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- Volume 18, Issue 1, 2013
South African Journal of Chemical Engineering - Volume 18, Issue 1, 2013
Volume 18, Issue 1, 2013
Detailed characterization of South African high mineral matter inertinite-rich coals and density fractions and effect on reaction rates with carbon dioxide : macerals, microlithotypes, carbominerites and mineralsSource: South African Journal of Chemical Engineering 18, pp 1 –16 (2013)More Less
An investigation was undertaken to determine the distribution of macerals and minerals in South African Highveld coal deposits as well as density fractions derived from a typical deposit. The corresponding effects on carbon dioxide gasification reaction rates were also studied. Detailed chemical, petrographic and mineral analyses, followed by reactivity measurements and reaction rate modeling were carried out. Coal samples from seven different coal mines and five density separated coal fractions (<1.4 g.cm-3 to >2.0 g.cm-3) were examined. It was found that the coal samples have ash contents in the range 21.6 to 38.8 wt. % and inertinite composition in the range 68 to 84 vol. %. The inertinites consist of high concentrations of semifusinites and inertodetrinite which is characteristic of South African Highveld coal deposits. The distribution of macerals and minerals in the different density fractions revealed high concentrations of inert inertodetrinite, carbominerite and ash in the dense fraction. The presence of carbominerites was also found to increase with mineral content within the density range of 1.4 g.cm-3 to 1.8 g.cm-3. The random pore model described the gasification reactivity very well with an increasing intrinsic reaction rate correlating with an increasing density of the coal which is attributed to an increasing pre-exponential factor.
Distribution of respirable suspended particulate matter in ambient air and its impact on human health and remedial measures at Bholabedha Joda-Barbil region in OrissaSource: South African Journal of Chemical Engineering 18, pp 18 –29 (2013)More Less
Indiscrete mining and transportation of Iron and Manganese ore by road clubbed with operation of huge numbers of sponge iron plants, iron ore crushers and stone crushers in the Joda-Barbil area of Orissa State, India has led to considerable deterioration of ambient air quality. Therefore in order to ascertain the ambient air quality, monitoring was conducted at 08 locations spread over a radial distance of 15 kms in all directions with Joda as the epi-centre for three seasons namely summer, post monsoon and winter during 2008-09. Results of Bholabedha-Joda-Barbil Region in Orissa presented in this paper. The Suspended Particulate Matter (SPM , >10 micron) and Respirable Particulate Matter (RSPM, ≤10 micron) concentration have been found to have exceeded the National Ambient Air Quality standards prescribed by Ministry of Environment and Forest (MoEF), Government of India at most of the locations. Health data collected from the District Health Department indicated that incidence of Pulmonary Tuberculosis amongst residents of the study area has increased between 1999 and 2008 during which the iron ore mining and road transportation was rampant. Therefore, an effective Air Pollution Management Plan was formulated with an intention to substantially reduce the impact of dust pollution on the surrounding areas.
Author Raj Kumar AryaSource: South African Journal of Chemical Engineering 18, pp 30 –40 (2013)More Less
Simulation study for drying induced phase separation has been done in cellulose acetate - water - acetone system. Effects of drying condition, nonsolvent and solvent concentrations have been studied. Simulation results show that porous asymmetric and symmetric membranes can be produced by changing the nonsolvent concentration or by the drying conditions without altering the polymer content using dry-casting process. At low initial nonsolvent concentration, phase separation may not take place and dense polymer film may be obtained rather than a porous membrane.
Source: South African Journal of Chemical Engineering 18, pp 41 –50 (2013)More Less
Sodium ethyl and potassium amyl xanthates are commonly used in bulk and selective froth flotation of pentlandite ores respectively. The xanthate collectors are sensitive to pH and their selectivity in treating complex ores is questionable. With deteriorating nickel sulphide ore reserves more selective collectors have to be used in the extraction of nickel. The dithiocarbamates and dithiophosphates are possible replacement as they are believed to be stable in a wider range of pH and more selective than xanthates respectively. The present study compared the effects of using di-methyl-dithiocarbamate (di-C1-DTC), di-ethyldithiophosphate di-C2-DTP, SEX and PAX in froth flotation of pentlandite ore. The collectors were dosed at molar equivalent of 80g/ton PAX. This study showed that the higher cumulative nickel grades and cumulative nickel recovery were obtained by the use of PAX and SEX respectively. Therefore, it was not beneficial to substitute xanthates with either di-C1-DTC or di-C2-DTP in the froth flotation of pentlandite containing ore.
Source: South African Journal of Chemical Engineering 18, pp 51 –69 (2013)More Less
The existence of heavy metals from industrial effluents can have serious effects in the aqueous system. Most of these metals cannot be effectively removed from the effluents using conventional methods because of various factors. Therefore, alternative methods are required. This paper presents a study for the removal of cobalt (Co2+), vanadium (V3+) and chromium (Cr3+) ions from synthetic wastewater using untreated and acid treated cassava waste biomass. Cassava waste biomass is a cellulosic material which possesses hydroxyl groups when untreated and sulfhydryl groups (or thiol groups) when treated with thioglycollic acid. Both these functional groups can act as binding sites for metal ions. The effects of various parameters (e.g., pH, temperature, agitation, metal ion concentration, etc.) on the removal of metal ions from the solutions were investigated in a batch process. Adsorption of metal ions was observed to increase with pH. The maximum metal ion adsorption was obtained at pH of 3 for V3+, 6 for Co2+ and 3 for Cr3+. Metal adsorption increased with an increase in temperature from 30 to 40°C at an initial metal concentration of 100mg/L. However, there was a reduction in adsorption beyond 40°C for all the metal ions. It was found that treated biomass had higher adsorption rates. Furthermore, the results showed that an increase in the concentration of thioglycollic acid improved the adsorptivity of the cassava waste biomass. The work also showed that the cassava biomass could be regenerated and reused up to six adsorption-desorption cycles. Amongst the two widely used isotherms tested (i.e., Langmuir and Freundlich models), the experimental data was found to fit the Freundlich isotherm better.
Thermodynamic characterization of adsorption of lead(II) ions on activated carbon developed from tamarind wood from aqueous solutionSource: South African Journal of Chemical Engineering 18, pp 70 –76 (2013)More Less
Batch kinetic studies were conducted for the adsorption of Pb(II) on activated carbon developed from tamarind wood (ATW). The adsorption studies were conducted for the adsorbent dose of 2 g/l and initial Pb(II) concentration of 10 mg/l and in the temperature range of 10 to 50 °C. With the increase in temperature from 10 to 50 °C, the lead uptake was observed to increase from 78.3 to 95.4 %. The equilibrium time was found to be 60 min. The adsorption was very fast from the beginning up to 30 min and then for next 30 min, uptake increased gradually from 78.3 to 99.15- %. This paper attempts to develop simple and easily understandable thermodynamic parameters related to the adsorption process at equilibrium. The Gibbs free energy (∆G°) at 10, 20, 30, 40 and 50 °C for the adsorption process of Pb(II) were obtained as -2.98, -3.86, -6.93, -9.05 and -12.34 kJ/mole respectively. The negative value of ∆G° confirms the feasibility of the adsorption process and spontaneous nature of adsorption. The values of ∆H° and ∆S° for Pb(II) were obtained as 36.85 kJ/mol and 140.92 J/mol respectively. The positive value of ∆H° indicates endothermic nature of adsorption, while positive ∆S° value confirms the increased randomness at the solid-liquid interface during adsorption. The activation energy for the sorption of Pb(II) was found as 32.47 kJ/mol, indicating chemisorptions.