Characterization of aescin as a biosurfactant for environmental remediation

Surface-tension-lowering capacity and emulsion-forming ability of aescin biosurfactant in pure water, seawater, 3 M urea, and 3 M glucose were investigated. Oils used in the emulsification tests were liquid paraffin, ethylbenzene, kerosene, 1-decene, and heavy oils A and C. Volumetric ratios of oil phase to aqueous (water) phase (O/W) were 0.5∶4.5, 2.5∶2.5, 3.0∶2.0, and 4.5∶0.5. Concentration of aescin was changed from 0.16 to 27.3 mM. The critical micelle concentration of eascin in water and its surface tension effectiveness were shown to be 0.78 mM and 28.5 mN/m, respectively. Surface-tension effectiveness of aescin was found to be highest in sea-water (33.5 mN/m). The emulsifying action of aescin was compared with that of decaglyceryl-monolaurylester (DGML). The performance of aescin was found to be as good as that of DGML and, depending on the O/W ratio and the concentration, aescin could yield emulsification efficiencies as high as 100%. These results indicated that aescin could be classified as a mild surfactant safe for living organisms. Because the surface activity of aqueous aescin solution was not satisfactorily good, attempts were made to improve the situation by addition of alcohols as cosurfactants. Ethanol, isoamyl alcohol, 2-ethylhexanol, n-hexanol, and n-octanol were used. They were added to the solutions at a concentration equimolar to aescin. These cosurfactants improved surface-tension effectiveness of aescin by as much as 53% and its emulsification efficiency by 67%.     

用弗雷德盐去除土壤淋洗液中的镉

用模拟酸雨(pH=4)对高镉土壤(全镉为10.590 mg/kg)进行浸取。实验结果表明,模拟酸雨对土壤中镉的浸出率仅为其总镉的1%左右,但浸出液中镉的含量(0.108 mg/L)仍远高出GB 3838—2002地表水Ⅴ类水质的要求,也高于GB 18918—2002城镇污水处理厂污染物排放标准(<0.01 mg/L),必须予以处理。弗雷德盐是以聚合铝为主要原料人工合成的层状双羟合物,它能以同晶取代、吸附或共沉淀形式去除水体中的重金属镉离子。研究表明,土壤浸出液中大量的Al3+、Fe3+会影响弗雷德盐对淋洗液中镉的去除,但处理后的镉含量仍可达到GB 18918—2002城镇污水处理厂污染物排放标准。     

Removal of mercury by foam fractionation using surfactin, a biosurfactant

The separation of mercury ions from artificially contaminated water by the foam fractionation process using a biosurfactant (surfactin) and chemical surfactants (SDS and Tween-80) was investigated in this study. Parameters such as surfactant and mercury concentration, pH, foam volume, and digestion time were varied and their effects on the efficiency of mercury removal were investigated. The recovery efficiency of mercury ions was highly sensitive to the concentration of the surfactant. The highest mercury ion recovery by surfactin was obtained using a surfactin concentration of 10 × CMC, while recovery using SDS required < 10 × CMC and Tween-80 >10 × CMC. However, the enrichment of mercury ions in the foam was superior with surfactin, the mercury enrichment value corresponding to the highest metal recovery (10.4%) by surfactin being 1.53. Dilute solutions (2-mg L(-1) Hg(2+)) resulted in better separation (36.4%), while concentrated solutions (100 mg L(-1)) enabled only a 2.3% recovery using surfactin. An increase in the digestion time of the metal solution with surfactin yielded better separation as compared with a freshly-prepared solution, and an increase in the airflow rate increased bubble production, resulting in higher metal recovery but low enrichment. Basic solutions yielded higher mercury separation as compared with acidic solutions due to the precipitation of surfactin under acidic conditions.     

混酸分解-电感耦合等离子体质谱法测定土壤中铬镉铅

本文采用HNO3-HF-HCl O4分解-电感耦合等离子体质谱法(ICP-MS)测定土壤样品中Cr、Cd、Pb,对样品预处理方法,条件等进行了改进和优化,同时给出了方法的检出限、线性范围、精密度、准确度、加标回收率等方法参数。经国家标准土壤样品验证,方法的精密度符合分析要求,结果令人满意。研究表明,该方法适用于土壤样品中Cr、Cd、Pb的分析测定。     

高铁酸钾混凝去除矿井水中的铅、镉、铁、锰

采用烧杯试验考察了投加高铁酸钾强化混凝去除矿井水中铅、镉、铁、锰的效果.结果表明,高铁酸钾为30 mg/L时,混凝沉淀对低浓度矿井水中铅、镉、铁、锰的去除率分别约为55%、28%、93%、54%;高铁酸钾对模拟高浓度矿井水中铅、镉、铁、锰的去除率随pH的升高而提高,pH 8～10范围内对铅、镉、铁、锰有较好的去除效果,去除率可分别达到约95%、61%、97%和92%.处理后的矿井水中重金属含量可以达到饮用水标准,这给矿井水提供了很好的利用前景.     

Heavy metal removal from water using the metallogelation properties of a new glycolipid biosurfactant

Water pollution by heavy metals is a problem in both western and developing countries. Heavy metal pollution can be associated with human activity, such as wastewaters from processing of ore mining, but also to simple contamination from metal-rich soils. Whichever the case, chemical and physical methods are generally employed to depollute water. Since most chemicals are themselves polluting agents, there is an increasing interest in finding biobased and biodegradable alternative chemicals, both efficient in removing metals and benign to the environment. Biosurfactants are green chemicals produced by fermentation of yeasts and bacteria and with a good environmental score. Among many applications, this class of compounds has been used to remove heavy metals from contaminated soils. Within this framework, we propose a new mechanism of depolluting water using a glucolipid biosurfactant, G-C18:1, composed of glucose (G) and a C18:1 fatty acid (oleic acid). This compound is able to form a metallogel by complexing cations in water, thus trapping heavy metals (Cu²⁺, Ni²⁺, Cr²⁺, and Co²⁺) in the gel phase. This mechanism allows to remove up to 95% for cobalt and 88 ± 10%, 80 ± 3%, and 59 ± 6% for Cu²⁺, Ni²⁺, and Cr²⁺, respectively. A dedicated structural study shows that this is possible because positively charged species induce gelation of G-C18:1 through a micelle-to-wormlike phase transition, most likely driven by a charge neutralization process. This work shows that wise control of the nanoscale properties of green chemicals can strongly benefit to develop a sustainable future.     

Use of biosurfactant in the removal of oil from contaminated sandy soil

The effectiveness of cell‐free rhamnolipid biosurfactant, derived from the culture medium at the end of fermentation was investigated for the removal of two different kinds of oil from contaminated sandy soils. The crude cultivation medium, containing 13.2 g L^?1 of rhamnolipids, had a surface tension, interfacial tension and critical micellar concentration of 30 mN m^?1, 2 mN m^?1 and 60 mg L^?1, respectively. The evaluation of biosurfactant in the culture medium (BM) and oil concentrations in the removal of oil from different contaminated sandy soil was performed using a statistical experimental design tool. Oil in sandy soil, containing predominantly aromatic or paraffinic hydrocarbons (5 to 10% w/w), was removed by as much as 91 and 78%, respectively, in the presence of reduced amounts of BM (6.3 to 7.9 g L^?1). The progress of oil removal was monitored for 101 days and results indicated that removal efficiency in sandy soil with aromatic characteristics was relatively stable over the entire period. Based on these studies, it is concluded that use of a BM was effective in reducing oil concentrations in contaminated sandy soil. Copyright © 2007 Society of Chemical Industry     

Sorption studies of cadmium and lead ions on hybrid polysaccharide biosorbents

The sorption of lead and cadmium ions on hybrid pectin-based biosorbents containing gellan, carob, and xanthan gum has been studied. The rate constant of the metal ions’ sorption on hybrid P + X beads (analyzed with the two kinetic models: pseudo-first-order and pseudo-second–order models) is at least two times higher than obtained on other pectin-based sorbents. The Langmuir equation fits experimental data better than Freundlich model. A greater equilibrium constant B for lead(II) than cadmium(II) indicates a stronger bond between Pb(II) and pectin-based beads. Prepared hybrid materials are promising biosorbents for heavy metals’ removal from waste waters.     

Removal of cadmium or lead from polluted water by biological amphiphiles

Biological amphiphiles were examined for the removal of Cd²⁺ or Pb²⁺ from polluted water within a pH range from 2.5 to 7.5 at a fixed ratio of amphiphilic concentration to heavy metal concentration (C _A /C _M ) on a molar basis of approximately 11. Tannic acid, among eight amphiphiles, was selected for Cd²⁺ or Pb²⁺ removal because it exerted noticeable improvement within limited pH ranges. In the presence of tannic acid, the removal of Cd²⁺ or Pb²⁺ was investigated as a function of pH ranging from 2.5 to 13 at C _A /C _M ratios from 1.2 to 11. The removal capacity (mass of metal/mass of tannic acid) increased with decreasing C _A /C _M for both Cd²⁺ and Pb²⁺. Removal capacities were 0.084 and 0.154 g/g-tannic acid for Cd²⁺ and Pb²⁺ at pH 6.9 and 4.4, respectively. The maximal removals for Cd²⁺ and Pb²⁺ were 99 and 96%, respectively.     

Removal of cadmium from wastewater by enhanced ultrafiltration using surfactants

In order to recover cadmium ion from wastewater, a process based on enhanced ultrafiltration was finalised. The originality of the solution here proposed lies on the coupled use of ceramic membranes and of a surfactant added to the water to be treated. This paper deals with the study of the influence of experimental conditions upon permeation flux and selectivity of the separation. The process is efficient and flexible since a single stage treatment allows to reduce the concentration of cadmium in the effluent by a factor of about 750; this high performance in selectivity is on a par with high fluxes of permeate (roughly 170 L.h.^?1.m^?2 at 25°C and 3 × 10⁵ Pa).     

纺织品中铅和镉的含量测定方法研究进展

介绍了纺织品中的重金属铅、镉元素的来源及毒性;综述了纺织品中铅和镉的含量测定方法研究进展;纺织品中铅和镉含量的传统测定方法有原子吸收光谱法、电感耦合等离子体原子发射光谱法、电感耦合等离子体质谱法、高效液相色谱法、电化学分析方法、X射线荧光光谱法、基于显色剂的分光光度法,快速检测方法有固体直接进样技术、基于金纳米颗粒目视比色法、胶体金层析试纸条、生物条形码检测技术;对传统检测方法存在的问题及快速检测技术的发展瓶颈进行了阐述;指出研制试样用量少、耗时短、成本低、简单便捷可靠、便于实现现场快速、准确检测纺织品试样的前处理方法是纺织品重金属铅镉元素安全快检技术的关键点;建议将高效便携仪器及车载仪器,溶剂提取、微波技术等试样快速前处理技术与纺织品快速检测技术联用,以便实现现场快速便捷、灵敏、准确地检测纺织品中重金属铅、镉含量。     

二甲酚橙浸渍树脂对铅和镉的吸附性能研究

用2g·L~(-1)二甲酚橙水溶液处理201×7阴离子交换树脂,制取得到二甲酚橙浸渍树脂。经过最佳条件选择,在同一水样中可以同时进行吸附、洗脱铅和镉。结果表明：二甲酚橙浸渍树脂在pH值为3～7时,对Pb~(2 )、Cd~(2 )具有较好的吸附性能。温度低有利于铅的吸附,而温度高则有利于镉的吸附。二甲酚橙树脂对Pb~(2 )和Cd~(2 )的平衡时吸附容量分别达到95和85mg·g~(-1)树脂,达到最大吸附容量平衡时仅需要50min。50mL 0．1mol·L~(-1)HCl就可以同时将铅、镉同时洗脱完全。二甲酚橙浸渍树脂吸附Pb~(2 )、Cd~(2 ),具有交换速度快、易于洗脱、富集倍数大、选择性好等优点。     

Sorption of cadmium and lead ions on modified groundnut (Arachis hypogea) husks

The removal of cadmium and lead ions from aqueous solutions by groundnut husks modified by reaction with EDTA (% N = 12.05) was examined by equilibrium sorption studies at 29°C. The maximum metal ion binding capacity of the EDTA-modified husk determined from the sorption isotherm from solutions of pH 6.8 was found to be 0.36 mmol g^?1 and 0.19 mmol g^?1 for Cd(II) and Pb(II) ions, respectively. It was found that the rate of sorption was particle-diffusion controlled, and the particle-diffusion control rate coefficient was determined to be of the order of 10^?2 min^?1.     

Waste spider crab shell and derived chitin as low‐cost materials for cadmium and lead removal

Crab shell and inexpensive chitin obtained from it have been studied to determine their capability to remove cadmium and lead from aqueous solutions. Factors affecting the process such as pH, metal concentration, time and temperature have been critically analysed. Results show that only cadmium uptake on crab shell is strongly influenced by the pH of the solution. The crab shell was also found to be more efficient. Equilibrium data analysis using the Langmuir isotherm indicates that crab shell can remove at least 1.4 mmol of metal per gram of sorbent at optimum pH. Temperature studies for metal sorption on chitin showed that the effect of temperature is very small for both the kinetic constant of the sorption process and for maximum uptake. Copyright © 2006 Society of Chemical Industry     

电感耦合等离子体质谱法测定仿真饰品用塑料珠中可萃取的铅和镉含量

为了解仿真饰品用塑料珠对人体的安全性,讨论了用不同萃取方法(模拟人工汗液、0.07 mol/L的盐酸溶液、4%的乙酸溶液)处理塑料珠后,通过ICP-MS法测定塑料珠中可萃取的铅和镉的含量。实验结果表明,在弱酸性溶液条件下,塑料珠中的铅和镉对人体有潜在的健康危害。本方法操作简便,灵敏度高,准确性好,可以在高盐的情况下直接测定铅和镉的含量。在选定的实验条件下,铅和镉的浓度在0~20μg/L范围内线性关系良好,铅和镉的检出限分别为0.71μg/L和0.01μg/L,相对标准偏差(RSD)<1%。     

Removal of lead ions from wastewater using novel Schiff-base functionalized solid-phase adsorbent

ABSTRACT

This article discusses the synthesis, characterization and lead ions sorption capability of a novel recyclable Schiff-base anchored cross-linked polyacrylamide. The synthesized polymeric adsorbent was characterized by FT-IR technique, XRD and SEM analysis. Sorption parameters, such as solution’s pH, contact time, polymer dose, lead ions initial concentration, etc., were studied and optimized. Experimentally, the optimum sorption pH was around 5.0 and the sorption equilibrium was attained after 30 min. Under the optimal conditions, the maximum sorption capacity was found to be 355 mg/g, which is considered high when compared with different adsorbents. Effect of interfering ions on the sorption capacity was explored. Sorption isotherms, kinetic and thermodynamic studies were considered to identify the sorption behavior of the new polymeric adsorbent. Sorption isotherm studies showed that the maximum sorption capacity was attended as a result of homogeneous monolayer sorption of lead ions on the surface of the synthesized polymeric adsorbent. The mechanism of lead ions sorption by the synthesized polymeric adsorbent was found to be chemisorption complexation mechanism. Moreover, kinetic studies revealed that the sorption process followed a pseudo second order kinetic model. Thermodynamic data depicted that the sorption process is spontaneous, reversible and exothermic in nature. Experiments on elution and reusability of the synthesized polymeric adsorbent were executed and the results showed its validity for reuse for at least four cycles with 11% loss in its original capacity. Finally, the applicability of the synthesized Schiff-base anchored solid phase adsorbent for the removal of lead ions from industrial wastewater was explored and the results indicated its good removal efficiency.     

Removal of lead ions from aqueous solutions using powdered corn cobs

This paper is a report on an investigation conducted on adsorption of lead ions (Pb²⁺) onto powdered corn cobs (PCC). Corn cobs were collected from a selected location in Nigeria. The corn cobs were crushed and pulverised into different particle sizes. Its compositions and adsorption properties of Pb²⁺ onto PCC were studied. The effects of pH, particle size of PCC, and initial concentration of Pb²⁺ on the adsorption properties were monitored. The adsorption capacities were analysed by using standard adsorption models. The models were evaluated statistically (total error, coefficient of determination (CD), model of selection criterion (MSC), and root mean square error). The study revealed that PCC contained 2.33%, 86.89%, 10.78%, 0.52%, and 4.56% ash, volatile, moisture, solubility in water, and solubility in 0.25 M of HCl by mass, respectively. Acid digestion of a gram of PCC indicated that PCC contained no chromium and lead, but contained 131 mg Fe, 54.79% carbon, 8.03% hydrogen, 0.41% nitrogen, 0.010 mg of Al, and 1.70 mg calcium. The isotherm models parameters were 28.509 L/mg and 0.141 mg/g; 0.138 mg/g and 11.494 L/mg; 0.142 L/mg and 0.013 mg/g; 0.129 mg/g and 25.641 L/mg, 28.509 L/mg, 3.795 mg/g and 2.336 for Langmuir, Freundlich, Temkin, activated sludge, and Redlich–Peterson. The PCC particle size, initial pH, and initial Pb²⁺ concentration had effects on the adsorption parameters. The statistical evaluations showed that the best model for adsorption of lead ions from raw water onto PCC based on lower errors, high CD (0.88), reliability (97.5%), and MSC (1.86) was Freundlich and followed by activated sludge model. It was concluded that PCC is a good adsorbent like powdered eggshell and other carbon‐based materials.     

阳极溶出伏安法测定硫酸锌中的铅和镉

采用玻碳电极为工作电极，以醋酸钠－醋酸－氯化钾溶液为底液，用二次导数阳极溶出伏安法测定了硫酸锌中的微量铅和镉，峰电位分别为－0．43V（Vs,SCF)和－0．62V（Vs,SCE)，线性范围分别为0－2．0μg/925mL)和0－0．8μg/(25mL)，方法准确，快速、简便。     

Removal of cadmium and production of cadmium powder using a continuous undivided electrochemical reactor with a rotating cylinder electrode

The behaviour of a continuous undivided electrochemical reactor with a rotating cylinder electrode under potentiostatic control is examined for the abatement of cadmium from synthetic sodium sulfate solutions with Cd(II) concentrations lower than 500 mg dm^?3 at a reactor inlet pH ? 7. The process was designed to convert the metal ions in solution to metal powder, which settles to the conical of the reactor and may be removed at intervals as a sludge by opening a drop valve. The effect of applied potential, inlet cadmium concentration, rotation speed and hydrogen evolution as side cathodic reaction on the ‘figures of merit’ of the reactor are analysed. The best results were obtained for cathode potentials in the range from ?0.9 V to ?1.0 V against the saturated calomel electrode. Therefore, when the rotation speed was 1000 rpm the space time yield and the normalized space velocity were 0.64 ×10^?2 mol m^?3 s^?1 and 0.89 h^?1 respectively, while the fractional conversion per pass was 35% with a current efficiency higher than 74%. The surface morphology of the deposits as a function of the process variables is also reported. © 2002 Society of Chemical Industry     

改性淀粉在低浓度含镉废水处理中的应用实验

对淀粉（St）接枝共聚丙烯酰胺（AM）并与巯基乙酸（MCAA）反应进行了研究,将得到的产物用于低浓度含镉废水处理取得了较好的效果。研究了淀粉与丙烯酰胺配比不同对St-AM接枝率和接枝效率的影响并对巯基化后得到的产物St-AM-MCAA的巯基含量进行了测定。对低浓度（0.4mg/L）含镉废水的处理研究发现：含镉废水在pH=8,添加量为50mg时镉去除率可达89.7%;St-AM-MCAA较St-AM产物能提高Cd2+去除率10%以上。