Integrated Adsorption-Photodegradation of Organic Pollutants by Carbon Xerogel/Titania Composites.

Recent studies on the removal of pollutants via adsorption include the use of carbon-based adsorbents, due to their high porosity and large surface area; however, such materials lack photoactive properties. This study evaluates the synergistic effect of integrated mesoporous carbon xerogel (derived from resorcinol formaldehyde) and titanium dioxide (TiO2) for combined adsorption and photodegradation application. The complex formed between carbon xerogel and TiO2 phase was investigated through FTIR, proving the presence of a Ti-O-C chemical linkage. The physicochemical properties of the synthesised adsorbent-photocatalyst were probed using FESEM, BET analysis and UV-Vis analysis. The kinetics, equilibrium adsorption, effect of pH, and effect of adsorbent dosage were investigated. The expansion of the absorbance range to the visible range was verified, and the corresponding band gap evaluated. These properties enabled a visible light response when the system was exposed to visible light post adsorption. Hence, an assistive adsorption-photodegradation phenomenon was successfully executed. The adsorption performance exhibited 85% dye degradation which improved to 99% following photodegradation. Further experiments showed the reduction of microorganisms under visible light, where no microbial colonies were observed after treatment, indicating the potential application of these composite materials.

Concentration Dependence of TiO2 Nanoparticles in Carbon Xerogels on Adsorption-Photodegradation Applications.

A suite of composite materials comprising carbon xerogel content and TiO2 was synthesised via a modified sol-gel method. The textural, morphological, and optical properties of the composites were extensively characterised and correlated with the observed adsorption and photodegradation performances. The homogeneity and porous structure of the composites depended on the amount of TiO2 deposited in the carbon xerogel. During polymerisation, Ti-O-C linkages were formed, which favoured the adsorption and photocatalytic degradation of the target methylene blue dye. Adsorption was deemed favourable, and most accurately fitted by the Sips model, exhibiting a maximum uptake of 209 mg g-1 estimated for the sample containing 50% TiO2. However, the synergistic effect of adsorption and photocatalytic degradation for each composite depended on the amount of TiO2 deposited in the carbon xerogel. The dye degradation process for the composites with 50%, 70%, and 90% TiO2 improved by 37%, 11%, and 2%, respectively, after exposure to visible light after adsorption. Repeated runs demonstrated over 80% of activity was retained after four cycles. Thus, this paper provides insight into the optimal amount of TiO2 required within such composites for maximum removal efficiency via adsorption and visible light photocatalysis.

Effective Carbon/TiO2 Gel for Enhanced Adsorption and Demonstrable Visible Light Driven Photocatalytic Performance.

A new strategy to synthesise carbon/TiO2 gel by a sol-gel method is proposed. Textural, morphological, and chemical properties were characterised in detail and the synthesised material was proven to be an active adsorbent, as well as a visible light photocatalyst. Homogenously distributed TiO2 is mesoporous with high surface area and, hence, exhibited a high adsorption capacity. The adsorption equilibrium experimental data were well explained by the Sips isotherm model. Kinetic experiments demonstrated that experimental data fitted a pseudo second order model. The modification in electronic structure of TiO2 resulted in a reduced bandgap compared to commercial P25. The absorption edge studied through UV-Vis shifted to the visible region, hence, daylight photocatalytic activity was efficient against degradation of MB dye, as an example pollutant molecule. The material was easily removed post treatment, demonstrating potential for employment in industrial water treatment processes.