Thermal degradation of mango (Mangifera indica) wood sawdust in a nitrogen environment: characterization, kinetics, reaction mechanism, and thermodynamic analysis.

For better utilization of 11 million tonnes of Mangifera indica wood (MIW) sawdust produced annually in India, the present study was planned for its characterization followed by determination of its pyrolysis kinetics from TGA data under a N2 atmosphere. The characterization process included proximate-, ultimate-, biopolimeric components-, and heating value-analysis, as well as TG/DTG analysis. The distributed activation energy (DAE)- and Starink-methods were implemented on non-isothermal thermograms to compute the isoconversional values of activation energy for the pyrolysis of MIW. Further, the reaction mechanism for the pyrolysis of MIW was predicted using the Coats-Redfern (C-R) model-fitting method. Two distinct pyrolysis regions, region-I from 0.05-0.5 and region-II from 0.51-0.7, were observed in the complete conversion ranges. The estimated activation energy for region-I ranged from 143.03 to 176.46 kJ mol-1 with an average value of 157.12-157.97 kJ mol-1 and that of region-II varied between 143.03 and 161.68 kJ mol-1 with an average of 151.51-152.45 kJ mol-1. The one-dimensional diffusion model (D1) followed by the five and a half reaction order model (F5.5) were recommended to describe the pyrolysis reaction mechanism of MIW for the two above regions, respectively. Further, the activation energies obtained via the DAE and Starink methods were used for the computation of thermodynamic parameters such as frequency factor, and change in-enthalpy, -entropy, and -Gibbs free energy.

Supercritical extraction of sunflower oil: A central composite design for extraction variables.

Supercritical carbon dioxide (SC-CO2) extraction of sunflower seed for the production of vegetable oil is investigated and compared to conventional methods. The effects of extracting variables, namely pressure, temperatures, particle size, SC-CO2 flow rate and co-solvent, on SC-CO2 extraction are investigated. The maximum yield for sunflower oil is found to be about 54.37 wt%, and is obtained when SC-CO2 extraction is carried out at 80 °C, 400 bar, 0.75 mm particle and 10 g/min solvent flow with 5% co-solvent. A central composite design is used to develop the model and also to predict the optimum conditions. At optimum conditions obtained based on desirability function, 80.54 °C, 345 bar, 1.00 mm, 10.50 g/min and 7.58% ethanol, SC-CO2 extraction has performed and found that extraction yield dropped by 2.88% from the predicted value. Fatty acid composition of SC-CO2 and hexane extracted oil shows negligible difference and found high source of linoleic acid.

Egg laying strategies and effect of temperature on egg development of Argulus siamensis.

Argulus siamensis is the most damaging fish parasite prevalent in the freshwater aquaculture systems of India. In an attempt to further understand the behavior of this economically important parasite, the means of biological transmission, egg laying strategies and effect of temperature on development of eggs was studied. A. siamensis showed opportunistic egg laying behavior where in it used both living and non-living substrata for egg laying. It was marked that the parasites used the shells of freshwater snails of the family Viviparidae, the runners of the water weeds of genus Nymphoides and dead fish in the culture ponds for laying of eggs. This study confirmed that the maximum eggs were laid by the parasite in the habitat usage zone of the host fish. The optimum temperature for development of the eggs of A. siamensis into the infective naupliar stage and hatching was found to be 28 °C. These new insights into the behavior of A. siamensis would be helpful to devise biological control methods against the parasite.

A multikinetic model approach to predict gluconic acid production in an airlift bioreactor.

This paper uses a multikinetic approach to predict gluconic acid (GA) production performance in a 4.5 L airlift bioreactor (ALBR). The mathematical model consists of a set of simultaneous firstorder ordinary differential equations obtained from material balances of cell biomass, GA, glucose, and dissolved oxygen. Multikinetic models, namely, logistic and contois equations constitute kinetic part of the main model. The main model also takes into account the hydrodynamic and mass transfer parameters. These equations were solved using ODE solver of MATLAB v6.5 software. The mathematical model was validated with the experimental data available in the literature and is used to predict the effect of change in initial biomass and air sparging rate on the GA production. It is concluded that the mathematical model incorporated with multikinetic approach would be more efficient to predict the change in operating parameters on overall bioprocess of GA production in an ALBR.

A laboratory study for the treatment of arsenic, iron, and manganese bearing ground water using Fe(3+) impregnated activated carbon: effects of shaking time, pH and temperature.

This paper deals with the experimental investigation related to removal of arsenic from a simulated contaminated ground water by the adsorption onto Fe(3+) impregnated granular activated carbon (GAC-Fe) in presence of Fe(2+), Fe(3+), and Mn(2+). Similar study has also been done with granular activated carbon (GAC) for comparison. The effects of shaking time, pH, and temperature on the percentage removal of As(T), As(III), As(V), Fe(2+), Fe(3+), and Mn have been discussed. The shaking time for optimum removal of arsenic species has been noted as 8h for GAC-Fe and 12h for GAC, respectively. As(T) removal was less affected by the change in pH within the pH range of 2-11. Maximum removal of As(V) and As(III) was observed in the pH range of 5-7 and 9-11, respectively, for both the adsorbents. Under the experimental conditions at 30 degrees C, the optimum removal of As(T), As(III), As(V), Fe, and Mn are 95.5%, 93%, 98%, 100%, and 41%, respectively, when GAC-Fe is used. For GAC these values are 56%, 41%, 71%, 99%, and 98%. The adsorbent dose (AD) and its particle size (PS) for both GAC and GAC-Fe were 30 g/l and 125-150 mum, respectively. The initial arsenic concentration in the synthetic water sample was 200 ppb.