Influence of the surface modification of granular-activated carbon synthesized from macauba on heavy metal sorption.

Adsorption on activated carbon is a promising technique for the treatment of low-concentration heavy metal pollutants in water with high efficiency and simple operation. However, commercial-activated carbon is often associated with high costs. Therefore, much attention has been given to activated carbon derived from low-cost agricultural and residual biomass. In this work, adsorption of Zn, Cd, and Pb ions in aqueous solutions was conducted using granular-activated carbon obtained from macauba palm, biomass waste of biofuel production, after surface modification using different methods. The adsorbents were obtained in granular form which facilitates all steps of the use, recovery, and reuse of the material, differently from the powdered-activated carbon normally used. The materials were characterized by using XPS, elemental analysis, N2 sorption (BET method), and zeta potential measurements. Such techniques allowed observation of the functionalization of the carbon surface. The materials presented high adsorption capacities when compared to other works in the literature, with a capacity of approximately 7.69, 8.42, and 1.63 mmol g-1 for Zn2+, Cd2+, and Pb2+, respectively. In addition, the materials showed a high capacity to be reused, removing 75% of Pb and 99% of both Cd and Zn after 4 cycles.

Photocatalysis Meets Magnetism: Designing Magnetically Recoverable Supports for Visible-Light Photocatalysis.

While magnetic supports have been widely used to immobilize homogeneous catalysts in organic chemistry, this strategy has so far found very little application in photocatalysis. Indeed, magnetic supports are dark colored, and thus compete for photon absorption with photocatalysts themselves. We have developed a series of core-shell Fe(0)-silica nanoparticles as supports for immobilizing the photosensitizer Ru(bpy)32+, featuring various silica shell thicknesses-16-34 nm SiO2-on 9 nm Fe cores. The supports and the resulting photocatalytic systems were studied for their magnetic, optical, and catalytic properties in the context of the photooxidation of citronellol, and we found that thicker silica shells lead to higher catalytic activity. We correlated this effect as well as Ru(bpy)32+ fluorescence and singlet oxygen generation to the absorption properties of the supports. We were able to reuse our optimal system three times with minimal loss of activity and achieved turnover numbers largely surpassing the performance of homogeneous Ru(bpy)32+. This work highlights the role of material design in the conception of new supports for applications in heterogeneous photocatalysis.