Issue 4

In this study, the removal of a cationic dye, basic red 18, used in the textile industry with montmorillonite was investigated as a function of initial dye concentration, pH, agitation speed, adsorbent dosage, ionic strength, and temperature. Adsorption process was attained to the equilibrium within 30 minutes. The adsorption capacity of basic red 18 increased with increasing ionic strength, initial dye concentration, pH, agitation speed, and temperature, but decreased with increasing adsorbent dosage. The experimental data were analyzed by Langmuir, Freundlich, Temkin, Elovich and Dubinin-Radushkevich isotherms, and it was found that the isotherm data were reasonably correlated by Freundlich isotherm. Pseudo-first order, pseudo-second order, Elovich kinetic equations and intraparticle diffusion model were used to examine the experimental data of different initial conditions. It was found that the pseudo-second order kinetic equation described the data of dye adsorption onto montmorillonite very well. Furthermore, for the removal of basic red 18, a semi-empirical model was established. Thermodynamic analysis was carried out for basic red 18 onto montmorillonite. It was found that the adsorption processes were endothermic in nature. The values of Ea, ΔH*, ΔS* and ΔG* at 293 K for basic red 18 adsorption on clay were calculated as 27.635 kJ mol-1, 25.041kJ mol-1, -0.090 kJ mol-1 K-1 and 51.412 kJ mol-1, respectively. The results indicated that montmorillonite could be employed as an alternative to commercial adsorbents in wastewater treatment for the removal of color and dyes.

The effect of different operational parameters in UV/TiO2 process, such as initial dye concentration (20-50 mg l-1), light intensity (8-45 W m-2), pH (2.83-10.22), hydrogen peroxide concentration (100-500 mg l-1), temperature (21-45 ˚C) and photocatalyst concentration (150-900 mg l-1) were investigated on the decolorization of Acid Yellow 23 as a model compound from monoazo textile dyes. The apparent first-order rate constants (kap) were evaluated which confirms pseudo first-order kinetics. kap increased with the enhancement of pH, light intensity and temperature. A desired concentration found for hydrogen peroxide (400 mg l-1) and photocatalyst concentration (750 mg l-1). The SnO2 photocatalyst was not as effective as TiO2 but had the same desired concentration (750 mg l-1). Then TiO2+SnO2 suspensions (375+375 mg l-1) as photocatalysts were employed for decolorization at different solution thicknesses. The results showed that the coupled particles were not much different from single TiO2 system at the solution thickness of 4.5 cm in a batch reactor. But the coupled system was more effective when the solution thickness was reduced to 2.5 cm. Over 90% of decolorization occurs at the solution thickness of 1.1 cm after 30 min of irradiation while 90% decolorization takes place at the solution thickness of 4.5 cm after 100 min of irradiation.

The present study has successfully explored the use of pomegranate seed de-oiled cake as a major additive and micronutrients solution as a minor additive to enhance production of biogas and enrich its methane content, using mango peel as the initial substrate. While micronutrients solution has activated enzymes to carry out anaerobic digestion for optimal production of biogas and methane, pomegranate seed de-oiled cake has (a) provided buffering capacity for stabilized pH/alkalinity:acidity ratio, (b) reduced C:N ratio of the substrates to facilitate anaerobic digestion, cumulatively effecting enhanced biogas generation (0.82 m3 kg-1 VS fed) and its rich methane content (0.64 m3 kg-1 VS fed)