排序方式: 共有90条查询结果,搜索用时 500 毫秒
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磁性海藻酸铁介孔碳微球的合成及对水体中砷的去除 总被引:3,自引:0,他引:3
本研究以海藻酸钠作为基体前驱材料,利用离子交联法合成了海藻酸铁微球,然后进一步运用真空冷冻和高温裂解法制备了表面附着纳米铁氧化物的磁性海藻酸铁介孔碳微球(MAMC).同时,采用热场发射扫描电镜显微镜、X射线光电子能谱、热重分析仪、磁学测量系统、BET比表面孔径分析仪等对MAMC进行表征,并研究了MAMC对As(Ⅲ)和As(Ⅴ)的吸附性能,重点考察投加量、pH、时间、初始污染物浓度对吸附性能的影响,并对吸附过程进行了动力学拟合和等温吸附方程拟合,最后对材料进行了再生实验.结果表明,MAMC对As(Ⅲ)和As(Ⅴ)均表现出良好的吸附性能,对As(Ⅲ)的吸附能力优于As(Ⅴ);当pH值为5~7时,MAMC对两种价态As的吸附效率最优;材料的吸附量随着时间的增加而增加.动力学拟合结果表明,MAMC的吸附过程较好地满足准二级动力学方程,等温吸附曲线较好地满足于Langmuir方程.此外,使用0.1 mol·L~(-1)的Na OH对材料的再生和脱附效果较好,能够实现材料的二次利用.本研究结果对处理含砷废水提供了重要的理论依据. 相似文献
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Methacrolein(MACR) is an abundant multifunctional carbonyl compound with high reactivity in the atmosphere. In this study, we investigated the hydroxyl radical initiated oxidation of MACR at various NO/MACR ratios(0 to 4.04) and relative humidities( 3% to80%) using a flow tube. Meanwhile, a box model based on the Master Chemical Mechanism was performed to test our current understanding of the mechanism. In contrast to the reasonable predictions for hydroxyacetone production, the modeled yields of formaldehyde(HCHO) were twice higher than the experimental results. The discrepancy was ascribed to the existence of unconsidered non-HCHO forming channels in the chemistry of CH_3-UC(=CH_2)OO, which account for approx. 50%. In addition, the production of hydroxyacetone and HCHO were affected by water vapor as well as the initial NO/MACR ratio. The yields of HCHO were higher under humid conditions than that under dry condition. The yields of hydroxyacetone were higher under humid conditions at low-NO_x level, while lower at high-NOxlevel. The reasonable explanation for the lower hydroxyacetone yield under humid conditions at high-NO_x level is that water vapor promotes the production of Umethacrolein nitrate in the reaction of HOCH_2 C(CH_3)(OO)CHO with NO due to the peroxy radical-water complex formation, which was evidenced by calculational results. And the minimum equilibrium constant of this water complex formation was estimated to be 1.89 × 10~(-18) cm~3/molecule. These results provide new insights into the MACR oxidation mechanism and the effects of water vapor. 相似文献
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为了揭示不同流域滨岸带的生态功能,于2015年夏季采集太湖西部苕溪流域和天目湖流域不同滨岸带(林地、耕地、草地、荒地)土壤,利用连续顺序提取法获得无机磷形态,分析土壤磷形态的空间分布特征、影响因素以及土壤磷形态与地下水中TDP(总溶解性磷)的联系.结果表明:苕溪滨岸带的磷形态含量总体上高于天目湖滨岸带,但组成方面有所差异.滨岸带土壤的NH4Cl-P(弱吸附态磷)、BD-P(还原态磷)、NaOH-P(金属氧化物结合态磷)含量随土壤深度的增加而降低,HCl-P(钙结合态磷)含量随土壤深度的增加而增加,耕地表现得最为明显.从高地到滨水带,草地和荒地的磷形态含量有略微增加的趋势,而林地和耕地的磷形态含量均降低,耕地同样表现得最为明显.苕溪滨岸带磷形态含量的水平变幅大于天目湖滨岸带.相关性分析表明,土壤NaOH-P对地下水中TDP的贡献较大,有机质、黏土矿物和碳酸盐对磷形态有明显的影响;苕溪滨岸带土壤性质对其磷形态的影响较弱,而天目湖滨岸带比较明显.因此,苕溪和天目湖流域不同滨岸带土壤磷形态的空间分布存在差异,影响因素也不同;土壤磷形态与地下水中TDP有明显关系,尤其是NaOH-P. 相似文献
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Is emission intensity of carbon dioxide (CO2) spatially correlated? What determines the CO2 intensity at a provincial level? More importantly, what climate and economic policy decisions should the China’s central and local governments make to reduce the CO2 intensity and prevent the environmental pollution given that China has been the largest emitter of CO2? We aim to address these questions in this study by applying a dynamic spatial system generalized method of moment technique. Our analysis suggests that provinces are influenced by their neighbours. In addition, CO2 intensities are relatively higher in the western and middle areas, and that the spatial agglomeration effect of the provincial CO2 intensity is obvious. Our analysis also shows that CO2 intensity is nonlinearly related to gross domestic product, positively associated with secondary-sector share and foreign direct investment, and negatively associated with population size. Important policy implications are drawn on reducing carbon intensity. 相似文献
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长沙地区是长江中下游重要的经济发展核心区,受本地排放与外来源输送等多因素的共同作用,其大气污染状况一直都是区域乃至国家高度重视的生态环境问题.前期研究揭示了长沙地区大气污染的扩散规律,为进一步研究该地区大气细颗粒物(PM2.5)外来源特征,采用拉格朗日混合型单粒子轨迹模式(HYSPLIT)探究2013—2020年长沙地区PM2.5外来源区分布特征,继而采用轨迹聚类、潜在源贡献因子分析(PSCF)、浓度权重轨迹(CWT)方法等从年、季节等不同尺度分析区域PM2.5时空分布规律及其外来污染物输送源特征.结果表明,在国家与地区大气污染联防联控等政策的驱动下,2013—2020年长沙地区年均PM2.5浓度由81.80 μg·m-3下降至42.96 μg·m-3并呈显著季节差异,大气污染防治措施成效显著.季节尺度上,PM2.5浓度主要呈现冬高夏低的态势,冬季最高(81.48 μg·m-3),其次为秋季(50.90 μg·m-3)与春季(47.39 μg·m-3),最小值出现在夏季(25.74 μg·m-3);另一方面,2013—2020年长沙地区外来源潜在源区主要分布于湘东北、赣西北、豫南和鄂中地区.具体而言,春、秋、冬三季大气污染物主要来源于蒙古国西南部的长距离西北气流,分别占当年轨迹比重的4.73%、12.93%、12.66%,而夏季大气污染物主要来源于南海南部的中长距离南方气流,占当年轨迹比重的19.06%. 相似文献
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流域内社会经济发展水平与水资源环境条件存在空间差异,导致水环境承载力具有空间差异特征.因此,有必要在流域水环境承载力分区基础上,实施差异化监管.以湟水河流域小峡桥监测断面上游为例,基于国家控制单元划分16个子单元,从水环境承载力大小、水环境承载状态、水系统脆弱程度及水环境承载力开发利用潜力4个角度,构建水环境承载力聚类分区指标体系,并对其进行量化.在此基础上,利用k-均值聚类法对控制子单元进行合并分区.通过轮廓系数验证,将研究区划分为4类最合理,即重点保护水环境敏感区、限制开发水资源约束区、控制开发水环境超载区和优化开发高开发潜力区.针对不同分区特点,提出具有针对性的水环境承载力双向调控措施,为流域水系统精细化管理及可持续发展提供科学依据. 相似文献