The photocatalysts Pd/TiO2, Ag/TiO2 and Ag/Pd-TiO2 were prepared using the sol immobilization method. The photocatalysts were characterized by the use of diffuse reflectance spectra (DRS) and photoluminescence spectra. Analysis of Ag/TiO2 and Ag/Pd-TiO2 using diffuse reflectance spectra (DRS) indicated reduction of band gap energy from 3.2 eV to 2.7 eV for Ag/Pd-TiO2 which makes it possible for the use of sunlight as excitation energy. Photo luminescence spectra analysis carried out on the dopants of Ag/TiO2, Pd/TiO2 and Ag/Pd-TiO2 measured the intensity which gives the rate of recombination of photo-generated electron-hole pairs in TiO2. The result indicated that reduction in intensity was highest for the co-doped Ag/Pd-TiO2. This accounts for its increase in photo catalytic property. Therefore, modification of TiO2 with Ag and Pd will provide the platform for its enhanced photocatalytic performance relevant in environmental science.
The effect of modified TiO2with palladium, silver and co-dopant of palladium and silver on TiO2with its photocatalytic efficiency were studied using X-ray diffraction (XRD) and Brunauer-Emmet-Teller (BET). The photocatalysts were prepared by sol immobilization method and characterized using XRD and BET techniques. The X-ray diffraction patterns of the dopants were found to be uniform with the standard P25 degussa TiO2. From the peak formation of anatase and rutile phases, it was found that the Pd/TiO2formed uniform matrix of anatase and rutile indicating that palladium ion disperses evenly on P25 degussa TiO2. The peak formation on Ag/TiO2 and Pd/AgTiO2shows the same uniform distribution of silver and palladium ion, only that foreign peak were observed on the formation of anatase and rutile because of impurity on silver. The crystalline size of the catalyst and full width at half maximum (FWHM) were also calculated at different angles of diffraction. The BET shows that the photocatalysts were mesoporous and is type IV isotherm. The high mesopore of the catalyst increases its photocatalytic activity, so also type IV isotherm. The BET analysis shows that the pore size distribution of the catalyst is between 2nm and 50nm which shows that the catalyst is mesoporous. It also gives high surface area with high volume and low pore size (crystalline size) which increases the photocatalytic efficiency. So co-doping of palladium and silver on TiO2 can serve as a strategy for design of high performance photocalysts for environmental benefits.
This work is aimed at assessing the effect of incorporating Pseudomonas macerans and Bacillus subtilis on burnt kaolin (BK) during the biodegradation of 1-methyl naphthalene. The biodegradation was monitored by determining the concentration of CO2 released. Immobilized Pseudomonas macerans on BK released CO2 in the range of 0.72-0.83 mg/L, while this was 0.68-0.78 mg/L with Bacillus subtilis; for the degradation alone the range was 0.39-0.46 mg/L after 72 h. Generally, the concentration of carbon (IV) oxide released by the immobilized Pseudomonas macerans was more than that by Bacillus subtilis. Therefore, immobilization using BK resulted to better removal of the organic pollutant. The FTIR indicated presence of new peaks within the regions 3272-3265cm-1 and 1647-1640cm-1 attributed to overlapping of hydroxyl (-OH) and carbonyl (C=O) stretching in carboxylic acid. The absorptions within 1114-1088 cm-1 , and at 1408cm-1 are due to CO stretching and O-H in plane bending of carboxylic acid respectively. The use of kaolin for environmental clean-up of organic pollutants will enhance the value chain of solid minerals in Nigeria.
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