Adsorption kinetic equation has been derived assuming that the process follows the behavior of a heterogeneous chemical reaction at the solid–liquid interface. This equation is converted into the Langmuir isotherm at equilibrium and describes well the unsteady-state adsorption process. Based on that, a working equation has been developed, which gives adsorption-rate-constant independent of operating parameters including concentration. Also, a kinetic model expressed as a sum of first- and second-order systems available in the literature has been applied (modified with the interface reaction concept) to determine the adsorption rate constant. Both methods gave similar results. Three dimensionless numbers have been developed to determine and distinguish pseudo-first-order and pseudo-second-order kinetics justified from the viewpoint of chemical kinetics. It is shown that curve-fitting with a high correlation coefficient could validate an empirical kinetic model, but the fitted model parameters could not automatically be related to chemical kinetic parameters if the model itself is not grounded on well-defined chemical kinetics. Finally, it is concluded that the currently applied empirical approach could not provide reliable data for comparison among similar systems, while the Langmuir kinetic equation developed based on the concept of heterogeneous reaction would be a good basis for standardization of the method for adsorption system characterization.

In the present study, tin oxide (SnO2) nanoparticles were prepared by precipitation method using tin tetrachloride (SnCl4) as precursor and ammonia solution as precipitating agent followed by calcination at 400 ºC for 2 h. As-prepared SnO2 particles were characterized by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR). The powder XRD results revealed that the SnO2 nanoparticles had a typical tetragonal rutile (cassiterite) structure and the average crystallite size calculated by using the Debye –Scherrer equation was found to be approximately 5.1 nm. The photocatalytic activity of the as-prepared photocatalysts was investigated by degrading methylene blue (MB) dye. The effect of pH, catalyst loading and initial dye concentration on photocatalytic degradation was investigated. Results showed that the SnO2 nanoparticles represented excellent photocatalytic activity for the degradation of MB under UV light with 200 min of irradiation time. The results also showed that the pH of solution had a direct influence on the photocatalysis process and basic pH was favorable for the degradation of MB. The effect of pH on photocatalytic activity was explained with the help of zero point charge (pHpzc). Furthermore, the photocatalysts could be easily recycled without significant change in the catalytic activity.

An analysis has been done on the existing models for the prediction of the elastic modulus of fiber-reinforced polymer composites (FRPC). The experimental data reported in different specialized research journals have been fitted to the models. It is found the theoretical models such as the Parallel, Series and Halpin-Tsai model, by no means, predict the modulus within an acceptable deviation factor of 0.1. The semi-empirical models such as modified Halpin-Tsai and Bowyer-Bader model, which have one adjustable parameter, and are expressed in terms of volume fraction describe the modulus satisfactorily. In this paper, a mass fraction based model with one adjustable parameter is proposed, which also describe the modulus successfully. The proposed model, being mass fraction-based, is more convenient to work with than any volume-fraction based model, and unlike all other models (theoretical and semi-empirical), it has the potentials to have practical applications in structural material design.Keywords: Fibers; Polymer-matrix composites (PMCs); Short-fiber composites; Mechanical properties; Prediction model.© 2011 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi:10.3329/jsr.v3i2.6881 J. Sci. Res. 3 (2), 225-238 (2011)

The present study aimed to estimate the growth pattern through length-weight relationships (LWRs), condition (Fulton’s condition factor, KF) and prey-predator status through relative weight (WR) of 9 fish species e.g., Netuma thalassina, Epinephelus coioides, Acanthopagrus berda, Acanthopagrus latus, Acanthopagrus bifasciatus, Parastromateus niger, Aluterus monoceros, Sphyraena putnamae, and Lates calcarifer belong 7 families from the Arabian Sea of Pakistan. Occasionally samples were collected from marine waters of the Arabian Sea connected to Baluchistan and Sindh province from June 2018 to May 2019 by bottom and midwater trawl nets, gill nets, and trammel nets. Individual whole body weight (BW) and total length (TL) were measured. The growth pattern either allometric (+/-) or isometric was calculated as LWR: BW = a × TLb. a and b were the LWR parameters. Condition factor was calculated as KF = (BW/TL3) ×100 and prey-predator status was as WR = (W/WS) × 100, where WS = a×TLb. This study recorded a new maximum TL (150.0 cm) for S. putnamae. The b values of LWR ranged from 2.02 to 2.76 with r2 ≥ 0.95 that indicated a negative allometric growth pattern. Additionally, the study estimated KF mostly above 1.0 except A. bifasciatus, A. monoceros, and S.putnamae. The prey-predator status was mostly balanced except for L. calcarifer. The findings of this study will be valuable for fishery managers to impose sustainable fishery management in the Arabian Sea (Baluchistan and Sindh), Pakistan, and adjacent ecosystems.