Current Organic Chemistry - Volume 16, Issue 18, 2012

Oxidizing radical formation was tested in paper mill water together with biocides. The investigation of electrochemical behavior of biocides on SS 2343 and MMO (mixed metal oxide) electrode surfaces was conducted in synthetic paper mill water (cPMW). Hydrogen peroxide and peracetic acid gave response to the polarization on the anodic and cathodic sides on the SS 2343 electrode surface. At the MMO electrode the phenomenon was not observed. Other biocides did not show response with the polarization treatment. Hence, hydrogen peroxide polarized together with stainless steel electrode could cause radical reactions in paper mill water, and thus improve the process efficiency compared to hydrogen peroxide used alone. A synergistic effect of hydrogen peroxide with the polarization at the SS 2343 electrode could also help to keep the paper making process less sensitive to slime problems caused by microbes living in this environment.

Electro-Fenton process has gained considerable interest for its application in water treatment for the removal of recalcitrant organic pollutants. This review is based on an overview of the electro-Fenton process applied for water treatment. The process mechanisms and fundamentals of the operation are explained. The applications of the process in water treatment have been reviewed. The major advantages of the process are that it uses electricity and does not generate secondary wastes. This review also covers the electro-Fenton based hybrid technologies developed hitherto, including some of the novel approaches in the field.

This study reports on comparative performance of electro-Fenton and photo-Fenton processes in the mineralization of three cationic dyes: BB41, BR46 and BY28. Primary objective was to determine the optimal conditions for both processes. It has been shown that the mineralization rate by electro-Fenton process depends on operating parameters such as applied current density, catalyst concentration, pH, etc. It was also observed that dyes degradation by hydroxyl radicals follows pseudo first-order reaction kinetics. Under the optimal operating conditions ([Fe 3+ ] = 0.2 mM, j = 3 mA cm -2 , and pH = 3), electro-Fenton process leads to an almost mineralization of dyes solutions reaching 93, 86 and 77% of TOC abatement for BB41, BR46 and BY28 respectively. The dye mineralization rate during photo-Fenton (UV/Fe 3+ /H2O2) process is a function of reagent doses, and their concentration ratio R = [H2O2]/[Fe3+]. Thus, mineralization rates obtained are around 95, 93 and 85% for BB41, BR46 and BY28 respectively for a treatment time of 5 h with a ratio R = 10 and [Fe3+] = 0.2 mM. The mineralization of a mixture of the three cationic dyes was also studied in a second step. Results showed that both photo-Fenton and electro-Fenton processes are able to reach almost complete mineralization rates. Finally the electro-Fenton process is considered the more efficient and interesting technique due to its environmentally friendly character with low energy consumption and no use of chemical reagents.

Aqueous solutions of Rhodamine 6G (R6G), one of the more used xanthene dye, were treated by hydroxyl radicals (.OH) electrocatalytically generated through the electro-Fenton process, a powerful and environmentally friendly electrochemical method. Platinum (Pt) or boron-doped diamond (BDD) anodes were used with a carbon-felt cathode. The effect of anode nature and applied current on the degradation and mineralization kinetics was investigated. The applied current value of 500 mA was found as optimum operating parameter for both anodes under our operating conditions. Kinetic data of R6G disappearance follow the pseudo-first order reaction decay process. The rate constant of the oxidation reaction between R6G and hydroxyl radicals was determined by competition kinetics method and found as 3.41 x 109 M-1 s-1. The mineralization efficiency was found very high with both anodes reaching 99% and 98% for BDD and Pt respectively at 500 mA. Oxalic acid was identified as ultimate end-product before complete mineralization. The two secondary amine groups of R6G were converted mainly into NH4 + ions whereas NO3 - ions are released to the solution at relatively low proportion.

The present work studied, for the first time, the removal of organic pollutants from a reverse osmosis (RO) concentrate by a three-dimensional electrode reactor using γ-Al2O3 /Sn-Sb oxide as particle electrodes. The morphological characterization and composition of the particle electrodes was studied by SEM, XRD and XPS, and the effects of current density and initial pH on the COD removal were investigated. The three-dimensional electrode reactor demonstrated much higher efficiency than that of two-dimensional system, which could remove COD completely in 2 h and kept stable performance after 7 continuous runs, confirming the feasibility for the treatment of RO concentrate.

The low-valent titanium (LVT) reagents have gained widespread acceptance in organic synthesis since their first use in 1973. McMurry coupling reaction uses the LVT (low-valent titanium) reagents. This article is an attempt to review the broad synthetic utilizations of this reagent in inter and intramolecular coupling of carbonyl groups in olefination, resulting in the formation of heterocyclic compounds.

Polycyclic aromatic hydrocarbons (PAHs) are of great interest due to their excellent optoelectronic properties and selfassembling properties. As a class of PAHs, star-shaped PAHs have a particular two-dimensional architecture and can self-assemble into three dimensional packed structures. Therefore, star-shaped PAHs have displayed comprehensive application in organic semiconducting materials. In this review, we will focus on the synthetic strategies toward triphenylene, trinaphthylenes, N-hetero-triphenylenes and starphenes, benzotrithiophene, truxene, and triazatruxene.