Cyanamide-Modified Iron(III) Oxide Photocatalysts for Degradation of Phenol in the Presence of Urea and Formaldehyde

Cyanamide as the source of carbon and nitrogen was used to modify iron(III) oxide (Fe2O3) photocatalyst. While X-ray diffraction (XRD) patterns confirmed that the cyanamide-modified Fe2O3 photocatalysts have comparable crystallinity to that of the unmodified Fe2O3, the diffuse reflectance ultraviolet-visible (DR UV-vis) spectra obviously showed additional light absorption around 500-800 nm on the cyanamide-modified Fe2O3, resulting in a better absorption capability under visible light irradiation. The presence of cyanamide modifier decreased the fluorescence emission intensity of Fe2O3, implying the reduced electron-hole recombination on the Fe2O3 and/or blocked emission sites by the modifier. The presence of carbon and nitrogen on the modified Fe2O3 photocatalysts was confirmed by the elemental analyzer. Photocatalytic activities of Fe2O3 and cyanamide-modified Fe2O3 were then evaluated for degradation of phenol under UV and visible light irradiation. Modification of Fe2O3 with cyanamide significantly improved the degradation of phenol from 30 to 75% under UV light irradiation and from 0 to 80% under visible light irradiation. Photocatalytic degradation of phenol was also investigated in the presence of urea or formaldehyde or both urea and formaldehyde. Even though the percentage of phenol degradation decreased in the presence of other pollutants, it was demonstrated that cyanamide modified iron(III) oxide photocatalysts still gave good activity towards degradation of phenol even in the presence of other organic pollutants.

Isolation and Molecular Identification of Phenol Degrading Bacterium from Industrial Wastes, Collected from Jeddah Saudi Arabia

In the past two decades, phenolic compounds have had different applications, however their use in densification has increased considerably due to Covid 19. Discharge of these dangerous materials is highly toxic and causes risk and severe problems to the environment and health of human and animals, in addition to it being harmful to the aquatic life. Phenol degradation is very important due to high toxicity and stability. The aim of this study is to isolate phenol-degrading aerobic bacteria from hydrocarbon contaminated soil or wastewater, collected from the industrial area of Jeddah. Minimal medium containing phenol as carbon source was used to isolate different bacteria. About 30 actinomycete isolates were obtained, purified and preserved on Starch nitrate. Out of 30 isolates, eight isolates (27%) grow well in medium containing 0.1% phenol. After growing in broth medium, isolate BA4 and isolate BA8 were very active in phenol degradation. Growth and phenol degradation was measured in liquid medium for the two isolates. Morphological and physiological characters of these isolates were detected using different methods. Using molecular methods, they were belonging to a genus of actinomycetes. They were identified as Streptomyces flavabus BA4 and Streptomyces sp. BA8.The effects of some growth factors on growth and phenol degradation were determined. Growth was measured by dry weight (mg/l) while phenol degradation was detected by assaying the residual phenol concentration. The presence of electron donors such as glucose, starch, glycine, peptone, and Na acetate affect both growth and phenol degradation. It was clear that addition of 1 g/l peptone enhanced both growth and phenol degradation. The isolate use phenol and its derivatives m-cresol and o-cresol as carbon sources and addition of vitamin B complex increased the bacterial growth. In conclusion, phenol degradation was detected by actinobacteria and was affected by some physical and biochemical factors. It was noticed that optimization of growth conditions enhanced both growth and phenol degradation by the two selected Streptomyces isolate. Degradation process by isolate BA4 could be a promising solution for removal of phenol from wastewater.

Synthesis and Photocatalytic Activity of TiO2 on Phenol Degradation

Photocatalysis is a process of accelerating reactions that are assisted by energy from light irradiation. Titanium dioxide (TiO2) is one of the most widely developed photocatalysis materials, and is used because of its high catalytic activity, stability and very affordable. The most commonly used precursors of TiO2 are titanium butoxide (TBOT) and titanium tetraisopropoxide (TTIP). These variations in precursor can lead to phase difference in the formation of TiO2 crystals, which further improves its nature in the activity of photocatalysis. In this study, the sol-gel method was used to synthesize titanium dioxide nanoparticles from variations of TBOT and TTIP. Furthermore, the structure, crystallite size and band gap of TiO2 were determined by X-ray diffraction (XRD) and UV-vis reflectance spectroscopy (DRS). Subsequently, TiO2 photocatalytic activity was evaluated in phenol photodegradation as a contaminant model with UV irradiation. The results showed the structure synthesized from TBOT had a higher amount of anatase, higher crystallinity, smaller crystallite size, larger band gap, and better photocatalytic activity than those from TTIP. Furthermore, it was shown that TiO2 from TBOT had an efficiency of 147% greater than TiO2 P25 Degussa, while TiO2 from TTIP had 66% efficiency compared to TiO2 P25.

Fabrication of Adsorbed Fe(III) and Structurally Doped Fe(III) in Montmorillonite/TiO2 Composite for Photocatalytic Degradation of Phenol

The Fe(III)-doped montmorillonite (Mt)/TiO2 composites were fabricated by adding Fe(III) during or after the aging of TiO2/Ti(OH)4 sol–gel in Mt, named as xFe-Mt/(1 − x)Fe-TiO2 and Fe/Mt/TiO2, respectively. In the xFe-Mt/(1 − x)Fe-TiO2, Fe(III) cations were expected to be located in the structure of TiO2, in the Mt, and in the interface between them, while Fe(III) ions are physically adsorbed on the surfaces of the composites in the Fe/Mt/TiO2. The narrower energy bandgap (Eg) lower photo-luminescence intensity were observed for the composites compared with TiO2. Better photocatalytic performance for phenol degradation was observed in the Fe/Mt/TiO2. The 94.6% phenol degradation was due to greater charge generation and migration capacity, which was confirmed by photocurrent measurements and electrochemical impedance spectroscopy (EIS). The results of the energy-resolved distribution of electron traps (ERDT) suggested that the Fe/Mt/TiO2 possessed a larger amorphous rutile phase content in direct contact with crystal anatase than that of the xFe-Mt/(1 − x)Fe-TiO2. This component is the fraction that is mainly responsible for the photocatalytic phenol degradation by the composites. As for the xFe-Mt/(1 − x)Fe-TiO2, the active rutile phase was followed by isolated amorphous phases which had larger (Eg) and which did not act as a photocatalyst. Thus, the physically adsorbed Fe(III) enhanced light adsorption and avoided charge recombination, resulting in improved photocatalytic performance. The mechanism of the photocatalytic reaction with the Fe(III)-doped Mt/TiO2 composite was proposed.

Potential Application of Algae in Biodegradation of Phenol: A Review and Bibliometric Study

One of the most severe environmental issues affecting the sustainable growth of human society is water pollution. Phenolic compounds are toxic, hazardous and carcinogenic to humans and animals even at low concentrations. Thus, it is compulsory to remove the compounds from polluted wastewater before being discharged into the ecosystem. Biotechnology has been coping with environmental problems using a broad spectrum of microorganisms and biocatalysts to establish innovative techniques for biodegradation. Biological treatment is preferable as it is cost-effective in removing organic pollutants, including phenol. The advantages and the enzymes involved in the metabolic degradation of phenol render the efficiency of microalgae in the degradation process. The focus of this review is to explore the trends in publication (within the year of 2000–2020) through bibliometric analysis and the mechanisms involved in algae phenol degradation. Current studies and publications on the use of algae in bioremediation have been observed to expand due to environmental problems and the versatility of microalgae. VOSviewer and SciMAT software were used in this review to further analyse the links and interaction of the selected keywords. It was noted that publication is advancing, with China, Spain and the United States dominating the studies with total publications of 36, 28 and 22, respectively. Hence, this review will provide an insight into the trends and potential use of algae in degradation.

Statistical Assessment of Phenol Biodegradation by a Metal-Tolerant Binary Consortium of Indigenous Antarctic Bacteria

Since the heroic age of Antarctic exploration, the continent has been pressurized by multiple anthropogenic activities, today including research and tourism, which have led to the emergence of phenol pollution. Natural attenuation rates are very slow in this region due to the harsh environmental conditions; hence, biodegradation of phenol using native bacterial strains is recognized as a sustainable remediation approach. The aim of this study was to analyze the effectiveness of phenol degradation by a binary consortium of Antarctic soil bacteria, Arthrobacter sp. strain AQ5-06, and Arthrobacter sp. strain AQ5-15. Phenol degradation by this co-culture was statistically optimized using response surface methodology (RSM) and tolerance of exposure to different heavy metals was investigated under optimized conditions. Analysis of variance of central composite design (CCD) identified temperature as the most significant factor that affects phenol degradation by this consortium, with the optimum temperature ranging from 12.50 to 13.75 °C. This co-culture was able to degrade up to 1.7 g/L of phenol within seven days and tolerated phenol concentration as high as 1.9 g/L. Investigation of heavy metal tolerance revealed phenol biodegradation by this co-culture was completed in the presence of arsenic (As), aluminum (Al), copper (Cu), zinc (Zn), lead (Pb), cobalt (Co), chromium (Cr), and nickel (Ni) at concentrations of 1.0 ppm, but was inhibited by cadmium (Cd), silver (Ag), and mercury (Hg).