Search

Polyolefin plastics play an important role in both production and life due to the excellent characteristics, such as east processing, low price and outstanding performance. It has become the most widely used plastics at present. The main raw materials of polyolefin plastics are non-renewable resources such as coal and oil. Waste polyolefin plastics are difficult to degrade in the natural environment, and will break into small particles. The micro plastics are transferred into lakes, rivers, oceans and soil, which will cause serious impact and damage to the environment and the health of animals and plants. Therefore, in terms of energy conservation and environmental protection, the recycling of polyolefin plastics is a very important topic. Among the recycling methods of polyolefin plastics, oxidative degradation can effectively degrade macromolecular polyolefin plastics to generate high-value small molecule chemical raw materials, realize the recycling and high-value utilization of polyolefin plastics, and provide a good solution to the existing micro plastic pollution problem in the environment. In this paper, the oxidative degradation of polyolefin plastics is studied, and the research progress related to the oxidative degradation in recent years is summarized. The reaction process, oxidation mechanism and degradation products of three oxidative degradation methods, chemical oxidative degradation, biological oxidative degradation and photooxidative degradation, are analyzed and discussed. Based on the current research situation, the development prospect of the oxidative degradation and recovery of polyolefin plastics in the future is also prospected.

The current work investigates the efficacy of acoustic cavitation (AC) based pretreatment as a process intensification method for improving the conventional biological oxidation (BO) treatment of the effluent from common effluent treatment plant (CETP) mainly containing pharmaceutical compounds. The effluent acclimatized with cow dung-based sludge was utilized for the aerobic oxidation with an optimum condition of 1:3 ratio of sludge to effluent and 6 h as duration. COD reduction of 19.58% was achieved with the conventional biological oxidation, which was demonstrated to be improved by incorporating acoustic cavitation-based pretreatment approaches under optimized conditions of 125 W and 70% duty cycle for only AC as well as oxidant loadings as 1000 mg/L for H2O2, 250 mg/L Fe(II) with 1000 mg/L H2O2 for Fenton, 1000 mg/L for KPS and 0.5 L/min for the O3 during the combination approaches. The improved COD reduction after the use of pretreatment approaches followed by the BO of 6 h duration was 29.26%, 72.42%, 85.47%, 45.68% and 69.26% for the AC, AC + H2O2, AC + Fenton, AC + KPS and AC + O3 based approaches respectively. The toxicity assay of the effluent before and after every pretreatment approach using bacterial strains of Staphylococcus aureus and Pseudomonas aeruginosa ensured the biodegradability of the treated effluent as no toxic intermediates could be seen. Overall, the present work elucidated the effectiveness of acoustic cavitation-based pretreatment approaches for the improvement of conventional BO of CETP effluent.

Bio-oxidation leaching test was conducted on a low-grade primary gold mine in Inner Mongolia. The acid consumption of ore, cyanidation, bio-oxidation stirred leaching, column leaching, add sulfur and sulfur concentrate to reduce acid consumption , and impact on gold leaching efficiencies were investigated. The results showed that with grinding fineness at -74 μm 80%, acid leaching for 1h, consumption of sulfur acid at 31 kg/t; After cyanidation for 24 h, the gold leaching efficiencies were 51%~55% ; After Bio-oxidation stirring leaching for 6 d, the sulfur oxidation efficiencies was reaching 80%, and the gold leaching efficiencies was reaching 91.4%; Bio-oxidation column leaching tests on gold ore of particle size at -2 mm 80% for 350 d（oxidation 170 d and cyanide leaching 180 d）, the gold leaching efficiencies was increased by 3.72%~23.54% than the direct cyanide leaching 360 d; The addition of sulfur and sulfur concentrate was not conducive to gold cyanide leaching, and the bio-oxidation of sulfur outside the column could reduce the consumption of sulfuric acid by 15.7 kg/t.

ABSTRACT Phenazines are secreted metabolites that microbes use in diverse ways, from quorum sensing to antimicrobial warfare to energy conservation. Phenazines are able to contribute to these activities due to their redox activity. The physiological consequences of cellular phenazine reduction have been extensively studied, but the counterpart phenazine oxidation has been largely overlooked. Phenazine-1-carboxylic acid (PCA) is common in the environment and readily reduced by its producers. Here, we describe its anaerobic oxidation by Citrobacter portucalensis strain MBL, which was isolated from topsoil in Falmouth, MA, and which does not produce phenazines itself. This activity depends on the availability of a suitable terminal electron acceptor, specifically nitrate. When C. portucalensis MBL is provided reduced PCA and nitrate, it oxidizes the PCA at a rate that is environmentally relevant. We compared this terminal electron acceptor-dependent PCA-oxidizing activity of C. portucalensis MBL to that of several other gammaproteobacteria with various capacities to respire nitrate. We found that PCA oxidation by these strains in a nitrate-dependent manner is decoupled from growth and strain dependent. We infer that bacterial PCA oxidation is widespread and genetically determined. Notably, oxidizing PCA enhances the rate of nitrate reduction to nitrite by C. portucalensis MBL beyond the stoichiometric exchange of electrons from PCA to nitrate, which we attribute to C. portucalensis MBL’s ability to also reduce oxidized PCA, thereby catalyzing a complete PCA redox cycle. This bidirectionality highlights the versatility of PCA as a biological redox agent. IMPORTANCE Phenazines are increasingly appreciated for their roles in structuring microbial communities. These tricyclic aromatic molecules have been found to regulate gene expression, be toxic, promote antibiotic tolerance, and promote survival under oxygen starvation. In all of these contexts, however, phenazines are studied as electron acceptors. Even if their utility arises primarily from being readily reduced, they need to be oxidized in order to be recycled. While oxygen and ferric iron can oxidize phenazines abiotically, biotic oxidation of phenazines has not been studied previously. We observed bacteria that readily oxidize phenazine-1-carboxylic acid (PCA) in a nitrate-dependent fashion, concomitantly increasing the rate of nitrate reduction to nitrite. Because nitrate is a prevalent terminal electron acceptor in diverse anoxic environments, including soils, and phenazine producers are widespread, this observation of linked phenazine and nitrogen redox cycling suggests an underappreciated role for redox-active secreted metabolites in the environment.

The proposed method for calculation of the energy value of culture media is based on stoichiometric properties of biological oxidative reactions in the cell and allows for assessment of the nutritional value of organic substrates with consideration of their elemental composition. Three organogen elements (carbon, hydrogen and oxygen) participate in the third stage of catabolism, which is the universal way of biological oxidation of organic nutritive substrate compounds. Their content in the composition of an organic compound (or food substrate) allows for calculation of the amount of energy converted into work during cellular metabolism. The idea to calculate the energy value of a food substrate is based on the principle of energetic conjugation, according to which the useful energy of food substrates within the cell is accumulated in the energy-rich adenosine triphosphate (ATP) bonds formed by biological oxidation of the substrate. Calculation of the energy values of organic substrate is traditionally based on the energy of the abiotic oxidation. The proportion of the useful energy converted into work is not considered in this case. The inherent problem of this approach is that the amount of ATP has been calculated only for several universal metabolites with known oxidative pathways, such as pyruvate and acetate. The proposed method is based on stoichiometric patterns and makes it possible to calculate the amount of ATP from the elemental composition of compounds and the mass fractions of carbon, hydrogen and oxygen. The results of calculation of biological oxidation energy obtained by this method coincide with the published data on biological oxidation metabolites in the citric acid cycle. The presented method, based on the composition of the compounds, allows for calculation of the energy value of any food substrate or culture medium containing a variety of organic compounds, including the case when their metabolic pathway of biological oxidation is unknown and the calculation of the bioenergetic value seems impossible.

The aim of the present work is to investigate the utility of redox chemical delivery prodrug approach for the targeted and sustained release of an alkylating anticancer agent in the brain. The N-methyl-1,4-dihydronicotinate ester of an alkylating nitrogen mustard NM-CDS (4) was synthesized in three step reactions. Structures of all the synthesized compounds were confirmed by UV, IR, (1H&13C) NMR and CHN elemental studies. In vitro chemical oxidation studies with silver nitrate of NM-CDS (4) indicated that it can be readily converted into its corresponding quaternary salt (3) with half life of 8 min. In vitro biological oxidation studies showed facile oxidation in biological media and rate of oxidation followed pseudo first-order kinetics with reasonable half-lives of 32.5 min in rat blood, 24.2 min in human blood and 19.4 min in brain homogenate. The in vivo studies on Sprague–Dawley rats were performed. The NM-CDS (4) at a dose of 40 mg/kg, was injected into rats. At selected time intervals, blood samples and the brains were collected and analyzed by UV spectrophotometer. The results demonstrated that NM-CDS (4) was able to cross the blood–brain barrier (BBB) at detectable concentration, oxidized to its active quaternary salt (Q-salt) (3) and sustained there for some period of time. The in silico ADME descriptors required for CNS activity were determined by computational, online (Molinspiration) and QikProp 3.2 software (Schrodinger, USA) that further indicated that NM-CDS (4) has a good potential to cross the BBB and show CNS antitumor activity.

Dye wastewater is one of typically non-biodegradable industrial effluents. A new process linking Fenton’s oxidation with biological oxidation proposed in this study was investigated to degrade the organic substances from real dye wastewater. During the combination process, the Fenton’s oxidation process can reduce the organic load and enhance biodegradability of dye wastewater, which is followed by biological aerated filter (BAF) system to further remove organic substances in terms of discharge requirement. The results showed that 97.6% of chemical oxygen demand (COD) removal by the combination process was achieved at the optimum process parameters: pH of 3.5, H2O2 of 2.0 mL/L, Fe(II) of 500 mg/L, 2.0 h treatment time in the Fenton’s oxidation process and hydraulic retention time (HRT) of 5 h in the BAF system. Under these conditions, COD concentration of effluent was 72.6 mg/L whereas 3020 mg/L in the influent, thus meeting the requirement of treated dye wastewater discharge performed by Chinese government (less than 100 mg/L). These results obtained here suggest that the new process combining Fenton’s oxidation with biological oxidation may provide an economical and effective alternative for treatment of non-biodegradable industrial wastewater.

The paper deals with the theoretical issues of biological oxidation of oil hydrocarbons from alkanes to polycyclic aromatics. We analyze the mechanisms of biochemical processes of decomposition of oil components and provide an overview of data from common databases. Studies of microbial communities of natural oil seeps in the Uzon caldera are described in detail. It is the first study of ecophysiological characteristics of oil-degrading microorganisms isolated from thermal oil seeps of the caldera.

Coka Marin is a polymetallic deposit which in addition to desired metals contains Hq and As, so that the concentrate produced by the ore processing from this deposit cannot be processing in smelter in Bor. Plants for treatments of ore with mentioned content by using pretreatment the biological oxidation exist in world for many years. This plants are proved to be good alternative to pyro metallurgical processes of ore processing. The advantage is ecological and economical. For these reasons it would be useful to investigate the possibility of the application of this procedure on the concentrate obtained from ore Coka Marin.