Removal of polychlorinated naphthalenes by desulfurization and emissions of polychlorinated naphthalenes from sintering plant

Polychlorinated naphthalenes in farmed Chinese mitten crabs in China: Concentration, distribution and source analysis

Polychlorinated naphthalenes (PCNs) are both highly toxic and bioaccumulative environmental contaminates. Dietary intake is the primary pathway for human exposure to PCNs, and PCN concentrations in aquatic foodstuffs are relatively high. Chinese mitten crab (Eriocheir sinensis) is one kind of popular aquatic foodstuffs in Asian countries. Farmed crabs could exposure to PCNs both through feed and environment. However, information on the occurrence of PCNs in farmed crabs is scarce. The present study investigated 75 PCN congeners in farmed Chinese mitten crabs, crab compound feed and sediments collected from Anhui Province and Shanghai in China. The total PCN concentrations in farmed Chinese mitten crabs from Anhui Province and Shanghai were 11.2-42.2 and 5.46-43.8 pg/g wet weight (ww), respectively. The PCN homologue profiles in crabs from both areas were similar, and both were dominated by di-CNs and penta-CNs. In contrast, lower chlorinated PCNs (di-CNs, tri-CNs and tetra-CNs) were the most common homologues in specimens of crab compound feed and sediment samples, indicating that selective bioaccumulation and metabolism of PCNs might occur in farmed crabs. No regional differences were found in the PCN congener profiles of farmed crabs, feed and sediment samples taken from Anhui Province and Shanghai. An assessment found no significant health risk associated with Chinese exposure to PCNs through farmed Chinese mitten crab consumption.

Phototransformation of three polychlorinated naphthalenes on surface of atmospheric particulate matter

Polychlorinated naphthalenes (PCNs) are a new class of persistent organic pollutants. Photoconversion is an important pathway for their transformation in the environment. In this work, silica gel was used to simulate atmospheric mineral particles, and the photochemical reaction of three PCNs 1-chloronaphthalene (CN-1), 2-chloronaphthalene (CN-2) and 2,3-dichloronaphthalene (CN-10)) on silica gel surface was studied under the irradiation of high-pressure mercury lamp, the phototransformation intermediates and pathways of PCNs were investigated, effects of reactive oxygen species (ROS, ·OH, ¹O₂ and O₂^-·) were proved by free radical scavenging method and the effects of co-existing components (water, inorganic ions and fulvic acid) were examined. The results showed that all the three PCNs could be photochemical degraded on silica gel surface. The order of the apparent rate constants was CN-2 ≈ CN-1 > CN-10. ROS accelerated the photochemical reaction. The three PCNs didn't produce completely identical photoproducts, but all underwent a series of reactions such as reductive dechlorination, hydroxylation, oxidation, decarboxylation and ring opening. In addition, for the photoconversion of CN-1, the presence of water, NO₃^- or fulvic acid all promoted the photochemical transformation, while the presence of Cu²⁺ had an inhibitory effect.

Characterization of PCN emission and removal from secondary copper metallurgical processes

This study investigates the characteristics of PCN emission and removal from two secondary copper metallurgical processes (plants A and B) equipped with different air pollution control devices (APCDs). Different operating conditions and feeding materials result in varying emission factors of PCNs from two plants. The average PCN concentration emitted from plant B (7597 ng Nm^-3) is significantly higher than that emitted from plant A (32.5 ng Nm^-3) and those reported in China (5.8-2845 ng Nm^-3). Similar trend is found for fly ash samples collected from two plants. Low chlorinated homologues (Mono-to Tri-CNs) are the major contributors to total PCNs measured in flue gas, fly ash and slag samples. Combination of semi-dry absorber, activated carbon injection and baghouse is effective for PCN removal in plant A, with the overall removal efficiency of 98%. The overall removal efficiency of PCNs achieved with APCDs equipped in plant B is 90%, however, increases of some homologues as the flue gases passing through baghouse and wet scrubber are found, suggesting the occurrence of memory effect within baghouse and wet scrubber.

Temporal trends in polychlorinated naphthalene emissions from sintering plants in China between 2005 and 2015

The Chinese Government has established stringent policies since 2005 to control SO₂, particulate matter, and NO_x emissions from sintering plants with the aim of tackling severe air pollution in China. Notably, sintering is also important sources of polychlorinated naphthalenes (PCNs), but it is not clear whether the air pollution control policies have led to decreased PCN emissions. In this study, the PCN concentrations in 144 stack gas, 87 discarded fly ash, and 24 desulfurization by-product samples from 24 Chinese sintering plants were determined. This study revealed that desulfurization processes decreased PCN emissions by 47.2%-72.2%. However, these PCNs were not completely eliminated, and transformed to desulfurization by-product. PCN emission in such previously ignored solid residues, including of desulfurization by-product and fine particles, produced in the process of cutting down air pollutants emissions from Chinese sintering plants between 2005 and 2015 was found contained 324 kg, and these residues therefore need to be managed better than currently. Furthermore, PCN concentrations were higher from produced in old plants than produced in new plants, so it is necessary to increase the rate at which out-of-date sintering plants are eliminated. Phasing out old sintering processes decreased total PCN emissions in China by 1549 kg between 2005 and 2015.

Levels and fingerprints of chlorinated aromatic hydrocarbons in fly ashes from the typical industrial thermal processes: Implication for the co-formation mechanism

Municipal solid waste incineration (MSWI) and iron and steel making plants are two of important sources of chlorinated aromatic hydrocarbons (CAHs). In this study, the typical CAHs including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs) and chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs) in fly ash samples collected from MSWI, iron ore sintering (IOS) and steel smelting (SS) plants were simultaneously identified and quantified. The total concentrations of quantified CAHs in different fly ashes showed a large variation (5.88-4255 ng/g). Cl-PAHs were found to be predominant CAH species in most of fly ash samples, and the concentrations of mono-chlorinated PAHs in all fly ashes were obviously higher than those of di-chlorinated PAHs. The fingerprints of CAHs in MSWI fly ashes were mainly characterized by the high content of PCDDs, especially the hexa-CDD homologue. However, in IOS and SS fly ashes, tetra- to hexa-CDF homologues showed the higher abundance, and tetra-to octa-CDFs predominated over tetra- to octa-CDDs by factors of 3-26. The strong concentration correlations were observed between tetra- to octa-CDF homologues, middle-chlorinated PCN and PCB homologues, between tetra- to octa-CDD homologues, between low-chlorinated PCB and PCN homologues, between di-chlorinated PAH homologues, and between deca-CB and highly chlorinated PCN homologues. These results implied that the main formation mechanism of CAHs might be significantly varied with the change of chlorination degree and aromatic ring structure.

Distribution of polychlorinated naphthalenes (PCNs) in the whole blood of typical meat animals

The concentrations and distribution of polychlorinated naphthalenes (PCNs) in the whole blood of eight typical terrestrial meat animals (chicken, duck, rabbit, pig, cattle, sheep, horse and donkey) consumed daily in our life were investigated. The total concentrations (on a liquid volume basis) of PCNs were in a range from 305 to 987pg/L. Donkey blood contained the highest PCN concentrations. Mono-CNs were the dominant homolog group, accounting for 38%-71% PCNs. Apart from the mono-CNs and tri-CNs homolog groups, two hepta-CNs (mean: 9.5%) contributed most, followed by tetra-CNs (mean: 6.5%). The congeners CN1, 5/7, 24/14, 27/30, 52/60, 66/67, and 73 were the most abundant congeners or congener groups. The highest toxicity equivalencies (TEQs) were observed in cattle blood (117.4fg TEQ/L) then chicken blood (117.1fg TEQ/L). CN73 contributed 65% to total TEQs, followed by CN70 (20%) and CN66/67 (14%). The dietary intakes of PCNs were also estimated. Chicken meat, which forms the second largest component of meat product consumption in China, contributed most to the total TEQs (61%), followed by beef (27%) and pork (5.9%). The consumption of chicken might pose the highest risk from exposure to PCNs than other types of meat to populations who prefer to eat chicken meat.

Effects of Desulfurization Processes on Polybrominated Dibenzo- p-dioxin and Dibenzofuran Emissions from Iron Ore Sintering

Installing desulfurization operations and closing outdated facilities can effectively decrease pollutant emissions from iron ore sintering plants (IOSPs). Polybrominated dibenzo- p-dioxin and dibenzofuran (PBDD/F) emissions from different-sized IOSPs with different desulfurization operations were analyzed. The desulfurization operations' PBDD/F removal efficiencies were 53.6%-97.1%, and were higher for wet desulfurization operations than for semidry and dry operations. The removed PBDD/Fs were transferred to the desulfurization products. The removal efficiencies of PBDF homologues increased with the degree of bromination. A PBDD/F emission inventory for Chinese IOSPs was compiled. PBDD/F emissions in stack gases, desulfurization products, and discarded fly ash (previously ignored) from 2003 to 2015 were 1218, 400, and 245 g toxic equivalents, respectively. PBDD/F concentrations in stack gases and fly ash were higher for small IOSPs (<90 m²), indicating the importance of phasing them out. Indeed, in China, such phasing out decreased PBDD/F emissions in stack gases, desulfurization products, and discarded fly ash by 1021, 891, and 3253 g toxic equivalents, respectively, between 2003 and 2015. PBDD/F emissions in stack gases have been controlled in Chinese regions with the highest emissions, but PBDD/F emissions in desulfurization products and fly ash are increasing.

High organic sulfur removal performance of a cobalt based metal-organic framework

Synthesis of a new porous cobalt based metal-organic framework, [Co₆(oba)₆(CH₃O)₄(O)₂]n·3DMF (TMU-11) has been carried out to introduce a new and highly efficient adsorbent of dibenzothiophene (DBT). This compound has been synthesized by solvothermal method using a nonlinear dicarboxylate ligand and characterized by single-crystal X-ray crystallography. To study the adsorption properties of the synthesized compound, TMU-11, for DBT removal, various factors, such as amount of adsorbent, contact time and temperature were examined. On the basis of the results, maximum efficiency and reusability in DBT removal occur under the mild reaction conditions. Furthermore, the DBT removal follows the pseudo-second order reaction kinetic. The maximum adsorption value is 825mg/g. The selectivity test of DBT over naphthalene (NA) clearly shows that π-π interactions between organic linkers of TMU-11 and the aromatic ring of DBT are not responsible for the adsorption desulfurization (ADS) process and the main part of adsorption takes place on unsaturated site around Co centres. Our findings may provide some insight into the preparation of the adsorbent with superior performance in practical applications.