Light-driven methane conversion: unveiling methanol using a TiO2/TiOF2 photocatalyst

A TiO2/TiOF2 composite has been synthesized through a hydrothermal method and characterized using X-ray diffraction, Raman spectroscopy, UV-vis diffuse reflectance, SEM-EDX, TEM, and N2 adsorption-desorption isotherms. The percentage of exposed facet [001] and the composition of TiO2/TiOF2 in the composite were controlled by adjusting the amount of HF and hydrothermal temperature synthesis. Three crucial factors in the photocatalytic conversion of methane to methanol, including the photocatalyst, electron scavenger (FeCl2), and H2O2 were evaluated using a statistical approach. All factors were found to have a significant impact on the photocatalytic reaction and exhibited a synergistic effect that enhanced methanol production. The highest methanol yield achieved was 0.7257 μmole h-1 gcat-1. The presence of exposed [001] and fluorine (F) in the catalyst is believed to enhance the adsorption of reactant molecules and provide a more oxidative site. The Fenton cycle reaction between FeCl2 and H2O2 was attributed to reducing recombination and extending the charge carrier lifetime. Incorporating Ag into the TiO2/TiOF2 catalyst results in a significant 2.2-fold enhancement in methanol yield. Additionally, the crucial involvement of hydroxyl radicals in the comprehensive reaction mechanism highlights their importance in influencing the process of photocatalytic methane-to-methanol conversion.

Recent Advances in Photocatalytic Oxidation of Methane to Methanol

Methane is one of the promising alternatives to non-renewable petroleum resources since it can be transformed into added-value hydrocarbon feedstocks through suitable reactions. The conversion of methane to methanol with a higher chemical value has recently attracted much attention. The selective oxidation of methane to methanol is often considered a “holy grail” reaction in catalysis. However, methanol production through the thermal catalytic process is thermodynamically and economically unfavorable due to its high energy consumption, low catalyst stability, and complex reactor maintenance. Photocatalytic technology offers great potential to carry out unfavorable reactions under mild conditions. Many in-depth studies have been carried out on the photocatalytic conversion of methane to methanol. This review will comprehensively provide recent progress in the photocatalytic oxidation of methane to methanol based on materials and engineering perspectives. Several aspects are considered, such as the type of semiconductor-based photocatalyst (tungsten, titania, zinc, etc.), structure modification of photocatalyst (doping, heterojunction, surface modification, crystal facet re-arrangement, and electron scavenger), factors affecting the reaction process (physiochemical characteristic of photocatalyst, operational condition, and reactor configuration), and briefly proposed reaction mechanism. Analysis of existing challenges and recommendations for the future development of photocatalytic technology for methane to methanol conversion is also highlighted.

Photocatalytic Degradation of Palm Oil Mill Effluent (POME) Waste Using BiVO4 Based Catalysts

Disposal of palm oil mill effluent (POME), which is highly polluting from the palm oil industry, needs to be handled properly to minimize the harmful impact on the surrounding environment. Photocatalytic technology is one of the advanced technologies that can be developed due to its low operating costs, as well as being sustainable, renewable, and environmentally friendly. This paper reports on the photocatalytic degradation of palm oil mill effluent (POME) using a BiVO4 photocatalyst under UV-visible light irradiation. BiVO4 photocatalysts were synthesized via sol-gel method and their physical and chemical properties were characterized using several characterization tools including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), surface area analysis using the BET method, Raman spectroscopy, electron paramagnetic resonance (EPR), and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). The effect of calcination temperature on the properties and photocatalytic performance for POME degradation using BiVO4 photocatalyst was also studied. XRD characterization data show a phase transformation of BiVO4 from tetragonal to monoclinic phase at a temperature of 450 °C (BV-450). The defect site comprising of vanadium vacancy (Vv) was generated through calcination under air and maxima at the BV-450 sample and proposed as the origin of the highest reaction rate constant (k) of photocatalytic POME removal among various calcination temperature treatments with a k value of 1.04 × 10-3 min-1. These findings provide design guidelines to develop efficient BiVO4-based photocatalyst through defect engineering for potential scalable photocatalytic organic pollutant degradation.

Photocatalytic Technology for Palm Oil Mill Effluent (POME) Wastewater Treatment: Current Progress and Future Perspective

The palm oil industry produces liquid waste called POME (palm oil mill effluent). POME is stated as one of the wastes that are difficult to handle because of its large production and ineffective treatment. It will disturb the ecosystem with a high organic matter content if the waste is disposed directly into the environment. The authorities have established policies and regulations in the POME waste quality standard before being discharged into the environment. However, at this time, there are still many factories in Indonesia that have not been able to meet the standard of POME waste disposal with the existing treatment technology. Currently, the POME treatment system is still using a conventional system known as an open pond system. Although this process can reduce pollutants’ concentration, it will produce much sludge, requiring a large pond area and a long processing time. To overcome the inability of the conventional system to process POME is believed to be a challenge. Extensive effort is being invested in developing alternative technologies for the POME waste treatment to reduce POME waste safely. Several technologies have been studied, such as anaerobic processes, membrane technology, advanced oxidation processes (AOPs), membrane technology, adsorption, steam reforming, and coagulation. Among other things, an AOP, namely photocatalytic technology, has the potential to treat POME waste. This paper provides information on the feasibility of photocatalytic technology for treating POME waste. Although there are some challenges in this technology’s large-scale application, this paper proposes several strategies and directions to overcome these challenges.

Role of defects on TiO2/SiO2 composites for boosting photocatalytic water splitting

Defect engineering of semiconductor photocatalysts is considered as an evolving strategy to adjust their physiochemical properties and boost photoreactivity of the materials. Here, hydrogenation and UV light pre-treatment of TiO₂/SiO₂ composite with the ratio of 9 : 1 (9TiO₂/1SiO₂) were conducted to generate Ti³⁺ and non-bridging oxygen holes center (NBOHC) defects, respectively. The 9TiO₂/1SiO₂ composite exhibited much higher photocatalytic water splitting than neat TiO₂ and SiO₂ as a consequence of the electronic structure effects induced by the defect sites. Electron paramagnetic resonance (EPR) indicated that hydrogenated and UV light pre-treated of 9TiO₂/1SiO₂ boosted a higher density of Ti³⁺ and NBOHC defect which could serve to suppress photogenerated electron-hole pair recombination and act as shallow donors to trap photoexcited electron. Overall, both defect sites in 9TiO₂/1SiO₂ delivered advantageous characteristic relative to neat TiO₂ and SiO₂ with the finding clearly illustrating the value of defect engineering in enhancing photocatalytic performance.

Karakterisasi Produk Biosolubilisasi Batubara Oleh Kapang T4 Hasil Isolasi dari Tanah Pertambangan Tanjung Enim Sumatera Selatan

Biosolubilisasi batubara adalah teknologi yang memiliki potensi untuk mengubah batubara padatmenjadi bahan bakar cair/senyawa kimia dengan bantuan mikroorganisme. Tujuan dari penelitianini adalah untuk mengkarakterisasi produk biosolubilisasi batubara oleh kapang T4 hasil isolasidari tanah di area pertambangan batubara Tanjung Enim Sumatera Selatan. Hasil penelitianmenunjukkan bahwa terjadi interaksi antara kapang T4 dengan batubara yang dilihat dari adanyakolonisasi miselia di permukaan batubara. Kadar asam humat mengalami peningkatan hingga harike-7, sedangkan kadar asam fulvat terus meningkat hingga hari ke-28. Analisa gugus fungsibatubara hasil biosolubilisasi dengan FTIR memperlihatkan terjadinya perubahan strukturbatubara yang didominasi oleh penurunan serapan C=C aromatic dan C-O fenolik.. Karakterisasiproduk biosolubilisasi batubara oleh kapang T4 dengan GC-MS menunjukkan terbentuknyasenyawa-senyawa baru dan senyawa yang mengalami peningkatan antara lain naftalena dansenyawa alkana rantai pendek.