A novel application of H2O2-Fe(II) process for arsenate removal from synthetic acid mine drainage (AMD) water

Batch experiments were carried out to investigate the influences of H₂O₂/Fe(II) molar ratio, pH, sequence of pH adjustment, initial As(V) concentration, and interfering ions on As(V) removal in H₂O₂-Fe(II) process from synthetic acid mine drainage (AMD). The optimum H₂O₂/Fe(II) molar ratio was one for arsenate removal over the pH range of 4-7. Arsenate removal at pH 3 was poor even at high Fe(II) dosage due to the high solubility of Fe(III) formed in situ. With the increase of Fe(II) dosage, arsenate removal increased progressively before a plateau was reached at pH 5 as arsenate concentration varied from 0.05 to 2.0 mg L⁻¹. However, arsenate removal was negligible at Fe/As molar ratio <3 and then experienced a striking increase before a plateau was reached at pH 7 and arsenate concentration ≥1.0 mg L⁻¹. The co-occurring ions exerted no significant effect on arsenate removal at pH 5. The experimental results with synthetic AMD revealed that this method is highly selective for arsenate removal and the co-occurring ions either improved arsenate removal or slightly depressed arsenate removal at pH 5-7. The extended X-ray absorption fine structure (EXAFS) derived As-Fe length, 3.27-3.30 Å, indicated that arsenate was removed by forming bidentate-binuclear complexes with FeO(OH) octahydra. The economic analysis revealed that the cost of the H₂O₂-Fe(II) process was only 17-32% of that of conventional Fe(III) coagulation process to achieve arsenate concentration below 10 μg L⁻¹ in treated solution. The results suggested that the H₂O₂-Fe(II) process is an efficient, economical, selective and practical method for arsenate removal from AMD.     

Exposure to PCBs, through inhalation, dermal contact and dust ingestion at Taizhou, China--a major site for recycling transformers

Air samples containing gaseous and particulate phases were collected from e-waste workplaces and residential areas of an intensive e-waste recycling area and compared with a reference site. The highest total concentration of PCBs was detected at transformer recycling workshops (17.6 ng m(-3)), followed by the residential area (3.37 ng m(-3)) at Taizhou, and the lowest was obtained at the residential area of the reference site, Lin'an (0.46 ng m(-3)). The same trend was also observed with regards to PCB levels in dust samples. The highest average PCBs level of 2824 ng g(-1) (dry wt) was found in the transformer recycling workshops, and was significantly higher than that of residential areas of Taizhou (572 ng g(-1) dry wt) and Lin'an (42.4 ng g(-1) dry wt). WHO-PCB-TEQ level in the workshops of Taizhou was 2216 pg TEQ(1998)g(-1) dry wt or 2159 pg TEQ(2005)g(-1) dry wt, due to the high abundance of PCB 126 (21.5 ng g(-1) dry wt), which contributed 97% or 99% of WHO-PCB-TEQs. The estimated intake of PCBs via dust ingestion and dermal absorption by transformer recycling workers were 77.5×10(-5) and 36.0×10(-5) pg WHO-PCB-TEQ(1998)kg(-1)d(-1), and 67.3×10(-5) and 31.3×10(-5) pg WHO-PCB-TEQ(2005)kg(-1)d(-1), respectively.     

用碳纳米管-纳米TiO2/Nafion修饰电极测定对苯二酚

利用Nation(商品名,杜邦公司生产的一种聚四氟乙烯阳离子交换膜)的成膜作用,将纳米TiO2和碳纳米管同时负载到玻碳电极表面,制得碳纳米管-纳米TiO2/Nafion修饰电极,研究了对苯二酚在该修饰电极上的循环伏安电化学行为.实验结果表明:与玻碳电极相比,该修饰电极在对苯二酚的0.1 mol/L H2SO4溶液体系中...     

多目标决策方法在防台风中的应用

提出了一种基于不确定信息和蒙特卡罗模拟的多目标决策方法,在投入一定的情况下,选取最合适的台风防灾减灾措施.该方法允许决策者对不同属性指标给出相应的效用函数和属性权重区间值,通过随机选取权重值和效用函数区间内的值相乘得出结果,并使用蒙特卡罗模拟技术对结果进行了敏感性分析.最后,以浙江省台风灾害防灾减灾措施的比较为例,详细讨论了该方法的应用.     

Polybrominated diphenyl ethers in sediments of the Daliao River Estuary, China: levels, distribution and their influencing factors

The concentrations, compositional profiles, possible sources of polybrominated diphenyl ethers (PBDEs) in sediments of the Daliao River Estuary as well as the factors influencing the distribution of PBDEs were investigated. The total concentrations of PBDEs ranged from 0.13 to 1.98 ng g⁻¹ d.w. BDE209 was the dominating congener in all sediment samples, indicating the pollution of PBDEs in the Daliao River Estuary mainly came from the use of deca-BDE commercial mixtures. The intrusion of sea waters promoted the deposition of the colloid-associated PBDEs in the estuary. There were significantly negative correlations between PBDE concentration in sediment with pH value and salinity in the bottom water. The higher river flow in the flood season (summer) obviously accelerated the transport of PBDEs, and thereby increased the risk of PBDE contamination to the deep ocean. Moreover, a positive correlation between TOC and PBDE distributions was observed, suggesting that TOC regulated the distributions of PBDEs in sediments of Daliao River Estuary.     

芬顿氧化法处理水中酸性品红的研究

研究了酸性品红在Fenton体系中的降解过程,反应30 min后,在[Fe2+]0=0.06 mmol/L、[H2O2]0=0.3 mmol/L、pH=3、T=30℃的条件下,初始浓度为20 mg/L的酸性品红的去除率达到97%以上。升高反应温度,有利于Fenton体系中酸性品红的降解,但影响并不显著。根据不同温度下的速率常数,并结合Arrhenius方程求出了Fenton试剂降解酸性品红的反应活化能,仅为11.63 kJ/mol。C1?的存在对酸性品红在Fenton体系中的降解表现出明显的阻碍作用,并且随着C1?浓度的增加,抑制作用越来越大;SO24-和NO3-的存在也降低了Fenton试剂的氧化性能。     

重金属离子对活性污泥处理污水的影响

研究了Hg2+、Cd2+、Pb2+3种金属离子对活性污泥系统处理污水效能的影响。通过对出水理化指标和生物指标的测定反映Hg2+、Cd2+、Pb2+对活性污泥系统运转效能的影响。结果表明:实验第4 d,Hg2+(0.3、0.4、0.5和0.6 mg/L),Cd2+(15、20、25和30 mg/L)和Pb2+(300、400、600和800 mg/L)各实验组出水的COD、SVI等均有显著影响。在实验中得出,对COD影响最为明显的为浓度600 mg/L和800 mg/L Pb2+实验组,在第4 d时,出水的COD去除率已经为零。锐利楯纤虫对Hg2+的浓度变化耐受力较强;点钟虫对Cd2+的浓度变化耐受力较强;杯钟虫对Cd2+的浓度变化耐受力较强。锐利楯纤虫对Pb2+和Cd2+的浓度变化较为敏感;点钟虫对Hg2+的浓度变化较为敏感;小口钟虫对Pb2+的浓度变化较为敏感。     

金融危机对我国银行信贷风险的影响

金融危机爆发以来,我国企业尤其是中小企业受到了严重影响,国家为了保证中小企业的健康发展,中央政府、各地政府及各级商业银行相继出台了多项措施,来帮助小企业融资。其中部分措施在执行过程中无形中增加了商业银行的中小企业信贷风险。结合当前的金融危机背景,通过分析国家出台的政策给商业银行带来的信贷风险,分别从不同角度就如何加强当前商业银行的信贷风险控制进行了研究。     

煤质活性炭丁烷吸附脱附性能研究

本文对不同产地、不同煤质、不同工艺生产的煤质气相吸附用活性炭,进行了丁烷吸附脱附性能研究.结果表明,丁烷工作容量(脱附容量)是评价活性炭气相吸附脱附应用的重要参数;丁烷活性与四氯化碳吸附率具有线性对应关系;文章指出我国应建立丁烷工作容量试验方法国家标准.