RESUMO
Adsorbents with hydrophilic and hydrophobic natures were designed by intercalating a bioderived molecule; 4,4'-diammonium-α-truxillic acid (4ATA) and 4,4'-diammonium-α-truxillic acid dimethyl ester (E4ATA), which both are bioderived molecules, into a smectite (purified bentonite) to concentrate o-phenylphenol and biphenyl, respectively, from water. The adsorption isotherm showed high affinity between the 4ATA-smectite hybrid and o-phenylphenol with a high Langmuir constant (0.98 L mg-1). Meanwhile, the E4ATA-smectite hybrid adsorbed biphenyl with a high Langmuir constant (3.61 L mg-1). The adsorption properties of 4ATA- and E4ATA-smectite hybrid were contributed by the chemical characteristics of 4ATA and E4ATA in the interlayer space of the smectite.
RESUMO
CO2 reduction as an artificial photosynthetic system is a promising technology to produce green energies and chemicals because it uses light energy to convert H2O and CO2 into valuable products such as CO, HCOOH, CH3OH, CH4, and preferably higher hydrocarbons. In photocatalytic reduction, water should be used as hydrogen and electron sources for CO2 reduction. Moreover, CH4 formation is an attractive and challenging topic because of the eight-electron-reducing product of CO2. Herein, we report the development of a new Rh-Ru cocatalyst decorated on an alkaline earth-doped NaTaO3 surface for the photocatalytic CO2 reduction to form CH4 using water as an electron donor. CH4 was obtained by a photocatalytic "uphill" reaction of CO2 reduction using Rh-Ru cocatalyst-loaded NaTaO3:Sr, water, and CO2 in an aqueous suspension system. About 10% of a selectivity (electronic efficiency) was obtained for CH4 formation under ambient conditions accompanied with O2 evolution of the oxidation product of H2O.
RESUMO
Various amounts of Rh-doped titanate nanosheets (Ti3NS:Rh(x), where x is doped amount) were prepared to develop a new nanostructured photocatalyst based on metal oxide compounds that can split water to produce H2 under sunlight. Ti3NS:Rh(x) was obtained by acid exchange, intercalation, and exfoliation of Rh-doped layered sodium titanate compound (Na2Ti3-x Rh x O7). A new energy gap was found in the diffuse reflection spectrum of the Ti3NS:Rh(x) colloidal suspension solution; this new energy gap corresponds to electrons in the 4d level of Rh3+ or Rh4+, which are doped in the Ti4+ site. A photocatalyst activity of Ti3NS:Rh(x) for H2 evolution in water with triethylamine (TEA) as an electron donor was investigated. The appropriate amount of Rh doping can improve the photocatalytic activity of Ti3NS for H2 evolution from water using triethylamine (TEA) as a sacrifice agent. The reason was related to the rich state of Rh3+ or Rh4+ doped in the Ti4+ site of Ti3NS. Doping Rh 1 mol % of Ti, Ti3NS:Rh(0.03) shows the H2 evolution rates up to 1040 nmol/h, which is about 25 times larger than that of nondoped Ti3NS under UV irradiation (>220 nm) and 302 nmol/h under near-UV irradiation (>340 nm). These results show that the development of new nanostructured photocatalyst based on Rh-doped titanate compounds that can produce H2 under near-UV irradiation present in sunlight was a success.