Oxidation of nine petroleum hydrocarbon compounds by combined hydrogen peroxide/sodium persulfate catalyzed by siderite

Remediation of diesel contaminated soil by using activated persulfate with Fe3O4 magnetic nanoparticles: effect and mechanisms

In this study, Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) were assessed for their ability to enhance the activity of persulfate (PS). Various controlling factors including PS dosages, initial pH, water-soil ratio, ratio of Fe2+, and Fe3O4 MNPs to PS were considered in both the Fe2+/PS system and the Fe3O4 MNPs/PS system. Results showed that the Fe3O4 MNP-activated PS system exhibited high processing efficiency owing to the gradual release of Fe2+. This process occurred in a wide pH range (5-11), attributed to the synergistic action of sulfate radicals (SO4-·) and hydroxyl radicals (OH·) under alkaline conditions, effectively mitigating soil acidification. The ratio of Fe3O4 MNPs to PS and water-soil ratio significantly influenced the degradation rate with the highest petroleum hydrocarbon degradation rate exceeding 80% (82.31%). This rate was 3.1% higher than that achieved by the Fe2+/PS system under specific conditions: PS dosage of 0.05 mol/L, Fe3O4 MNPs to PS ratio of 1:10, water-soil ratio of 2:1, and initial pH of 11. Meanwhile, oxidant consumption in the Fe3O4 MNPs/PS system was halved compared to the Fe2+/PS system due to the slow release of Fe2+ and less ineffective consumption of SO4-·. Mechanistically, the possible degradation process was divided into three parts: the initial chain reaction, the proliferating chain reaction, and the terminating chain reaction. The introduction of Fe3O4 MNPs accelerated the degradation rate of pentadecane, heneicosane, eicosane, tritetracontane, and 9-methylnonadecane.

Siderite's green revolution: From tailings to an eco-friendly material for the green economy

Siderite, extensively mined as a natural iron mineral, is often discarded as tailings due to the low grade of the ore and due to the high cost of current sorting technologies. Yet, this mineral has demonstrated significant potential in several pivotal areas of the environmental remediation. Siderite not only possesses exceptional adsorption, catalytic, and microbial carrier capabilities but also offers an eco-friendly and cost-effective solution for the environmental pollution management. This article consolidates research advancements and achievements over the past few decades concerning siderite's role in pollution control, delving deeply into its various remediation pathways. Initially, the paper contrasts the performance differences between natural and synthetic siderite, followed by a comprehensive overview of siderite's adsorption mechanisms for various inorganic pollutants. Furthermore, this paper analyzes the unique physicochemical attributes of siderite as both, a reductant and the catalyst, with a special emphasis on its use in the preparation of SCR catalysts and in the catalytic advanced oxidation processes for organic pollutants' degradation. This paper also enumerates and discusses the myriad advantages of siderite as a microbial carrier, thereby enhancing our understanding of biogeochemical cycles and pollutant transformations. In essence, this review systematically elucidates the mechanisms and intrinsic physicochemical properties of siderite in pollution control, paving the way for novel strategies to augment siderite's environmental remediation performance.

Abatement of Naphthalene by Persulfate Activated by Goethite and Visible LED Light at Neutral pH: Effect of Common Ions and Organic Matter

Naphthalene (NAP) has received particular attention due to its impact on the environment and human health, mandating its removal from water systems. In this work, the abatement of NAP in the aqueous phase was achieved using persulfate (PS) activated by Fe (III) and monochromatic LED light at a natural pH. The reaction was carried out in a slurry batch reactor using goethite as the Fe (III) source. The influence of the PS concentration, goethite concentration, irradiance, temperature and presence of organic matter, chloride, and bicarbonate on the abatement of NAP was studied. These variables were shown to have a different effect on NAP removal. The irradiance showed a maximum at 0.18 W·cm−2 where the photonic efficiency was the highest. As for the concentration of goethite and PS, the influence of the first one was negligible, whereas for PS, the best results were reached at 1.2 mM due to a self-inhibitory effect at higher concentrations. The temperature effect was also negative in the PS consumption. Regarding the effect of ions, chloride had no influence on NAP conversion but carbonates and humic acids were affected. Lastly, this treatment to remove NAP has proved to be an effective technique since minimum conversions of 0.92 at 180 min of reaction time were reached. Additionally, the toxicity of the final samples was decreased.

A catalogue of signal molecules that interact with sensor kinases, chemoreceptors and transcriptional regulators

Bacteria have evolved many different signal transduction systems that sense signals and generate a variety of responses. Generally, most abundant are transcriptional regulators, sensor histidine kinases and chemoreceptors. Typically, these systems recognize their signal molecules with dedicated ligand-binding domains (LBDs), which, in turn, generate a molecular stimulus that modulates the activity of the output module. There are an enormous number of different LBDs that recognize a similarly diverse set of signals. To give a global perspective of the signals that interact with transcriptional regulators, sensor kinases and chemoreceptors, we manually retrieved information on the protein-ligand interaction from about 1,200 publications and 3D structures. The resulting 811 proteins were classified according to the Pfam family into 127 groups. These data permit a delineation of the signal profiles of individual LBD families as well as distinguishing between families that recognize signals in a promiscuous manner and those that possess a well-defined ligand range. A major bottleneck in the field is the fact that the signal input of many signaling systems is unknown. The signal repertoire reported here will help the scientific community design experimental strategies to identify the signaling molecules for uncharacterised sensor proteins.