Environmental pollution by heavy metal ions has received worldwide attention due to their long-term toxicity, non-biodegradability and accumulation in living organisms. Mesoporous calcium-silicate material (MCSM), a cost-effective sorbent synthesized from the desilication liquor of coal fly ash, has been tested its potential for the removal of Cd(II), Cr(III), Ni(II) and Pb(II) from acidic solutions. The effect of initial concentration, m/V ratios, solution pH and ionic strength on the sorption was investigated, and the performance of the material on the removal of heavy metals from simulated wastewater was evaluated. At a m/V ratio of 2 g L-1, the maximum sorption capacity of MCSM for metals follows the order: Cd(II)≈Ni(II) (5.52 mmol g-1) > Cr(III) (2.88 mmol g-1) > Pb(II) (2.17 mmol g-1). However, the capacity for Cr(III) significantly decreased with comparatively higher metal concentration due to the strong hydration of Cr(III) which destroyed the crystalline phase of material. The initial concentration had a limited positive effect on the sorption, and the removal efficiency of metals only maintained at a relatively higher level with m/V ratios of up to 2 – 5 g L-1. At a low m/V ratio (0.75 g L-1), sorption was significantly influenced by solution pH and competition cations under strongly acidic conditions (pHinitial= 2), and the adverse effect disappeared when solution pHinitial ≥3. At an m/V ratio of 5 g L-1, the removal efficiency of metals maintained in the range of 96.2 – 100.0% varied with different heavy metal ions. Considerable uptake of Zn(II), Mn(II), Fe(III) and Cu(III) by MCSM was also observed in the simulated wastewater, and the 8 metal ions (each 0.001 M) were efficiently removed and the remaining metal concentration < 0.1 mg L-1 (except remaining Ni(II) concentration < 1.0 mg L-1) at an m/V ratio of 20 g L-1. The mechanism responsible for the sorption included surface complexation, ion exchange, and probably precipitation at a high m/V ratio (20 g L-1). Ion exchange with Ca(II) in MCSM occurred when m/V ratios ≥ 2 g L-1(42.1 – 89.6% for m/V = 2 – 5 g L-1), whereas surface complexation would probably occur when m/V ratios less than 1 g L-1 due to its structural damage by extensive dissolution to form crosslinked structure which resembles vitreous silica. The results suggest that MCSM has the potential for use as an effective and low-cost sorbent for removing hazardous metal ions from wastewater. Besides, MCSM is suitable for use as a substitute of cement and disposed by inexpensive solidification/stabilization technique after being used as a sorbent. Such a process is helpful for the simultaneous realization of the reutilization of coal fly ash and the removal of toxic metals from wastewater.
Physical contracts and financial contracts are common terms in the electricity market. However, due to the different contexts used, these two terms often have certain conceptual biases in actual research. The concepts of physical contracts and financial contracts, and the similarity between power physical contracts and financial contracts from the characteristics of the electric commodities are analyzed. Based on the summary of the typical foreign electricity market operation mode, the power contract transactions in the UK and PJM power market are taken as examples for in-depth analysis. The analysis shows that the actual electricity market construction does not have to be rigidly attached to the basic pattern of the electricity market, and the physical contracts or financial contracts can be selected according to the actual situation.
Surface potential decay characteristics of specimens extracted from in-service aged and reference HVDC composite insulator sheds are reported and analyzed in this paper. In the experiments, surfaces of the insulator samples were charged by dc corona and the decay was recorded utilizing a non-contact technique. In addition, surface and bulk conductivities of the specimens were determined and used for analyzing by means of computer simulations their impact on the potential distribution profiles and its decay. Based on the performed experiments, trap density distributions, mobility of charge carriers and field dependent bulk conductivities are deduced for the investigated samples with the aim to evaluate the ageing severity.
In this work, CMOS compatible MEMs platform process was developed on 200mm Cu BEOL Line. The fabrication technology was dedicated to micro-bridge structure based MEMs application. The integration scheme was post interconnect single chip integration, in which MEMs was built directly on standard CMOS interconnect structure and can share Si area with standard CMOS circuit. Because of the shared Si area and single chip integration scheme, the application cost can be greatly reduced with increasing performance. Modified CMOS-BEOL process was used to develop the CMOS-MEMs interface structure, and top metal was used both as the functional layer and PAD layer with lower step height by optimized planarization process. As to the bridge structure, TaN was used as electrode material, and alpha-Si film was used as the sacrificial material fabricated by low Temperature PECVD technology. No metal or dielectric material plug was used for the anchor supporting structure, which make the process much more controllable and flexible. For one of the Sensor product application, the sensing material was using B-doped alpha-Si film fabricated by PECVD and in situ doping process. To obtain good contact between TaN electrode and sensing material, reactive preclean was chosen instead of low-power Ar-preclean in order to control the sensing material loss. TaN was etched by standard Cu BEOL tool using CF4/CHF3 gas. The sensing material loss can be well controlled to less than 30nm, and the uniformity of sensing resistor was about 2sigma/mean < 3% for 200A TaN. The TCR of the sensing resistor was about −1.5% ∼ −2% which is compatible to the as-deposited sensing material film, and can well match this sensor application.
Polypropylene (PP)-based nanocomposite is a promising insulation material for recyclable high-voltage direct current (HVDC) cables, where the coupling agent plays an important role. In this study, four silane coupling agents with different alkyl chain groups (methyl, propyl, octyl, and octadecyl) were used to surface-modify magnesium oxide (MgO) nanoparticles. The surface-modification effect on the electrical properties of PP/MgO nanocomposites was investigated. The results show that surface-modified nanoparticles introduce quantities of deep traps, whose quantity increases as the alkyl chain length increases. The similar tendency also occurs on DC volume resistivity. All these nanocomposites show remarkable space charge suppression ability and improved DC breakdown strength. Among them, the nanocomposites with octyl-modified MgO show the best electrical properties, which could be attributed to the introduction of a large quantity of deep traps. The work may give a reference for the selection of coupling agents in PP-based nanocomposite insulation material for HVDC cable.
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