Current Organic Chemistry - Volume 21, Issue 12, 2017

The paper essentially summarizes and provides a comprehensive evaluation of degeneration of substrate utilization in terms of short and long term effects and biodegradability of the selected antibiotics; sulfamethoxazole, erythromycin, and tetracycline; under different conditions. This review focuses on acute and chronic tests to evaluate the inhibitory effects of the antibiotics and to control them at the source. Acute impact based on batch tests was conducted using antibiotic dozing in the range of 1-1000 mg/L. Substrate removal was monitored by means of soluble COD and VFA measurements. At low antibiotic dosing VFA mixture was completely removed; at higher doses propionate utilization was impaired and butyrate was reduced. Higher doses induced total inactivation of microbial metabolism. For chronic impacts, the antibiotic dozing was gradually increased in lab-scale anaerobic reactors. COD, VFA, and methane generation were monitored during each phase. For each antibiotic, a threshold concentration level was determined, which did not impair substrate utilization. High concentration of antibiotics (3 mg/L<) caused toxic effects on the mixed microbial culture and affected substrate removal and biogas generation and finalized a total collapse of the reactors. Each antibiotic reflected a different impact and biodegradation pattern related to its specific mode of action. Complete removal of antibiotics could be achieved at low concentration levels. The main removal mechanism for all three antibiotics was biodegradation and not sorption. When the sorption increased in the system, the system collapsed.

Year-by-year, the amount of antibiotics for human and veterinary use increases. Their presence in both treated and untreated wastewater was highlighted in several studies, suggesting that traditional activated sludge processes are unsuitable for their efficient removal. In this review paper, we summarized the role of advanced oxidation processes (AOPs) in antibiotics removal evidencing their pros, cons and limitations. In most cases, they are still applied at laboratory or pilot scale, with just few examples of full-scale applications. Main constraints are related to energy cost, catalyst management and potential residual toxicity in treated effluents. The main advantages are related to the full mineralization of target compounds or the ability to increase their relative biodegradability. Future challenges include nano-based green synthetized catalysts maximizing the use of solar radiation for energy saving. Generally, AOPs application is part of a more structured wastewater treatment process including operating units at various technological contents.

Many synthetic food dyes and their by-products, such as aromatic amines and phenolic compounds, occurring in industrial wastewater, are toxic to aquatic environment and, because of their carcinogenic and mutagenic nature, they result in a risk for the environment and human health when wastewater is reused or released into environment. Therefore, an effective wastewater treatment is required before effluent possible reuse or disposal. In the last years, advanced oxidation processes (AOPs) have been successfully investigated in the removal of a wide range of organic and inorganic contaminants from water and wastewater because of their capacity to promote the formation of highly reactive radicals (especially hydroxyl radicals). However, most of the studies available in scientific literature have been focused on the application of AOPs in the degradation of organic dyes from textile industries rather than food dyes. Therefore, while the literature about dye treatment by AOPs in textile wastewater is consolidated, less information is available for food dyes. Accordingly, this manuscript summarizes the main results related to the removal of food dyes by AOPs. In particular, conventional methods (biological and adsorption processes) are shortly introduced before to focus this mini-review on consolidated (namely, ozonation and homogeneous Fenton/photo-Fenton) and new (namely heterogeneous photocatalytic processes) AOPs.

The aim of this paper is to provide an overview on the different approaches that can be employed to drive a photo-Fenton process under mild conditions, using both heterogeneous and homogeneous iron sources. For this purpose, sections are devoted to the following strategies: a) addition of iron at low concentrations; b) using the matrix of the effluent in order to avoid deactivation of iron; c) addition of chemical auxiliaries to form photoactive complexes with iron, such as carboxylates, chelating agents and humic-like macromolecules; d) strategies leading to the application of heterogeneous photo-Fenton process, by using iron-based solid particles or by hosting iron on different supports and; e) using heterogeneous iron sources as a reservoir for constant dosing of homogeneous iron photocatalyst. In particular, the review will focus on the elimination of emerging pollutants (e.g. drugs, personal care products or pesticides at low concentrations) which are the effluents where applying neutral photo-Fenton seems especially meaningful, although relevant works with other families of pollutants are also considered.

Being regarded as one of the critical components of water recycling programs, membrane treatment in particular reverse osmosis process has gained special interest. Although reduced cost of membrane modules caused an increase in the application, a major challenge has come up with the generation of reverse osmosis concentrate. The major concern of reverse osmosis concentrate is that it contains almost all the constituents 6-7 times more concentrated than the reverse osmosis feed. Therefore, treatment of toxic and/or bio-accumulative contaminants of reverse osmosis concentrates to an appropriate level has become a crucial topic. This paper aimed to review organic constituents of municipal reverse osmosis concentrate (ROCm) in terms of their characteristics and their treatment by physicochemical and advanced oxidation processes. It could be concluded that the application of advanced oxidation processes either alone or in combination with pretreatment processes could be regarded as promising technologies on the removal of organic constituents of ROCm. On the other hand, these technologies should be cautiously assessed from different perspectives, such as energy efficiency, operational parameters, combination with other technologies and potential hazard risk to the environment in terms of toxicity.

Meldrum's acid, a white solid which was prepared for the first time by Andrew Norman in 1908, is a versatile and efficient motif in chemistry. The rigid structure, low steric hindrance, in addition with high acidity of the C5–H, are some unique chemical properties of this O-containing heterocycle. Several organic compounds based on Meldrum's acid have interesting applications in biology, industry and drugs. Its special structure makes it a good target for both nucleophilic as well as electrophilic attack. Preparation of different forms of these scaffolds, with a glance on the reaction media, has been reviewed. In addition, other part of the manuscript is based on heat and solvent of the reaction media. These factors focused on green chemistry rules. This review classified the multi-component transformations of Meldrum's acid as one of their substrates with respect to these two important aspects of green synthesis up to middle of 2016.

Background and Objective: Continuing our studies in the field of a new rearrangement in the 2,7- naphthyridine series, the synthesis and rearrangement of mono- 2 and di-amino derivatives 3 of 2,7- naphthyridine was carried out. Taking into account the wide range of pharmacological activities of pyrazole derivatives the synthesis of some 3-amino-1-(3,5-dimethyl-1H-pyrazol-1-yl)-2,7-naphthyridines 8 and of pyrazolo[3,4-c]-2,7-naphthyridine 12 was described. Methods: Compounds 2 were reacted with amines furnishing the relevant rearrangement products 4. Starting from the 7-benzyl-3-chloro-1-hydrazino-5,6,7,8-tetrahydro-2,7-naphthyridine-4-carbonitrile 6 and 5-hydrazino- 6,7,8,9-tetrahydro-3H-pyrazolo[3,4-c]-2,7-naphthyridin-1-amine 12 the 7-benzyl-3-chloro-1-(3,5-dimethyl-1Hpyrazol- 1-yl)-5,6,7,8-tetrahydro-2,7-naphthyridine-4-carbonitrile 7 and 3,5-dimethyl-1H-pyrazol-1-yl-9,11- dimethylpyrimido[1',2':1,5]pyrazolo[3,4-c]-2,7-naphthyridine 13 were synthesized, via the Knorr synthesis of pyrazoles. Results: The syntheses of 2-benzyl-6,8-diamino-3,4-dihydro-2,7-naphthyridin-1(2H)ones 4 deriving from the rearrangement of compounds 2 and/or 3 were performed. By reaction with benzylamine compound 2a or 3g gave the unexpected formation of N,7-dibenzyl-8-(benzylimino)-3-pyrrolidin-1-yl-5,6,7,8-tetrahydro-2,7- naphthyridin-1-amine 5: in fact, the rearrangement was followed by condensation between the C-1 carbonyl group of the 2,7-naphthyridine ring and the benzylamine. Starting from the 7-benzyl-3-chloro-1-(3,5-dimethyl- 1H-pyrazol-1-yl)-5,6,7,8-tetrahydro-2,7-naphthyridine-4-carbonitrile 7 the relevant 3-amino-7-benzyl-1-(3,5- dimethyl-1H-pyrazol-1-yl)-5,6,7,8-tetrahydro-2,7-naphthyridine-4-carbonitriles 8 were obtained. In harsh experimental conditions the nucleophilic substitution of the 1-pyrazolyl residue took place with formation of 7- benzyl-1,3-bis[(2-hydroxypropyl)amino]-5,6,7,8-tetrahydro-2,7-naphthyridine-4-carbonitrile 10. Moreover, compound 7 reacted with hydrazine hydrate giving the pyrazolo[3,4-c]-2,7-naphthyridine 12, which, in turn, furnished a new tetra-heterocyclic system: 3-benzyl-5-(3,5-dimethyl-1H-pyrazol-1-yl)-9,11-dimethyl-1,2,3,4- tetrahydropyrimido[1',2': 1,5]pyrazolo[3,4-c]-2,7-naphthyridine 13. Conclusion: Replacement of methyl group on piperidine ring of 2,7-naphthyridine system with the benzyl one led to new results. Reaction of compound 2a or 3g with benzylamine brought to an unexpected formation of N,7-dibenzyl-8-(benzylimino)-3-pyrrolidin-1-yl-5,6,7,8-tetrahydro-2,7-naphthyridin-1-amine 5. The reactivity of 7-benzyl-3-chloro-1-(3,5-dimethyl-1H-pyrazol-1-yl)-2,7-naphthyridine 7 with nucleophiles was investigated, observing the unexpected substitution of the 1-pyrazolyl residue.