重金属吸附剂壳聚糖的改性研究进展

综述了重金属吸附剂壳聚糖改性研究的新进展,介绍了交联与接枝等改性方式对壳聚糖稳定性的影响及改性后的壳聚糖对水体中重金属离子吸附性能的改善.针对壳聚糖改性中仍然存在的一些问题,指出今后研究中值得关注的方向.     

改性壳聚糖处理微生物浸矿废水

为解决采矿行业微生物浸矿酸性废水中和处理沉渣多、固液分离困难的问题,采用柠檬酸钠和环氧氯丙烷改性处理的壳聚糖在pH=2.2条件下吸附模拟废水中的Cu²⁺和Fe³⁺,用正交实验优化了壳聚糖改性工艺条件。实验结果表明,最适宜的工艺条件为：处理100 mL壳聚糖质量分数为2%的壳聚糖-冰醋酸溶液,柠檬酸钠缓冲溶液加入量200 mL,环氧氯丙烷加入量300 mL,反应时间6 h。改性壳聚糖对Fe³⁺的最大吸附容量为6.703 7 mg/g,对Cu²⁺的最大吸附容量为4.378 7 mg/g,Fe³⁺和Cu²⁺在改性壳聚糖上的吸附是单分子层形式。     

壳聚糖改性凹凸棒土对重金属离子的吸附

采用浸渍法将壳聚糖负载在凹凸棒土上,制备了改性的凹凸棒土。用该吸附剂吸附溶液中Pb^2＋,Cd^2＋的实验结果表明：未负载壳聚糖时,凹凸棒土对Cd^2＋的吸附率为55%;当负载壳聚糖的质量分数为0.04时,凹凸棒土对Cd^2＋的吸附率达最大值（为91%）,对Pb2＋的吸附率也达最大值（为75%）。其吸附行为符合Langmuir等温吸附方程和Freundlich等温吸附方程。该吸附剂可重复使用。     

改性膨润土对水中蒽的吸附和解吸

分别用长碳链季铵盐阳离子型表面活性剂溴化十六烷基三甲铵（HDTMAB）、短碳链季铵盐阳离子型表面活性剂四甲铵化溴（TMAB）及非离子型表面活性剂聚乙二醇（PEG）对天然膨润土进行改性。比较了不同类型改性膨润土对水中蒽的吸附性能，探讨了吸附机理。实验结果表明，天然膨润土及改性膨润土对水中蒽的吸附能力依次为HDTMAB改性膨润土〉PEG改性膨润土〉TMAB改性膨润土〉天然膨润土；吸附等温线均是直线，说明该吸附行为是分配作用的结果。不同蒽初始质量浓度下，各种改性膨润土对蒽的吸附量由大至小的顺序为HDTMAB改性膨润土〉PEG改性膨润土〉TMAB改性膨润土，而天然膨润土对蒽的吸附量随蒽初始质量浓度的变化很小。改性膨润土加入量为30～80g/L时，各种改性膨润土对水中蒽的去除率均可达到90％以上，且解吸率均在5％以下。     

沸石和糠醛渣对硝酸盐吸附性影响的研究

利用沸石和糠醛渣改性制得硝酸盐吸附剂,研究吸附剂的饱和吸附能力和各种影响因子(温度、pH值、吸附时间、吸附质浓度、吸附剂用量和干扰离子)对硝酸盐吸附性能的影响。结果表明,改性沸石和糠醛渣的硝酸盐吸附能力大大增强;影响因子对吸附剂吸附硝酸盐能力的影响很大,其中升温有利于解吸、在中性pH值附近脱除率较高、干扰离子可降低吸附剂的硝酸盐脱除率;影响因子对改性糠醛渣MF的吸附影响要比对改性沸石的影响大。因此,改性沸石在实际应用中比改性糠醛渣MF的硝酸盐吸附能力强,具有更好的应用前景。     

风化煤粒状离子交换剂及其吸附特性研究

利用三门峡风化煤研制出粒状腐植酸系重金属离子交换剂,并研究它对汞、铅、镉、镍及多种共存金属离子的吸附特性。用测定离子交换剂吸附金属离子与其脱附(ca~(2+)+Mg~(2+))相关性的方法,研究了这种离子交换剂对金属离子的吸附机理。     

改性生物炭对Ni~(2+)和Cu~(2+)的吸附

以废弃松木屑为原料制备了生物炭,采用六亚甲基四胺(HMTA)和/或CO2对其进行改性,并将其用于水中Ni2+和Cu2+的吸附。表征结果显示,以HMTA和CO2共同改性的生物炭BC1的表面积最小但表面含氧官能团含量最高。实验结果表明:生物炭经改性后,其吸附性能明显提高,且以BC1为最优;在不调节溶液p H、初始重金属离子质量浓度为50 mg/L、吸附剂加入量分别为2.0 g/L和1.0 g/L、吸附时间分别为360 min和240 min的优化条件下,BC1对Ni2+和Cu2+的去除率分别达到99.81%和95.88%;改性生物炭对Ni2+和Cu2+的吸附过程可以用Langmuir等温吸附模型来描述,而其吸附动力学具有拟二级动力学方程特征。     

壳聚糖对酸性染料的吸附性能研究

采用壳聚糖为吸附剂,研究了壳聚糖对兰纳洒脱酱红B(ABB)和尼龙山黄N-3RL(NYN)两种酸性染料模拟废水的吸附性能.在染料废水初始质量浓度为100 mg/L、体积为50 mL的条件下,壳聚糖对两种染料废水的最佳吸附条件:壳聚糖脱乙酰度为75%,壳聚糖粒径为0.054～0.076 MM,壳聚糖加入量为20 mg,搅拌时间为2.0 h,搅拌速率为400 r/min,废水pH为6,ABB废水温度为10～30 ℃,NYN废水温度为20-50℃.在最佳的吸附条件下,壳聚糖对ABB和NYN的吸附容量分别为244.45 mg/g和239.14 mg/g.壳聚糖对ABB的吸附较符合Freundlich方程,对NYN的吸附较符合Langmuir方程.     

壳聚糖吸附废水中铅离子的研究

研究了壳聚糖对废水中Pb2+的吸附特性,考察了壳聚糖溶液加入量、吸附时间及体系pH等条件对壳聚糖吸附溶液中Pb2+效果的影响。当质量分数为0.8%的壳聚糖溶液加入量为0.4 mL、吸附时间为30 m in、体系pH为5~6时,处理浓度为1×10-4mol/L的含Pb2+溶液,Pb2+去除率可达98%;同样条件处理印染废水,Pb2+去除率可达92.6%。     

改性多壁碳纳米管对Pb2+、Cu2+和Co2+的竞争吸附研究

采用HNO3改性的多壁碳纳米管（MWCNTs）分别对Pb^2＋、Cu^2＋和Co^2＋进行吸附，并在含3种离子的混合溶液中进行竞争吸附。单一离子吸附结果表明，在室温、pH=5的条件下，MWCNTs对单一离子的饱和吸附量分别为：Pb^2＋91mg／g；Cu^2＋24mg／g；Co^2＋12mg／g。竞争吸附结果表明，在溶液中各金属离子的平衡质量浓度均为30mg／L时，MWCNTs对Pb^2＋、Cu^2＋和Co^2＋的平衡吸附量分别为43，15，6mg／g。MWCNTs对3种金属离子的吸附选择性大小顺序为：Pb^2＋〉Cu^2＋〉Co^2＋分别用Langmuir和Frundlich模型对单一吸附和竞争吸附进行拟合，结果表明，该吸附过程更符合Langmuir模型。     

炭基载体含氧基团对Mn-Ce双金属吸附剂脱硫活性的影响

以无烟煤、烟煤、褐煤以及工业半焦、烟煤半焦为载体,采用超声辅助加压浸渍法制备了Mn-Ce双金属吸附剂。利用固定床装置对吸附剂的烟气脱硫活性进行了评价,并运用BET、XRD和FTIR技术对其进行了表征。结果表明：吸附剂的脱硫活性主要由焙烧后的金属氧化物提供,金属离子本身无脱硫活性;炭基载体中的酯基是影响金属组分脱硫活性的主要因素,酯基在焙烧过程中分解使得金属组分暴露出来,提高了吸附剂的脱硫活性;中等变质程度的烟煤是制备吸附剂的良好载体,含有适量酯基,使得吸附剂表面金属组分分散均匀。     

加载絮凝—超滤—反渗透组合工艺处理PCB电镀废水

采用加载絮凝—超滤—反渗透组合工艺处理含大量重金属离子的印制电路板（PCB）电镀废水。考察了絮凝污泥回流比和水力条件对加载絮凝效果的影响,确定了最佳工艺参数：在加碱沉淀pH 10.5、混凝pH 9.0、PAC投加量10 mg/L、PAM投加量1.0 mg/L的条件下,污泥回流比为47%,加碱沉淀、混凝、絮凝的搅拌转速分别为250,150,50 r/min,搅拌时间分别为6,8,4 min。中试结果表明：经加载絮凝预处理后,总铜、总镍和浊度的平均去除率分别为99.4%、99.3%和93.1%;预处理出水经超滤—反渗透系统处理后,出水水质全部达标。     

A case study of microwave processing of metal hydroxide sediment sludge from printed circuit board manufacturing wash water

The large quantity of wash water used in the electroplating and etching process in the manufacturing of printed circuit boards (PCBs) contains a high level of heavy metal ions (Cu⁺⁺, Zn⁺⁺, Ni⁺⁺, Cr⁺⁺⁺, Pb⁺⁺). These potentially toxic ions are removed from the wash water effluent through a polyelectrolyte flocculation and hydroxide precipitation process during which a hydroxide sediment sludge rich in metal ions and polymers is generated. This sediment sludge possesses some unique characteristics and properties in terms of composition, fine particle size distribution, high specific surface area, and a tendency to agglomerate after drying. Direct disposal of this classified “special waste” (Department of Environment of Northern Ireland, The Special Waste Regulations, Northern Ireland, 1998) at landfill sites may cause serious soil and underground water pollution through a gradual ionic leaching process. This paper describes an experimental investigation, exploratory in nature, which employs microwave radiation for detoxification of the sediment sludge through microwave heating, drying and metal ion immobilization within the sediment solids. The effectiveness of microwave assisted binding and immobilization of the metal ions within the sediment solids was studied in conjunction with an evaluation of microwave energy efficiency in comparison to the more conventional convective heating and drying processes. Given a sufficient amount of microwave radiation, leaching of Cu²⁺ and Pb²⁺ was reduced by 2700% and 1080%, respectively, over a period of 12 weeks, and further leaching was not detectable within six months at simulated local landfill aqueous conditions. This paper also attempts, through experimental observation, to add to the very limited understanding of the complex interactions and binding of free metal ions with the polymeric materials and metal hydroxides under the influence of an electromagnetic field. The high specific surface of the sediment solids and their adsorption properties were further explored and characterized in a study of adsorption of reactive dyes by the microwave processed solids.     

Poultry litter-based activated carbon for removing heavy metal ions in water

Utilization of poultry litter as a precursor material to manufacture activated carbon for treating heavy metal-contaminated water is a value-added strategy for recycling the organic waste. Batch adsorption experiments were conducted to investigate kinetics, isotherms, and capacity of poultry litter-based activated carbon for removing heavy metal ions in water. It was revealed that poultry litter-based activated carbon possessed significantly higher adsorption affinity and capacity for heavy metals than commercial activated carbons derived from bituminous coal and coconut shell. Adsorption of metal ions onto poultry litter-based carbon was rapid and followed Sigmoidal Chapman patterns as a function of contact time. Adsorption isotherms could be described by different models such as Langmuir and Freundlich equations, depending on the metal species and the coexistence of other metal ions. Potentially 404 mmol of Cu²⁺, 945 mmol of Pb²⁺, 236 mmol of Zn²⁺, and 250–300 mmol of Cd²⁺ would be adsorbed per kg of poultry litter-derived activated carbon. Releases of nutrients and metal ions from litter-derived carbon did not pose secondary water contamination risks. The study suggests that poultry litter can be utilized as a precursor material for economically manufacturing granular activated carbon that is to be used in wastewater treatment for removing heavy metals.     

交联阳离子淀粉的合成及其对重金属离子的吸附

通过正交实验合成了取代度为0．568的交联阳离子淀粉。考察了溶液pH、螯合剂用量、重金属离子初始浓度对交联阳离子淀粉去除重金属离子效果的影响。当重金属离子初始质量浓度为50mg／L、螯合剂投加量为0．5g／U时,Pb^2 ,Cu^2 ,Cr^3 在溶液pH为6时的去除率达到最高,分别为97．94％,99．46％,84．30％,而Cd^ 在溶液pH为7时的去除率达到最高,为99．36％。实验结果表明,交联阳离子淀粉是一种有效去除废水中重金属的处理剂。     

Biosorptive removal of Pb(II) and Cu(II) from wastewater using activated carbon from cassava peels

The ability of activated carbon from cassava peels to remove heavy metals like Cu(II) and Pb(II) from hospital wastewater was investigated. The study showed that a pH of 8 was the best for the sorption of both metal ions onto the biosorbent. The time-dependent experiments for the metal ions showed that the binding of the metal ions to the biomass was rapid and occurred within 20–120 min. Sorption efficiency increased with a rise in adsorbent dosage. It increased from 12 to 73 % for Pb(II) and 26 to 79 % for Cu(II) when the adsorbent dose increased from 2 to 12 g. An increase in temperature led to an increase in sorption for both metal ions. The Langmuir model showed that the biomass has a higher sorption capacity for Cu(II) than Pb(II), with q _m = 5.80 mg g^?1 for Pb(II) and 8.00 mg g^?1 for Cu(II). The Freundlich isotherm K _f was 1.4 for Pb(II) and 1.8 for Cu(II), indicating a preferential sorption of Cu(II) onto the biosorbent. Adsorption capacity was found to decrease with an increase in particle sizes. Sorption occurred by physical mechanisms and was mainly controlled by intraparticle diffusion.     

Leachability and metal-binding capacity in ageing landfill material

In order to study the stability of landfilled heavy metals, landfill material from a combined household and industrial waste landfill was aerated for 14 months to simulate the natural ageing processes as air slowly begins to penetrate the landfill mass. During aeration, the pH of the landfill material decreased from around 8.6 to 8.1 and the carbon content also decreased. In order to investigate the possible fate of metals in ageing landfills, a four-stage sequential extraction technique was applied. The ability of the materials to bind metal ions by electrostatic attractions and to form stronger complexes was studied separately. The amount of exchangeable cations, the capacity to bind metal ions by electrostatic attraction and the capacity of the landfill material to complex copper ions were increased by the aeration process. However, results from the sequential analysis showed an increased solubility of sulphur and some metals (Cd, Co, Cu, Ni and Zn). Equilibrium speciation models (Medusa) indicated that the organic matter deposit had a significant capacity to bind metal ions provided that pH was sufficiently high. However, as carbonates are consumed over time, the risk for metal mobility increases. Therefore, the landfills can become an environmental risk, depending on variations in the solubility of metal ions due to changes in pH, redox status and the availability of organic material.     

磁性纳米γ-Fe2O3/SiO2去除水中亚甲基蓝

以纳米γ-Fe₂O₃为磁性介质制备了磁性纳米γ-Fe₂O₃/SiO₂，并将其用于水中亚甲基蓝的吸附。表征结果显示：制备的γ-Fe₂O₃/SiO₂呈不规则核壳结构，平均粒径为38 nm，比表面积为74.35 m²/g，比饱和磁化强度为55 A·m²/kg。实验结果表明：γ-Fe₂O₃/SiO₂对亚甲基蓝的吸附适宜在中碱性条件下进行，4 h即可达吸附平衡;在初始亚甲基蓝质量浓度为180 mg/L、γ-Fe₂O₃/SiO₂加入量为2 g/L、初始溶液pH为7.0、吸附温度为298 K的条件下，吸附量最高为25.4 mg/g;共存金属离子会降低吸附效率，而少量的腐殖酸则会促进吸附;吸附过程符合准二级动力学方程，颗粒内扩散不是唯一的控速步骤;等温吸附满足Langmuir模型，该吸附是一个物理吸附过程;用乙醇洗涤的γ-Fe₂O₃/SiO₂重复使用4次时仍能保持约80%的原吸附量。     

Chemical Composition and Acidity of Rain at the Gulf of Iskenderun,North-East Mediterranean

The purpose of the present work was to investigate the chemistry of rain in the Gulf of Iskenderun, North East Mediterranean, Turkey. The Gulf region has a large number of industries. Main industries existing in the region are iron and steel works, fertilizer plants, a cement plant, and several medium and mini size steel mills in addition to the international pipe line terminals. This study aims to apportion the local sources contributing to the overall pollution of the region. To this end a precipitation sampling program was started in January 2000, and over 48 precipitation samples were collected from each of 5 stations located at Iskenderun city center, Iskenderun industrial zone, Payas city center, the campus of Iskenderun Technical College and the campus of Mustafa Kemal University. Samples were analysed for pH, NO₃ ⁺, Cl^-. Ca, Al, Ba, Na, Cd, Co, Cr, Cu, Pb, Li, Mg, Mn, Ni, Zn, Fe, K. Concentrations of metal ions were determined by ICP-AES. NO₃ ^- ions and pH were determined by using NO₃ ^- selective electrode and pH meter, respectively.pH values of the collected samples at the industrial zone and at Payas city center, ranged between 5.02 and 7.38, respectively. NO₃ ^- and metal ions concentrations were highly variable. Concentrations of Ca and Fe ions were higher in the industrial zone and Payas city center. In the other three stations, concentrations of metal ions and NO₃ ^- ion were lower than that of industrial zone and the values of pH ranged between 6 and 7.4. The average pH values at Iskenderun Gulf showed that the precipitation was not acidic, because of the high concentration of Ca. The highest concentrations of Na and Cl ions were recorded in the University campus because the campus is located by the Mediterranean Sea.     

Adsorption Efficiency of Polyaspartate-Montmorillonite Composite Towards the Removal of Pb(II) and Cd(II) from Aqueous Solution

The selective modification of sodium montmorillonite (Na⁺-Mt) surface with polyionene followed by poly (succinimde-co-aspartate) has been considered. Na⁺-Mt was allowed to react with well characterized polyionene in two fold excess. The resulting polyionene/Mt (IC) was further modified with poly (succinimide-co-aspartate) through an ion exchange process. The obtained polyaspartate/Mt (IPS) composite was characterized by elemental analysis, X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and BET surface analyzer. The adsorption efficiency of IPS composite was investigated for the removal of Pb(II) and Cd(II) from aqueous solution under different experimental conditions including initial metal ions concentration, temperature and single and binary mixture systems of metal ions. The experimental data were analyzed by Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models. Langmuir model reveals that the monolayer adsorption capacity of IPS was 92.59 and 67.57 mg/g for Pb(II) and Cd(II), respectively. The modification of parent Na⁺-Mt enhanced their adsorption capacity by about 87.91 and 29.84% for Pb(II) and Cd(II), respectively, due to inclusion of extra active sites of polyaspartate. The mean sorption energy, E calculated from Dubinin–Radushkevich isotherm were 2.75 and 1.98 kJ/mol for the adsorption of Pb(II) and Cd(II), respectively, indicating physical adsorption process. Also, The thermodynamic parameters were calculated and indicated that the adsorption was spontaneous and exothermic process. The mechanism of cation exchange and complexation of metal ions was suggested. IPS composite has a considerable potential for the removal of heavy metal ions from aqueous solution and wastewater stream.