Global NEST Journal

In recent years, n-hexadecane, a component of diesel petroleum hydrocarbons, is frequently detected as the contaminant in many soils and water resources. The main aims of this study were focused on the feasibility of using the biodegradation for the removal of n-hexadecane from the soil-slurry system, by assessing the effects of phosphorus sources on biodegradation rate and determining the optimal conditions of the process. This study was carried out using an experimental method at the laboratory scale. The Taguchi method was used to optimize variables and their levels using the Qualitek-4 (w32b) software. We investigated the effects of initial concentration of n-hexadecane as the sole source of carbon (1-80 g/kg of soil), the role of phosphorus sources, at the concentration ranges from 10 to 600 g per Kg of soil, released by different bacterial species (Acinetobacter radioresistens, Pseudomonas aeruginosa, Bacillus subtilis, and the bacterial consortium) at the incubation time between 0 and 30 days. The optimum values of the response variables were predicted through signal-to-noise ratio (S/N). Results indicated that Bacillus subtilis were more effective in n-hexadecane degradation compared to the others (42%). Optimization process by Taguchi method suggested that the optimal conditions for the removal of n-hexadecane in a soil-slurry system are as follows: the initial n-hexadecane concentration as sole source of carbon in soil, Na2HPO4.12H2O as phosphorus source at the concentration of 300 mg per kg of soil and, finally, level of significance for the study parameters were 74.31, 6.48 and 8.51, respectively. In conclusion, bioaugmentation of soil with n-hexadecane-degrading bacteria providing an adequate supply of phosphorus source may enhance the biodegradation rate in a polluted soil.

The growing expectations of the population and the increasingly stringent regulations about air pollution have resulted in the need to minimize and conveniently treat the waste gas from different emission sources. The emissions from a large variety of plants, including waste and wastewater treatment plants, result mainly from the degradation of organic matter. These emissions are composed of a complex of substances emitted at low concentrations from diffusive sources. These characteristics make complex their treatment in economically efficient conditions. The design and management of environmental protection and industrial plants, therefore, require the implementation of focused processes for the control of the target compounds. The present study shows the applicability of an UV-Ozone lab-scale system for odours and VOCs removal. An artificial gaseous stream contaminated by toluene, at different incoming concentrations, was treated evaluating the abatement efficiencies in terms of odours and total VOCs as a function of power and contact time. The residue ozone concentrations was determined in order to optimize the set-up conditions. The results were discussed with the aim of evaluating the feasibility of the investigated solution for the advanced treatment of the waste gas from environmental facilities. Removal efficiencies up tp 91% were reached for the investigated conditions. Lower inlet concentrations resulted in high residue ozone outgoing the processes and, thus, it resulted over dimensioned for inlet load lower than 1,22 mg per minute.

Methylene blue is one of the most widely used dyes in various industries such as textiles and dyeing which, due to toxicity, causes several environmental problems as well as difficulties in wastewater treatment process. Therefore, many studies have been carried out on the removal of the dye from industrial wastewater and aqueous solutions using various adsorbents. In the present study, a Luffa adsorbent surface was first modified by sodium dodecyl sulfate anionic surfactant and then methylene blue dye removal from aqueous solution was studied under various operating conditions in batch experiments. The parameters addressed included of the dye solution pH, adsorbent amount, initial methylene blue concentration in the dye medium, and the duration of adsorption. The use of anionic surfactant changed the adsorbent surface charge and thus increasing absorbent ion exchange capacity. The results showed that the highest removal efficiency occurs in mediums with an initial concentration of 50 mg L-1 and pH 6-9, where 99% of the dye was removed from the medium using 1 gr modified adsorbent in 60 minutes. Since the obtained pH range covered the neutral and near neutral media, the adsorbent can be used in a variety of industries. Finally, the dye adsorption process was modeled and examining the adsorption isotherms, it was observed that the empirical data appropriately followed the Freundlich model.

In this research, the Ag2CO3-PANI composite was synthesized with a simple precipitation method and then used as an effective adsorbent for adsorption of Methylene Blue cationic dyes from aqueous solution. Characterization of the adsorbent was carried out using UV–visible diffuse reflectance spectroscopy (UV–Vis DRS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The various parameters such as pH, contact time, sorbent dosage, initial dye concentration, and dye solution temperature were investigated. The optimum photo-catalytic activity of Ag2CO3-PANI at a weight content of 50% PANI for the degradation of MB was almost 86% that is much higher than the pure Ag2CO3 and PANI. The results showed an efficient removal at pH 10.0, within 60 min, and by using 1 g L-1 Ag2CO3-PANI composite at the temperature of 32˚C. The kinetic and equilibrium data fit into pseudo-second-order kinetic (R2> 0.84) and Freundlich isotherm (R2> 0.99) models, respectively. Adsorption capacity (q0) calculated from Langmuir isotherm was found to be 55 mg/g. Thermodynamic studies indicated that the adsorption process was endothermic (ΔH°˃0). The adsorption/desorption experiments were carried out attaining regenerations of up to 97% from MB, using distilled water and 0.1N HCl. The composite indicated high efficiency adsorptive properties and high reusability.