Keeping in view the growing concern regarding desulphurization of petroleum products, the present study was under taken to investigate the efficiency of tin impregnated activated charcoal (Sn-AC) as a potential adsorbent for the desulphurization of model and real commercial straight run kerosene and diesel oil samples. The adsorbent Sn-AC was prepared by wet impregnation process in the laboratory and characterized by SEM, EDX and surface area analysis. Initial experiments were carried out using model oil, which was prepared by dissolving dibenzothiophene (DBT) in cyclohexane, the optimum conditions for desulfurization were found to be, 60°C temperature, 1h contact time and adsorbent dosage of 0.8g, under which about 99.4% of DBT removal was attained. Under optimized conditions the desulfurization of real oil i.e., kerosene and diesel oil was also investigated. Kinetic studies revealed that DBT adsorption followed pseudo second order kinetics and the data best fits in the Langmuir adsorption isotherm as compared to Freundlich adsorption isotherm model. The adsorbent could be easily regenerated simply by washing with toluene for a multiple cycles and reused without losing its efficiency.

No abstract

The current study addresses the improved desulphurization activity of activated charcoal modified by acetic acid treatment. The modified activated charcoal was investigated as an adsorbent for the elimination of sulfur compounds from the model oil (consisting of dibenzothiophene (DBT) dissolved in cyclohexane) as well as real oil samples including kerosene and diesel oil. In the case of model oil, about 99.5% of DBT was removed under conditions optimized in the laboratory, which included 15 mL feed (model oil) volume, 0.8 g of adsorbent, 60 °C temperature, stirring speed of 100 rpm, and contact time of 1 h under neutral pH. In the case of real oil samples, i.e., kerosene and diesel oil, sulfur removal of 78.69% and 74.29% was attained under optimized conditions, respectively. Experimental results were interpreted through model adsorption isotherms, which indicated that the adsorption process is in close agreement with the Langmuir adsorption isotherm in comparison to the Freundlich adsorption isotherm. The spent adsorbents were regenerated to view their repeated use, simply by washing separately with organic solvents such as toluene, acetonitrile, methanol, and chloroform. Among these, toluene was found to be the best solvent for the regeneration of the spent adsorbents. The regenerated adsorbents were reused and regenerated for six consecutive regeneration cycles.

The present study was planned to explore the selective desulphurization efficiency of the acid-modified activated charcoal (AC) as an adsorbent. The oil samples selected were the model oil and the commercial kerosene & diesel. The adsorption capacity of the AC was evaluated for the removal of one of the sulfur analogs i.e. dibenzothiophene (DBT) present in the fuel samples under a set of experimental conditions. The kinetics and thermodynamics of the DBT desulphurization were studied. It was observed that the adsorption firmly followed pseudo-second order kinetic model. Moreover, the experimental value of the amount of DBT adsorbed at equilibrium "q e " was nearly equal to the value calculated from the pseudo-second order kinetic model. Langmuir and Freundlich adsorption isotherm models were applied and the experimental data best fitted with the Langmuir and Freundlich adsorption isotherm models. Compared to other commercially available adsorbents, the acid-modified AC was found to be cost-effective, highly efficient and selective for the DBT removal from the model as well as real petroleum based oils.

Keeping in view the growing concern regarding polymer degradation, the present study was undertaken with the view to study the effect of UV irradiation on degradation of used polystyrene. Polystyrene was collected from TV and computer packing. It was peeled into pieces and dissolved in toluene. The viscosity measurement was made according to the well reported standard method. The polystyrene sample was irradiated with UV irradiations having wavelength range of 365 nm. The irradiated polystyrene samples were accordingly dissolved in toluene. The viscosity measurements were made to calculate molecular weight. The number of chain sessions per polymer was also calculated. It was observed from the compiled results that UV irradiation has profound effect on the reduction of molecular weight of polystyrene samples. The reduction in the molecular weight indicated the degradation of polystyrene macro molecules by irradiating with UV radiations. It was also observed that the number of chain sessions per polymer was increased by increasing irradiation time. The study will be very helpful for degradation of polymeric materials being dumped into the environment particularly in landfills.

No abstract

Filamentous fungi have been proved to have a pronounced capability to recover metals from mineral ores. However, the metal recovery yield is reduced due to toxic effects triggered by various heavy metals present in the ore. The current study highlights the fungal adaptations to the toxic effects of metals at higher pulp densities for the enhanced bio-recovery of aluminum from lowgrade bauxite. In the previous studies, a drastic decrease in the aluminum dissolution was observed when the bauxite pulp density was increased from 1 to 10% (w/v) due to the high metal toxicity and low tolerance of Aspergillus niger and Penicillium simplicissium to heavy metals. These fungi were adapted in order to increase heavy metal tolerance of these fungal strains and also to get maximum Al dissolution. A novel approach was employed for the adaptation of fungal strains using a liquid growth medium containing 5% bauxite pulp density supplemented with molasses as an energy source. The mycelia of adapted strains were harvested and subsequently cultured in a low-cost oat-agar medium. Batch experiments were performed to compare the aluminum leaching efficiencies in the direct one-step and the direct two-step bioleaching processes. FE-SEM analysis revealed the direct destructive and corrosive action by the bauxite-tolerant strains due to the extension and penetration of the vegetative mycelium filaments into the bauxite matrix. XRD analysis of the bioleached bauxite samples showed a considerable decline in oxide minerals such as corundum and gibbsite. Results showed a high amount of total Al (≥ 98%) was successfully bioleached and solubilized from low-grade bauxite by the adapted fungal strains grown in the presence of 5% pulp density and molasses as a low-cost substrate.

Hydrogels have attracted great attention as good adsorbents due to their extraordinary water retention capacity, unique hydrophilic nature, biocompatibility, and abundance in availability. In this work, a superabsorbent polymer (SAP) hydrogel and its composite were synthesized, with the introduction of activated charcoal (SAP-AC) for deep removal of the ecotoxic organic dye methylene blue (MB). The formation of the hydrogel was confirmed by FTIR analysis, and scanning electron microscopy (SEM) revealed the appearance of a porous microstructure due to the incorporation of AC. A continuous upflow column was set up, and the adsorption parameters were optimized using an experimental Doehlert uniform array design. The residual concentration of MB was analyzed by UV-Vis spectrophotometry at 665 nm (λmax). The experimental data were also discussed in terms of adsorption kinetics and adsorption isotherm models. Accordingly, MB adsorption followed pseudo second-order kinetics and better fits the Freundlich isotherm, suggesting a chemisorption mechanism and a multilayer MB adsorption system. The maximum adsorption capacity was 202.84 mg g−1 (96.96%) using the SAP and 213.2 mg g−1 (99.48%) using the SAP-AC. The present study proved that the synthesized composite hydrogel has good activity and selectivity for deep removal of the MB dye and can be effectively used in wastewater treatment.