Modification of natural chitosan with Fe and Ce cations as photocatalyst beads: Degradation of dye chemicals and textile wastewater under UVA light.

The photocatalytic effect of ferrous and cerium loaded catalysts produced from chitosan beads (CB) was investigated for dye removal and textile wastewater degradation. Commercially available chitosan was initially shaped into beads form and modified with ferrous and cerium compounds. The amount of ferrous and cerium loaded on the chitosan beads were calculated as 22 mg Fe/g CB, 60 mg Ce/g CB, respectively. The chemical formation and morphology of the catalysts were characterized with SEM-EDS. Photocatalytic studies with UVA irradiation were carried out using 20 mg/L Direct Orange 46 (DO46) textile dye solution, 1 g/L catalyst and 10 mM H2O2 and the dye removal efficiencies for CB, Fe/CB and Ce/CB were obtained as 10%, 60% and 26%, respectively As a result of the characterization and photocatalytic studies, the produced Fe/CB was then used for the treatment of the textile industry wastewater and while 21% total organic carbon (TOC) removal efficiency was obtained, 30, 23 and 26% color removal efficiencies were calculated for 436, 525 and 620 nm wavelengths, respectively.

A mixed integer linear programming model for long-term planning of municipal solid waste management systems: Against restricted mass balances.

Long-term planning of municipal solid waste management systems is a complex decision making problem which includes a large number of decision layers. Since all different waste treatment and disposal processes will show different responses to each municipal solid waste component, it is necessary to separately evaluate all waste components for all processes. This obligation creates an obstacle in the programming of mass balances for long-term planning of municipal solid waste management systems. The development of an ideal mixed integer linear programming model that can simultaneously respond to all essential decision layers including waste collection, process selection, waste allocation, transportation, location selection, and capacity assessment has not been made possible yet due to this important modeling obstacle. According to the current knowledge of the literature, all mixed integer linear programming studies aiming to address this obstacle so far have had to restrict many different possibilities in their mass balances. In this study, a novel mixed integer linear programming model was formulated. ALOMWASTE, the new model structure developed in this study, was built to take into consideration different process, capacity, and location possibilities that may occur in complex waste management processes at the same time. The results obtained from a case study showed the feasibility of new mixed integer linear programming model obtained in this study for the simultaneous solution of all essential decision layers in an unrestricted mass balance. The model is also able to provide significant convenience for the multi-objective optimization of financial-environmental-social costs and the solution of some uncertainty problems of decision-making tools such as life cycle assessment.

Kinetic and equilibrium studies in removing lead ions from aqueous solutions by natural sepiolite.

The capacity of sepiolite for the removal of lead ions from aqueous solution was investigated under different experimental conditions. The Langmuir and Freundlich equations, which are in common use for describing sorption equilibrium for wastewater-treatment applications, were applied to data. The constants and correlation coefficients of these isotherm models for the present system at different conditions such as pH, temperature and particle size were calculated and compared. The equilibrium process was well described by the Langmuir isotherm model and the maximum sorption capacity was found to be 93.4 mg/g for the optimal experimental condition. The thermodynamic parameters (DeltaG(o), DeltaH(o) and DeltaS(o)) for lead sorption on the sepiolite were also determined from the temperature dependence. The influences of specific parameters such as the agitation speed, particle size and initial concentration for the kinetic studies were also examined. The sorption kinetics were tested for first order reversible, pseudo-first order and pseudo-second order reaction and the rate constants of kinetic models were calculated. The best correlation coefficients were obtained using the pseudo-second order kinetic model, indicating that lead uptake process followed the pseudo-second order rate expression.

Removal of phosphate from aqueous solutions by electro-coagulation.

The aim of this paper was to investigate the feasibility of the removal of phosphate from aqueous solution by electro-coagulation (EC). The current density (CD) between 2.5 and 10 mA cm(-2) and duration in the limits of 5-20 min were tried for different concentrations. In order to determine optimal operating conditions, the EC process used for the phosphate removal was examined in dependence with the CD, initial concentrations and time. The results of the experimental batch processing showed high effectiveness of the EC method in removing phosphate from aqueous solutions.