天然含铁矿物对砷的吸附效果及机制

自然界中丰富的含铁矿物作为天然的铁氧化物,可作为一类修复材料用于砷污染水体和土壤稳定化修复.本文通过吸附-解吸附实验对比研究了天然赤铁矿、天然褐铁矿、天然菱铁矿、天然钛铁矿、天然磁铁矿、Fe_2O_3、Fe_3O_4及铁锰双金属材料(FMBO)对砷的吸附-解吸特性,结合光谱学手段研究其作用机制.吸附实验结果表明,9种含铁材料对As(Ⅲ)和As(Ⅴ)的吸附过程更符合准二级动力学方程和Langmuir方程,表明反应机制主要为单层化学吸附作用.其中,FMBO对As的吸附效率和吸附容量远高于其余材料,天然含铁矿物中褐铁矿对As吸附效果表现最好,对As(Ⅲ)和As(Ⅴ)的吸附容量分别为3. 96 mg·g-1和2. 99 mg·g-1.光谱学手段表明天然褐铁矿中含有较为丰富的针铁矿等弱结晶态矿物成分,具有相对丰富的砷吸附位点,是一种具有潜在修复能力的天然材料.     

钛改性锰矿的除砷效果及机理研究

天然锰矿是一种廉价、易得的除砷矿物材料,为了进一步提高天然锰矿的除砷效果和吸附容量,采用TiCl4对广西桂林天然锰矿进行改性,并对其改性的条件进行优化。实验结果表明最佳的改性条件为:TiCl4浓度为10 mg/L,浸泡时间为18 h,pH=3.05,振荡吸附时间为1 h。与天然锰矿的去除效率(82.95%和77.93%)相比,改性锰矿对As(Ⅲ)和As(Ⅴ)去除率分别可达94.87%和99.31%,相应的饱和吸附量分别为3.48 mg/g和3.27 mg/g,较天然锰矿各自提高了1.25 mg/g和1.21 mg/g。改性锰矿对As(Ⅲ)的吸附符合Freundlich等温吸附模型,对As(Ⅴ)的吸附更符合Langmuir等温吸附模型。     

Fe-La二元氢氧化物对水中As(Ⅴ)和As(Ⅲ)的吸附行为与机制

采用共沉淀法制备了铁-镧二元氢氧化物(Fe-La)吸附剂,通过吸附动力学、pH的影响和吸附等温线等吸附批实验研究了其对水溶液中砷的去除行为,并通过扫描电子显微镜-X射线能谱分析(SEM-EDS)、傅里叶红外光谱分析(FTIR)、X射线衍射分析(XRD)等方法对铁-镧二元氢氧化物进行了表征,研究其对砷的去除机制.吸附批实验表明,Fe-La二元氢氧化物对As(Ⅴ)具有较强的去除能力,而对As(Ⅲ)的去除能力较弱.吸附动力学实验表明,Fe-La二元氢氧化物对As(Ⅴ)和As(Ⅲ)在前2 h内吸附速率较快,其去除过程均符合伪二级动力学模型.溶液的pH值会显著影响Fa-La二元氢氧化物对As(Ⅴ)和As(Ⅲ)的去除效率,其中,对As(Ⅴ)的吸附量在pH=3.0～4.0时升高,在pH=5.0～11.0时随pH升高而降低;对As(Ⅲ)的吸附量在pH=3.0～6.0时升高,在pH=6.0～10.0范围内保持不变,在pH=10.0～11.0时吸附量减少.Langmuir吸附等温线拟合结果表明,pH=4.0时Fe-La二元氢氧化物对As(Ⅴ)的最大吸附量为303.03 mg·g^-1,...     

天然菱铁矿改性及强化除砷研究

我国高砷地下水分布广泛,经济、高效地饮用水除砷技术受到广泛关注.静态批实验采用资源丰富、价格便宜的天然菱铁矿为主要原材料,考虑灼烧温度、时间及添加黏合剂等因素确定最优改性条件使除砷效果达到最佳.结果表明,在加铝量为10 mg.g-1、350℃下恒温灼烧90 min后造粒达到强度要求并除砷效果较优.25℃、固液比为0.5 g∶50 mL、As(Ⅲ)和As(Ⅴ)初始浓度为5 mg.L-1时,吸附后溶液中残留As浓度均<10μg.L-1.静态吸附批实验结果表明,25℃时,接触反应时间为12 h可达到吸附平衡,吸附过程较好地符合Lagergren假二级吸附速率方程;最优改性天然菱铁矿对砷的吸附规律可用Langmuir和Freundlich等温吸附模型很好地描述,As(Ⅲ)、As(Ⅴ)饱和吸附容量分别可以达到1 039、1 026μg.g-1.结合XRD、SEM等研究方法和比表面及孔结构分析初步探讨天然菱铁矿改性以及除砷的主要机制.分析表明,改性后天然菱铁矿比表面积大幅度增大,孔径减小,且在表面活化生成一层圆球状的含Fe(Ⅱ)和Fe(Ⅲ)的化合物.改性天然菱铁矿是一种值得进一步研究并实际应用的除砷材料.     

磁性海藻酸铁介孔碳微球的合成及对水体中砷的去除

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.     

铁铈氧化物对土壤As (Ⅴ)和P的稳定化效果

本文以铁铈氧化物(Fe-Ce,FC)为研究对象,评估其对中国3种典型砷(As)污染土壤的稳定化修复效果,并通过电子扫描显微镜能散X线分析仪(SEM-EDS)和X射线光电子能谱仪(XPS)等光谱学技术探索FC对As(Ⅴ)的微观吸附特征.结果表明,FC能使土壤毒性浸出As含量显著降低84. 1%～98. 3%,且在碱性土壤中表现出较强的高p H适应性,能显著增加吸附态As(F1+F2)向水合铁铝氧化物结合态(F3+F4)的稳定化. FC能使不同类型土壤的有效态P含量显著下降47. 13%～60. 32%,不仅能缓解P竞争土壤As(Ⅴ)吸附位点,而且能有效预防周边水体的面源污染.通过SEM-EDS和XPS分析,发现As(Ⅴ)吸附产物表面均检测到Fe、Ce和As这3种元素,且As主要吸附于Fe原子表面. FC在我国土壤砷污染稳定化修复领域具有较好地应用前景.     

镧改性生物炭对砷、镉的吸附特征研究

为研究改性生物炭对砷镉复合污染水体中镉和砷的吸附特征。本研究以牛粪、污泥、竹屑三种不同原料制备生物炭,利用镧(La)对生物炭进行改性,并采用元素分析、扫描电镜、傅里叶变换红外光谱和X射线光电子能谱等分析手段对改性前后的生物炭进行表征,结合等温吸附实验及吸附动力学实验,对比各生物炭对As (V)、Cd (II)的吸附性能并探讨其内在机理。结果表明,竹屑炭(BB)的芳香性大于牛粪炭(CB)和污泥炭(SB)。La改性使三种生物炭在热解过程中形成了酮类、酯类、羰基等含氧官能团,并在表面引入羟基。X射线光电子能谱结果显示La以氢氧化物的形式负载在生物炭表面。各生物炭对Cd (II)、As (V)的吸附符合准二级吸附动力学和Langmuir等温吸附方程。La改性生物炭对As (V)的最大拟合吸附量达到3.47～4.51 mg/g,显著高于未改性生物炭(1.82～2.50 mg/g)(p<0.05)。在As (V)、Cd (II)吸附过程中,La改性生物炭表面的La与As (V)发生络合反应,同时Cd (II)与镧基氢氧化物发生配体交换,生成Cd (OH)₂沉淀。本研究证明了La改性有效提高了生物炭对As (V)、Cd (II)同时吸附的能力。     

拉曼光谱及其理论模拟在砷吸附过程中的应用

由于全球砷污染问题日益严重,迫切需要开发新型砷污染物形态及浓度的快速检测分析方法。拉曼光谱是一种强大的材料表征及分析工具,表面增强拉曼光谱(SERS)技术已应用在砷污染物吸附形态和络合结构分析等方面。文章综述了近年利用拉曼光谱对水介质中无机砷和有机胂定性及定量的相关研究,讨论了SERS基底的类型、砷的拉伸模式、拉曼光谱峰位移等相关因素,提出了拉曼光谱在砷环境分析中的发展趋势。当以纳米银为SERS基底,As(Ⅴ)和As(Ⅲ)的As-O拉曼位移差较大(～60 cm^-1),能够分别测定地下水样中的As(Ⅴ)和As(Ⅲ)污染物。而且,可以通过有机砷污染物特定化学键拉曼位移来识别砷污染物种类。砷污染物浓度与拉曼光谱强度呈线性相关,因此可通过测定拉曼光谱对无机和有机砷污染物进行定量分析。通过密度泛函理论进行分子建模,可以预测无机和有机砷污染物特定化学键拉曼位移。研究结果可以为拉曼光谱在砷吸附过程中的应用提供重要参考。     

铁改性杭锦土吸附剂对水中砷的去除研究

为提高天然杭锦土对水溶液中砷的吸附性能,采用氯化铁（FeCl₃·6H₂O）浸渍天然黏土矿物杭锦土（HJ）,制备表面负载铁氧化物的铁改性杭锦土除砷吸附剂（FHJ）.通过比表面积（BET）和扫描电镜（SEM）分析技术对材料进行表征以观察其微观形貌特点,通过X射线光电子能谱分析（XPS）和傅里叶红外光谱（FTIR）技术测定材料组成及化学基团,以初步探究材料吸附除砷机理.通过批试验考察FHJ投加量、初始pH、共存离子及腐殖酸浓度对FHJ除砷效能的影响.结果表明:①当铁负载比在0~50wt%范围内时,FHJ对溶液中As（Ⅴ）吸附容量随着铁负载比的增加而增加,最佳铁负载比为33wt%,此时铁与杭锦土的理论质量比为1:3.②BET分析结果表明经铁改性后,杭锦土比表面积显著增加,由71.14 m2/g增至158.50 m2/g;SEM分析显示,经改性后杭锦土表面形貌发生明显变化,结合Mapping图表明铁被有效负载到杭锦土表面.③批试验结果表明,As（Ⅴ）去除率随着FHJ投加量的增加而升高;溶液pH对As（Ⅴ）去除率有较大的影响,pH的降低有利于FHJ对砷酸盐的吸附.④FHJ除砷性能受溶液中共存离子CO₃2-、SiO₃2-影响较大,但受Cl-、SO₄2-、NO₃-及腐殖酸影响程度比较小.⑤吸附动力学过程符合准二级动力学模型,Freundlich等温吸附模型可更好地描述FHJ吸附除砷行为（R2=0.999）.⑥XPS分析结果显示,铁氧化物主要以FeOOH和Fe₂O₃的形态负载于杭锦土表面,FTIR表明FeOOH的羟基基团同As（Ⅴ）发生吸附作用,在FHJ除砷过程中,化学吸附是主要的吸附除砷机理.研究显示,铁改性杭锦土除砷效果良好,具有一定的应用潜力.      

氢氧化铁对砷的吸附与沉淀机理

研究了吸附反应时间为50d和1120d时,As(V)初始浓度和pH值对氢氧化铁吸附砷的影响,并利用傅利叶红外光谱(FTIR)和粉末X射线衍射技术对吸附砷后的氢氧化铁固体进行了表征.结果表明,氢氧化铁对砷的吸附能力与pH有关,在弱酸性到弱碱性条件下,吸附砷的能力最强;在低初始砷浓度(0.01～1 mmol·L-1)和相同pH条件下,吸附率随砷浓度增高而增大.当pH=3、7和12时,吸附等温线都可用Freundlich公式来进行拟合,低初始砷浓度下(0.001～1 mmol·L-1),R2>0.99,高初始砷浓度下(5～1000 mmol·L-1),R2>0.93,吸附反应时间对吸附能力影响不大.红外光谱分析表明,在pH=3条件下,初始砷浓度为50mmol·L-1和500mmol·L-1时,吸附后氢氧化铁固体的红外光谱图上As-O键的伸缩振动谱带分别位于806.11cm-1和821.54cm-1;表明吸附后的氢氧化铁表面有少量的砷酸铁晶体沉淀存在,砷在氢氧化铁表面的平均密度对砷在氢氧化铁表面存在形态有影响.X射线衍射分析表明.在中性和酸性条件下,砷可能是以双配位表面络合的质子化的=FeO2As(O)(OH)-和非质子化的=FeO2As(O)2-形态存在于氢氧化铁表面.     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Degradation of metabolites accumulated of benzo[a]pyrene by coupling Penicillium Chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.     

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

ＲｅｍｏｖａｌｏｆｈｅａｖｙｍｅｔａｌｓｆｒｏｍｓｅｗａｇｅｓｌｕｄｇｅｂｙｌｏｗｃｏｓｔｉｎｇｃｈｅｍｉｃａｌｍｅｔｈｏｄａｎｄｒｅｃｙｃｌｉｎｇｉｎａｇｒｉｃｕｌｔｕｒｅＷｕＱｉｔａｎｇ，ＮｙｉｒａｎｄｅｇｅＰａｓｃａｓｉｅ，ＭｏＣｅｈｕｉＦ...     

Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.     

Isolation and preliminary characterization of a 3-chlorobenzoate degrading bacteria

A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.     

Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China

A field study was conducted in the Taihu Lake region, China in 2004 to reveal the organochlorine pesticide concentrations in soils after the ban of these substances in the year 1983. Thirteen organochlorine pesticides (OCPs) were analyzed in soils from paddy field, tree land and fallow land. Total organochlorine pesticide residues were higher in agricultural soils than in uncultivated fallow land soils. Among all the pesticides, ΣDDX (DDD, DDE and DDT) had the highest concentration for all the soil samples, ranging from 3.10 ng/g to 166.55 ng/g with a mean value of 57.04 ng/g and followed by ΣHCH, ranging from 0.73 ng/g to 60.97 ng/g with a mean value of 24.06 ng/g. Dieldrin, endrin, HCB and α-endosulfan were also found in soils with less than 15 ng/g. Ratios of p,p'-(DDD DDE)/DDT in soils under three land usages were: paddy field ＞ tree land ＞ fallow land, indicating that land usage inlfuenced the degradation of DDT in soils. Ratios of p,p'-(DDD DDE)/DDT ＞1, showing aged residues of DDTs in soils of the Taihu Lake region. The results were discussed with data from a former study that showed very low actual concentrations of HCH and DDT in soils in the Taihu Lake region, but according to the chemical half-lives and their concentrations in soils in 1980s, the concentration of DDT in soils seemed to be underestimated. In any case our data show that the ban on the use of HCH and DDT resulted in a tremendous reduction of these pesticide residues in soils, but there are still high amounts of pesticide residues in soils, which need more remediation processes.     

Sorption of 1-naphthol by plant cuticular fractions

The contribution of aliphatic-rich plant biopolymer to sorption of hydrophobic organic compounds is significantly important because of their preservation and accumulation in the soil environment,but sorption mechanism is still not fully understood.In this study, sorption of 1-naphthol by plant cuticular fractions was examined to better understand the contributions of respective fraction.Toward this end,cuticular materials were isolated from the fruits of tomato by chemical method.The tomato cuticle sheet consisted of waxes (6.5 wt%),cuticular monomer (69.5 wt%),and polysaccharide (24.0 wt%).Isotherms of l-naphthol to the cuticular fractions were nonlinear (N value (0.82-0.90)) at the whole tested concentration ranges.The KodKow ratios for bulk cuticle (TC1),dewaxed cuticle (TC2),cutin (TC4),and desugared cuticle (TC5) were larger than unity,suggested that tomato bulk cuticle and cutin are much powerful solption medium.Sorption capability of cutin (TC4) was 2.4 times higher than the nonsaponifiable fraction (TC3).The 1-naphthol interactions with tomato cuticular materials were governed by both hydrophobic-type interactions and polar (H-bonding) interactions. Removal of the wax and polysaccharide materials from the bulk tomato cuticle caused a significant increase in the sorption ability of the cuticular material.There was a linear negative trend between K_(oc) values and the amount of polysaccharides or fraction's polarities ((N O)/C);while a linear positive relationship between K_(oc) values and the content of cutin monomer (linear R~2=0.993) was observed for present in the cuticular fractions.Predominant sorbent of the hydrophobic organic compounds (HOCs) in the plant cuticular fraction was the cutin monomer,contributing to 91.7% of the total sorption of tomato bulk cuticle.