An effective utilization of the slag from acid leaching of coal-waste: Preparation of water glass with a low-temperature co-melting reaction

This paper presents an effective utilization of slag from acid leaching of coal-waste with a novel approach, namely low-temperature co-melting method, for preparation of sodium silicate (Na₂O·nSiO₂) using slag from acid leaching of coal-waste as feedstock. It is very interesting that the co-melting reaction temperature of the mixture of Na₂CO₃ and the feedstock (50?100 μm) was as low as 850 °C, which was significantly lower than the temperature used in traditional sodium silicate production (1400 °C). The optimum SiO₂/Na₂O ratio was identified as 7:3 according to the results of thermogravimetry–differential scanning calorimetry (TGA-DSC), ICP-AES, and X-ray diffraction (XRD) analyses. In this condition, the main product was sodium disilicate (Na₂O·2SiO₂), with water solubility of 85.0%. More importantly, the impurities such as aluminum in the feedstock, which had adverse effect on subsequent treatment, were concentrated almost completely in the filter residue as insoluble sodium alumunosilicates, i.e., Na(Si₂Al)O₆·H₂O. The lower co-melting temperature of this process demonstrates a significant energy-saving opportunity and thus a promising approach for highly effective utilization of coal-waste.

Implications:Recently, alumina extraction from coal-waste has been extensively investigated and industrial applied in China. However, the slag-containing silica generated from the acid leaching process of coal-waste led to a secondary pollution, which hindered large-scale production. The proposed low-temperature co-melting method for preparation of sodium silicate (Na₂O·nSiO₂) using slag from acid leaching of coal-waste as feedstock indicated that it is an efficient approach for the recovery of silica from the acid-leached slag of coal-waste with minimal environmental impact.     

无锡市酸雨变化特征及气象条件影响研究

基于无锡市2008~2011年酸雨观测资料,利用功率谱分析、后向轨迹和聚类分析方法,研究了无锡市酸雨的变化特征,分析了气象因素对酸雨的影响,探讨了1 500 m高度的气团移动路径特征。结果表明：2008~2011年,无锡市酸雨pH值呈现逐年递增趋势,而且酸雨逐月pH值、逐月弱酸雨和强酸雨频率分别存在不同的周期性变化;酸雨酸性随降水量增加表现为先增强后减弱,但夏季降水与酸雨pH值的相关性并不显著;春季相对湿度与酸雨pH值呈现显著负相关,夏季气温则与酸雨pH值呈显著正相关;各季节1 500 m高度的轨迹存在一定差异,春冬季无锡市受内陆气团影响为主,夏秋季西太平洋水汽输送作用明显。总体而言,江浙赣和西太平洋是无锡酸雨前体物的主要来源地     

The distribution pattern of different patch types and heterogeneity of the light and temperature: Larix chinensis Beissn in Qinling Mountains (China)

Based on a field investigation in the sample of an old growth subalpine coniferous forests in Qinling Mountains (China), we recognized the gap-forming processes in Larix chinensis forest for four representative patches (gap phases (G), building phases (B), mature phases (M) and degenerate phases (D)). The distribution pattern of four different patches and heterogeneity of the light and temperature were analyzed. The percentages of four different patch types (G, B, M and D) were 32.3%, 24.5%, 23.5% and 19.7%, respectively. The light and temperature had significant change among four patch types. From 6 to 20 o’clock, gap patch types changed more significantly than other three phases. The light and temperature regimes in mature patch type had a relatively mild change. Such micro-environmental heterogeneity among four different patches can lead to species niche partitioning, and some deterministic factors are benefit to the coexistence of various species with different characteristics within forest community.     

Absorption of NO and NO2 in Caprolactam Tetrabutyl Ammonium Halide Ionic Liquids

ABSTRACT

To explore environmentally benign solvents for the absorption of NO and NO₂, a series of caprolactam tetrabutyl ammonium halide ionic liquids were synthesized. The solubility of NO and NO₂ was measured at temperatures ranging from 298.2 to 363.2 K and atmospheric pressure, and the following trend in the solubility of NO and NO₂ in ionic liquids with various halide anions was observed, respectively: F > Br > Cl and Br > Cl > F. Moreover, as the temperature increased from 308.15 to 363.15 K and the mole ratio of caprolactam increased from 2:1 to 6:1, the solubility of NO increased. Alternatively, the solubility of NO₂ decreased as the temperature increased from 298.15 to 363.15 K, and the mole ratio of caprolactam increased from 2:1 to 6:1. The absorption and desorption of NO and NO₂ was practically reversible in the ionic liquids, which was characterized by nuclear magnetic resonance. The method, which is at least partially reversible, offers interesting possibilities for the removal of NO and NO₂.

IMPLICATIONS Basic ionic liquids with amino groups were synthesized and used to capture CO₂, SO₂, and H₂S, and to promote hydrogenation of CO₂. In this paper, the authors used caprolactam tetrabutyl ammonium halide ionic liquid (IL) as absorbing medium in which NO_x could be absorbed. NO_x desorbed from the absorbent could be efficiently reduced by right catalysts at high temperature. The absorbed NO and NO₂ gas could be desorbed at higher temperature, allowing the ionic liquids to be reused several times without loss of capability. It was believed that caprolactam tetrabutyl ammonium bromide (CPL-TBAB) ILs may be useful for NO_x removal reagent for pollution control.     

用废弃印刷线路板制备粒状活性炭

以废旧印刷线路板非金属分离物为前躯体,经热解、成型、炭化和水蒸汽活化制备粒状活性炭.研究了热解温度对残碳收率的影响,煤焦油配比对成型碳强度的影响,活化反应条件对活性炭烧蚀率、比表面积和碘吸附值的影响.结果表明,随着热解温度的提高残碳收率下降;随着煤焦油配比增大,成型碳的强度呈现先增大后减少的趋势,成型碳机械强度最大时的...     

序批式膜生物反应器(SMBR)处理生活污水的研究

实验模拟生活污水,考察了连续式膜生物反应器(continuous membrane bioreactor,CMBR)和序批式膜生物反器(sequencing batch membrane bioreactor,SMBR)的膜污染和污染物去除效果.结果表明CMBR和SMBR出水COD的平均浓度分别为15.42 mg/L和...     

An evaluation on the environmental consequences of residual CFCs from obsolete household refrigerators in China

Chlorofluorocarbons (CFCs) contained in household refrigerators consist mainly of CFC-11 and CFC-12, which will be eventually released into the environment. Consequentially, environmental releases of these refrigerants will lead to ozone depletion and contribute significantly to the greenhouse effect, if waste refrigerators are not disposed of properly. In the present paper, the potential release of residual CFCs and their substitutes from obsolete household refrigerators in China is examined, and their contributions to ozone depletion and greenhouse effect are compared with those of other recognized ozone-depleting substances (ODS) and greenhouse gases (GHGs). The results imply that annual potential amounts of released residual CFC-11 and CFC-12 will reach their maximums at 4600 and 2300 tons, respectively in 2011, and then decrease gradually to zero until 2020. Meanwhile, the amounts of their most widely used substitutes HCFC-141b and HFC-134a will keep increasing. Subsequently, the contribution ratio of these CFCs and their substitutes to ozone depletion will remain at 25% through 2011, and reach its peak value of 34% by 2018. The contribution to greenhouse effect will reach its peak value of 0.57% by 2010. Moreover, the contribution ratio of these CFCs to the total global release of CFCs will steadily increase, reaching its peak of 15% by 2018. Thus, this period from 2010 to 2018 is a crucial time during which residual CFCs and their substitutes from obsolete household refrigerators in China will contribute significantly to ozone depletion.     

Collaborative control of fine particles and ozone required in China for health benefit

● Increased DAAO offsets 3/4 of the decrease of DAAP in 2013–2020. ● DAAO increases are mainly due to O₃ concentration increase and population aging. ● Health benefit from PM_2.5 reduction after 2017 is larger than that before 2017. ● Reducing PM_2.5 concentration by 1% results in 0.6% reduction of DAAP. ● Reducing O₃ concentration by 1% results in 2% reduction of DAAO. PM_2.5 concentration declined significantly nationwide, while O₃ concentration increased in most regions in China in 2013–2020. Recent evidences proved that peak season O₃ is related to increased death risk from non-accidental and respiratory diseases. Based on these new evidences, we estimate excess deaths associated with long-term exposure to ambient PM_2.5 and O₃ in China following the counterfactual analytic framework from Global Burden Disease. Excess deaths from non-accidental diseases associated with long-term exposure to ambient O₃ in China reaches to 579 (95% confidential interval (CI): 93, 990) thousand in 2020, which has been significantly underestimated in previous studies. In addition, the increased excess deaths associated with long-term O₃ exposure (234 (95% CI: 177, 282) thousand) in 2013–2020 offset three quarters of the avoided excess deaths (302 (95% CI: 244, 366) thousand) mainly due to PM_2.5 exposure reduction. In key regions (the North China Plain, the Yangtze River Delta and the Fen-Wei Plain), the former is even larger than the latter, particularly in 2017–2020. Health benefit of PM_2.5 concentration reduction offsets the adverse effects of population growth and aging on excess deaths attributed to PM_2.5 exposure. Increase of excess deaths associated with O₃ exposure is mainly due to the strong increase of O₃ concentration, followed by population aging. Considering the faster population aging process in the future, collaborative control, and faster reduction of PM_2.5 and O₃ are needed to reduce the associated excess deaths.     

Prediction and cause investigation of ozone based on a double-stage attention mechanism recurrent neural network

● Used a double-stage attention mechanism model to predict ozone. ● The model can autonomously select the appropriate time series for forecasting. ● The model outperforms other machine learning models and WRF-CMAQ. ● We used the model to analyze the driving factors of VOCs that cause ozone pollution. Ozone is becoming a significant air pollutant in some regions, and VOCs are essential for ozone prediction as necessary ozone precursors. In this study, we proposed a recurrent neural network based on a double-stage attention mechanism model to predict ozone, selected an appropriate time series for prediction through the input attention and temporal attention mechanisms, and analyzed the cause of ozone generation according to the contribution of feature parameters. The experimental data show that our model had an RMSE of 7.71 μg/m³ and a mean absolute error of 5.97 μg/m³ for 1-h predictions. The DA-RNN model predicted ozone closer to observations than the other models. Based on the importance of the characteristics, we found that the ozone pollution in the Jinshan Industrial Zone mainly comes from the emissions of petrochemical enterprises, and the good generalization performance of the model is proved through testing multiple stations. Our experimental results demonstrate the validity and promising application of the DA-RNN model in predicting atmospheric pollutants and investigating their causes.     

CF2ClBr在短紫外光照射下光解离过程的研究

以低压汞为激发光源,气相色谱和红外光谱为主要分析手段,研究了气态ＣＦ２ＣｌＢｒ在１８５ｎｍ紫外光照射下的光解离过程及其人在Ｏ２存在下的光氧化机理,发现ＣＦ２ＣｌＢｒ在１８５ｎｍ紫外光照射下的主要产物ＣＦ２Ｂｒ２ＣＦ２Ｃｌ２和Ｃｌ２,Ｂｒ２,而当Ｏ２存在时,主要光解产物为ＣＦ２Ｏ,在本实验条件下,纯ＣＦ２ＣｌＢｒ极限分解率约为２６％,在ＣＦ２ＣｌＢｒ－Ｏ２体系中,ＣＦ２ＣｌＢｒ的解离为一级反应,速率