Applicability of Nickel-Based Catalytic Systems for Hydrodehalogenation of Recalcitrant Halogenated Aromatic Compounds

This review summarizes recent applications of nickel as a nonprecious metal catalyst in hydrodehalogenation (HDH) reactions of halogenated aromatic compounds (Ar–Xs). Nickel-based HDH catalysts were developed for reductive treatment of both waste containing concentrated Ar–Xs (mainly polychlorinated benzenes) and for wastewater contaminated with Ar–Xs. Ni-catalyzed HDH enables the production of corresponding nonhalogenated aromatic products (Ar–Hs), which are principally further applicable/recyclable and/or Ar–Hs, which are much more biodegradable and can be mineralized during aerobic wastewater treatment. Developed HDH methods enable the utilization of both gaseous hydrogen via the direct HDH process or other chemical reductants as a source of hydrogen utilized in the transfer of the hydrodehalogenation process. This review highlights recent and major developments in Ni-catalyzed hydrodehalogenation topic since 1990.

Effect of Sodium Chloride and Thiourea on Pollutant Formation during Combustion of Plastics

Thermal decomposition of different samples containing a mixture of plastics (polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and nylon) combined with NaCl and metal oxides (Fe2O3, CuO) was studied under an air atmosphere at 850 °C using a reactor, followed by analysis of the evolved products. Combustion runs were performed to study how the presence of such compounds influences the production of pollutants. Here, we report the analyses of the emissions of the main gases, as well as volatiles and semivolatiles, including polyaromatic hydrocarbons (PAHs), polychlorinated benzenes and phenols, and polybrominated phenols. Results show that the production of chlorinated pollutants did not increase in the presence of NaCl, but the presence of other metals during the decomposition led to the production of a great amount of pollutants. In this regard, the emission of chlorinated phenols increased from 110 to ca. 250 mg/kg when the sample included a small quantity of a transition metal oxide. Additionally, the presence of an inhibitor—thiourea (TUA)—was tested. Results confirm that adding TUA to the sample reduced these emissions to a considerable extent, with the emission of chlorinated phenols amounting to 65 mg/kg.

Detection of polychlorinated benzenes (persistent organic pollutants) by a luminescent sensor based on a lanthanide metal–organic framework

An effective luminescent sensor for polychlorinated benzenes based on a new metal–organic framework was reported.

Dissociative electron transfer in polychlorinated aromatics. Reduction potentials from convolution analysis and quantum chemical calculations

The combination of convolution analysis and quantum-chemical calculations at DFT and CCSD(T)-F12 levels allows the determination of standard redox potentials and the mechanism type of dissociative ET in environmentally relevant polychlorinated benzenes.

Correlation between PCDD/F, PCB and PCBz Formed by De Novo Synthesis

Large amounts of polychlorinated dibenzo-p-dioxin and furans (PCDD/F), polychlorinated biphenyls (PCB) and polychlorinated benzenes (PCBz) were formed by de novo synthesis using model ashes. The de novo synthesis was affected by SO2and H2O. Knowledge of congener pattern and homologue profiles of PCDD/F, PCB and PCBz is help for elaborating the mechanism of formation and influence of the toxic compounds formed by de novo synthesis. By the help of the component analysis (CA) the best correlated congeners are effectively detected. Various good correlated pairs between PCDD/F, PCB and PCBz have been elaborated by using linear regression between the 15 samples. It was found that a good correlation between PCBz and PCDF.