Abstract
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.
Highlights
The rapid growth of the palm oil industry worldwide has invited serious water pollution in aquatic systems
When the calcination temperature increases to 450 ◦C (BV-450), the tetragonal phase peak disappeared while it predominantly consists of the monoclinic phase
The BiVO4 photocatalyst was successfully synthesized using the sol-gel method and it was optimized by different calcination temperatures
Summary
The rapid growth of the palm oil industry worldwide has invited serious water pollution in aquatic systems. Various treatment methods have been developed to eliminate and reduce POME pollution [3] These methods include composting [4], fermentation [5], coagulation flocculation [6], adsorption [7], flotation, membrane technology [8], steam reforming [9], and advanced oxidation processes [10]. The obtained photocatalytic rates for POME degradation will be discussed on the basis of characterization data which is highly dependent on the calcination temperature in the range of 300–600 ◦C This is attributed to the variation in crystallinity, morphology, optical and electronic properties, and local structure distortion (existence of defect sites, namely vanadium vacancy) of the BiVO4 upon calcination treatment
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