Highly efficient biosorptive removal of lead from industrial effluent

This study has been focused on the efficient removal of Pb (II) from contaminated waters by biosorption using plant derived material. Accordingly an indigenous shrub, Tinospora cordifolia has been identified as the most suitable biosorbent. The plant biomass was subjected to optimization of various parameters such as the pH, equilibrium time, dosage, concentration, temperature and the applicable adsorption models. The optimum pH identified was 4.0 with a contact time of 60 min at room temperature (27 ± 2 °C). The experimental data fitted well to adsorption isotherms and the uptake capacity of Pb (II) was found to be 20.83 and 63.77 mg/g in batch mode and column mode, respectively. The high correlation factors obtained for Langmuir and Freundlich models indicated that both models were obeyed by the system. Kinetic study for adsorption of Pb (II) follow only pseudo second order rate of reaction. The accumulation of lead in biomass was confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. The FTIR analysis indicated the involvement of hydroxyl (−OH), alkenes (=CH) and carbonyl group (C = O) chelates in metal binding. The SEM and EDX analysis showed the structural changes and the filling of voids in the biomass thus, it indicated the metal-binding mechanism. In elution studies, the 0.1 M Na₂CO₃ was found to be the best with about 71% elution of the adsorbed metal. The biomass was then used for the removal of Pb (II) in synthetic and real wastewater samples from a lead-acid battery industry. It is also noteworthy that even at a very high concentration of 450 mg/L, the biomass was showing about 92% removal. The result is to establish the efficacy of T. cordifolia as a very good bioadsorbent for the Pb (II) removal from contaminated water.

     

Semi-analytical study on environmental dispersion of settling particles in a width-independent wetland flow

Environmental Fluid Mechanics - Predicting the evolution of environmental dispersion of settling particles in wetland flows has a wide range of applications in ecological engineering. In the...     

Testing the rational expectations hypothesis in a secondary materials market

In the context of a supply-demand model for wastepaper in the United States, it is demonstrated that the estimated low adjustment rate associated with the hypothesis of adaptive expectations on price changes translates into an almost instantaneous adjustment in terms of price levels. Further, it is shown that the rational expectations hypothesis is an acceptable framework to analyze this market, and that using this hypothesis, the price elasticity of supply is estimated to be 0.23, which is nearly twice the value obtained using adaptive expectations.     

An econometric model of wastepaper recycling in the USA

A simultaneous model describing the demand for and supply of wastepaper in the USA during 1952-74 has been estimated using the three stage least squares procedure. In our analysis, a low supply elasticity coupled with a zero price elasticity of demand explains the volatile nature of wastepaper prices. The structural estimates indicate that neither the elimination of differential rail freights nor the elimination of preferential tax treatment of stumpage profits will have a significant effect in stimulating the recycling effort.