Pattarapan Prasassarakich

Degradation of styrene-g-cassava starch filled polystyrene plastics

Starch-g-polystyrene copolymers were prepared by the technique of simultaneous irradiation by γ-rays from a 60Co-source. The graft copolymers were used as part of the styrene-based polymer for studies of the degradation of the plastic. The mixture of starch, styrene and methanol solution was irradiated by gamma rays to various total doses ranging from 2 to 16 kGy at a fixed dose rate of 2.5×10−3 kGy s−1. The copolymers were characterized in terms of the homopolymer content, grafting efficiency, grafting ratio, conversion, and percentage add-on. The highest percentage grafting efficiency (62.2%) was obtained at a total dose of 10 kGy. The effects of nitric acid inclusion for enhancing the grafting of styrene onto cassava starch were also studied. Polystyrene (PS) plastics cannot disintegrate naturally by themselves. The degradation of polystyrene plastics containing cassava starch and graft copolymers was investigated by outdoor exposure, soil burial testing, UV irradiation, and the resistance of the plastic to bacteria. All degradation processes were followed by monitoring tensile properties, an index of the extent of degradation, by carbonyl index, molecular weight, and thermal properties of the plastic. It was found that the physical properties of graft copolymer-filled PS sheets rapidly deteriorated upon outdoor exposure, or UV irradiation as evidenced by calculated activation energies of the plastics to decompose. The PS plastics containing the graft copolymer needed less activation energy to start the decomposition process than the control PS plastics. In contrast, no samples significantly degraded upon indoor exposure. All the plastics took a longer time to degrade by the soil burial test. Bacillus coagulans 352 was used for a test of biodegradability resistance of the plastic sheets to bacteria. The composite PS sheets revealed the destroyed areas of starch, indicating that the bacteria help promote the biodegradation of polystyrene plastics before other disintegrations take place.

Coal desulphurization in aqueous hydrogen peroxide

Abstract Coals from Thailand were desulphurized by leaching in a small stirred autoclave with aqueous hydrogen peroxide/sulphuric acid solution. Most of the inorganic sulphur and a small portion of the organic sulphur were removed, and ash was substantially reduced. The effect of process conditions (temperature, time, hydrogen peroxide and sulphuric acid concentrations) on the degree of desulphurization was studied and optimum conditions were established. The kinetics of the oxidation of pyritic sulphur were investigated for Mae Moh coal. The rate of reaction was found to be well represented by a continuous reaction model that was second order with respect to pyritic sulphur.

Coal desulfurization with methanol/water and methanol/KOH

Mae Moh coal from northern Thailand was desulfurized by leaching with methanol/water and methanol/KOH in a batch reactor. The effect of methanol concentration, KOH concentration, coal particles, reaction temperature and reaction time on the removal of ash and sulfur was investigated. Depending on the desulfurization conditions, the reductions ranged from 36 to 74% in pyritic sulfur, 20 to 42% in organic sulfur and 33 to 62% in total sulfur. Methanol/KOH enhanced the desulfurization process in which the inorganic and organic sulfur were removed preferentially. KOH addition can improve the sulfur removal. The kinetics of the oxidation of pyritic sulfur was investigated for Mae Moh coal. The rate of reaction was found to be well represented by a continuous reaction model that was second order with respect to pyritic sulfur.

Kinetics of coal desulfurization with sodium benzoxide

Mae Moh coal of Lampang province, northern Thailand, was desulfurized by leaching with organometallic compounds. Most of the inorganic sulfur and some organic sulfur were removed. The effect of process conditions (temperature, time and particle size) on the degree of desulfurization was studied and optimum conditions were established. It is shown that sodium benzoxide can leach ∼ 68% of pyritic sulfur and ∼ 33% of organic sulfur. The kinetics of pyritic sulfur reaction was investigated. The kinetic data are well described by the shrinking-core model, indicating that the pyritic sulfur reaction was predominantly diffusion-controlled. The organic sulfur reaction is zero-order with respect to organic sulfur.

Styrene/Acrylonitrile Graft Natural Rubber as Compatibilizer in Rubber Blends

A graft copolymer of acrylonitrile (ACN) and styrene (ST) on natural rubber (NR) was prepared by solution polymerization initiated by benzoyl peroxide. The effect of graft NR (GNR) applied as a compatibilizer for NR/nitrile rubber (NBR) blends on their mechanical and physical properties was investigated. The results revealed that the tensile properties and oil-swelling resistance of the blends increased with increasing %graft copolymer of GNR. The tensile fracture surfaces of the compatibilized NR/NBR vulcanizates attested by scanning electron microscopy indicated the improvement of interfacial adhesion between two rubber phases. Moreover, the dynamic mechanical properties of compatibilized vulcanizates were also reported.

Natural Rubber-g-Glycidyl Methacrylate/Styrene as a Compatibilizer in Natural Rubber/PMMA Blends

Abstract Graft copolymer of glycidyl methacrylate and styrene onto natural rubber latex was synthesized by emulsion polymerization using cumene hydroperoxide and tetraethylene pentamine as a redox ...

Supercritical desulfurization of low rank coal with ethanol/KOH

Abstract Desulfurization of Mae Moh coal with supercritical ethanol/potassium hydroxide in a semicontinuous reactor was studied. A two-level factorial experimental design was applied to study the main effects on sulfur reduction. The variables investigated in this work were temperature, pressure, time and potassium hydroxide concentration. The measured responses in the experimental design were coal yield, sulfur reduction and ash reduction. The analysis of the results from the design showed that two variables, temperature and KOH concentration, can be considered to have a significant effect on the pyritic sulfur and total sulfur reduction.

Gold Recovery by pH-Switching Process via Cloud Point Extraction

Poly(oxyethylene)-9-nonylphenyl ether (PONPE-9) was employed for cloud point extraction of gold(III) ion and its phase separation behavior under different experimental conditions was evaluated. The effect on extraction efficiency, including equilibration time, ratio of PONPE-9 to gold, settling temperature, and pH of the solution, was demonstrated. The results indicate that PONPE-9 can be utilized for the extraction of gold in a manner akin to previous work using PONPE-7.5. The optimum experimental results obtained were applied to design a process scheme, pH switching via CPE, to overcome the drawback of the difficulty of separating gold from a gold-entrapped surfactant. The utility of the proposed scheme was demonstrated through the application of recovering gold(III) ion from a multimetal solution. Recoveries of greater than 63% of gold were obtained. Even if this is not so high a percentage recovery, it indicates the feasibility of the process scheme. On the other hand, it proved to be an even simpler and easy method for recovering gold from the leaching solution of printed substrates without spending harmful organic solvent.

Styrene-Divinylbenzene Copolymers: Influence of the Diluents on Absorption and Desorption Properties

Styrene-divinylbenzene copolymers with porous structures were prepared by seeded suspension polymerization using toluene and heptane as diluents. The influence of each diluent on the formation of porous structure and the swelling ratio was investigated. The styrene-DVB beads are capable of absorption and desorption of organic solvents having solubility parameters in the range of 17.6–19.6 (MPa)1/2. Styrenic imbiber beads were swelled in toluene and the kinetics of absorption was studied. The imbiber bead could absorb toluene completely within 90 min and yielded a maximum swelling ratio of 12.7. The diffusion coefficient values of these beads were in the range of 1.55 × 10−5 to 3.68 × 10−5 cm2 · s−1.

Kinetics of coal desulphurization in aqueous copper(II) sulphate

Abstract Mae Moh coal of Lampang province, northern Thailand, was leached in a copper(II) sulphate solution. Most of the inorganic sulphur, pyritic and sulphate sulphur were removed. The parameters affecting conversion of pyritic sulphur were investigated. The pyritic sulphur conversion was found to increase significantly with increasing temperature (120–150 °C) and copper(II) sulphate concentration (10–20%) but decrease with increasing coal particle size (150–600 μm). The kinetics of chemical desulphurization by oxidation of the pyritic sulphur was investigated. The kinetic data are well described by the unreacted shrinking core model, indicating that the desulphurization was predominantly diffusion controlled. The effective diffusivity depended on temperature.