Photocatalytic Simulation of Phenol Waste Degradation Using Titanium Dioxide (TiO2) P25-Based Photocatalysts

Phenol waste treatment is vital in industries such as polymer production, coal gasification, refinery, and coke production. Photocatalytic technology using semiconductor materials offers an effective and ecofriendly approach to degrade phenol. TiO2 P25 is a widely used photocatalyst, known for its cost-effectiveness, favorable optical and electronic properties, high photoactivity, and photostability. The PHOTOREAC application, a recently developed MATLAB-based software, simulates the degradation of phenol using visible light. A study that combines existing literature and research revealed that pH significantly influences photocatalytic activity, with an optimum pH of 7 for TiO2 P25-mediated phenol degradation. The recommended photocatalyst concentration ranged from 0 to 10 g/L for reactor volumes between 25 and 60 mL, and from 0 to 5 g/L for 100-mL reactors. Phenol wastewater volume and light intensity also impact degradation efficiency. Adequate oxygen supply, achieved through bubbling and mixing, is essential for the formation of radical compounds. The Ballari kinetic model proved to be the most suitable for phenol degradation with TiO2 P25. Thus, by combining PHOTOREAC simulations with experimental data, the treatment process could be optimized to achieve higher degradation efficiency and estimate the treatment time for specific waste degradation levels. This study contributes to the advancement of phenol waste treatment and the development of improved photocatalytic wastewater treatment technologies

Studi Pengaruh Konsentrasi Katalis ZnO untuk Degradasi Limbah Palm Oil Mill Effluent (POME) Menggunakan Teknologi Fotokatalitik

Indonesia is among the world’s largest palm oil market countries leading to significant growth in the domestic palm oil industry. However, the increase in palm oil trading has also led to a rise in the production of waste known as Palm Oil Mill Effluent (POME). Currently, the majority of factories use open ponds for POME processing, but this method is considered ineffective for treating POME. To address this issue, researchers are exploring photocatalytic technology, which utilizes light energy (UV, visible, sunlight) to produce radical compounds that act as oxidizing agents for POME degradation. In this study, ZnO was employed as a catalyst. The XRD and UV-vis DRS characterizations confirmed that ZnO had a hexagonal wurtzite crystal structure with a band gap energy of 3,22 eV. The photocatalytic activity test results revealed that using 0.5 g/L ZnO catalyst proved to be efficient in degrading organic content in POME. The percentage of chemical oxygen demand (COD) degradation reached 22.85%, color degradation reached 48.53% and the reaction rate kinetics constant of COD degradation was at 2.6´10-3 min-1.Indonesia merupakan salah satu negara center market kelapa sawit terbesar di dunia sehingga perkembangan industri kelapa sawit dalam negeri tumbuh dengan sangat pesat. Namun, meningkatnya aktivitas perdagangan kelapa sawit berdampak terhadap meningkatnya limbah yang dihasilkan yaitu Palm Oil Mill Eflluent (POME). Mayoritas pabrik saat ini masih menggunakan open pond sebagai teknologi pengolahan POME, namun penggunaan teknologi ini dinilai belum efektif untuk pengolahan POME. Fotokatalitik merupakan teknologi berbasis energi sinar (UV, tampak, sinar matahari) untuk menghasilkan senyawa radikal yang dimanfaatkan sebagai agen pengoksidasi limbah POME. Katalis yang digunakan pada penelitian ini adalah ZnO. Berdasarkan hasil karakterisasi XRD dan UV-vis DRS, struktur kristal dari ZnO adalah hexagonal wurtzite dengan energi celah pita sebesar 3,22 eV. Berdasarkan hasil uji aktivitas degradasi fotokatalitik limbah POME, diperoleh bahwa penggunaan katalis ZnO dengan konsentrasi 0,5 g/L dinilai cukup efisien untuk mendegradasi kandungan organik pada limbah POME dengan persentase reduksi chemical oxygen demand (COD) mencapai 22,85%, warna 48,53% dengan konstatnta laju reaksi COD (k) adalah 2,6´10-3 menit-1

Photocatalytic Simulation of Phenol Waste Degradation Using Titanium Dioxide (TiO2) P25-Based Photocatalysts

Phenol waste treatment is vital in industries such as polymer production, coal gasification, refinery, and coke production. Photocatalytic technology using semiconductor materials offers an effective and ecofriendly approach to degrade phenol. TiO2 P25 is a widely used photocatalyst, known for its cost-effectiveness, favorable optical and electronic properties, high photoactivity, and photostability. The PHOTOREAC application, a recently developed MATLAB-based software, simulates the degradation of phenol using visible light. A study that combines existing literature and research revealed that pH significantly influences photocatalytic activity, with an optimum pH of 7 for TiO2 P25-mediated phenol degradation. The recommended photocatalyst concentration ranged from 0 to 10 g/L for reactor volumes between 25 and 60 mL, and from 0 to 5 g/L for 100-mL reactors. Phenol wastewater volume and light intensity also impact degradation efficiency. Adequate oxygen supply, achieved through bubbling and mixing, is essential for the formation of radical compounds. The Ballari kinetic model proved to be the most suitable for phenol degradation with TiO2 P25. Thus, by combining PHOTOREAC simulations with experimental data, the treatment process could be optimized to achieve higher degradation efficiency and estimate the treatment time for specific waste degradation levels. This study contributes to the advancement of phenol waste treatment and the development of improved photocatalytic wastewater treatment technologies

Promoting catalytic oxygen activation on noble metal and metal oxide based-catalyst by UV light pre-treatment approach

UV light pre-treatment has been shown to boost catalytic oxygen activation by Pt/TiO2 particles. In this work, the key active sites generated during UV light pre-treatment of noble metals and metal oxide catalysts were studied to provide a deeper understanding of the generation of catalytic active sites following light pre-treatment.As a model system, aqueous phase formic acid oxidation was used as the probe reaction. The enhancement effect of UV light pre-treatment on Pt/TiO2 was attributed to the generation of surface active oxygen species, comprising adsorbed oxygen, on Pt surfaces (PtOads) and active oxygen species (O-ads). Electrocatalytic assessment and DFT calculations indicated that UV light pre-treatment lowered the energy for oxygen activation. The UV light pre-treatment effect was observed for other noble metal deposits (Au and Pd) loaded on TiO2, proceeding via a process analogous to the Pt system although, in the instance of Au/TiO2, the effect was not as prevalent.UV light pre-treatment was also able to boost the catalytic oxygen activation of Pt loaded on different metal oxide supports (TiO2, CeO2 and SiO2). The key active species were PtOads and O-ads under dark catalytic conditions while under photocatalytic conditions, photo-generated holes and electrons were believed to form reactive hydroxyl and superoxide radicals, respectively. Surprisingly, Pt/SiO2 showed the highest activity under dark catalytic conditions. The cuboctahedral shape of the Pt deposits on the SiO2 surface was believed to have been advantageous for activating adsorbed oxygen species.Finally, catalytic oxygen activation on neat metal oxide-based catalysts was examined. The hydrogenation and subsequent UV light pre-treatment of neat SiO2 and TiO2-SiO2 generated two distinct defect types which provided a strong synergistic catalytic activity. Hydrogenation created oxygen vacancy sites capable of activating oxygen while UV light pre-treatment introduced silica-based non-bridging oxygen hole center sites with both sites working in tandem to accelerate formic acid oxidation. The findings were supported by XAS and DFT calculations.Ultimately, understanding the role of noble metals and defects in metal oxide-supported catalysts for oxygen activation under UV light pre-treatment conditions opens an avenue for designing efficient and low-cost catalysts for energy storage and conversion

Recent advances in the development of photocatalytic technology for nitrate reduction to ammonia

The pursuit of achieving net zero emissions by 2050, a target established following the adoption of the SDGs in 2015, has had a significant impact on the industrial sector. The conventional method for producing ammonia (NH3) known as the Haber-Bosch process, currently employed for commercial purposes, has adverse environmental effects and is not economically feasible due to its high operating temperatures and pressures (approximately 500 °C and 200 MPa). This results in the generation of substantial CO2 emissions, inefficient energy usage, and unsustainable reliance on fossil-based raw materials. To address this, researchers are focusing on alternative methods for converting nitrates to ammonia, given that nitrates are pollutants stemming from agriculture, power generation, and related industrial activities. One promising approach under development is photocatalysis which employs solar energy and catalyst to convert nitrates into ammonia using more environmentally friendly and cost-effective means. This review paper provides an extensive and detailed exploration of the reduction of nitrate to ammonia through photocatalytic technology. The discussion encompasses various aspects including thermodynamics and kinetics, photocatalysts development, factors affecting the ammonia production efficiency, the detailed mechanism behind ammonia production based on experimental and DFT calculations approach, challenges, and prospective areas of advancement based on earlier research. In essence, this comprehensive review steers researchers toward the necessary future endeavors that are essential for the broad adoption of the photocatalytic method in addressing nitrates as toxic pollutants

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

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

Torrefaction of Rubberwood Waste: The Effects of Particle Size, Temperature & Residence Time

Agriculture waste has created massive challenges over the last few decades and yet also opportunities. This work aimed to produce high-quality biochar from rubberwood waste with calorific properties close to subbituminous coal. Using a tubular vertical reactor, the effects of rubberwood particle size (wood chips and shredded wood), torrefaction temperature (220, 260, and 300 °C), and residence time (30, 60, and 90 minutes) on the quality of torrefied rubberwood were studied. The results showed that the mass loss of the rubberwood increased as the temperature increased. Also, the particle size and residence time increased due to excessive devolatilization. A higher fixed-carbon content and calorific value as well as lower moisture and volatile-matter content were achieved by increasing the torrefaction temperature and residence time in comparison to the untreated sample (raw rubberwood). The highest fixed-carbon content and calorific value were found to be 56.7% and 6313 kcal/kg, respectively, for the wood chip particles that were torrefied at 300 °C for 60 minutes. Based on the Van Krevelen diagram, torrefaction of woodchip rubberwood at 300 °C with a residence time of 60 minutes demonstrated the optimum condition to generate a product with properties that are close to those of subbituminous rank coal

Highly Selective Reduction of CO₂ to Formate at Low Overpotentials Achieved by a Mesoporous Tin Oxide Electrocatalyst

A well-ordered mesoporous SnO₂ prepared by a simple and inexpensive nanocasting method was used as catalysts for the electrochemical reduction of CO₂ to formate. The as-prepared catalyst exhibited high activity toward CO₂ reduction, which was capable of reducing CO₂ to formate with 38% of Faradaic efficiency (FE) at an applied overpotential as low as 325 mV. The maximum FE for formate generation (75%) was achieved at an applied potential of −1.15 V (vs RHE), accompanied by a high current density of 10.8 mA cm^–2. The enhanced catalytic activity obtained with the mesoporous SnO₂ electrocatalyst is attributed to its high oxygen vacancy defects (promotes CO₂ adsorption and lowers overpotential) and crystallinity that provides sufficient active sites for CO₂RR as well as its distinctive structural configurations which reduces impedance to facilitate faster CO₂RR reaction kinetics