GC-MS (gas chromatography with mass selective detector).

The results demonstrated that compound 1 was quite photostable even as Cu complex while compounds 2 and 3 were found to be photodegradable. Over 90% reduction of compound 3 was achieved during one week and 80% reduction of compound 2 in two weeks' time when they were added as Na salt to lake water and exposed to sunlight. Compound 3 as Cu complex degraded totally in the sunlight in less than one week. In the case of compound 3, the degradation rate decreased depending on the counter cation in the order Cu > Na  Ca. The study demonstrated that photodegradation of Na₆-compound 3 does not result in total mineralization of the compound. A photodegradation pathway for Na₆-compound 3 is proposed.     

The chelation of metal ions by the acylpolyamine toxins from the web-spider Nephilengys cruentata: effects in the intoxication/detoxification of preys

Summary. Orb-web-spiders present a series of different strategies for prey capture, involving the use of different types of silk for web building, the use of adhesive traps in the webs, the secretion of toxic compounds to the spider’s preys in the adhesive coating of the capture web and the biosynthesis of a wide range of structurally related acylpolyamine toxins in their venoms. The polyamine toxins usually block neuromuscular junctions and/or the central nervous system (CNS) of Arthropods, targeting specially the ionotropic glutamate receptors; this way these toxins are used are as chemical weapons to kill / paralyze the spider’s prey. Polyamine toxins contain many azamethylene groups involved with the chelation of metal ions, which in turn can interact with the glutamate receptors, affecting the toxicity of these toxins. It was demonstrated that the chelation of Ni⁺², Fe⁺², Pb⁺², Ca⁺² and Mg⁺² ions by the desalted crude venom of Nephilengys cruentata and by the synthetic toxin JSTX-3, did not cause any significant change in the toxicity of the acylpolyamine toxins to the model-prey insect (honeybees). However, it was also reported that the chelation of Zn⁺² ions by the acylpolyamines potentiated the lethal / paralytic action of these toxins to the honeybees, while the chelation of Cu⁺² ions caused the inverse effect. Atomic absorption spectrometry and Plasma-ICP analysis both of N. cruentata venom and honeybee’s hemolymph revealed that the spider’s venom concentrates Zn⁺² ions, while the honeybee’s hemolymph concentrates Cu⁺² ions. These results are suggesting that the natural accumulation of Zn⁺² ions in N. cruentata venom favors the prey catching and/or its maintenance in the web, while the natural accumulation of Cu⁺² ions in prey’s hemolymph minimizes the efficiency of the acylpolyamine toxins as killing/paralyzing tool.