Individual and simultaneous degradation of brominated high impact polystyrene and brominated acrylonitrile-butadiene-styrene and removal of heteroelements (Br,N, and O) from degradation oil by multiphase catalytic systems

Brominated high-impact polystyrene (HIPS-Br), which contained decabromodiphenyl ether flame retardant, and brominated acrylonitrile butadiene styrene (ABS-Br), which contained bromine-containing epoxy-type flame retardant, were degraded at 450°C individually and in a 1/1 mixture by a thermal and catalytic procedure using folded sheet mesoporous (FSM) and ZSM-5 zeolite in liquid phase contact mode. The two polymers produced similar degradation oils but at a higher yield for HIPS-Br. However, the composition and distribution of Br-, N-, and O-containing compounds depended on the type of flame retardant in HIPS-Br and ABS-Br. Multiphase catalytic systems consisting of FSM in liquid phase contact mode and various CaH-, FeO-, CoMo-, and NiMo-based catalysts, or combinations of these catalysts, in vapor phase contact mode were used to decrease the amount of heteroatoms (Br, N, and O) in the degradation oils. Each system gave particular results in terms of mass balance and concentrations of heteroatoms. A FSM (liquid phase contact)/CaHC (vapor phase contact) combination was the best catalytic system to remove Br-, N-, and O-containing compounds from degradation oils.     

Concentrations of various elements and inorganic ions in rice straw and ash

Various elements and inorganic ions in rice straw and ash samples were analyzed by using inductively coupled plasma atomic emission spectrometry (ICP‐AES) and ion chromatography (IC). Five major elements: Mg, Mn, Al, Ca, and Fe and eight minor and trace elements: Cr, Cu, Ti, Zn, La, Sr, Ba, and Hg were detected in these samples, at more than ppm‐level. In ash samples the trace elements such as Y, As, V, Se, and Sc were also identified. The concentrations of SO₄, PO₄, Cl, Na, and K ions in these samples were higher than those of other ions measured. These elements and inorganic ion concentrations were approximately one order of magnitude higher in the ash than in the straw samples. Gas chromatography/mass spectrometry (GC/MS) and library search showed the presence of fatty‐, carboxylic‐ and nicotinic acids, and their derivatives in small quantities in the straw samples.     

Organophosphorus flame retardants in house dust from the Philippines: occurrence and assessment of human exposure

The use of organophosphorus flame retardants (PFRs) as flame retardants and plasticizers has increased due to the ban on common polybrominated diphenyl ether mixtures. However, only limited information on PFR contamination is available so far from Southeast Asia. In the present study, residual levels of PFRs in house dust and exposure through dust ingestion were investigated in the Philippines. House dust samples (n?=?37) were collected from Malate (residential area) and Payatas (municipal dumping area) in the Philippines and analyzed using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry. Among the targeted seven PFRs, triphenyl phosphate (TPP) was the predominant compound. Median levels of ΣPFRs in Malate (530 ng/g) were two times higher (p?<?0.05) than in Payatas (240 ng/g). The estimated daily intake of PFRs in the Philippines (of areas studied) via house dust ingestion was below the guideline values. House dust may be an important contributor in the overall exposure of humans to TPP even when considering dietary sources. To our knowledge, this is a first report on PFR contamination in house dust from developing country. PFRs were ubiquitously detected in the home environments in the Philippines. Although estimated exposure levels through dust ingestion were below the guideline, it was suggested that toddlers are at higher risk. Therefore, further investigations to understand the behavior of PFRs in house and other microenvironments and overall exposure pathways for the country’s populace to PFRs are necessary.     

PCDD/DF formations by the heterogeneous thermal reactions of phenols and their TiO2 photocatalytic degradation by batch-recycle system

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/DFs) formation by the thermal reactions of phenols with CuCl2 under oxygen flux were carried out in relation to their formation mechanisms. To evaluate the effect of photocatalytic degradation of titanium dioxide (TiO2) thin film prepared by the sol-gel method, the photocatalysis of PCDD/DFs in acetonitrile/water solution by batch-recycle system was conducted. For the thermal reaction system of powder mixtures of 2,4,5-trichlorophenol (2,4,5-TCP) and CuCl2, the formation rates were 8.1 microg/g-2,4,5-TCP/min for total PCDD/DFs and 6.9 microg/g-2,4,5-TCP/min for PCDDs, and total PCDD/DF rate was higher by approximately 40 fold compared to phenol vapor/oxygen/CuCl2 powder system. For the system of 2,4,5-TCP, PCDDs were mainly formed via ortho-phenoxyphenols (POP) intermediate by the condensation of 2,4,5-trichlorophenate. For PCDD/DF photocatalytic degradations, most PCDD congeners photodecomposed rapidly and the rates presented more than 70% (as dechlorination rates of 76% for PCDDs) at 24 h after irradiation, using PCDD/DFs formed with 2,4,5-TCP. The rate constants were in the order of 4.8-6.1 x 10(-3) min(-1), assuming the pseudo-first-order reactions for their low levels.     

The photolysis of organic substances under atmospheric conditions with a cylindrical photoreactor using ethyl nitrite and nitrogen dioxide

The first-order rate constants of 8 organic substances were measured using the ethyl nitrite and nitrogen dioxide photolyses and their relative rates with respect to n-hexane rate constant were calculated. These were compared with literature data. Relatively small photolysis rates of alkane and aromatics were shown for our photosystems and the alkenes were rapidly photolyzed. For mixed photooxidation reactions of various organics, it would be reasonable for organics of the group classified by their molecular structures to be discussed on their reactivities with OH radicals.     

Alkaline hydrothermal treatment of brominated high impact polystyrene (HIPS-Br) for bromine and bromine-free plastic recovery

A method to recover both Br and Br-free plastic from brominated flame retardant high impact polystyrene (HIPS-Br) was proposed. HIPS-Br containing 15% Br was treated in autoclave at 280 degrees C using water or KOH solution of various amounts and concentrations. Hydrothermal treatment (30 ml water) leads to 90% debromination of 1g HIPS-Br but plastic is strongly degraded and could not be recovered. Alkaline hydrothermal treatment (45 ml or 60 ml KOH 1M) showed similar debromination for up to 12 g HIPS-Br and plastic was recovered as pellets with molecular weight distribution close to that of the initial material. Debromination occurs at melt plastic/KOH solution interface when liquid/vapour equilibrium is attained inside autoclave (280 degrees C and 7 MPa in our experimental conditions) and depends on the plastic amount/KOH volume ratio. The antimony oxide synergist from HIPS-Br remains in recovered plastic during treatment. A pictorial imagination of the proposed debromination process is presented.     

Photoreduction of Cr(VI) in wastewater by anodic nanoporous Nb2O5 formed at high anodizing voltage and electrolyte temperature

Environmental Science and Pollution Research - In this study, nanoporous anodic film was produced by anodization of niobium, Nb in a fluoride ethylene glycol electrolyte. The effect of anodization...