Photocatalytic degradation of oily waste and phenol from a local South Africa oil refinery wastewater using response methodology

Abstract

The photocatalytic degradation of a local South Africa oil refinery wastewater was conducted under UV radiation using an aqueous catalyst of titanium dioxide (TiO2), Degussa P25 (80% anatase, 20% rutile) in suspension. the experiment was carried out in a batch aerated photocatalytic reactor based on a central composite design (CCD) and analyzed using response surface methodology (RSM). The effects of three operational variables viz. TiO 2 dosage (2-8 g/L), runtime (30-90 minutes), and airflow rate (0.768-1.48 L/min) were examined for the removal of phenol and soap oil and grease (SOG). The data derived from the CCD, and the successive analysis of variance (ANOVA) showed the TiO 2 dosage to be the most influential factor, while the other factors were also significant (P < 0.0001). Also, the ANOVA test revealed the second-order of tio 2 dosage and runtime as the main interaction factors on the removal efficiency. To maximize the pollutant removal, the optimum conditions were found at runtime of 90 minutes, TiO 2 dosage of 8 g/L, and an aeration flow rate of 1.225 L/min. Under the conditions stated, the percentage removal of phenol (300 ± 7) and SOG (4000 ± 23) were 76% and 88% respectively. At 95% confidence level, the predicted models developed results were in reasonable agreement with that of the experimental data, which confirms the adaptability of the models. The first-order kinetic constants were estimated as 0.136 min −1 and 0.083 min −1 for SOG and phenol respectively. Photocatalysis has attracted worldwide interest due to its potential to use solar energy not only to solve environmental problems but also to provide renewable and sustainable energy 1,2. However, the ever-increasing demand for good water quality and oil refinery products have become expensive commodities with major challenges, which requires thoughtful attention 3,4. Oily waste from petroleum refinery has aliphatic and phenolic compounds, are considerably carcinogenic and toxic to the ecosystem and human health, and therefore their removal from wastewater is of global concern 3,5,6. The tox,icity and extreme instability of oily waste make them not degradable easily, this pose a significant threat to the water bodies and soil 5-7. Meanwhile, the processing of crude oil consumes large volumes of water and generates about 0.4-1.6 times the amount of crude oil processed as oil refinery wastewater (ORW) 8-10. The discharge of ORW with adequate or no treatment, due to their inertness, endocrine-disrupting abilities, and carcinogenic behaviour could also affect water bodies and soil profile negatively 9-11. Therefore, there is the need to develop sustainable and eco-effective methods to mitigate the oily pollutants from the ORW, to produce clean water and a sustainable environment 12. In this case, the photocatalysis technology was considered. Unfortunately, the production of polluted wastewater (ORW) is based on the raw crude oil type, plant configuration, and operational procedure, which varies in physicochemical parameters as compared to urban wa...

Fate of COVID-19 Occurrences in Wastewater Systems: Emerging Detection and Treatment Technologies—A Review

“…Current emerging micropollutants contaminants (RNA of COVID-19, pesticides, antibiotics, endocrine disrupting compounds) in WWTPs discharges impacts on the likelihood to reuse these waters after treatment [68,69]. When aquatic animals inject the micropollutants contaminants, they alter their endocrine system due to the endocrine-disrupting compounds [70,71].…”

“…Additionally, the process offers other diverse approaches of producing hydroxyl radicals making it more versatile and consequently gives a better approach to adhering to strict guidelines during wastewater treatment. AOPs which include Photocatalysis, ultrasonic process, Fenton and photo-Fenton processes ( [68,69,74,75]. A remarkable feature realized during the process was the eco-friendliness of the end-product, giving it a more efficient outlook to mineralize a broad spectrum of organic pollutants, including COVID-19.…”

“…A remarkable feature realized during the process was the eco-friendliness of the end-product, giving it a more efficient outlook to mineralize a broad spectrum of organic pollutants, including COVID-19. The process is eco-friendly, which can rely on solar energy instead of artificial light sources which is hazardous and costly [69,75]. Furthermore, due to the highly reactive nature of •OH, it can attack almost any organic materials without any discernment.…”

“…As AOP generates high influential oxidative agents such as hydroxide (OH − ), yet more explicitly, a neutral variant of hydroxyl radical (•OH) [68,69]. In essence, AOP oxidation potential is twice that of chlorine (commonly used disinfectant), therefore employing AOP as a polishing step in WWTPs is useful [10].…”

Optimization of copper removal from wastewater by fly ash using central composite design of Response surface methodology

“…This technique is beneficial for modeling and analysis of processes where multiple independent variables potentially influence the response. In recent years, RSM techniques have been effectively used for the optimization of the various water treatment process [26,27]. Kiran and Thanasekaran [28] employed RSM technique to optimize the copper adsorption capacity of an indigenously developed biosorbent.…”