Recent trends in legislation across the world are aimed toward the reduction of the levels of sulfur in fuel oils to less than 10 ppm (ultra low sulfur diesel, ULSD) due to its toxic and environmental effects. Hydrodesulfurization (HDS) is the current method used for desulfurization and faces technical challenges, due to the extreme conditions and energy consumption necessary to reach low sulfur levels. Recently, ionic liquid (IL) technology has been proposed as a possible solution toward achieving ULSD. ILs represent a new class of “green” solvents that are gaining popularity due to their favorable properties and have recently been shown to be effective extractants for desulfurization on a laboratory scale. In this work, the feasibility of industrial scale IL-extractive processing of ULSD has been examined via the simulation and optimization of a conceptual process in ASPEN Plus. The widely used [Cnmim] [NTF2] series of ionic liquids have been employed, due to their favorable properties and the availability of experimental data in literature. User-defined ionic liquid components have been created within ASPEN Plus, incorporating several thermodynamic and physical property parameters derived from literature, to allow the process to be simulated via the UNIFAC thermodynamic method. On the basis of the technical analysis, it is proposed that the most feasible process configuration consists of HDS as a preliminary treatment, followed by IL extraction as intermediate treatment to reduce the sulfur content to 50 ppm, with adsorption as the final treatment to achieve ULSD levels.

Hexavalent chromium removal from wastewater using sheep wool was investigated at several equilibration periods. The influence of contact time, pH, adsorbent dosage and initial concentration was investigated. Adsorption isotherms for long and short periods were fitted to the Langmuir and Freundlich isotherms. For short contact times, the Langmuir adsorption isotherm was obeyed with no detectable change in the oxidation state but removal percentages did not exceed 90%. Long contact times resulted in more than 99% removal of Cr(VI). A 2-step mechanism for the removal is proposed. Free wool and wool loaded with Cr(VI) were characterized by FTIR and SEM.

Alizarin red S (ARS) removal from wastewater using sheep wool as adsorbent was investigated. The influence of contact time, pH, adsorbent dosage, initial ARS concentration and temperature was studied. Optimum values were: pH = 2.0, contact time = 90 min, adsorbent dosage = 8.0 g/L. Removal of ARS under these conditions was 93.2%. Adsorption data at 25.0 °C and 90 min contact time were fitted to the Freundlich and Langmuir isotherms. R2 values were 0.9943 and 0.9662, respectively. Raising the temperature to 50.0 °C had no effect on ARS removal. Free wool and wool loaded with ARS were characterized by Fourier Transform Infrared Spectroscopy (FTIR). ARS loaded wool was used as adsorbent for removal of Cr(VI) from industrial wastewater. ARS adsorbed on wool underwent oxidation, accompanied by a simultaneous reduction of Cr(VI) to Cr(III). The results hold promise for wool as adsorbent of organic pollutants from wastewater, in addition to substantial self-regeneration through reduction of toxic Cr(VI) to Cr(III). Sequential batch reactor studies involving three cycles showed no significant decline in removal efficiencies of both chromium and ARS.

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Two novel nitrogen-rich aminal linked porous organic polymers, NRAPOP-O and NRAPOP-S, have been prepared using a single step-one pot Schiff-base condensation reaction of 9,10-bis-(4,6-diamino-S-triazin-2-yl)benzene and 2-furaldehyde or 2-thiophenecarboxaldehyde, respectively. The two polymers show excellent thermal and physiochemical stabilities and possess high porosity with Brunauer–Emmett–Teller (BET) surface areas of 692 and 803 m2 g−1 for NRAPOP-O and NRAPOP-S, respectively. Because of such porosity, attractive chemical and physical properties, and the availability of redox-active sites and physical environment, the NRAPOPs were able to effectively remove Cr(VI) from solution, reduce it to Cr(III), and simultaneously release it into the solution. The efficiency of the adsorption process was assessed under various influencing factors such as pH, contact time, polymer dosage, and initial concentration of Cr(VI). At the optimum conditions, 100% removal of Cr(VI) was achieved, with simultaneous reduction and release of Cr(III) by NRAPOP-O with 80% efficiency. Moreover, the polymers can be easily regenerated by the addition of reducing agents such as hydrazine without significant loss in the detoxication of Cr(VI).