Treatment Of Phenolic Compounds Research Articles

Formation of nitro(so) by-products of concern during the treatment of phenolic compounds by the hydroxylamine-enhanced Fe(ii)/peroxymonosulfate process

The transformation pathway of hydroxylamine and the formation mechanism of nitro(so) by-products during the treatment of phenols using the Fe(ii)/peroxymonosulfate/hydroxylamine system are elaborated.

Effects of different phenolic compounds on the interfacial behaviour of casein and the action mechanism

The effects of different phenolic compounds on the interfacial behaviour of casein were investigated, and the action mechanism was further explored. Tannic acid, epigallocatechin gallate, quercetin and quercitrin promoted the aggregation of casein and decreased its solubility. Although the emulsifying and foaming capabilities of casein showed slight decrease with the treatment of phenolic compounds, its emulsifying and foaming stabilities were both greatly improved. By using fluorescence and circular dichroism spectra, phenolic compounds exhibited the capability to bind and form complexes with casein. Meanwhile, the binding interaction by phenolic compounds increased the α-helix content in casein and decreased its random coil content, which indicated a transition of the spatial conformation of casein from disorder to order. By using molecular docking, hydrogen bonds, hydrophobic interactions and Van der Waals were found in the interactions between phenolic compounds and casein. According to the analysis of spectroscopy and simulation results, the structure characteristics of phenolic compounds, including molecular weight, number and position of hydroxyl groups, acylation and glycosylation, exhibited significant effects on their interactions with casein, so as to affect the interfacial behaviour of casein. All present results suggested that phenolic compounds had the potential to improve the properties of casein in food and chemical industries.

Formation of nitrosated and nitrated aromatic products of concerns in the treatment of phenols by the combination of peroxymonosulfate and hydroxylamine

Recently, the combination of peroxymonosulfate (PMS) and hydroxylamine (HA) has been proposed as a green and efficient sulfate radical (▪)-based advanced oxidation process (AOP) for eliminating organic contaminants. However, we found that toxic nitrosated and nitrated aromatic compounds were generated during the treatment of phenolic compounds by PMS/HA system, indicating the involvement of reactive nitrogen species (RNS) during the interaction of PMS with HA. Specifically, considerable production of p-nitrosophenol (p-NSP) and mononitrophenol were obtained when phenol was oxidized by PMS/HA system under various conditions. At the molar ratio between HA and PMS of 1.0 and pH 5.0, sum of the yields of p-NSP and nitrophenols reached their maxima (around 50%). Moreover, production of p-NSP was inhibited while that of nitrophenols was promoted when applied NH2OH1/2H2SO4 was replaced by NH2OHHCl, which was possibly related to the formation of secondary reactive species induced by the reaction of ▪ with chloride ion. Further, formation of undesirable nitrosated and nitrated aromatic products was obtained in the treatment of other phenolic compounds including acetaminophen, bisphenol A, and bisphenol S by PMS/HA system. Considering the toxicity of nitrosated and nitrated aromatic compounds, practical application of PMS/HA system for environmental decontamination should be scrutinized.

Laccase treatment of phenolic compounds for bioethanol production and the impact of these compounds on yeast physiology

Laccase treatment of phenolic compounds found in lignocellulosic hydrolysates is an alternative to reduce the growth inhibitory effect of these compounds on fermenting microorganisms. In order to determine the main factors that affect the efficiency of this biocatalytic approach, laccase oxidation of individual and mixtures of phenolic compounds was evaluated. Additionally, the effect of phenolic compounds on Saccharomyces cerevisiae cell physiology and their effect on yeast membrane liposome models were evaluated. Trametes versicolor laccase showed complete oxidation of six phenolic compounds, while Agaricus bisporus laccase showed oxidation percentages ranging between 30–100%. High Performance Liquid Chromatography (HPLC) analyses suggested that compounds such as syringic acid, catechol and gallic acid were not completely polymerised after laccase treatment, which could explain the increase of negative effects observed when they were added to S. cerevisiae cultures. Ferulic acid and vanillin oxidation led to a 6.4 and 6.5-fold increase in ethanol production, respectively, compared with the untreated cultures. In phenolic mixtures, chemical interactions between phenolic compounds led to biotransformation of these compounds since different by-products were observed in HPLC chromatograms. Moreover, after laccase treatment, the negative effects of these mixtures were reduced, resulting in an increase in ethanol production yields. No correlation was observed between growth inhibition data, the effect on liposomes and the detoxification efficiencies. Thus, the efficiency of laccase detoxification was not related to the toxicity of the compounds but could be conditioned by the heterogeneity in the chemical structure and properties of these compounds (functional side groups, hydrophobicity, pKa).

Carbon Materials Inhibit Formation of Nitrated Aromatic Products in Treatment of Phenolic Compounds by Thermal Activation of Peroxydisulfate in the Presence of Nitrite.

Recent studies have reported that toxic nitrated aromatic products are generated during treatment of phenolic compounds by thermally activated peroxydisulfate (thermal/PDS) in the presence of nitrite (NO2-). This work explored the potential of carbon materials on controlling the formation of nitrated aromatic products using phenol as a model compound. In the presence of selected carbon materials including diverse carbon nanotubes (CNT) and powdered activated carbon (PAC), the transformation kinetics of phenol was significantly enhanced, primarily attributed to nonradical activation of PDS by carbon materials. Nitrophenols (NPs) including 2-NP and 4-NP were formed in phenol oxidation by the thermal/PDS/NO2- process, due to the reaction of phenol with reactive nitrogen species generated from NO2- oxidation. The addition of carbon materials obviously inhibited NPs formation under various experimental conditions. The bonding of nitro groups on the CNT surface was clearly confirmed by means of various characterizations, probably resulting from the competitive reaction of reactive nitrogen species with CNT vs phenol. The controlling effect of carbon materials was also verified in the cases of other phenolic compounds. Therefore, the addition of carbon materials may be a promising approach to control the formation of undesirable nitrated byproducts by the thermal/PDS process in the presence of NO2-.

A novel strategy using peroxymonosulfate to control the formation of iodinated aromatic products in treatment of phenolic compounds by permanganate

Formation of iodinated aromatic products during Mn(vii) oxidation of phenolic compounds in the presence of I− was reduced by the addition of PMS.

Transformation of bisphenol AF and bisphenol S by permanganate in the absence/presence of iodide: Kinetics and products

Recent studies have reported that permanganate (Mn(VII)) shows a good performance in treatment of phenolic compounds, and the presence of iodide (I−) may display a great impact on Mn(VII) oxidation with the formation of toxic iodinated aromatic products. In this work, transformation of bisphenol AF (BPAF) and bisphenol S (BPS) by Mn(VII) in the absence or presence of I− was studied. Mn(VII) showed considerable reactivity towards BPAF with apparent second-order rate constants (0.09–1.65 M−1s−1) higher than those of Mn(VII) with BPS (0.02–0.12 M−1s−1) reported in literature over the pH range of 5–9. The presence of I− apparently accelerated the transformation rates of BPAF and BPS by Mn(VII), and these results could be explained by the contribution of hypoiodous acid (HOI) in situ formed from Mn(VII) oxidation of I−. A kinetic model involving the competitive reactions (i.e., Mn(VII) with I− and bisphenols, HOI with Mn(VII) and bisphenols) well simulated BPAF/BPS transformation by Mn(VII) in the presence of I− under various conditions. Hydroxylated, bond-cleavage, and polymeric products were identified from BPAF/BPS oxidation by Mn(VII), and iodinated aromatic products (e.g., mono- and multi-iodinated BPAF/BPS) were additionally detected in the presence of I−. Reaction pathways involving Mn(VII) one-electron oxidation as well as HOI substitution of BPAF/BPS were proposed. Eco-toxicity analysis by ECOSAR showed that the toxicity of these products generally followed the order of polymeric and iodinated aromatic products > parent BPAF/BPS > hydroxylated products > bond-cleavage products.

Transformation of phenolic compounds by peroxymonosulfate in the presence of iodide and formation of iodinated aromatic products

In this work, the transformation of several phenolic compounds by peroxymonosulfate (PMS) in the presence of iodide (I−) was investigated with a focus on the potential formation of iodinated aromatic products of concerns. The addition of I− greatly enhanced the transformation of phenol and bisphenol A (BPA) by PMS, and this enhancement was strongly influenced by several factors (i.e., I− and PMS concentrations and solution pH). This result could be well explained by the competition reactions of hypoiodous acid (HOI) formed in situ with phenols vs PMS under various conditions. Five iodophenols were identified from HOI reaction with phenol, and four iodinated BPA (including mono-, di-, tri- and tetra-iodinated BPA) together with two bond-cleavage iodinated aromatic products were detected in the case of BPA. Reaction pathways mainly involving stepwise substitution of HOI on phenol and BPA were proposed, and β-scission of isopropyl moiety also took place for iodinated BPA. Moreover, evolution of these iodinated aromatic products from phenol and BPA in the PMS/I− system was monitored, and a lower pH or a higher [I−]:[PMS] ratio favored their formation. Comparatively, I− accelerated the transformation of catechol and hydroquinone by PMS but with negligible formation of iodinated aromatic products, where these two phenols underwent oxidation rather than substitution in the presence of HOI formed in situ. This work clearly demonstrates a high potential of forming iodinated aromatic products during treatment of phenolic compounds by PMS in the presence of I−, which depends on the reaction conditions as well as the reactivity and pathway of HOI.

Horseradish peroxidase microcapsules based on layer-by-layer polyelectrolyte deposition

Polyelectrolyte multilayer microcapsules have been prepared for encapsulating horseradish peroxidase (HRP). The CaCO 3 microparticles containing HRP molecules were prepared and subsequently enwrapped with layer-by-layer (LbL) deposited multilayer films. The LbL films were constructed via an alternate electrostatic adsorption of poly(allylamine) and poly(styrene sulfonate). The CaCO 3 templates were then dissolved in an ethylenediaminetetraacetic acid solution, leaving HRP in the microcapsules. Optical microscope and fluorescence microscope observations indicated that the microcapsules are homogeneous spheres with an average diameter about 7 μm. The encapsulated HRP showed catalytic activity in the oxidation of pyrogallol, suggesting the microcapsules provide a suitable environment for enzymatic reaction. A leakage of HRP from the microcapsules was negligibly small. Therefore, the HRP-containing microcapsules is promising for detection and treatment of phenolic compounds.