A Rancieite type material (K2Mn4O9) nanomaterial was synthesized and tested for the removal of chromium (III) and chromium (VI) from aqueous solutions. The synthesized nanomaterial was characterized using powder XRD and SEM. XRD showed weak diffraction peaks at only at the angles associated with K2Mn4O9. The SEM corroborated that the nanoparticles were present; however, the nanoparticles were clustered into larger aggregates. Batch studies were performed to determine the optimum pH, capacity, time dependency, interferences, and the thermodynamics of the binding. The optimum pH for the binding of Cr(III) and Cr(VI) were determined to be pH 5 and pH 2, respectively. Isotherm studies were performed at temperatures of 4 , 25 , and 45 for Cr(III) and Cr(VI) and showed binding capacities of 21.7 mg/g, 36.5 mg/g, 41.8 mg/g for Cr(III). The Cr(VI) binding capacities were 4.22 mg/g, 4.08 mg/g, and 3.25 mg/g at the respective temperatures. The thermodynamic studies showed that the binding processes for the reactions were spontaneous and endothermic, with a ΔH was 17.54 kJ/mol for Cr(III) and 6.05 kJ/mol for Cr(VI). The of sorption for Cr(III) were determined to be −3.88 kJ/mol, −5.83 kJ/mol and −7.03 kJ/mol at the aforementioned temperatures. The ΔG values for the Cr(VI) sorption were determined to be −4.89 kJ/mol, −5.64 kJ/mol, and −6.05 kJ/mol. In addition, the ΔS values for Cr(III) and Cr(VI) were determined to be 77.92 J/mol and 39.49 J/mol, respectively. The thermodynamics indicate that the binding of Cr(III) and Cr(VI) is spontaneous and endothermic.

Highlights  A TiS2 nanomaterial was synthesized through a solvothermal process  The binding of Cu 2+ and Pb 2+ ions from aqueous solution to the TiS2 was pH dependent  Lead bound by chemisorption copper bound by a combination of chemi/physi sorption  Hard cations showed little to no effect on the binding of Pb 2+ ions to TiS2  Hard cations affected Cu 2+ ion binding to TiS2

Highlights:  A triphasic La-Co-Mo sulfide HDS catalyst was successfully synthesized using solvothermal synthesis  LaCoMoS2 showed enhanced activity over CoMoS2 catalysts.  The LaCoMoS2 activity as improved with increasing La doping  LaCoMoS2 showed less carbon than CoMoS2 after once catalytic cycle.  The La doping of the CMoS2 catalyst led to improvement in the direct desulfurization pathway.

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