Structure and activity of TiO2/FeO co-doped carbon spheres for adsorptive-photocatalytic performance of complete toluene removal from aquatic environment

• Photocatalytic carbon spheres were synthesized by doping of TiO2-FeO NPs.
• Carbonization-activation process was conducted under N2/CO2 atmosphere.
• Synthesized composites were used as sorbent and photocatalyst for toluene removal.
• The ban gap energy of photocatalyst (CB-TiO2-FeO) is reduced to 2.68 V.
• Toluene was removed by the photocatalyst (CB-TiO2-FeO) under visible light.

TiO2 and TiO2-FeO co-doped carbon spheres (CB) synthesized with a suspension polymerization process, followed by carbonization and activation, were used to promote the sorption and photocatalytic removal of toluene from aqueous media. The TiO2 nanoparticles (NPs) and Fe doped TiO2 NPs were incorporated during the middle stage of the suspension polymerization reaction. A porous surface texture on the doped CB was developed by a carbonization and activation process at 800 °C under N2 and CO2 atmospheres, respectively. The doped TiO2-FeO NPs acted as visible-light sensitizers for photo-degradation of toluene under visible light irradiation. The maximum removal capacity of toluene (5–100 mg/L of aqueous solution) was found to be 48.3, 78.1 and 103.1 mg/g, for the TiO2, CB-TiO2 and CB-TiO2-FeO, respectively. The great adsorptive-photo-catalytic process for complete removal of toluene with CB-TiO2-FeO was 98.2%. However, reduction of total organic carbon (TOC) and chemical oxygen demand (COD) was achieved 84.2 and 94.6% respectively, after 3.5 h under visible light irradiation at an initial pH of 3.5. The catalytic removal of toluene followed a pseudo-first-order reaction. The toluene removal in the dark phase indicated that nonpolar toluene molecules are initially sorbed onto the porous structure of CB-TiO2-FeO via electrostatic bonding between nonpolar molecule moieties with phenolic surface of CB-TiO2-FeO. The greatly enhanced photocatalytic performance of CB-TiO2-FeO mainly stemmed from their strong visible-light-harvesting ability of photo-generated electron–hole pairs.

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