O-NiCoP/Ni2P电催化还原2,4-二氯苯酚性能研究

针对电催化还原工艺处理氯酚类有机废水受到限制等问题,制备了过渡金属O-NiCoP/Ni₂P催化电极,并用于目标污染物2,4-二氯苯酚废水的电催化还原降解.同时,主要考察了2,4-二氯苯酚浓度、电流密度、电解质浓度、pH和温度等因素对O-NiCoP/Ni₂P催化电极降解效能的影响.结果表明,在2,4-二氯苯酚初始浓度为10 mg·L^-1,温度为25℃,溶液pH=7,Na₂SO₄电解质浓度为50 mmol·L^-1,电流密度为10 mA·cm^-2的条件下,O-NiCoP/Ni₂P电极催化降解180 min,对2,4-二氯苯酚去除率可达到72.2%.同时,催化电极循环使用10次,2,4-二氯苯酚的去除效率保持在72.1%~72.7%,表明电极具有良好的稳定性和实际应用的潜在价值.     

One-step preparation of polyimide-inlaid amine-rich porous organic block copolymer for efficient removal of chlorophenols from aqueous solution

A novel polyimide-inlaid amine-rich porous organic block copolymer (PI-b-ARPOP) was prepared via one-step polymerization by using different molar ratios of melamine (MA)/terephthalaldehyde (TA)/pyromellitic dianhydride (PMDA), at molar ratios of 4/3/1, 4/2/2 and 4/1/3. The copolymer contained both aminal groups belonging to ARPOP and imide groups belonging to PI, and the bonding styles of the monomers and growth orientations of the polymeric chains were diversiform, forming an excellent porous structure. Notably, MA/TA/PMDA (4/2/2) had a surface area and pore volume of 487.27?m²/g and 1.169?cm³/g, respectively. The adsorption performance of the materials towards 2,4-dichlorophenol (2,4-DCP) in ultra-pure water was systematically studied. The pH value of 7 was optimal in aqueous solution. Na⁺ and Cl^? ions did not negatively affect the adsorption process, while humic acid (HA) slightly decreased the capacity. The equilibrium time was 40 sec, and the maximum adsorption capacity reached 282.49?mg/g at 298?K. The removal process was endothermic and spontaneous, and the copolymer could maintain its porous structure and consistent performance after regeneration by treatment with alkali. Moreover, to further assess the practical applicability of the material, the adsorption performance towards 2,4-DCP in river water was also investigated. This paper demonstrated that the PI-b-ARPOP can be an efficient and practical adsorbent to remove chlorophenols from aqueous solution.     

A high activity of Ti/SnO2-Sb electrode in the electrochemical degradation of 2,4-dichlorophenol in aqueous solution

Electrochemical degradation of 2,4-dichlorophenol (2,4-DCP) in aqueous solution was investigated over Ti/SnO₂-Sb anode. The factors influencing the degradation rate, such as applied current density (2-40 mA/cm²), pH (3-11) and initial concentration (5-200 mg/L) were evaluated. The degradation of 2,4-DCP followed apparent pseudo first-order kinetics. The degradation ratio on Ti/SnO₂-Sb anode attained > 99.9% after 20 min of electrolysis at initial 5-200 mg/L concentrations at a constant current density of 30 mA/cm² with a 10 mmol/L sodium sulphate (Na2SO4) supporting electrolyte solution. The results showed that 2,4-DCP (100 mg/L) degradation and total organic carbon (TOC) removal ratio achieved 99.9% and 92.8%, respectively, at the optimal conditions after 30 min electrolysis. Under this condition, the degradation rate constant (k) and the degradation half-life (t_1/2) were 0.21 min^-1 and (2.8±0.2) min, respectively. Mainly carboxylic acids (propanoic acid, maleic acid, propanedioic acid, acetic acid and oxalic acid) were detected as intermediates. The energy efficiencies for 2,4-DCP degradation (5-200 mg/L) with Ti/SnO₂-Sb anode ranged from 0.672 to 1.602 g/kWh. The Ti/SnO₂-Sb anode with a high activity to rapid organic oxidation could be employed to degrade chlorophenols, particularly 2,4-DCP in wastewater.     

EDTA对Pd/Fe体系还原脱氯2,4-D的影响

针对Pd/Fe体系对含氯有机物催化还原脱氯过程中,零价铁易腐蚀并在颗粒表面形成钝化层,阻碍目标污染物的进一步脱氯去除,本研究利用乙二胺四乙酸(EDTA)与Fe2+和Fe3+的络合作用,消除Pd/Fe颗粒表面的钝化层,使还原脱氯过程得到持续进行.实验考察了EDTA的投加方式和投加量、p H、钯负载率、温度等因素对2,4-二氯苯氧乙酸(2,4-D)还原脱氯的影响.结果表明:1EDTA浓度为25.0 mmol·L-1、投加速率为20 m L·h-1时,苯氧乙酸(PA)生成率在20 min达到了90.7%.而未加EDTA的反应体系,反应210 min后,PA的生成率仅为74.5%;2EDTA可以络合Pd/Fe体系在催化脱氯过程中生成的Fe2+和Fe3+,防止或减缓了Pd/Fe颗粒表面钝化层的形成,提高了反应活性;3适宜的2,4-D催化脱氯条件为:浓度25.0mmol·L-1的EDTA溶液,投加速率20 m L·h-1、初始p H为4.2、钯负载率0.050%、温度30.0℃、搅拌速率200 r·min-1,反应210 min,20.0 mg·L-1的2,4-D几乎可完全转化为PA;42,4-D催化脱氯的中间产物主要是2-氯苯氧乙酸及微量的4-氯苯氧乙酸,最终产物为苯氧乙酸.     

UiO-66对废水中二氯苯氧乙酸的吸附特性

以Ui O-66型金属有机框架为吸附剂,研究了时间、p H值和温度对自制金属有机框架Ui O-66吸附2,4-D性能的影响.结果表明,Ui O-66的吸附平衡时间为24 h;初始溶液最佳p H值为4.0;Ui O-66上的平衡吸附量随温度的升高而增加,实验最佳温度应控制在30℃.Ui O-66对2,4-D的吸附符合Langmuir吸附模型;吸附动力学符合拟二级模型;颗粒内扩散过程是吸附速率控制步骤;热力学计算结果显示ΔG0、ΔH0、ΔS0,由此判断吸附是自发、吸热、熵增加的化学过程.本实验表明,Ui O-66在去除农业废水中2,4-D领域有实际应用的潜力.     

Toxic effects of 2,4‐D herbicide on fish

Abstract

Acute and subacute 2,4‐D toxicity to carp (Cyprinus carpio L.) were investigated. Acute toxicity (LC‐ 50) was investigated in semi‐static test during a 24, 48, and 96‐ hours exposition. Subacute toxicity was investigated by exposing fish to different 2,4,‐D concentrations (150, 200, and 250 mg/L) for 14 days. Biochemical and morphological changes in certain organs and tissues were investigated.

LC‐ 50 values at 24 hours exposure was 310.0 mg/L, 295.0 mg/L for 48 hours, and 270.0 mg/L for 96 hours exposure.

Subacute toxicity tests show that 2,4‐D induce changes in the enzyme activities (AP, GOT, GPT) and morphological changes in the gills, liver and kidneys, but changes are of limited biological importance.     

2,4-二硝基酚厌氧生物降解动力学研究

研究了间歇试验条件下,2,4-二硝基酚(2,4-DNP)与葡萄糖共基质时的厌氧降解动力学.结果表明:2,4-DNP与葡萄糖能同时被微生物降解;葡萄糖浓度高低对2,4-DNP的降解影响不大,而2,4-DNP的存在明显影响COD的降解.当2,4-DNP浓度<225 mg/L时,其比降解速率随浓度增大而增大,浓度为225 mg/L时比降解速率达到最大;由于底物抑制,当2,4-DNP浓度>225 mg/L时,其比降解速率呈下降趋势.选用Andrews非竞争性抑制模型描述2,4-DNP厌氧降解动力学,对实验数据进行非线性拟合,求得模型参数q_max、K_s和K_i分别为3.24 mg/(h·g)、196.23 mg/L和165.91mg/L,实验数据与该动力学方程拟合较好.     

大气甲醛稳定碳同位素分析方法研究

利用气相色谱/燃烧/同位素比值质谱(GC/C/IRMS)技术,采用2,4-二硝基苯肼(DNPH)衍生化,初步研究了单体化合物稳定碳同位素方法研究大气甲醛来源问题.根据不同同位素组成的甲醛与DNPH反应,模拟大气采样,具体讨论了甲醛与DNPH衍生化过程的同位素效应及分析方法的重现性与精确度.结果表明,每个甲醛2,4-二硝基苯腙样品分析的最大标准偏差为0.3‰;不同同位素组成的甲醛衍生化产物甲醛2,4-二硝基苯腙与理论值的平均偏差为0.24‰±0.14‰(从0.03‰到0.35‰),小于仪器分析误差0.5‰,该衍生化过程不存在同位素分馏.采用该方法对酒店大厅内外大气甲醛碳同位素组成进行了初步研究,结果表明不同来源的甲醛同位素组成具有显著差异,可以为大气甲醛的来源分析提供非常有效的信息.     

微塑料PES与2,4-DCP复合污染对厌氧污泥胞外聚合物与微生物群落的影响

考察了聚醚砜（PES）微塑料及2,4-二氯苯酚（2,4-DCP）对厌氧颗粒污泥疏松胞外聚合物（LB-EPS）和紧密胞外聚合物（TB-EPS）组分的影响,并利用高通量测序技术对厌氧颗粒污泥的微生物群落及基因功能变化进行了分析.结果表明,2,4-DCP以及PES+2,4-DCP实验组COD去除率分别为35%和37%,与空白对照组相比降低了57%和55%;而PES实验组COD去除率仍在90%左右.投加PES+2,4-DCP后,厌氧颗粒污泥LB-EPS中的蛋白及多糖含量与对照组相比出现了降低,TB-EPS中多糖含量增加最少.无论投加PES还是2,4-DCP均会抑制辅酶F₄₂₀的活性.通过高通量测序发现投加了PES或2,4-DCP实验组厌氧颗粒污泥的微生物丰度及多样性均减少.在对照组和实验组中,门水平下优势菌群为Proteobacteria（13.45%~44.47%）、Firmicutes（6.86%~21.67%）和Actinobacteria（3.16%~18.11%）;纲水平下PES+2,4-DCP实验组中β-Proteobacteria含量与对照组相比减少了15.28%,γ-Proteobacteria含量与对照组相比增加了28.44%.基于PICRUSt分析发现PES或2,4-DCP实验组中,污泥中能量代谢功能相关基因比对照组增多了0.25%~0.72%;而2,4-DCP实验组污泥中膜运输功能组相关基因丰度减少明显.     

Organoclays for Aquifer Bioremediation: Adsorption of Chlorobenzene on Organoclays and its Degradation by RHODOCOCCUS B528

The adsorption and degradation of chlorobenzene on partially modified organoclays and by the autochthonous microorganism Rhodococcus B528 were studied by means of the batch technique. Organoclays were prepared from Na-montmorillonite (MM) by using dodecyltrimethylammonium (C₁₂) and dioctadecyldimethylammonium (2C₁₈) bromides. The degree of modification was 35 (2C₁₈-35-MM) and 89% (C₁₂-89-MM) of the cation exchange capacity of MM. The adsorption experiments were carried out using headspace GC. The intercalation of chlorobenzene into the interlayers of organo-MM was detected by X-ray diffraction. The adsorption isotherms found were of the S1 type indicating a cooperative effect. Chlorobenzene showed a higher affinity for 2C₁₈-35-MM than C₁₂-89-MM, which could not only be explained by the organic carbon content. The comparison with 2,4-dichlorophenol adsorption has implied that for the studied systems the different adsorption mechanisms are primarily governed by the different molecular properties and not by the type of absorbent. The presence of 2C₁₈-35-MM caused no negative effect on the investigated microorganisms and complete biodegradation of chlorobenzene was achieved without desorption limitation for growth, demonstrating the applicability of partially modified organoclays for bioremediation.