Mesoporous pyrophyllite–titania nanocomposites: synthesis and activity in phenol photocatalytic degradation

Mineral-Supported Photocatalysts: A Review of Materials, Mechanisms and Environmental Applications

Although they are of significant importance for environmental applications, the industrialization of photocatalytic techniques still faces many difficulties, and the most urgent concern is cost control. Natural minerals possess abundant chemical inertia and cost-efficiency, which is suitable for hybridizing with various effective photocatalysts. The use of natural minerals in photocatalytic systems can not only significantly decrease the pure photocatalyst dosage but can also produce a favorable synergistic effect between photocatalyst and mineral substrate. This review article discusses the current progress regarding the use of various mineral classes in photocatalytic applications. Owing to their unique structures, large surface area, and negatively charged surface, silicate minerals could enhance the adsorption capacity, reduce particle aggregation, and promote photogenerated electron-hole pair separation for hybrid photocatalysts. Moreover, controlling the morphology and structure properties of these materials could have a great influence on their light-harvesting ability and photocatalytic activity. Composed of silica and alumina or magnesia, some silicate minerals possess unique orderly organized porous or layered structures, which are proper templates to modify the photocatalyst framework. The non-silicate minerals (referred to carbonate and carbon-based minerals, sulfate, and sulfide minerals and other special minerals) can function not only as catalyst supports but also as photocatalysts after special modification due to their unique chemical formula and impurities. The dye-sensitized minerals, as another natural mineral application in photocatalysis, are proved to be superior photocatalysts for hydrogen evolution and wastewater treatment. This work aims to provide a complete research overview of the mineral-supported photocatalysts and summarizes the common synergistic effects between different mineral substrates and photocatalysts as well as to inspire more possibilities for natural mineral application in photocatalysis.

Application of aluminosilicate clay mineral-based composites in photocatalysis

Aluminosilicate clay mineral (ACM) is a kind of typical raw materials that used widely in manufacturing industry owing to the abundant reserve and low-cost exploring. In past two decades, in-depth understanding on unique layered structure and abundant surface properties endows ACM in the emerging research and application fields. In field of solar-chemical energy conversion, ACM has been widely used to support various semiconductor photocatalysts, forming the composites and achieving efficient conversion of reactants under sunlight irradiation. To date, classic ACM such as kaolinite and montmorillonite, loaded with semiconductor photocatalysts has been widely applied in photocatalysis. This review summaries the recent works on ACM-based composites in photocatalysis. Focusing on the properties of surface and layered structure, we elucidate the different features in the composition with various functional photocatalysts on two typical kinds of ACM, i.e., type 1:1 and type 2:1. Not only large surface area and active surface hydroxyl group assist the substrate adsorption, but also the layered structure provides more space to enlarge the application of ACM-based photocatalysts. Besides, we overview the modifications on ACM from both external surface and the inter-layer space that make the formation of composites more efficiently and boost the photo-chemical process. This review could inspire more upcoming design and synthesis for ACM-based photocatalysts, leading this kind of economic and eco-friendly materials for more practical application in the future.

Interfacial engineering coupling with tailored oxygen vacancies in Co2Mn2O4 spinel hollow nanofiber for catalytic phenol removal

Herein, one-dimensional Co₂Mn₂O₄ (CMO) hollow nanofibers with a general spinel structure were constructed by electrospinning and tunning thermal-driven procedures. The resultant catalyst was endowed with appreciable active interfacial engineering effect, which revealed improved peroxymonosulfate (PMS) activation efficiency in catalytic phenol degradation with nearly 12.9 folds increment in reaction rate constant compared to the hydrothermally synthesized counterpart. Besides, tailored oxygen-vacancy sites including chemical environment and contents in the bimetallic spinel were rationally validated compared to the monometal spinel counterparts. The improved catalytic phenol degradation by reactive-oxidative-species (ROS) from PMS was well correlated with the more active Co(II) and Mn(II) species, reactive active oxygen-vacancy and the interfacial engineering effect in the CMO catalyst. These correlations were comprehensively demonstrated by various characterization techniques, catalytic results, and Density-Functional-Theoretical (DFT) calculations of the adsorption and activation of PMS. Besides, the results revealed that the specific content of cobalt species in the structural unit of the Co₂Mn₂O₄ spinel resulting from the optimized thermal treatment could further improve the catalytic activity by the intermetallic synergy along with the beneficial electron transfer cycles. This work provides a practical understanding of the improvement of interfacial systems in catalysis efficiency and environmental remediation.

Phenol biodegradation by Acinetobacter radioresistens APH1 and its application in soil bioremediation

Phenol accounts for a large proportion of the contamination in industrial wastewater discharged from chemical plants due to its wide use as a raw chemical. Residual phenol waste in water and soil significantly endangers human health and the natural environment. In this study, an Acinetobacter radioresistens strain, APH1, was isolated and identified for its efficient capability of utilizing phenol as sole carbon source for growth. A draft genome sequence containing 3,290,330 bases with 45 contigs was obtained, and 22 genes were found to be involved in phenol metabolism and 51 putative drug-resistance genes were annotated by genomic analysis. The optimal conditions for cell culture and phenol removal were determined to be 30 °C, pH 6.0, and a phenol concentration of 500 mg/L; the upper limit of phenol tolerance was 950 mg/L. Based on GC-MS analysis, the key metabolites including cis,cis-muconic acid, catechol, and succinic acid were detected. During bioremediation experiment using 450 mg/kg (dry weight) of phenol-contaminated soil, the strain APH1 removed 99% of the phenol within 3 days. According to microbial diversity analysis, the microbial abundance of Chungangia, Bacillus, Nitrospira, Lysinibacillus, and Planomicrobium increased after the addition of phenol. Furthermore, at day 23, the abundance of strain APH1 was greatly reduced, and the microbial diversity and structure of the whole microbial community were gradually recovered, indicating that strain APH1 would not affect this microbial ecosystem. These findings provide insights into the bioremediation of soil contaminated with phenol.

Pineapple Bark Performance in Dyes Adsorption: Optimization by the Central Composite Design

This work is concerned with the study of the adsorption in aqueous medium of a three-dye mixture which contains Methylene Blue, Brilliant Green, and Congo Red on the pineapple bark. This adsorbent material has been characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The experimental design methodology, based on the response surface methodology (RSM) by the central composite design (CCD), has been applied for the optimization of the parameters, namely, the temperature, dose of the adsorbent, and pH. The yield reached 98.91% under optimal conditions (T = 30°C; adsorbent dose = 2.5 g·L−1; pH = 9.8) at an initial concentration of 20 mg·L−1.