Structure of the amorphous titania precursor phase of N-doped photocatalysts

Amorphous titania samples prepared by ammonia solution neutralization of titanyl sulphate have been characterized by chemical and thermal analyses, and with reciprocal-space and real-space fitting of wide-angle synchrotron X-ray scattering data.

APPLICATION OF TITANYL SULPHATE FOR MANUFACTURING PAPER CONTAINING TIO2 FILLER

The aim of research was first, to study the interactions between components for finding out how pH effects on ζ-potential, dewatering rate and retention of TiO2/MCC mixtures with/without titanyl sulphate in order to find a way to titanyl sulphate hydrolysis in a papermaking process. The maximum heterocoagulation interactions between TiO2, MCC and TiOSO4 were revealed in the pH range 4.4–5.6. Second, handsheets made from refined chemical pulp, titanyl sulphate and TiO2 at pH 4.4 were investigated. The handsheets were formed and studied conventionally and with scanning electron microscopy (SEM). It was shown that titanyl sulphate hydrolysis leads to formation of translucent polymer film covering the fibres and TiO2 particles. The maximum first-pass ash retention reached is lower than its values usually obtained with an organic polymer. Addition of titanyl sulphate led to higher strength, but lowered opacity and brightness compared to a reference sample. The use of low dosage of titanyl sulphate together with a filler improved air permeability. As there exist certain advantages/disadvantages of titanyl sulphate application, extended research is needed to find suitable conditions for its applying to mass paper and board grades production.

Effect of calcination temperature and calcination time on the kaolinite/tio2 composite for photocatalytic reduction of CO2

The kaolinite/TiO2 composite (60 wt% of TiO2) was prepared by thermal hydrolysis of a raw kaolin suspension in titanyl sulphate and calcined at different temperatures (600, 650 and 700°C) and for different times (1, 2 and 3 h). The obtained samples were characterized by XRPD, N2 physical adsorption and SEM, and tested for photocatalytic reduction of CO2. The different calcination conditions did not influence TiO2 phase composition, only slightly changed the specific surface area, and significantly affected crystallite size of kaolinite/TiO2 composite. A higher temperature and longer duration of calcination lead to higher crystallinity of the powder. The photocatalytic results showed that the crystallite size determined the efficiency of kaolinite/TiO2 photocatalysts.

High-temperature growth of anatase on kaolinite substrate

When a fine fraction of kaolinite (less than 2 μm) is mixed with titanyl sulphate (weight ratio approx. 1:7), hydrolysed, washed, dried and heated to temperatures between 750 and 900 ° C, it transforms into metakaolin, and titania crystallizes as anatase with a small particle size (approx. 20–30 nm). In parallel experiments with plain titania (without kaolinite), rutile is the sole product phase at 850 and 900 ° C and the dominant phase in a mixture with anatase at 750 ° C. The particle sizes are much larger (approx. 400–1100 nm). It appears that kaolinite is instrumental in preserving titania in the anatase form and with a small particle size even at fairly high temperatures and hindering its transformation to rutile. However, this anatase exhibits poor photocatalytic activity.