Study on dust–gas coupling pollution law and selection of optimal purification distance of air duct during tunneling process

During the excavation of high gas mine, gas and dust often exist at the same time. In order to ensure that the gas concentration remains within a safe range and minimize the risk of workers’ pneumoconiosis, we simulated the interaction mechanism of airflow, gas, and dust, explored the pollution law of gas and dust, and obtained the optimal purification distance (L_p) by the CFD method. The reliability of the numerical simulation was verified by field measurements. Firstly, the properties of the gas and dust affected the structure of the airflow field. At the same time, the change in the airflow field affected the concentration distributions of the gas and dust. During the diffusion process, some high-risk regions in which the gas or dust concentrations exceeded 0.80% or 200 mg/m³, respectively, were discovered. Moreover, we have found that the airflow velocity in the top region of the tunnel and at the intersection corner between the cutting face and tunnel wall was the main factor affecting the purification effects. When L_p = 5–8 m, the gas concentration remained below 0.50%. When L_p = 6 m, the dust concentration reached a minimum of 287.5 mg/m³. Therefore, the optimal purification distance was determined to be 6 m; in which case, the gas and dust concentrations decreased by 32.84% and 47.02%, respectively.

     

多种固废协同处理电解锰渣固锰除氨的最优配比及效果分析

为降低电解锰渣中Mn²⁺和NH₄⁺-N的污染,实现多种固体废物减量化处理,采用锰渣、赤泥、粉煤灰3种大宗固废协同处理,并加入少量生石灰,制备无害化固结体,利用水浸法评估无害化效果,并通过BCR提取、XRD和SEM对最佳处理固结体固锰除氨机理进行分析。结果表明,通过正交实验和单因素优化实验,当固结体中锰渣、赤泥、粉煤灰、生石灰的质量分数分别为30%、44%、24%、2%时,浸出液中可溶性Mn²⁺质量浓度降至5.23 μg·L⁻¹,固化率达99.99%;NH₄⁺-N质量浓度降至0.70 mg·L⁻¹,去除率达到99.93%,pH=8.86,能够满足《污水综合排放标准》 (GB 8978-1996) 最高允许排放浓度和一级标准限值;同时浸出液中Mn²⁺、NH₄⁺-N的质量浓度均满足《锰渣污染控制技术规范》 (HJ 1241-2022) 中锰渣利用污染控制要求,可以作为替代原料用于生产除水泥之外的其它建筑材料产品。赤泥、生石灰为处理体系提供碱度,粉煤灰增加胶凝作用,使得无害化处理效果良好。本研究结果可为大宗固废协同无害化、减量化处理提供参考。     

Mn-Ce复合金属氧化物催化氧化甲苯性能

通过等体积浸渍法制备了一系列Mn-Ce/γ-Al₂O₃催化剂, 并考察不同CeO₂负载量对MnO₂/γ-Al₂O₃催化剂催化氧化甲苯性能的影响。利用XRD、N₂吸脱附曲线、TEM、H₂-TPR、XPS和O₂-TPD等方法表征催化剂比表面积、表面形貌及氧化还原性能。结果表明,CeO₂的负载一定程度上降低了MnO₂/γ-Al₂O₃催化剂的比表面积, 且催化剂仍保持介孔结构。CeO₂的存在增加了催化剂表面的化学吸附氧含量,其良好的储放氧能力促进了Mn³⁺向Mn⁴⁺的转化;Mn和Ce之间存在较强的协同作用, 与MnO_x相邻的CeO₂更容易打开Ce—O键释放活性氧, 加速氧化还原进程,Mn_0.6Ce_0.4/γ-Al₂O₃催化剂T₁₀和T₉₀与MnO₂/γ-Al₂O₃催化剂相比分别降低20和40 ℃。本研究可为VOCs催化氧化技术中低成本金属催化剂的开发提供参考。     

电解锰渣煅烧时Mn、N元素形态分布与微观结构变化

电解锰行业的发展会产生大量的电解锰渣,易导致严重的环境污染,高温煅烧已成为当前无害化处理电解锰渣的高效方法之一。为探究高温煅烧时电解锰渣中特征污染物的化学形态及物相组成,选取广西某电解锰企业经不同工艺产生的电解碳酸锰渣(EMCR)与电解二氧化锰渣(EMDR),通过其理化特性及Mn、N元素形态分布与微观结构变化分析,研究了不同温度煅烧处理对电解锰渣污染物的影响。结果表明,电解二氧化锰渣中Mn元素的可氧化态与可还原态分布均大于电解碳酸锰渣。当煅烧温度在1 000 ℃以上时,2种电解锰渣中Mn元素基本上以残渣态的形式存在,通过风险评估代码(RAC)结果可知样品处于低风险甚至无风险状态,可进行后续的处理处置。2种电解锰渣中N元素的形态随着温度的升高主要以NO形式为主。通过对煅烧过程中微观结构的变化分析可知,在800 ℃时电解碳酸锰渣中石英相(SiO₂)的衍射峰强度最佳,有利于活性发展,此时的能谱分析结果显示Fe元素占比达到了52.40%,有利于Fe的回收利用,而电解二氧化锰渣的最佳煅烧处理温度显示为1 000 ℃。该研究结果可为2种电解锰渣经煅烧处置后的资源化再利用工作提供有效的数据支撑。     

Effects of green spaces on alleviating mortality attributable to PM2.5 in China

Environmental Science and Pollution Research - Increasing research suggested that green spaces are associated with many health benefits, but evidence for the quantitative relationship between green...     

A model for evaluation of the phytoavailability of trace elements to vegetables under the field conditions

Currently, several single extraction methods are used for the evaluation of the phytoavailability of metals using pot experiments. A systematic comparison, however, is lacking. It is especially true for the field studies. This study was to investigate the phytoavailability of trace elements to vegetables grown on metal-contaminated soils under the field conditions. All soils collected were typical calcareous soils in northern China. Four frequently used methods using CaCl2, diethylenetriaminepentaacetic acid (DTPA), CH3COOH, and water as extractants were compared for phyto-availability. The concentrations of metals extracted by these four extraction methods ranged from 3.42 to 815, 1.51- 6965, 0.732-24473, 0.688-7863, 0.246-685, 1.99-5337 0.203-4649 ng/g for Cr, Ni, Zn, Cu, Cd, Pb and REEs, respectively. Simple correlation analysis indicated that a significant correlation (Cr: r = 0.5411**; Zn: r = 0.6352**; Cd: r = 0.6979**; Pb: r = 0.5537** and REEs: r = 0.5185** -0.6684**) was observed between the CaCl2-extractable metals in soil solution and that in Chinese cabbage. In addition, soil pH, organic matter (OM), and cation exchange capacity (CEC) also affect the phytoavailability. An empirical model was developed to express the combined effect of soil properties on the phytoavailability. The stepwise multiple regression analysis demonstrated that the phytoavailability of trace elements strongly correlated with the extractable fraction by CaCl2, total metal concentration in soils, and soil pH, OM, CEC. This model can describe approximately 75-95% of the variability of metal uptake and the r2 values ranged from 0.741** to 0.954**, which were much better than the single correlation analysis. For celery and cole, a strong correlation was obtained for Cr, Ni, Zn, Cu, Cd, La, Ce, Pr and Nd. For spinach and Chinese cabbage, however, a positive correlation was only observed for 1 and 3 metals, respectively. Generally, the developed empirical model can integrate the combined effects of soil properties, extractable metal fractions in soil solutions and plant species on the phytoavailability of metals to vegetables in the field conditions.     

纳米二氧化铈上活性氧物种的氧空穴团簇捕集位点

二氧化铈（CeO2）是一种性能优异的催化材料,已广泛应用于大气污染物的控制,这与其优异的储放氧性能即氧空穴的形成、消除相关;研究氧空穴在上氧物种的形成及活性对设计高效的铈基催化剂具有重要意义。X射线光电子能谱(XPS)、正电子湮没寿命谱(PAS)、氢气-程序升温还原(H2-TPR)研究结果表明,不同形貌的CeO2纳米材料上氧空穴团簇大小、相对强度、单位面积上Ce3+浓度的乘积与高活性氧物种的量之间呈线性相关,这一定量关系揭示氧空穴团簇是CeO2纳米材料上活性氧物种的捕集位点,对认识CeO2催化作用机制具有理论指导意义。     

稻壳灰在陶粒烧制中的应用

针对目前每年产生的大量稻壳灰废弃物,本研究提出了利用稻壳灰作为发泡剂来制备多孔陶粒的利用途径。实验表明,对于粘土、建筑垃圾、粉煤灰等陶粒原料,稻壳灰都有很好的发泡效果。利用SEM、XRD等检测分析手段对稻壳灰的发泡机理进行了探讨,并证明了稻壳灰中残余碳化合物和活性硅组分是发泡能力的关键因素。本研究为稻壳灰找到了一种高价值的资源利用方式,同时也为陶粒制备提供了一种高效的发泡剂。     

Fe3+和Cu2+对饮用水氯消毒副产物三卤甲烷形成的影响

为了研究水中存在Br-的情况下,Fe3+和Cu2+对三卤甲烷(THMs)的生成及CHCl3、CHBrCl2、CHBr2Cl、CHBr3 4种消毒副产物相对分布的影响,以腐殖酸模拟氯消毒过程中的前体物进行实验。结果表明,在pH为6、7和9 3种条件下,Fe3+抑制了THMs的生成,pH=6时只有CHCl3生成量随着Fe3+浓度的增加逐渐减少,其余3种消毒副产物均在增加,pH=7时4种消毒副产物浓度均减小并在Fe3+浓度为2 mg/L时生成量最低,pH=9时的生成趋势与pH=6时类似。Cu2+能促进THMs的生成,在pH为6、7和9时,当加入0.5 mg/L Cu2+时,THMs总量分别增加了16.7%、22.6%和2.5%,随着pH增加,THMs总量增加。在3种pH环境中,Cu2+对THMs生成的影响大于Fe3+,在偏酸性环境中,Fe3+影响THMs生成,产生的致癌风险高,当金属离子浓度为2.5 mg/L时,致癌风险相差最高为15%,在中性和偏碱性环境中,Cu2+影响THMs生成,产生的致癌风险高。