Siew-Teng Ong

Heterocyclic benzothiazole-based liquid crystals: synthesis and mesomorphic properties

Two homologous series of 2-(4-alkanoyloxybenzylidenamino)benzothiazoles and 2-(2-hydroxy-4-alkanoyloxybenzylidenamino)benzothiazoles were synthesised and characterised. Their molecular structures differed wherein the latter comprised a lateral hydroxyl group, unlike the former. Spectroscopic techniques such as FT-IR, 1H & 13C NMR and mass spectrometry together with elemental analysis were employed to elucidate the molecular structures. The transition temperatures and their mesophases were determined by differential scanning calorimetry, optical polarising microscopy and X-ray diffraction techniques. Members with decanoyloxy till hexadecanoloxy chain in the series without the lateral hydroxyl group each exhibited a smectic A phase, while those in the series with the lateral hydroxyl group were non-mesogenic. The mesomorphic properties of the present series were compared with other structurally related series to establish the chemical structure–mesomorphic properties relationship.

Mesogenic Schiff's base ether with dimethylamino end group

A series of Schiff base ethers comprising a dimethylamino group at one terminal position and an even number of carbons at the other along the molecular axis was studied. The dimethylamino unit, acting as a charge-transfer donor in the formation of conjugative interactions, contributes to the molecules polarizability and in turn affecting its intermolecular interactions, leading to the formation of less-ordered mesophase. The mesomorphic properties were studied using polarizing optical microscopy and differential scanning calorimetry. Whilst the n-butyloxy to n-hexadecyloxy derivatives exhibited nematic phase, the n-ethyloxy, n-propyloxy and n-octadecyloxy derivatives were not mesogenic. Their phase transitions during heating and cooling run were presented. The title compounds were compared with other structurally related series to establish their chemical structure–mesomorphic property relationships.

Synthesis and Mesomorphic Properties of 2-(4-Alkyloxyphenyl)benzothiazoles

A homologous series of 2-(4-alkyloxyphenyl)benzothiazoles with an even number of carbons in the terminal alkoxyl chain was synthesized and characterized. The structure of the compounds was postulated using elemental analyses, FT-IR, NMR, and mass spectrometry techniques. Their liquid crystalline properties have been investigated by optical polarizing microscopy, DSC, and X-ray diffraction (XRD) techniques. Whilst the n-octyloxy to n-hexadecyloxy derivatives exhibited a monotropic smectic A phase, the n-ethoxy to n-hexyloxy and the n-octadecyloxy derivatives were not mesogenic. The mesomorphic properties of the present series were compared with other structurally related series to establish the chemical structure-mesomorphic properties relationship.

Utilization of sugarcane bagasse for removal of basic dyes from aqueous environment in single and binary systems

In the present study a biodegradable and low cost sorbent was investigated for its sorptive capacity for various basic dyes in both single and binary dye solutions. As wastewaters from textile industries may contain a variety of dyes, therefore, it is of great interest to have a sorbent capable of removing dyes either singly or simultaneously. The agricultural by-product has shown its potential to remove Basic Blue 3 (BB3), Methylene Blue (MB) and Basic Yellow 11 (BY11) in both single and binary systems. The effect of pH, contact time and initial concentration, dosage and particle size was studied in batch experiments at room temperature. The optimum pH for the removal of studied dyes was observed in the pH range 4–9 and the sorption reached equilibrium at 60 min. The optimum sorbent dosage was recorded at 0.10 g. The sorption process fitted well in the pseudo-second order kinetic model and Langmuir isotherm was applicable for all the dye systems studied. Maximum sorption capacities were 23.64 mg g−1, 28....

Removal of basic dyes from aqueous environment in single and binary systems by sugarcane bagasse in a fixed-bed column

Abstract The ability of natural sugarcane bagasse in the removal of Basic Blue 3, Methylene Blue and Basic Yellow 11 in both single and binary system from aqueous solutions was studied. Important parameters such as influent concentration, flow rate and sorbent dosage were investigated. Results revealed that the breakthroughs were influent concentration, flow rate and bed height dependent. Increase in influent concentration and flow rate resulted in faster breakthrough while increase in column height yielded longer service time. The sorption data were applied to the Thomas, Belter and Chu, and bed-depth service time (BDST) model. Theoretical breakthrough curves generated using Chu model agreed closely with the experimental values for all the dye systems under studied. In the regeneration study, BB3 dye could be recovered almost quantitatively by eluting the column with 0.1 M HCl and the column could be used repeatedly for at least 3 cycles.

Papaya (Carica papaya) seed as a low-cost sorbent for zinc removal

The potential of using papaya seed as a sorbent for the removal of Zn from aqueous solution was investigated. The sorption characteristics of the sorbent was studied under various experimental conditions, such as pH, contact time, concentration of Zn(II), agitation rate and sorbent’s particle size. The equilibrium data have been studied using Langmuir, Freundlich and Brunauer-Emmett-Teller equations. The best correlation was obtained using Langmuir isotherm with the regression coefficient value of 0.9799 and maximum sorption capacity of 19.88 mg/g. The effective pH for the maximum uptake of Zn(II) was at pH 5.0. An increase in percentage uptake of Zn(II) can be observed with increasing contact time and agitation rate. Decrease in sorbent particle size led to an increase in the sorption of Zn(II) and this could be explained by an increase in surface area and hence binding site. Equilibrium was attained around 60 min indicating this sorbent could be a potential material for continuous flow system.

Removal of reactive black 5 from aqueous solution using chitosan beads: optimization by Plackett–Burman design and response surface analysis

AbstractContaminations due to dyes pose not only a severe public health concern, but also many serious environmental problems. The present project aims to prepare an inexpensive and efficient sorbent that could remove dyes that are commonly used in the industry. Chitosan has been seen as a promising sorbent due to its significant properties, such as biocompatibility, biodegradability and non-toxicity. Batch studies were performed under various experimental conditions and the parameters studied included pH, contact time, initial concentration and agitation rate. The kinetics of dye sorption fitted a pseudo-second-order rate expression. Equilibrium data could be fitted into both Langmuir and BET isotherms. Plackett–Burman design was applied to identify the most significant factors in the removal of Reactive Black 5 (RB5) by chitosan. The effect of operating parameters on RB5 uptake was studied and a mathematical model showing the influence of each variable was obtained. The interaction between the factors a...

Cheap Materials to Clean Heavy Metal Polluted Waters

The rapid growth of the human population and industrialization in the world has increased the environmental problems such as water, air and land pollution. Heavy metals can be considered as one of the most problematic pollutants. This chapter reviews developments and technical applicability of treatments methods for the removal of heavy metals. We focus on the use of low-cost materials to remove heavy metals. Isotherm equilibrium models and kinetics are discussed. Designing adsorption columns under continuous flow conditions are evaluated.

Determination of Important Parameters in Affecting the Uptake of Reactive Black 5 by Chitosan Beads through Statistical Approach

Chitosan which can be obtained from fishery waste was studied as an alternative source to remove pollutants in the wastewater. The adsorption process of Reactive Black 5 (RB5) by chitosan was studied under batch experimental condition to identify the optimum condition in which the dye can be removed at a higher rate. The best fit kinetics model was determined to be the pseudo-second-order kinetics. From the isotherm study, the experimental result was better explained by Freundlich isotherm. Plackett-Burman was employed to identify the influential variables affecting the dye uptake. Response surface methodology (RSM) was used to determine the interactions between the factors and their optimum levels for maximum uptake of RB5. The optimum condition for the highest percentage uptake of RB5 dye was determined to be at pH 4, agitation rate of 200 rpm, sorbent dosage of 1.0 g, contact time of 300 minutes, and initial dye concentration of 25 mg/L.

Synthesis of a New Liquid Crystal, 3-Hydroxy-4-{[(6-methoxy-1,3-benzothiazol-2-yl)imino]methyl}phenyl Palmitate

A new Schiff base ester comprising of heterocyclic moiety, 3-hydroxy-4-{[(6-methoxy-1,3-benzothiazol-2-yl)imino]methyl}phenyl palmitate was synthesized and its IR, 1H NMR, 13C NMR, elemental analysis and MS spectroscopic data are presented.