Max Lu

Adsorption kinetics for the removal of chromium(VI) from aqueous solution by adsorbents derived from used tyres and sawdust

The batch removal of hexavalent chromium (Cr(Vl)) from wastewater under different experimental conditions using economic adsorbents was investigated in this study. These adsorbents were produced from the pyrolysis and activation of the waste tyres (TAC) and from the pyrolysis of sawdust (SPC). The performance of these adsorbents against commercial activated carbon F400 (CAC) has also been carried out. The removal was favoured at low pH, with maximum removal at pH = 2 for all types of carbon. The effects of concentration, temperature and particle size have been reported. All sorbents were found to efficiently remove Cr(VI) from solution. The batch sorption kinetics have been tested for a first-order reversible reaction, a first-order and second-order reaction. The rate constants of adsorption for all these kinetic models have been calculated. The applicability of the Langmuir isotherm for the present system has been tested at different temperatures. The thermodynamic parameters (AGO, K,) obtained indicate the endothermic nature of Cr(Vl) adsorption on TAC, SPC and CAC

Porous Clays and Pillared Clays-Based Catalysts. Part 2: A Review of the Catalytic and Molecular Sieve Applications

Metal oxide pillared clay (PILC) possesses several interesting properties, such as large surface area, high pore volume and tunable pore size (from micropore to mesopore), high thermal stability, strong surface acidity and catalytic active substrates/metal oxide pillars. These unique characteristics make PILC an attractive material in catalytic reactions. It can be made either as catalyst support or directly used as catalyst. This paper is a continuous work from Kloprogges review (J.T. Kloprogge, J. Porous Mater. 5, 5 1998) on the synthesis and properties of smectites and related PILCs and will focus on the diverse applications of clay pillared with different types of metal oxides in the heterogeneous catalysis area and adsorption area. The relation between the performance of the PILC and its physico-chemical features will be addressed.

Immobilization of aluminum chloride on MCM-41 as a new catalyst system for liquid-phase isopropylation of naphthalene

A great deal of effort has been made at searching for alternative catalysts to replace conventional Lewis acid catalyst aluminum trichloride (AlCl3). In this paper, immobilization of AlCl3 on mesoporous MCM-41 silica with and without modification was carried out. The catalytic properties of the immobilized catalyst systems for liquid-phase isopropylation of naphthalene were studied and compared with those of H/MCM-41 and H/mordenite. The structures of the surface-immobilized aluminum chloride catalysts were studied and identified by using solid-state magic angle spinning nuclear magnetic resonance (MAS NMR), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption, and X-ray diffraction (XRD) techniques. The catalytic activity of the immobilized catalysts was found to be similar to that of acidic mordenite zeolite. A significant enhancement in the selectivity of 2,6-diisopropylnaphthalene (2,6-DIPN) was observed over the immobilized aluminum chloride catalysts. Immobilization of aluminum chloride on mesoporous silica coupled with surface silylation is a promising way of developing alternative catalyst system for liquid-phase Friedel-Crafts alkylation reactions

A Framework for Transmission Planning in a Competitive Electricity Market

In this paper, a framework for optimal transmission system expansion planning in a competitive electricity market environment has been proposed. Open access transmission has created a deregulated power market and brought new challenges to system planning. The goal of transmission planning is to determine an optimal planning strategy for the transmission company. From the planners view, planning is the process for balancing the multiple conflicting objectives with many constraints. The primary objective of transmission planning is to ensure the reliable supply to the demand as economically as possible. The new approach in this paper is formed to minimize the expected energy not supplied (EENS), investment cost and maximize the benefit-cost ratio lambda subject to the power flow and security constraints. The computer program for reliability evaluation of bulk power systems CRUSE is used to perform reliability evaluation of the transmission system with predetermined outages. An advanced genetic algorithms (GAs) is utilized to solve the multi-objective optimisation problem. The advantages of the new approach include 1) it achieves the possible highest reliability with less cost; 2) it maximizes the cost efficiency, which increases the competitive advantage of a transmission company; and 3) the resulting plans contain the planners preference which is easy to adjust. The planning approach has been illustrated on the Roy Billinton Test System (RBTS)

Adsorption of Aromatic Compounds by Activated Carbon: Effects of Functional Groups and Molecular Size

The adsorption of three aromatic compounds on to an untreated carbon was investigated. The solution pH was lowered in all experiments so that all the solutes were in their molecular forms. It was shown that the difference in the maximum adsorption of the solutes was mainly a result of the difference in the sizes of the molecules and their functional groups. Furthermore, it was illustrated that the packing arrangement was most likely edge-to-face (sorbate–sorbent) with various tilt angles. On the other hand, the affinity and heterogeneity of the adsorption systems were apparently related to the pKa values of the solutes.

Transmission expansion planning flexibility

In recent years, the issue of flexibility has become increasingly important to power system planning. Generation flexibility has been under continuous research for many years; however there is little research on transmission expansion planning flexibility, which has attracted more and more attention due to the increasing uncertainties in a competitive electricity market environment. Planners have to carefully consider the resulting costs, benefits and risks during the planning phase. Future electricity demand is a main source of uncertainty facing transmission planners. Flexibility is a useful way to deal with it. The most flexible plan can reduce the probability of loss of demand, cut down the cost of reconfiguration and save reconstructing time. In this paper, we classify the transmission flexibility into three dimensions including market flexibility, operational flexibility and expansion flexibility with detailed definitions. Transmission expansion flexibility (TEF) is the main focus of this paper and can be used as an important criterion for decision making and transmission planning. Case studies based on two test systems are used to illustrate the proposed TEF and its application in power system planning. The case study results clearly demonstrate the effectiveness of the proposed method in transmission expansion planning. The use of TEF can also help transmission system investors to achieve more returns from the competitive market

A novel approach to evaluate congestion for composite power system planning in a competitive electricity market

Transmission lines play an important role in providing all participants the access to supply and demand in a competitive electricity market. Market size could be limited by the physical ability of transmission network to deliver electricity. Transmission line congestion as a primary indicator for transmission expansion planning has been investigated in this paper. The calculation on congestion cost under single side bid Poolco market is proposed and is defined as the social surplus difference between before the transmission line violation and after congestion. The generators bidding price change is considered as a result of market factors in a deregulated electricity market. Finally, a numerical example is applied on IEEE Reliability Test Systems (RTS) for illustrating the essential features of the proposed congestion cost evaluation approach. The results are conducted using the well-known Monte-Carlo Simulation method

Transport mechanism in weakly branched silica films

Activated transport is one of the most important properties of microporous membranes which results in molecular sieving separation with very high selectivities. The flux J (mol.m(-2).s(-1)) through microporous membranes as a function of temperature can be derived from the isosteric heat of adsorption Q (st) and the mobility energy E-m (kJ.mol(-1)). In this work, high quality molecular sieving membranes have been successfully synthesised using sol-gel process to prepare weakly branched silica films. Maximum permselectivities calculated are 846 (He/CH4), 130 (CO2/CH4) and 58 (H-2/CO2). The effect of mobility energy on silica films is demonstrated by preparation methods such as single-step and two-step catalysed hydrolysis of tetraethoxysilane (TEOS) which leads to the production of weakly branched silica films.

Synthesis and Hydrogen Storage Properties of Magnesium Nanoparticles with Core/Shell Structure

Magnesium nanoparticles were synthesized by using organo magnesium precursor. By changing synthesis parameters such as synthesis time and temperature, various morphologies of the magnesium nanoparticles were obtained. Sample synthesized at 250°C for 30 min exhibited agglomerated nanosheets of magnesium whereas the sample obtained at 2 hour had individual particles consisted of core/shell structure. The corresponding hydrogen storage properties of these samples were also influenced by the morphology. Hydrogen desorption data revealed that samples prepared at 2 hour could release hydrogen at lower temperature (343°C) than those samples prepared at 30 min and 1 hour.

Photocatalysts for the Destruction of Styrene as an Air Pollutant

Various photocatalysts have been produced for the oxidation of airborne styrene. Commercial Degussa P25 (supported on vanadia-doped/undoped silica gel) and synthesized titania-pillared clay was used. Selected catalysts were characterized using SEM, TEM, XRD, TGA, UV-vis spectrophotometry, and nitrogen adsorption. This work represents the first phase of a study, aimed at degrading styrene in a fluidized-bed photoreactor, of which will be reported separately.