Humic acid and metal ions accelerating the dechlorination of 4-chlorobiphenyl by nanoscale zero-valent iron

Transformation of polychlorinated biphenyls (PCBs) by zero-valent iron represents one of the latest innovative technologies for environmental remediation. The dechlorination of 4-chlorobiphenyl (4-ClBP) by nanoscale zero-valent iron (NZVI) in the presence of humic acid or metal ions was investigated. The results showed that the dechlorination of 4-ClBP by NZVI increased with decreased solution pH. When the initial pH value was 4.0, 5.5, 6.8, and 9.0, the dechlorination efficiencies of 4-ClBP after 48 hr were 53.8%, 47.8%, 35.7%, and 35.6%, respectively. The presence of humic acid inhibited the reduction of 4-ClBP in the first 4 hr, and then significantly accelerated the dechlorination by reaching 86.3% in 48 hr. Divalent metal ions, Co2+, Cu2+, and Ni2+, were reduced and formed bimetals with NZVI, thereby enhanced the dechlorination of 4-ClBP. The dechlorination percentages of 4-ClBP in the presence of 0.1 mmol/L Co2+, Cu2+ and Ni2+ were 66.1%, 66.0% and 64.6% in 48 hr, and then increased to 67.9%, 71.3% and 73.5%, after 96 hr respectively. The dechlorination kinetics of 4-ClBP by the NZVI in all cases followed pseudo-first order model. The results provide a basis for better understanding of the dechlorination mechanisms of PCBs in real environment.     

华南典型城市区域PM2.5中七种塑化剂污染特征和暴露研究

对华南地区某典型城市工业区和居民区两种不同区域的大气PM2.5中7种塑化剂污染分布特征和暴露水平进行了研究.结果表明,在监测期间两类区域大气PM2.5中主要以DnBP、DEHP为主,五日平均浓度分别为38.3～42.9 ng/m3、119～144 ng/m3,两类区域的PM2.5中7种塑化剂总体污染浓度水平相当,居民区总体污染情况略轻于工业区.7种塑化剂的成人室外PM2.5呼吸暴露水平范围为0.051 9 ～ 36.8 ng/(kg·d),其中工业区的DEHA暴露水平比居民区的高出一倍,其它的几种塑化剂在两类区域中的呼吸暴露水平相当.     

A hybrid fuel cell for water purification and simultaneously electricity generation

● A novel hybrid fuel cell (F-HFC) was fabricated. ● Pollutant degradation and synchronous electricity generation occurred in F-HFC. ● BiOCl-NH₄PTA photocatalyst greatly improved electron transfer and charge separation. ● Pollutant could act as substrate directly in ambient conditions without pretreatment. ● The mechanism of the F-HFC was proposed and elucidated. The development of highly efficient energy conversion technologies to extract energy from wastewater is urgently needed, especially in facing of increasing energy and environment burdens. Here, we successfully fabricated a novel hybrid fuel cell with BiOCl-NH₄PTA as photocatalyst. The polyoxometalate (NH₄PTA) act as the acceptor of photoelectrons and could retard the recombination of photogenerated electrons and holes, which lead to superior photocatalytic degradation. By utilizing BiOCl-NH₄PTA as photocatalysts and Pt/C air-cathode, we successfully constructed an electron and mass transfer enhanced photocatalytic hybrid fuel cell with flow-through field (F-HFC). In this novel fuel cell, dyes and biomass could be directly degraded and stable power output could be obtained. About 87 % of dyes could be degraded in 30 min irradiation and nearly 100 % removed within 90 min. The current density could reach up to ~267.1 μA/cm²; with maximum power density (P_max) of ~16.2 μW/cm² with Rhodamine B as organic pollutant in F-HFC. The power densities were 9.0 μW/cm², 12.2 μW/cm², and 13.9 μW/cm² when using methyl orange (MO), glucose and starch as substrates, respectively. This hybrid fuel cell with BiOCl-NH₄PTA composite fulfills the purpose of decontamination of aqueous organic pollutants and synchronous electricity generation. Moreover, the novel design cell with separated photodegradation unit and the electricity generation unit could bring potential practical application in water purification and energy recovery from wastewater.     

Variations and its driven factors of anthropogenic nitrogen loads in the Yangtze River Economic Belt during 2000–2019

Environmental Science and Pollution Research - Since the millennium, China has economically taken off with rapid urbanization, and anthropogenic nitrogen emission intensity has undergone remarkable...     

Automatic pH control system enhances the dechlorination of 2,4,4′-trichlorobiphenyl and extracted PCBs from contaminated soil by nanoscale Fe0 and Pd/Fe0

Purpose  

Dechlorination of polychlorinated biphenyls (PCBs) by nanoscale zerovalent iron (NZVI) is often strongly hindered by increased pH because large amounts of H⁺ ions were consumed during the surface reaction. The main objective of this work was to evaluate the effect of pH control in acid on the dechlorination processes of PCBs and to compare the dechlorination efficiency between 2,4,4′-trichlorobiphenyl (2,4,4′-CB) and the extracted PCBs from the field PCBs-contaminated soil in this system.     

稻壳活性炭制备及其对磷的吸附

利用农业废弃物稻壳经炭化、活化、酸洗、水洗和干燥等工艺制备出一种富含微孔和中孔结构的稻壳活性炭,其BET比表面积达886.3 m2/g。通过正交实验优化了稻壳活性炭对磷吸附条件,并在该条件下进行了吸附等温和吸附动力学实验研究。结果表明,稻壳活性炭对磷的吸附等温曲线能较好符合Langmuir模型(R2=0.9284)和Freundlich模型(R2=0.9208),由Langmuir线性拟合方程可得稻壳活性炭对磷饱和吸附量达6.93 mg/g;稻壳活性炭对磷的吸附过程可用准二级动力学方程描述(R2=0.9968),吸附速度较快,颗粒内扩散为该过程控速阶段。稻壳活性炭作为一种易得、廉价、高效的填料,在农村分散型污水生态处理技术中,具有良好的应用前景。     

电絮凝处理牛仔布印染废水

用铁分别作为电絮凝反应系统的阴极和阳极,研究电絮凝法对牛仔布印染废水的处理效果。考察了电极电压、反应时间和pH等因素对电絮凝法去除实验所用废水中COD和色度效果的影响。结果表明,电极电压和反应时间是主要的影响因素,pH次之。电极电压24 V,反应时间35 min,pH为7.4时,脱色率可达99%,COD去除率在70%左右,处理效果最佳。因此,电絮凝法可以作为印染废水的预处理工艺,有效降低废水COD和色度。     

组配改良剂对稻田土壤中镉铅形态及糙米中镉铅累积的影响

通过田间实验,研究了镉(Cd)和铅(Pb)复合污染稻田土壤中施加组配改良剂(LS,石灰石+海泡石)对黄华占和丰优9号2种水稻种植土壤中p H、Cd和Pb形态转化以及水稻糙米中Cd和Pb累积量的影响.结果表明,施加LS,通过提高2种水稻土壤的p H值,可以有效地改变土壤中Cd和Pb的存在形态,使土壤Cd和Pb由酸可提取态不同程度地转化为铁锰氧化态和有机结合态.LS施加量为2.0~8.0 g·kg-1时,使黄华占水稻土壤中Cd和Pb的酸可提取态含量分别降低19.6%~23.8%、7.7%~14.3%,丰优9号水稻土壤中Cd和Pb的酸可提取态含量分别降低7.6%~31.1%、11.7%~24.8%,且降低效果为CdPb.LS还能显著降低2种水稻糙米中Cd和Pb含量,LS施加量为2.0~8.0 g·kg-1时,黄华占和丰优9号2种水稻糙米中Cd含量分别降低了56.5%~67.2%、29.0%~38.7%,Pb含量分别降低了9.8%~34.2%、6.8%~45.4%,同种水稻Cd和Pb含量降低效果为CdPb.研究表明,土壤中Cd和Pb酸可提取态含量能很好地反映土壤中Cd和Pb的生物有效性和迁移性.     

基于FAHP-FCE模型的煤矿瓦斯爆炸危险性评价研究

为提高煤矿瓦斯爆炸危险性评价的准确性,针对现阶段瓦斯爆炸的模糊性、复杂性及多元性特征,将改进的模糊层次分析法运用于瓦斯爆炸危险性评价,引入9标度法、模糊一致判断矩阵确定各评价指标的综合权重;在改进的三类危险源理论的基础上,建立煤矿瓦斯爆炸危险性评价指标体系,并借助现场工作人员及专家对二级评价指标的评分,进行多层次模糊综合评价,构建了基于FAHP-FCE模型的瓦斯爆炸危险性评价方法,确立了基于该模型的瓦斯爆炸危险性等级量化标准。工程实例分析表明,该方法可有效地实现瓦斯爆炸危险性辨析和分级。     

基于GIS的高寒草原区土壤冻融侵蚀强度及空间分布特征

以位于青海南部高原高寒草原区的兴海盆地作为研究区,选取气温年较差、年降水量、植被盖度、坡度、坡向、海拔等因素作为冻融侵蚀强度评价指标,运用层次分析法计算各评价指标的权重,采取标准化值赋权重加权求和的方法计算冻融侵蚀强度指数,以等间隔方法对冻融侵蚀强度指数进行分级,获得了研究区冻融侵蚀强度等级类型,并利用Arc GIS的空间分析与统计分析功能对研究区冻融侵蚀的空间分布特征进行研究。结果表明:研究区冻融侵蚀发生的总面积是4784.34 km~2,其中,轻度侵蚀和中度侵蚀居多,分别占冻融侵蚀总面积的32.07%和40.06%;微度侵蚀、强烈侵蚀和极强烈侵蚀占少部分,分别占冻融侵蚀总面积的7.39%、16.08%和4.39%;冻融侵蚀主要分布在研究区的西部,不同的海拔与坡度等级下,4000—4800 m与5—35°冻融侵蚀最集中,其主要发生在高寒草甸、草原,低覆盖草地上冻融侵蚀尤为严重。研究区冻融侵蚀在各个坡向的波动较小,坡向对其影响亦较小。降水量330—455 mm和年较差24.85—26.04℃冻融侵蚀分布最集中。