Bojuru sand as a novel catalyst for refinery wastewater treatment and phenol degradation by heterogeneous photo catalysis

A review on recent advancements in extraction, removal and recovery of phenols from phenolic wastewater: Challenges and future outlook

Water pollution is the major problem seen in today's scenario and even pollutants at low concentration harms our environment. In industrial sector usage of phenol is seen even at low concentrations. The interaction of phenol in the environment provides adverse effects to living beings. This review focuses on the toxicity of phenol and its impact towards environment and human health. The treatment techniques such as distillation, extraction, wet air oxidation, membrane process, electrochemical oxidation, biological treatment and finally adsorption techniques were discussed. Among many treatment techniques so far utilized in the treatment of phenol, adsorption was considered as one of the best technique due to its advantages such as reusability, ease in operation, large availability etc., This review also highlights the adsorption technique for the cleaner removal of phenol from aqueous solution with novel as well as low-cost adsorbents in the removal of phenolic compounds. This review also discusses about the drawbacks and issues related with adsorption of phenolic compounds.

Mechanism of nitrogen-doped biochar activated peroxymonosulfate for degradation of 2,4-dichlorophenol

Biochar activated peroxymonosulfate has been widely used to degrade organic pollutants. However, the chemical inertness of the sp2 hybrid conjugated carbon framework and the limited number of active sites on the pristine biochar resulted in the low catalytic activity of the system, restricting its further application. In this study, nitrogen-doped biochar was prepared following a simple one-step synthesis method taking advantage of the similar atomic radius and significant difference in electronegativity of N and C atoms to explore the properties and mechanisms of biochar-mediated peroxymonosulfate activation to degrade 2,4-dichlorophenol. Results from degradation experiments revealed that the catalytic efficiency of the prepared nitrogen-doped biochar was approximately 37.8 times higher than that of the undoped biochar. Quenching experiments combined with Electron paramagnetic resonance (EPR) analysis illustrated that the generated singlet oxygen (¹O₂) and superoxide anion radical (O₂^•-) were the main reactive oxidative species that dominated the target organics removal processes. This work will provide a theoretical basis for expanding the practical application of nitrogen-doped biochar to remediate water pollution via peroxymonosulfate activation.

The role of TiO2 NPs catalyst and packing material in removal of phenol from wastewater using an ozonized bubble column reactor

Phenol is present as a highly toxic pollutant in wastewater, and it has a dangerous impact on the environment. In the present research, the phenol removal from wastewater has been achieved using four treatment methods in a bubble column reactor (treatment by ozone only, using packed bubble column reactor with ozone, utilizing ozone with TiO2 NPs catalyst in the reactor without packing, and employing ozone with TiO2 NPs in the presence of packing). The effects of phenol concentration, ozone dosage, TiO2 NPs additions, and contact time on the phenol removal efficiency were determined. It was found that at a contact time of 30 min, the phenol removal was 60.4, 74.9, 86.0, and 100% for the first, second, third, and fourth methods, respectively. The results indicated that the phenol degradation method using catalytic ozonation in a packed bubble column with TiO2 NPs is the best treatment method. This study demonstrated the advantages of using packing materials in a bubble column reactor to enhance the mass transfer process in an ozonation reaction and then increase the phenol removal efficiency. Also, the presence of TiO2 NPs as a catalyst improves the ozonation process via the production of hydroxyl routs. Additionally, the reaction kinetics of ozonation reaction manifested that the first order model is more applicable for the reaction. Eventually, the packed bubble column reactor in the presence of TiO2 NPs catalyst provided a highperformance removal of phenol with a high economic feasibility.

The Adsorptive and Photocatalytic Performance of Granite and Basalt Waste in the Discoloration of Basic Dye

The present work explored the adsorptive capacity and catalytic activity of rock powders from basaltic and granitic rocks in the discoloration of synthetic and industrial effluents containing the yellow dye Basic Yellow 96. The rock powders were characterized with scanning electron microscopy associated with energy-dispersive spectroscopy, photoacoustic spectroscopy, N2 physisorption and X-ray diffraction, the latter confirming the abundant presence of silica in the four materials studied. The basaltic powders presented specific surface areas between 7 and 10 times greater than those of granitic materials, which allowed up to 92% removal of the dye in 3 h of test using the basaltic powder. Despite the smaller area, the granitic materials showed considerable photocatalytic activity in 3 h, 94%, the same as that of the basaltic materials in the photocatalysis. Granitic and basaltic photocatalysts proved to be efficient in the discoloration of synthetic and industrial effluents, although TOC analyses indicated that it was not possible to promote the pollutant mineralization in the industrial effluent. Both artificial light and sunlight were effective in the photocatalysis of the dye, although the former was slightly faster.

Green synthesis of MIL-100(Fe) derivatives and revealing their structure-activity relationship for 2,4-dichlorophenol photodegradation

MIL-100(Fe), a kind of iron-based metal-organic framework materials (MOFs), can be synthesized at room temperature or hydrothermal conditions, which are promising precursor materials for preparing photocatalysts to degrade some recalcitrant chlorophenols in industrial wastewater. However, the relationship between the structural characterization of MIL-100(Fe) derivatives and their photodegradation behavior of chlorophenol pollutants is still unclear. Thus, in this work, a porous Z-scheme α-Fe₂O₃/MIL-100(Fe) composite was successfully fabricated via partial-pyrolysis of MIL-100(Fe) precursor synthesized through green synthesis route, which was further used for degrading high-concentration of 2,4-dichlorophenol under visible-light illumination (λ > 420 nm). The effects of synthesis route and pyrolysis temperature of MIL-100(Fe) on the degradation efficiencies of as-derived materials for 2,4-dichlorophenol were investigated. The structure-activity relationship was illuminated in detail. Otherwise, the influence of several process factors, i.e., initial concentration and pH of the 2,4-dichlorophenol solution, catalyst dosage on the degradation efficiency of 2,4-dichlorophenol has also been performed. The removal efficiency of 2,4-dichlorophenol with the initial concentration of 100 mg L^-1 reached up to 87.65% under optimized conditions. Lastly, the possible mechanism was explored based on trapping experiments and some other characterization results. The study in this paper not only exhibited new insight into the modified α-Fe₂O₃ material with high photocatalytic activity but also provided a promising method for treating wastewater containing 2,4-dichlorophenol or other similar organic pollutants.

Phenol removal kinetics from synthetic wastewater by activation of persulfate using a catalyst generated from shipping ports sludge

Disposal sludges from shipping docks contain elements that have the potential to catalyze the desired treatment process. The current work was designed to decompose phenol from wastewater by activation peroxymonosulfate (PMS) using a catalyst made from sea sediments (at 400 °C for 3 h). The catalyst had a crystalline form and contained metal oxides. The parameters of pH (3-9), catalyst dose (0-80 mg/L), phenol concentration (50-250 mg/L), and PMS dose (0-250 mg/L) were tested to specify the favorable phenol removal. The phenol removal of 99% in the waste sludge catalyst/PMS system was achieved at pH 5, catalyst quantity of 30 mg/L, phenol content of 50 mg/L, PMS dose of 150 mg/L, and reaction time of 150 min. From the results, it was implied that the pH factor was more important in removing phenol with the studied system than other factors. By-products and phenol decomposition pathways were also provided. The results showed that the sea sediment catalyst/PMS system is a vital alternative for removing phenol from wastewater medium.

Mesoporous LaFeO3: Synergistic Effect of Adsorption and Visible Light Photo-Fenton Processes for Phenol Removal from Refinery Wastewater

Mesoporous LaFeO3 as a visible light-driven photocatalyst was prepared by a nanocasting method using mesoporous silica (SBA-15) as a hard template. The as-prepared LaFeO3 photocatalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS), and optical absorption spectra. The characterization studies and experimental results showed that LaFeO3 with porous structure caused by the removal of SBA-15 hard template could enhance the specific surface area of the resulting photocatalyst, which improves the phenol adsorption ability of the photocatalyst and in turn enhances its photo-Fenton catalytic activity. The photo-Fenton catalytic activity of the photocatalyst was investigated by photo-Fenton degradation of aqueous phenol under visible light irradiation. The effects of catalyst dosage, H2O2 concentration, and solution pH on the photo-Fenton catalytic degradation of phenol using mesoporous LaFeO3 were studied and optimized. Under the optimal conditions of 20 mg L−1 phenol, 1.0 g L−1 catalyst, and 10 mM H2O2 at pH = 5, the photo-Fenton degradation of phenol (93.47%) was achieved in 180 min under visible light irradiation. Furthermore, our results proved the stability and reusability of mesoporous LaFeO3 and revealed its catalytic mechanism for the photo-Fenton degradation of phenol.