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Stem-like progenitor exhausted CD8 T cells are critical for maintaining long-term resistance during chronic infections and cancer, and represent an important checkpoint blockade immunotherapy target for functional reinvigoration and disease control. Hence, there is vigorous interest in understanding the ontogenesis of TCF-1Histem-like exhausted CD8 T cells, and in defining the signals that promote their development. Here, we show that virus-specific TCF1HiGzmBLoCD8 T cells develop during early stages of chronic viral infection, and are progressively deprogrammed from the stem-like lineage towards terminal differentiation by strong IL-2 signals. In vivo fate-tracking studies show that strong T cell-intrinsic IL-2 signals through the high affinity heterotrimeric IL-2Rα/β/γ receptor drive skewed development of terminally differentiated TCF-1LoGzmBHicells, which largely die in chronic antigenic environment. In contrast, tempered IL-2 signals through the intermediate affinity IL-2Rβ/γ heterodimer, or delayed priming in diminished IL-2 milieu support preferential development of TCF-1Histem-like exhausted CD8 T cells, capable of long-term persistence and potent responsiveness to PD-1 therapy in later stages of chronic viral infection. In human tumors as well, single cell RNA-seq analyses of tumor infiltrating lymphocytes from melanoma, human papillomavirus+ head and neck cancer and lung cancer patients revealed an inverse relationship between IL-2 signaling signature and T cell stemness. Moreover, melanoma patients with enriched IL-2 signaling signature showed poor responses to checkpoint blockade immunotherapy. Collectively, these findings bear relevance to clinical immunotherapies of chronic viral infections and cancers, and support exogenous IL-2 signal manipulation prior to therapy as a strategy for augmenting long-term clinical outcomes.ONE SENTENCE SUMMARYProgramming of exhausted T cell fates by differential IL-2

Modern multi-omic technologies can generate deep multi-scale profiles. However, differences in data modalities, multicollinearity of the data, and large numbers of irrelevant features make the analyses and integration of high-dimensional omic datasets challenging. Here, we present Significant Latent factor Interaction Discovery and Exploration (SLIDE), a first-in-class interpretable machine learning technique for identifying significant interacting latent factors underlying outcomes of interest from high-dimensional omic datasets. SLIDE makes no assumptions regarding data-generating mechanisms, comes with theoretical guarantees regarding identifiability of the latent factors/corresponding inference, outperforms/performs at least as well as state-of-the-art approaches in terms of prediction, and provides inference beyond prediction. Using SLIDE on scRNA-seq data from systemic sclerosis (SSc) patients, we first uncovered significant interacting latent factors underlying SSc pathogenesis. In addition to accurately predicting SSc severity and outperforming existing benchmarks, SLIDE uncovered significant factors that included well-elucidated altered transcriptomic states in myeloid cells and fibroblasts, an intriguing keratinocyte-centric signature validated by protein staining, and a novel mechanism involving altered HLA signaling in myeloid cells, that has support in genetic data. SLIDE also worked well on spatial transcriptomic data and was able to accurately identify significant interacting latent factors underlying immune cell partitioning by 3D location within lymph nodes. Finally, SLIDE leveraged paired scRNA-seq and TCR-seq data to elucidate latent factors underlying extents of clonal expansion of CD4 T cells in a nonobese diabetic model of T1D. The latent factors uncovered by SLIDE included well-known activation markers, inhibitory receptors and intracellular regulators of receptor signaling, but also honed in on several novel naïve and memory states that standard analyses missed. Overall, SLIDE is a versatile engine for biological discovery from modern multi-omic datasets.

Impaired chronic viral and tumor clearance has been attributed to CD8

Soil labile organic carbon (LOC) fractions are very sensitive to environmental change and closely related to soil quality. They play an important role in the study of terrestrial carbon cycles. This study aimed to explore the sensitivity of soil LOC fractions to environmental changes and analyze their main influencing factors during three seasonal water level periods for scientific management of Dongting Lake wetlands. Soil under three typical wetland types (Carextristachya wetland (CTW), Phragmites australis wetland (PAW) and Salix babylonica (SBW)) in East Dongting Lake in China were collected during the normal season (May), rainy season (August) and dry season (December). Seasonal dynamics of soil LOC fractions (i.e., dissolved organic carbon (DOC), microbial biomass carbon (MBC) and easily oxidized carbon (EOC)) within these wetlands and their relationship to soil nutrients and carbon-cycle enzyme activity were analyzed. The results showed that the soil DOC contents of the three wetlands first increased and then decreased, with the exception of CTW from the normal season to the dry season, while the seasonal changes of soil MBC and EOC for all wetlands followed an opposite pattern. CTW had the largest DOC concentration (228.29 mg·kg−1) during dry season, while the highest contents of soil DOC, MBC and EOC were found in PAW during the three observed seasons, which ranged from 82.05 to 203.60 mg·kg−1, 262.54 to 325.74 mg·kg−1 and 3.30 to 4.61 g·kg−1, respectively. However, the contents of soil DOC and their proportions to soil organic carbon (SOC) of all wetlands during the normal season were 56.58~82.05 mg·kg−1 and 0.41~0.47%, respectively, which were the lowest among the three seasons. Nevertheless, the contents of both MBC and EOC as well as their ratios to SOC in these wetlands showed similar seasonal dynamics, with the lowest values recorded in the rainy season. From the normal season to the dry season, invertase activity in all wetlands increased, while cellulase activity decreased by 12.5–31.3%. The seasonal variation of catalase activity for all wetlands was less distinctive, and the highest enzyme activity was during the rainy season. Correlation analysis revealed that soil LOC fractions for all wetlands were closely related to SOC, TN, TP and invertase for the three seasons, especially during the rainy season, but were negatively correlated with TK, cellulase and catalase activity. Generally, soil LOC fractions of the three wetlands were affected by the seasonal fluctuations of water levels and presented different distribution characteristics.

Inhibitory signaling in dysfunctional CD8 T cells through the programmed cell death 1 (PD-1) axis is well established in chronic viral infections and cancers. PD-1 is also transiently induced to high concentrations during priming of acute infections and immunizations, yet its impact on the development of long-lived antigen-independent T cell memory remains unclear. In addition to its expected role in restraining clonal effector expansion, here, we show that PD-1 expression on antigen-specific CD8 T cells is required for the development of a durable CD8 T cell memory pool after antigen clearance. Loss of T cell–specific PD-1 signaling led to increased contraction and a defect in antigen-independent renewal of memory CD8 T cells in response to homeostatic cytokine signals, thus resulting in attrition of the memory pool over time. Whereas exhausted CD8 T cells regain function after PD-1 checkpoint blockade during chronic viral infection, the preexisting pool of resting functional bystander memory CD8 T cells established in response to a previously administered immunogen decreased. Metabolically, PD-1 signals were necessary for regulating the critical balance of mTOR-dependent anabolic glycolysis and fatty acid oxidation programs to meet the bioenergetic needs of quiescent CD8 T cell memory. These results define PD-1 as a key metabolic regulator of protective T cell immunity. Furthermore, these results have potential clinical implications for preexisting CD8 T cell memory during PD-1 checkpoint blockade therapy.

A novel organic-inorganic hybrid supramolecular Complex (C2H8N)4SiMo12O40 based on Keggin building blocks has been successfully synthesized by solvothermal method. Single-crystal X-ray analysis revealed that it crystallized in orthorhombic system, Pnma space group. The supramolecular crystalline network is formed via intermolecular hydrogen bonds. The target product was characterized by Infrared spectrum, thermogravimetric-differentialthermal, cyclic voltammetry and fluorescent spectrum. Results prove that Complex emits blue fluorescence and has irreversible photochromic properties. Differential thermal-thermogravimetric and cyclic voltammetry shows that Complex has high thermal stability and strong oxidizability. The catalytic performances of Complex were investigated by solid-gas heterogeneous catalysis method. Using solid target product as catalyst, the catalyze degradation of methanol was tested in the temperature range from rt. to 160 °C. When the system flow rate is 5.0 mL min−1, initial concentration of methanol is 5.34 g m−3, reaction temperature is 150 °C, eliminating rate of methanol is 76%, those indicate that Complex has good catalytic activity.

Cement plants (CPs) are one of the most important anthropogenic sources of mercury (Hg) emissions in China. Over 1000 cement production lines operate in China and use various raw materials; however, little data on Hg emissions is recorded on site. This study investigated a CP in Guizhou Province that uses multiple mining and industrial wastes as part of the circular economy policy. Among the various raw materials, carbide slag had the highest Hg content (2.6 mg/kg) and contributed half of the Hg input. High Hg concentration (27 mg/kg) in the kiln tail dust and a strong Hg enrichment factor (39) was found, which was determined as the ratio of total Hg accumulated within the clinker production process to the daily Hg input from raw materials and fuel. The clinker had negligible Hg (0.001 mg/kg), while the Hg in cement products (0.04 mg/kg) mostly came from additives and retarders. The estimated atmospheric emission factor of Hg from this CP was 161.5 mg Hg/t clinker, which was much higher than those of other CPs in Guizhou that employ low-Hg raw materials. A five-step sequential extraction experiment with kiln tail dust indicates that Hg mainly existed in fraction of F4 (73-96% of the total Hg, possibly as Hg

Background: Autophagy has been confirmed to be closely related to the growth and drug resistance of cancer cells, and autophagy related 4B (ATG4B) performs a crucial role in the process of autophagy. lncRNA CRNDE (colorectal neoplasia differentially expressed) promotes the growth of hepatocellular carcinoma (HCC) cells, but it is unclear whether the tumor-promoting effect of CRNDE is associated with the regulation of ATG4B and autophagy. Methods: The expression of CRNDE and ATG4B in HCC tissues and cells was detected by quantitative real-time PCR (qPCR) and Western blot. The effect of CRNDE on autophagy of HCC cells was examined by fluorescent assay, GFP-LC3 analysis and Western blot. The relationship among CRNDE, miR-543 and ATG4B was clarified using bioinformatic analysis, qPCR, Western blot and dual-luciferase reporter assay. The effect of CRNDE on sensitivity of sorafenib in HCC cells was evaluated in vitro and in vivo by CCK-8 assay, Western blot, Hoechst staining, flow cytometry, IHC staining and TUNEL assay. Results: CRNDE induced autophagy via upregulating ATG4B in HCC cells. Mechanistically, CRNDE enhanced the stability of ATG4B mRNA by suppressing miR-543, leading to the increase of ATG4B expression and autophagy in HCC cells. Moreover, sorafenib dramatically elevated CRNDE and ATG4B as well as autophagy. Knockdown of CRNDE significantly sensitized HCC cells to sorafenib in vitro and in vivo . Conclusion: The study has revealed the presence of “CRNDE/ATG4B/autophagy” pathway which alleviates the sensitivity of sorafenib in HCC cells, suggesting that this pathway may serve as a novel target to improve the killing effect of sorafenib in HCC treatment.

Liver cancer is one of the most common and high recurrence malignancies. Besides radiotherapy and surgery, chemotherapy also plays an essential role in the treatment of liver cancer. Sorafenib and sorafenib-based combination therapies have been proven efficacy against tumors. However, previous clinical studies have indicated that some patients with liver cancer are resistant to sorafenib treatment and the existing strategies are not satisfactory in the clinic. Therefore, it is urgent to investigate strategies to improve the effectiveness of sorafenib for liver cancer and to explore effective drug combinations. In the present study, we found that dichloroacetate (DCA) could significantly enhance the anti-tumor effect of sorafenib on liver cancer cells, including reduced viability and dramatically promoted apoptosis in liver cancer cells. Moreover, compared to sorafenib alone, the combination of DCA and sorafenib markedly increased the degradation of anti-apoptotic protein Mcl-1 by enhancing its phosphorylation. Overexpression of Mcl-1 could significantly attenuate the synergetic effect of DCA and sorafenib on apoptosis induction in liver cancer cells. Furthermore, we found that the ROS-JNK pathway was obviously activated in the DCA combined sorafenib group. The levels of ROS and p-JNK were dramatically up-regulated in the two drug combination groups. Antioxidant NAC could alleviate the synergetic effects of DCA and sorafenib on ROS generation, JNK activation, Mcl-1 degradation, and cell apoptosis. Moreover, DCA and sorafenib's effects on Mcl-1 degradation and apoptosis could also be inhibited by JNK inhibitor 'SP'600125. Finally, the synergetic effects of DCA and sorafenib on tumor growth suppression, Mcl-1 degradation and induction of apoptosis were also validated in liver cancer xenograft in vivo. These findings indicate that DCA enhances the anti-tumor effect of sorafenib via the ROS-JNK-Mcl-1 pathway in liver cancer cells. This study may provide new insights to improve the chemotherapeutic effect of sorafenib, which may be beneficial for further clinical application of sorafenib in liver cancer treatment.

IL-2 signaling at the time of CD8 T cell activation is a critical factor dictating effector and memory CD8 T cell differentiation. However, how IL-2 signaling impacts exhausted CD8 T cell fate outcomes remains poorly defined. Here, we address the role of IL-2 signaling in regulating the differentiation of the stem-like and terminally exhausted CD8 T cells. Prolonged expression of the high affinity IL-2 receptor (IL-2Ra, CD25), and resultant increase in IL-2 signaling drives terminal differentiation of effector cells during acute infection. We hypothesized that curtailing this signal would prevent terminal differentiation and promote the formation of less exhausted stem-cell like TCF-1+CD8T cells in chronic antigenic setting. Our studies show that blocking IL-2 signals at the early phase of chronic infection significantly increased the proportions of TCF-1+CD8T cells. Similarly, knocking down Il2ra augmented the development of TCF-1+CD8T cells. The therapeutic success of PD-1/PD-L1 checkpoint blockade immunotherapy (CBI) relies primarily on stem-cell like cells for vigorous expansion and effector responses. Thus, we next investigated how FACS-purified CD25Hi and CD25Lo cells adoptively transferred into infection-matched chronically infected recipients respond to PD-1 CBI. In contrast to CD25Hi cells, CD25Lo cells underwent vigorous proliferation after PD-1 CBI and produced high amount of effector molecules (GzmB, TNF-α and IFN-γ). Collectively, these data highlight the role of IL-2 signaling in the regulation of CD8 T cell exhaustion, which may be therapeutically exploited to optimize treatments of chronic infections and cancers with immune checkpoint inhibitors. Supported by NIH R21AI154363 NIH R01AI32819

Differential interleukin-2 (IL-2) signaling and production are associated with disparate effector and memory fates. Whether the IL-2 signals perceived by CD8 T cells come from autocrine or paracrine sources, the timing of IL-2 signaling and their differential impact on CD8 T cell responses remain unclear. Using distinct models of germline and conditional IL-2 ablation in post-thymic CD8 T cells, this study shows that paracrine IL-2 is sufficient to drive optimal primary expansion, effector and memory differentiation, and metabolic function. In contrast, autocrine IL-2 is uniquely required during primary expansion to program robust secondary expansion potential in memory-fated cells. This study further shows that IL-2 production by antigen-specific CD8 T cells is largely independent of CD4 licensing of dendritic cells (DCs) in inflammatory infections with robust DC activation. These findings bear implications for immunizations and adoptive T cell immunotherapies, where effector and memory functions may be commandeered through IL-2 programming.

A novel organic–inorganic supramolecular compound (C4H6N3)2·(P2Mo18O62)·(C4H7N3)2·(H2O)4 was synthesized through hydrothermal methods and characterized by IR spectroscopy, UV–Vis, Fluorescence spectra, TG-DTA, single-crystal X-ray diffraction. The results indicate that the compound exhibit a two-dimensional supramolecular network via hydrogen bond interactions. Crystal data: orthorhombic, Pnma space group, a = 25.4728 (17) A, b = 20.3269 (8) A, c = 15.6810 (7) A, V = 8119.4 (7) A3, Z = 4, R1 = 0.1285, wR2 = 0.2214. There is a pore structure between six [P2Mo18O62]6− along the b-axis. The accessible volume is 17.9% as estimated using the SOLV function of PLATON. The color of this compound is gradually turned from yellow into green in the ultraviolet irradiation with UV lamp (8W, 253 nm) for 2 h. It is indicated that the compound has photochromic property.

It is crucial to prevent the secondary pollution when recycling wastes. During the recycling of waste printed circuit boards by the pyrometallurgical process, bromine in the raw materials is normally released in the form of HBr/Br2 into the flue gas. In the present work, for the first time the conversion of HBr to Br2 during the cooling of flue gas in the post combustion area (PCA) was studied to provide evidences for the control of PBDD/Fs and the recycling of Br. The 1200 °C flue gas was cooled down at various cooling rates in a lab-scale system. The influence of PCA operating conditions, i.e., cooling temperature (Tc), residence time in the cooling zone (RTcz) and Oxygen partial pressure (PO2), on the conversion ratio was studied systematically. And the study was based on the newly developed method to determine HBr and Br2 contents in the flue gas at various temperatures. For each RTcz, i.e., 0.3, 0.5 and 0.7s, the ratio first increases with decreasing Tc to a maximum value at Tcmax and then decreases as Tc further drops. Tcmax depends on RTcz. For Tc = 200 °C and RTcz = 0.3s, approximately 31.1% HBr is converted to Br2. This is 51% lower than the highest. Moreover, at lower Tc and longer RTcz, the ratio can be less than that at higher Tc and shorter RTcz, vice versa. Accordingly, when cooling the system to a certain temperature, the shorter the RTcz is, the lower the conversion ratio will be. PO2 slightly influences the ratio. These are vital to the determination of Br sources for PBDD/Fs formation in PCA, which is valuable for the future pollution control. Besides, extension of the cooling time in the lower temperature range (from 200 °C at RTcz = 0.3s to 50 °C) within 300s greatly improves the ratio up to 91%. This provides the basis for the Br recovery rather than removal by chemical agents.

Four new network organic–inorganic hybrid supramolecular compounds [PW12O40](C2H4N3)3·6H2O (1), [PMo12O40](C2H4N3)3·6H2O (2), [H4SiW12O40]8[C6NO2H4]4[C6NO2H5]16[C5NH6]4·39H2O (3) and [H3VW12O40] (C6H6NO2)2(CHO2)2·4H2O (4) composed by keggin type heteropolyanion and O/N-containing organic groups of 1H-1,2,4-Triazole or 2,3-Pyridinedicarboxylic acid have been successfully synthesized by hydrothermally method, and characterized by infrared spectrum (IR), thermogravimetric–differentialthermal analysis (TG–DTA), cyclic voltammetry (CV) and single crystal X-ray diffraction (XRD). Compounds 1–4 exhibit three dimensional supramolecular network via hydrogen bonds and/or π–π stacking interactions. These compounds exhibit good thermal stability and catalytic ability. They are active for catalytic oxidation of methanol in a continuous-flow fixed-bed micro-reactor, when the initial concentration of methanol is 2.5 g m−3 in air and flow rate is 10 mL min−1, the corresponding elimination rates of methanol are 65% (125 °C), 85% (125 °C), 94% (150 °C), and 80% (125 °C), respectively.

Two new 3D network organic-inorganic hybrid supramolecular complexes {[Na6(CoEDTA)2(H2O)13]·(H2SiW12O40)·xH2O}n (1) and [CoH4EDTA(H2O)]2(SiW12O40)·15H2O (2) (H4EDTA=Ethylenediamine tetraacetic acid) have been successfully synthesized by solution method, and characterized by infrared spectrum (IR), thermogravimetric-differential thermal analysis (TG-DTA), cyclic voltammetry (CV) and single−crystal X-ray diffraction (XRD). Both of the complexes are the supramolecules, but with different liking mode, they are two representative models of supramolecule. complex (1) is a 3D infinite network supramolecular coordination polymer with a rare multi-metal sturcture of sodium-cobalt-containing, which is mainly linked through coordinate-covalent bonds. While complex (2) is normal supramolecule, which linked by non-covalent interactions, such as H-bonding interaction, electrostatic interaction and van der waals force. Both of complex (1) and (2) exhibit good catalytic activities for catalytic oxidation of methanol, when the initial concentration of methanol is 3.0 g m−3, flow rate is 10 mL min−1, and the quality of catalyst is 0.2 g, for complex (1) and complex (2) the maximum elimination rates of methanol are 85% (150 °C) and 92% (120 °C), respectively.

A novel Ni/Na – containing inorganic-organic hybrid supramolecule {(PW12O40)·[Na2(NiH2EDTA·H2O)(H4EDTA)·2H2O]·2H2O·H3O}n (short for NiEDTA-PW12) has been successfully synthesized by solution method, and investigated by thermogravimetric-differential thermal analysis (TG-DTA), ultraviolet visible (UV-Vis) spectroscopy, cyclic voltammetry (CV), photoluminescence (PL), ultraviolet visible diffuse reflectance spectrum (UV-vis DRS) and single-crystal X-ray diffraction (XRD). NiEDTA-PW12 exhibits intriguing infinite supramolecular structure with Na+ ions as linker. Furthermore, NiEDTA-PW12 displays a fast-responsive reversible photochromism under ultraviolet or visible light. The photochromic property of NiEDTA-PW12 has been investigated by techniques of UV-vis DRS and PL, and the impact of the O2 on fading of the colored NiEDTA-PW12 has been investigated.

An organic–inorganic hybrid supramolecular complex, (H3O)4[(CoC14H12N2O10)1.5(SiW12O40)]·2H2O, is constructed by tungstosilicate anion and 2,3-pyridinedicarboxylic acid cobalt coordination complex via intermolecular forces. Crystal data of the title complex: trigonal system, P-3c1 space group, a = 20.363(3) A, b = 20.363(3) A, c = 27.685(5) A, α = 90 °, β = 90 °, γ = 90 °, V = 9942(3) A3, Z = 4, Rint = 0.0383, R2 = 0.1645, GOOF = 1.083. The complex has been hydrothermally synthesized and characterized by Infrared spectra, TG-DTA, fluorescence, cyclic voltammetry, and single-crystal X-ray diffraction. The complex exhibits good catalytic activity for elimination of methanol in the gas phase, when the initial concentration of methanol is 2.76 g m−3, and flow rate is 10 mL min−1 at 140 °C, the elimination rate of methanol is 82.6% over 0.2 g of complex.

The high affinity IL-2 receptor (IL-2Ra, CD25) is a key activation marker, which is transiently and heterogeneously expressed during the priming . While IL-2 signals are deemed critical for expansion of antigen-specific CD8 T cells, the role of IL-2 in programing the fate of exhausted CD8 T cells in vivo is poorly understood. Exhausted CD8 T cells are broadly divided into 2 subsets: one with brightest levels of inhibitory receptors such as PD-1, and lower mitochondrial spare respiratory capacity (SRC) – these cells are terminally exhausted and are largely unresponsive to PD-1 checkpoint blockade immunotherapy. The other subset has intermediate levels of inhibitory receptors and retains higher mitochondrial SRC – these are the clinically relevant cells that are highly responsive to PD-1 blockade. Based on the ability of IL-2 signals to drive glycolytic burnout in T cells, we hypothesized that the stochastic heterogeneity in in vivo assimilation of IL-2 signals during priming drives distinct CD8 T cell fates late during exhaustion. We sorted in vivo primed CD8 T cells based on their heterogeneity in CD25 expression, and adoptively transferred them into infection-matched chronically infected recipients. We observed that the exhausted CD8 T cells generated from CD25Hi donor cells phenotypically and functionally resembled terminally exhausted cells. Furthermore, knocking down the expression of CD25 or Special AT-rich sequence binding protein 1 (SATB1), which is known to regulate CD25 expression, resulted in better survival and function of exhausted CD8 T cells. Our data underscores the critical role of IL-2 signals in the exhaustion of CD8 T cells and has clinical significance in current combination checkpoint blockade immunotherapies.

Two 3D organic-inorganic hybrid supermolecular complexes, Na(BiHEDTA·2H2O)3(PW12O40)·2H3O (BiPW) and Na(BiHEDTA·2H2O)3(PMo12O40)·2H3O·2H2O (BiPMo) (EDTA = ethylenediamine tetraacetic acid), have been synthesized by solution method and characterized by ultraviolet visible (UV-Vis) spectroscopy, thermogravimetric-differential thermal analysis (TG-DTA), photoluminescence (PL), cyclic voltammetry (CV) and single-crystal X-ray diffraction (XRD). XRD analysis reveals that BiPW and BiPMo are isostructural, with three-dimensional architectures assembled by the two-dimensional layer tetranuclear cation and a Keggin-type polyoxoanion. Although these two hybrids exhibit similar structures, the properties depend on the nature of polyoxoanion [PM12O40]3− (M = W, Mo). Under UV irradiation, BiPW and BiPMo show fast response of reversible and irreversible photochromism, respectively. BiPW exhibits excellent photocatalytic activity in degradation of methyl orange (MO) dyes under irradiation of UV-visible light. It can be reused for at least six cycles without obvious loss of activity in the degradation experiments; BiPMo shows catalytic activity in elimination of methanol. The elimination rate of methanol reaches 56.9% when the concentration of methanol is 2.3 g·m−3 and the flow velocity is 10 mL·min−1 at 100 °C.

High temperature combustion is crucial for the most promising pyrometallurgical processing among the present processing methods of waste printed circuit boards (PCBs). This article reports the experimental studies of pyrolysis and combustion characteristics of waste PCBs using thermogravimetric analysis (TGA) techniques, and inorganic bromine (HBr+Br2) evolution during the temperature ranges based on the TGA data using the batch reactor system. Emphasis is laid on the weight loss in predevolatilization stage and the volatiles evolution. In the predevolatilization stage, there are 0.7% and 1.0% weight losses under pyrolysis and combustion condition respectively. The evolution of inorganic bromine contributes 85% and 90% to the two weight losses respectively. Remarkably, in the stage of volatiles rapid evolution, compared with that under pyrolysis condition, the volatiles evolution decreases by 22.8 wt % under combustion condition. Besides, 62 wt % of the original bromine evolves in the form of HBr during this stage, and 67% HBr in effluent converts to Br2. Based on these findings, the primary mechanism of weight loss in the predevolatilization stage and the volatiles evolution were discussed and analyzed. The findings are valuable for the combustion organization practice of waste PCBs. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 1105–1110, 2014

Highlights: Black-Right-Pointing-Pointer The combustion efficiency of waste printed circuit boards (PCBs) depends on temperature, excess air factor, and high temperature zone residence time. Temperature has the most significant impact. Under the proposed condition, combustion of waste PCBs alone is quite complete within the furnace. Black-Right-Pointing-Pointer High temperature prompts a more complete bromine release and conversion. When temperature is high enough, 99.9% organobrominated compounds, the potential precursors for brominated dixoins formation, are destroyed efficiently and convert to inorganic bromine in flue gas, as HBr and Br{sub 2}. Black-Right-Pointing-Pointer Temperature has crucial influence over the inhibition of HBr conversion to Br{sub 2}, while the oxygen partial pressure plays a reverse role in the conversion to a very small extent. Increasing temperature will decrease the volume percentage ratio of Br{sub 2}/HBr in flue gas greatly. Black-Right-Pointing-Pointer The thermodynamic equilibrium approach of bromine conversion was investigated. The two forms of inorganic bromine in flue gas substantially reach thermodynamic equilibrium within 0.25 s. Under the proposed operating condition, the reaction of Br transfer and conversion finish. - Abstract: High temperature combustion experiments of waste printed circuit boards (PCBs) were conducted using a lab-scale system featuring a continuously-fed drop tube furnace. Combustion efficiency and the occurrencemore » of inorganic bromine (HBr and Br{sub 2}) were systematically studied by monitoring the main combustion products continuously. The influence of furnace temperature (T) was studied from 800 to 1400 Degree-Sign C, the excess air factor (EAF) was varied from 1.2 to 1.9 and the residence time in the high temperature zone (RT{sub HT}) was set at 0.25, 0.5, or 0.75 s. Combustion efficiency depends on temperature, EAF and RT{sub HT}; temperature has the most significant effect. Conversion of organic bromine from flame retardants into HBr and Br{sub 2} depends on temperature and EAF. Temperature has crucial influence over the ratio of HBr to Br{sub 2}, whereas oxygen partial pressure plays a minor role. The two forms of inorganic bromine seem substantially to reach thermodynamic equilibrium within 0.25 s. High temperature is required to improve the combustion performance: at 1200 Degree-Sign C or higher, an EAF of 1.3 or more, and a RT{sub HT} exceeding 0.75 s, combustion is quite complete, the CO concentration in flue gas and remained carbon in ash are sufficiently low, and organobrominated compounds are successfully decomposed (more than 99.9%). According to these results, incineration of waste PCBs without preliminary separation and without additives would perform very well under certain conditions; the potential precursors for brominated dioxins formation could be destroyed efficiently. Increasing temperature could decrease the volume percentage ratio of Br{sub 2}/HBr in flue gas greatly.« less