The use of steel slags in the heterogeneous Fenton process for decreasing the chemical oxygen demand of oil refinery wastewater

An ozone catalytic oxidation system for the degradation of organic compounds in secondary wastewater from refining and chemical processes

To overcome the low catalytic efficiency, insufficient catalyst strength, and poor ozone circulation in the advanced treatment of secondary wastewater, a hollow cylindrical Fe-Cu-Ce-Mn/Al2O3 catalyst was prepared by the step impregnation method. Compared with the common impregnation method, the step impregnation method produced a more uniform and compact distribution of each metal element, which was more conducive to generating the synergistic effect of various metals; thus, increasing the mineralization rate of organic matter. The hollow cylindrical design ensured the strength of the catalyst and the circulation of ozone. The reduction of the chemical oxygen demand (COD) was compared under different experimental conditions, with the optimal conditions found to be an ozone contact time of 40 min and ozone dosage of 40 mg/L. The average COD, ammonia nitrogen, and ultraviolet absorbance at 254 nm (UV254) removal rates were 36%, 19%, and 20%, respectively. After 3 weeks of continuous experiment, the removal rate was still high. Following analysis by three dimensional fluorescence, GC-MS, and the molecular weight detection of water samples before and after treatment, it was found that the catalyst enhanced the effect of ozone on wastewater treatment, with a significant removal of tryptophan-like aromatic proteins and soluble microbial metabolites, and the removal of most of the small molecular organic matter. In addition, part of the refractory organic matter could be converted into easily degradable organic matter, which greatly improved the biodegradability and mineralization rate of wastewater, and provided good conditions for subsequent treatment.

Treatment of Olefin plant spent caustic by combination of Fenton-like and foam fractionation methods in a bench scale

Spent Merox caustic (SMC) is a hazardous waste that is produced during the Merox desulfurization process in the petroleum refinery industry and should be treated before discharging to environment. In the present study, treatment of SMC was investigated by three methods including Fenton-like process, foam fractionation, and a combination of both processes. Immobilized TiO₂/Fe⁰ on modified silica nanoparticles was used as a heterogeneous Fenton-like catalyst. The chemical and physical characteristics of the catalyst were determined using Fourier-transform infrared spectroscopy, X-ray diffraction, diffuse reflectance spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and transmission electron microscopy techniques. The treatment performance of the combined method was measured as a cost-effective method with chemical oxygen demand (COD) removal percentage. The effect of parameters including pH, gas flow rate, surfactant type and concentration of hydrogen peroxide, catalyst, and chelate were investigated. It is found that the prepared heterogeneous catalyst has high activity for the treatment of SMC. In addition, the results showed that the combined method achieved 97.6 ± 0.5% COD removal, while the measured values for Fenton or foam fractionation methods alone did not exceed 85.5 ± 1% and 47.2 ± 0.4%, respectively. The advantage of combination process over foam fractionation was the use of an advanced oxidation process in the separating column to eliminate or reduce the secondary phase contamination load. Besides, the role of the column in the effective contact of contaminants with the rising bubbles improved the degradation performance of the proposed process and reduced the consumption of hydrogen peroxide by 46% compared to the Fenton-like method.

Engineered Aptamer-Organic Amphiphile Self-Assemblies for Biomedical Applications: Progress and Challenges

Currently, nucleic acid aptamers are exploited as robust targeting ligands in the biomedical field, due to their specific molecular recognition, little immunogenicity, low cost, ect. Thanks to the facile chemical modification and high hydrophilicity, aptamers can be site-specifically linked with hydrophobic moieties to prepare aptamer-organic amphiphiles (AOAs), which spontaneously assemble into aptamer-organic amphiphile self-assemblies (AOASs). These polyvalent self-assemblies feature with enhanced target-binding ability, increased resistance to nuclease, and efficient cargo-loading, making them powerful platforms for bioapplications, including targeted drug delivery, cell-based cancer therapy, biosensing, and bioimaging. Besides, the morphology of AOASs can be elaborately manipulated for smarter biomedical functions, by regulating the hydrophilicity/hydrophobicity ratio of AOAs. Benefiting from the boom in DNA synthesis technology and nanotechnology, various types of AOASs, including aptamer-polymer amphiphile self-assemblies, aptamer-lipid amphiphile self-assemblies, aptamer-cell self-assemblies, ect, have been constructed with great biomedical potential. Particularly, stimuli-responsive AOASs with transformable structure can realize site-specific drug release, enhanced tumor penetration, and specific target molecule detection. Herein, the general synthesis methods of oligonucleotide-organic amphiphiles are firstly summarized. Then recent progress in different types of AOASs for bioapplications and strategies for morphology control are systematically reviewed. The present challenges and future perspectives of this field are also discussed.

Pitfalls of Wastewater Treatment in Oil Refinery Enterprises in Kazakhstan—A System Approach

The present article is an assessment of wastewater treatment processes in the oil refinery sector in Kazakhstan by comparing relevant experience of developed and developing countries. The legislation in this sphere, the treatment methods, the discharge process and the effect on the environment were evaluated following international and national regulations. In our study, the wastewater systems in three factories in Kazakhstan were assessed. Results show that, even though the environmental regulation in Kazakhstan promotes the polluter pays principle and follows the World Health Organization (WHO) recommendations, the oil refinery plants in Kazakhstan still contain exceeding concentrations of pollutants in their effluents. One issue is that the local legislation allows disposal of wastewater to natural or artificial ponds as long as the concentrations of pollutants in effluents are less than the already existing concentrations in the pond. Consequently, the factories can use ponds with an initially high concentration of contaminants. The high initial concentration of pollutants in the pond water is due to wastewater discharged before the implementation of current environmental regulations. This issue in the current legislation leads to the situation where there is no incentive for efficient wastewater treatment. The national law also lacks regulations regarding which methodology should be used to assess the pollutants in the wastewater. Thus, the control by national environmental office for each enterprise is negotiated separately between the factory and the governmental body. This gives the factory a strong position to define the parameters assessing the effluents. This has led to none of the factories measuring, e.g., heavy metals in discharged wastewater. Total petroleum hydrocarbons (TPH) concentration in wastewater is often exceeded at each factory and there is no analysis done for different hydrocarbon fraction. To overcome the issues described in the present study, we strongly recommended a unified and transparent methodology for the country’s oil refinery industry to assess important pollutants in discharged wastewater.