TiO2 exists naturally in three crystalline forms: anatase, rutile, brookite, and TiO2 (B). These polymorphs exhibit different properties and consequently different photocatalytic performances. This paper aims to clarify the differences between titanium dioxide polymorphs, and the differences in homophase, biphase, and triphase properties in various photocatalytic applications. However, homophase TiO2 has various disadvantages such as high recombination rates and low adsorption capacity. Meanwhile, TiO2 heterophase can effectively stimulate electron transfer from one phase to another causing superior photocatalytic performance. Various studies have reported the biphase of polymorph TiO2 such as anatase/rutile, anatase/brookite, rutile/brookite, and anatase/TiO2 (B). In addition, this paper also presents the triphase of the TiO2 polymorph. This review is mainly focused on information regarding the heterophase of the TiO2 polymorph, fabrication of heterophase synthesis, and its application as a photocatalyst.
The danger from the content of dyes produced by textile-industry waste can cause environmental degradation when not appropriately treated. However, existing waste-treatment methods have not been effective in degrading dyes in textile waste. Zero-valent iron (ZVI), which has been widely used for wastewater treatment, needs to be developed to acquire effective green production. Tea (Camellia sinensis) leaves contain many polyphenolic compounds used as natural reducing agents. Therefore, this study aims to synthesize ZVI using biological reducing agents from tea-leaf extract and apply the Fenton method to degrade the color mixture of rhodamine B and methyl orange. The results show that the highest polyphenols were obtained from tea extract by heating to 90 °C for 80 min. Furthermore, PSA results show that ZVI had a homogeneous size of iron and tea extract at a volume ratio of 1:3. The SEM-EDS results show that all samples had agglomerated particles. The ZVI 1:1 showed the best results, with a 100% decrease in the color intensity of the dye mixture for 60 min of reaction and a degradation percentage of 100% and 66.47% for rhodamine B and methyl orange from LC-MS analysis, respectively. Finally, the decrease in COD value by ZVI was 92.11%, higher than the 47.36% decrease obtained using Fe(II).
The use of mineral/polyimide composites for lithium-ion battery separators provides an outstanding development direction. Minerals that can be used for lithium-ion battery separators are minerals that have good pores size and distribution, can be intercalated with lithium-ions, and are hydrophobic. Montmorillonite is a natural mineral belonging to the smectite group, and has the capacity to exchange cations but is hydrophilic so it is necessary to modify it to make it hydrophobic and to keep it rich in lithium ions for such purpose. In this study, organic modification has been carried out to change the hydrophilic nature of montmorillonite to become hydrophobic under lithium-ion-rich conditions. Montmorillonite was first isolated by sonicating the dispersion, then carefully separating its suspension after several days of aging. Afterward, the suspension was precipitated by centrifugation and finally dried at 80°C. Thereafter, carbonate cations, organic compounds, and metal oxides, especially ferrous oxide, are removed. The purified isolated montmorillonite is then lithiated with lithium chloride. Finally, the surface of the pre-lithiated montmorillonite was modified with cetyltrimethylammonium bromide to obtain organic-modified pre-lithiated montmorillonite. The results of characterization with an infrared spectrophotometer showed vibration peaks at 2928 cm-1, 2854 cm-1, and 1476 cm-1 as evidence of the presence of attached cetyltrimethylammonium, and vibration peaks at 520 cm-1 and 463 cm-1 as evidence of the presence of attached lithium. The results were also characterized by SEM and XRD which shows that the montmorillonite was organically modified, and lithium intercalated.
This study aims to develop an alternative method in the green synthesis of zero valent iron (ZVI) from tea leaves extract and its application as a Fenton catalyst for textile dyes removal. Tea leaves extract having high polyphenolic contents were used as reducing agents in this study and the ZVI obtained from them was characterized by UV-VIS, SEM-EDS, FTIR, PSA and XRD techniques. The synthesized zero valent iron (ZVI) was utilized as a Fenton like catalyst for textile dyes removal. The results showed that this system was highly efficient regarding the dyes removal of about 95.96% using 80 mg/L ZVI. Moreover, using 100 mg/L ZVI, the COD number reduced to 94.68%.
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