微塑料富集金属铅元素的能力与特征分析

以微塑料为载体,考察了其对溶液中铅离子的富集能力。首先利用2%HNO_3为解吸溶液,并用超声波仪进行辅助解吸,然后用电感耦合等离子体质谱仪(ICP-MS)测定其吸附的铅含量,从而研究微塑料吸附铅离子的能力。对微塑料的材质、吸附时间、粒径、离子浓度、选择性以及共存离子等进行了考察,分析了微塑料吸附铅离子的特征。实验结果表明:不同材质的微塑料对铅离子的吸附能力不同,其中聚氯乙烯(PVC)、聚丙烯(PP)吸附量最高,分别达到1.32μg/g和0.63μg/g。微塑料粒径越大,其对铅离子的吸附量越低。随着吸附时间和铅离子浓度的增加,微塑料对铅离子的吸附效率出现先升后降的趋势。共存离子实验表明,当溶液中存在其他离子时,不同材质的微塑料对铅离子的吸附能力受到不同程度的影响,当铅离子和铜离子共存时,2种离子存在竞争性吸附现象。该文探索了微塑料对铅离子的吸附特性,可为深入研究海洋中微塑料富集重金属及其环境行为提供理论基础。     

稻壳制备多孔炭对肌酐的吸附

研究了具有高比表面积稻壳基多孔炭(简称RHC)对人体内代谢产物肌酐(简称CR)的吸附, 将采用氢氧化钠活化稻壳制备的四种多孔炭和二种商业活性炭对肌酐的吸附进行了对比, 同时考察了盐酸、硝酸和双氧水对多孔炭进行表面处理及其经过高温处理(800 ℃)后对肌酐的吸附. 结果表明稻壳基多孔炭对肌酐的吸附超过商业炭,经过表面处理后多孔炭的吸附能力增强, 无氧化性盐酸处理后的多孔炭对肌酐的吸附量最大, 氧化性最强的硝酸处理后的多孔炭对肌酐的吸附量最小, 双氧水居中, 高温处理后的多孔炭吸附能力有所降低. 实验证实了多孔炭对CR的吸附符合Freundlich方程.     

交联羧甲基壳聚糖对铅离子的吸附研究

以壳聚糖为原料,先在氨基上引入羧甲基制备出N-羧甲基壳聚糖,再和环氧氯丙烷发生交联反应,合成出新型交联羧甲基壳聚糖,FTIR表征其结构。研究了交联羧甲基壳聚糖对Pb2+的吸附性能,探讨了交联剂用量、铅离子溶液的pH值、温度、吸附时间等因素对其吸附性能的影响,并考察了交联羧甲基壳聚糖对铅离子吸附动力学和热力学实验。实验结果表明,交联羧甲基壳聚糖对铅离子的吸附量优于壳聚糖,平衡吸附量可达297.6 mg/g。交联羧甲基壳聚糖对铅离子的吸附符合准二级动力学模型和Langmuier等温吸附,吸附主要依靠结构中的羧基和氨基基团。     

不同炭吸附材料对溶液中Pb^2＋的吸附性能比较

为比较不同炭吸附材料木炭、竹炭、改性木炭和改性竹炭对溶液中铅（Ⅱ）的吸附性能,研究了pH值、吸附剂用量、吸附平衡时间等因素对吸附量的影响。动力学研究表明,它们对铅（Ⅱ）的吸附均可用准一级动力学方程描述,测定了不同炭对铅（Ⅱ）吸附的表观速率常数,Freundlich等温吸附模型能较好地描述吸附过程;以我国饮用水标准中铅的限值0．05mg／L为标准,研究了一定质量浓度及一定量含铅废水处理时,所需吸附剂投料量的估算方法和实验验证结果,结果表明,控制合适的吸附条件,竹炭能较完全有效地除去废水中的铅。     

杯芳烃修饰玻碳电极吸附溶出伏安法测定微量铅

研究了以杯芳烃衍生物修饰玻碳电极,以其吸附溶出伏安法测定微量铅。对富集时间、铅的浓度、支持电解质、样品溶液pH值及部分离子干扰等进行了实验。实验发现以氢氧化钠溶液处理修饰电极可提高测定灵敏度,经过优化处理后,线性范围和检出限分别为5.0×10-7～1.0×10-5mol/L和1.0×10-8mol/L。应用本法对合成水样进行了测定,结果满意。本文还对吸附溶出机理进行了讨论。     

钛酸盐纳米管与二硫化碳修饰钛酸盐纳米管的合成、表征及其去除重金属离子性能

在水热法制备钛酸盐纳米管的基础上, 通过形成黄原酸基反应合成了CS2修饰的钛氧纳米管. 采用粉末X射线衍射(XRD)、透射电镜(TEM)、红外光谱(FTIR)和拉曼光谱(Raman)等技术对产物进行了表征. 以水溶液中铅离子、铜离子和银离子作为目标重金属离子, 分别用纯钛酸盐纳米管和CS2修饰后的钛氧纳米管对其进行反应和吸附, 通过一系列对比性实验, 评价了不同形式纳米管去除重金属的能力. 实验结果表明, 与文献报道的吸附剂对重金属离子的吸附量相比, 纯钛酸盐纳米管和CS2修饰的钛氧纳米管吸附重金属离子的容量非常大, 尤其是经CS2修饰后的钛氧纳米管去除铅离子的能力明显增强, 它们去除重金属离子的能力还与重金属盐的阴离子、溶液的pH值相关. 在相同的pH条件下, 钛酸盐纳米管去除铅离子、铜离子和银离子的能力分别为599.37, 163.22和474.73 mg/g; CS2修饰的钛氧纳米管去除铅离子、铜离子和银离子的能力分别为663.37, 160.21和423.05 mg/g.     

氧化多壁碳纳米管对Pb~(2+)的吸附性能研究

该文研究了氧化多壁碳纳米管(o-MWNTs)对Pb2+的吸附性能,考察了平衡时间、溶液pH值、溶液体积等因素对吸附行为的影响。在静态吸附条件下:Pb2+能大量并快速地被o-MWNTs吸附,45 min内即可达到吸附平衡,而活性炭(ACs)的吸附平衡时间为90 min。溶液pH值在1.0~7.0范围对吸附量有显著影响,在pH5.0~6.0时o-MWNTs对Pb2+的静态吸附容量为17.43 mg.g-1。o-MWNTs对铅离子的吸附量随着溶液体积的增加而增加,并逐渐趋于稳定,最大吸附量可达25 mg.g-1。在动态吸附实验中,30 mg.L-1的铅离子溶液在SPE小柱的穿透体积为235 mL,溶液体积为400 mL时可完全穿透。动态吸附实验表明,o-MWNTs对铅离子具有较大的吸附容量且萃取回收率高达94%。研究表明,氧化碳纳米管装填的固相萃取小柱可用于中药提取物中Pb2+的残留分析。     

铅离子印迹聚合物的制备表征及其吸附性能研究

以铅离子为模板,壳聚糖为功能单体,采用分子印迹技术,加入交联剂环氧氯丙烷,合成了铅离子印迹的交联壳聚糖。通过红外光谱对铅离子交联壳聚糖进行了结构表征,通过扫描电镜对其形态结构进行表征。研究了不同条件下交联壳聚糖对铅离子的吸附性能,结果表明,当溶液p H=4.5时,交联壳聚糖对溶液中铅离子的吸附效率较高。吸附在交联壳聚糖上的铅离子可用0.1mol·L的EDTA溶液洗脱,洗脱率达82.73%。利用原子吸收分光光度法对印迹聚合物的最大吸附量进行了研究,结果表明,所合成的模板交联壳聚糖分子印迹聚合物对铅离子具有良好的吸附性;对印迹聚合物的选择性吸收进行研究,研究表明,印迹聚合物对铅离子的选择性好,能用于水溶液中除去铅离子。     

新型黄原酸壳聚糖对铅离子的吸附及机理研究

以壳聚糖为原料,先合成O-羧甲基壳聚糖,再和二硫化碳反应制备出新型黄原酸壳聚糖,使用元素分析、FT-IR、UV和TG对其结构进行表征。比较了壳聚糖、O-羧甲基壳聚糖和黄原酸壳聚糖对铅离子的吸附能力,并研究黄原酸壳聚糖对水溶液中铅离子的吸附性能,探讨了铅离子溶液的pH值对吸附的影响和黄原酸壳聚糖对铅离子的吸附热力学。结果表明,黄原酸壳聚糖对铅离子吸附量是壳聚糖的8.37倍,平衡吸附量可达600.6mg/g。XPS表明,吸附过程主要通过吸附剂中的氨基、羧基和黄原酸基团与铅离子发生作用完成。     

基于非线性拟合的污泥衍生吸附剂对铅子等温吸附特性研究

利用城市污水厂污泥制取污泥衍生吸附剂，对溶液中铅离子进行吸附实验，研究一定条件下的等温吸附特性。利用线性拟合和非线性拟合两种方法对等温吸附方程进行模拟，得到非线性拟合求得的模型参数比较可靠，同时得到Langmuir模型比Freundlich方程更适合于描述铅离子在污泥衍生吸附剂表面上的吸附行为。     

Removal of lead ions in drinking water by coffee grounds as vegetable biomass

In an attempt to reuse food waste for useful purposes, we investigated the possibility of using coffee grounds to remove lead ions from drinking water. We studied the lead ion adsorption characteristics of coffee beans and grounds by measuring their fat and protein content, adsorption isotherms for lead ions, and adsorption rates for lead ions. The number of lead ions adsorbed by coffee grounds did not depend on the kind of coffee beans or the temperature at which adsorption tests were performed. The rate of lead ion adsorption by coffee grounds was directly proportional to the amount of coffee grounds added to the solution. When coffee grounds were degreased or boiled, the number of lead ions decreased. When proteins contained in coffee grounds were denatured, the lead ion adsorption was considerably reduced. The lead ion adsorption capacity of coffee grounds decreased with increased concentration of perchloric acid used for treating them and disappeared with 10% perchloric acid. The experiments demonstrated that proteins contained in coffee beans depend upon the adsorption of lead ion. The present study gave an affirmative answer to the possibility of using coffee grounds, an abundant food waste, for removing lead ions from drinking water.     

Thermal decomposition study on Jatropha curcas L. waste using TGA and fixed bed reactor

Pyrolysis experiments on Jatropha curcas L. (physic nut) waste were carried out using thermogravimetric analysis (TGA) and a fixed bed quartz reactor to determine suitable degradation model as well as investigate the effect of operating conditions on product distribution. It was found that the main thermal decomposition of physic nut waste generally occurred over the temperature range of 250–450 °C. The three-parallel reactions model was applied for simulating the degradation of this waste. The model agreed relatively well with the experimental data. From the model, the activation energy of hemicelluloses, cellulose and lignin was in the range of 41–68, 187–235, and 97–150 kJ/mol, respectively. Reaction orders of those fractions were in the range of 2.4–3.2. Results from pyrolysis process using fixed bed reactor indicated that increase in temperature and hold time lead to greater production of hydrogen, methane and light hydrocarbons with highest gas production detected at 900 °C. Tar decomposed at higher temperatures resulted in lower liquid yield while gas yield and total conversion increased. Liquid product consists of several fatty acids such as palmitic acid, stearic acid, and oleic acid in the range of 10–23%, 5–12%, and 35–42%, respectively. The amount of char residue decreased with increasing reactor temperature and hold time. Fixed carbon in char increased with temperature with the expense of volatile matter while there was little change on ash content. Generally, pyrolysis of this residue may be applied for the production of value-added products as well as fuels after some upgrading processes.     

PVA/DTC纳米纤维的制备及对铅离子的吸附行为

通过高压静电纺丝技术制备了聚乙烯醇/聚乙烯亚胺(PVA/PEI)纳米纤维膜, 对纤维膜进行功能化使其转化为对重金属离子具有高络合能力的聚乙烯醇/二硫代氨基甲酸盐功能化聚乙烯亚胺(PVA/DTC)纳米纤维膜. 研究了PVA/PEI纳米纤维膜的交联和功能化以及PVA/DTC纤维膜对铅离子的吸附行为. 结果表明, 高压静电纺丝法可制备出纤维直径分布均匀、 形貌良好的纳米纤维膜, 且交联、 功能化后仍能保持蓬松纳米纤维状的网状结构. PVA/DTC纳米纤维膜对铅离子吸附速率快, 吸附量容量高, 且具有良好的再生吸附能力, 是一种潜在的重金属离子高效吸附材料.     

Adsorption of fluoride ions onto carbonaceous materials

The characteristics of fluoride ion adsorption onto carbonaceous materials were derived as adsorption isotherms at different temperatures and in different pH solutions. The fluoride ion was adsorbed into pores in carbonaceous materials produced from wood; the larger the specific surface area, the more fluoride ions adsorbed. Bone char was the most effective adsorbent. The composition of bone char includes calcium phosphate, calcium carbonate, and so on. This suggests that the phosphate ion in bone char was exchanged with a fluoride ion. Moreover, the mechanism of fluoride ion adsorption onto bone char is clearly chemical in nature because the amount of fluoride ion adsorbed onto bone char increased with increasing temperature and decreasing pH. The amount of fluoride ion adsorbed onto bone char was also shown to depend on the concentration of sodium chloride in solution because of the "salting-out" effect. The adsorption of fluoride ion onto bone char is endothermic. Bone char can be utilized to remove fluoride ions from drinking water.     

Kinetic,mechanism and equilibrium studies on removal of Pb(II) using <Emphasis Type="Italic">Citrus limettioides</Emphasis> peel and seed carbon

The sorption behaviour of Pb(II) ions onto activated carbon prepared from Citrus limettioides peel (CLPC) and seed (CLSC), which is a novel waste material, was evaluated as a function of contact time, pH, adsorbent dose, ionic strength, initial metal ion concentration and temperature in batch adsorption processes with raw Citrus limettioides peel (CLP) and seed (CLS). The maximum uptake of lead(II) ions was obtained at pH range 4.0–6.0 for CLPC, CLSC and 5.0–6.0 for raw materials (CLP, CLS). The optimal contact time was found to be 3 h. Surface morphology and functionality of the adsorbent were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis and Fourier-transform infrared (FT-IR) spectroscopy. The equilibrium data fit well with the Langmuir isotherm, confirming monolayer coverage of lead(II) ions onto CLP, CLPC, CLS and CLSC. The Langmuir monolayer adsorption capacity of CLP, CLPC, CLS and CLSC was found to be 123.60, 166.67, 15.32 and 142.86 mg/g. The calculated thermodynamic parameters showed that the sorption process was feasible, spontaneous and exothermic in nature. Kinetic studies demonstrated that adsorption of lead(II) ions followed a pseudo-second-order equation, suggesting that the adsorption process is presumably chemisorption. The adsorbents were tested for removal of Pb(II) from electroplating wastewater in connection with the reuse and selectivity of the adsorbents.     

Adsorption of Cu(II) ions from aqueous solution by hazelnut husk activated carbon prepared with potassium acetate

Hazelnut husk (HH), an agricultural waste, was converted to carbonaceous material by chemical activation using potassium acetate. The produced activated carbon (KAHHAC) was characterized by FTIR, SEM, N₂ adsorption–desorption experiments, CHN elemental analysis, and determination of moisture, ash, and point of zero charge. KAHHAC was used for the batch adsorption of Cu(II) ions from aqueous solutions. Optimum pH and contact time were found to be 5.0 and 240 minutes, respectively. The adsorption equilibrium data were described well by the Langmuir equation providing 105.3?mg?g^?1 Cu(II) adsorption capacity. The pseudo-second-order model successfully described the kinetic of Cu(II) adsorption by KAHHAC. The adsorbed Cu(II) onto KAHHAC was completely desorbed by 0.5?M nitric acid. In conclusion, HH activated carbon (AC) produced by the potassium acetate activation method is a very useful and efficient sorbent material for the removal of Cu(II) from aqueous solution.     

Time-dependent ion selectivity in capacitive charging of porous electrodes

In a combined experimental and theoretical study, we show that capacitive charging of porous electrodes in multicomponent electrolytes may lead to the phenomenon of time-dependent ion selectivity of the electrical double layers (EDLs) in the electrodes. This effect is found in experiments on capacitive deionization of water containing NaCl/CaCl(2) mixtures, when the concentration of Na(+) ions in the water is five times the Ca(2+)-ion concentration. In this experiment, after applying a voltage difference between two porous carbon electrodes, first the majority monovalent Na(+) cations are preferentially adsorbed in the EDLs, and later, they are gradually replaced by the minority, divalent Ca(2+) cations. In a process where this ion adsorption step is followed by washing the electrode with freshwater under open-circuit conditions, and subsequent release of the ions while the cell is short-circuited, a product stream is obtained which is significantly enriched in divalent ions. Repeating this process three times by taking the product concentrations of one run as the feed concentrations for the next, a final increase in the Ca(2+)/Na(+)-ratio of a factor of 300 is achieved. The phenomenon of time-dependent ion selectivity of EDLs cannot be explained by linear response theory. Therefore, a nonlinear time-dependent analysis of capacitive charging is performed for both porous and flat electrodes. Both models attribute time-dependent ion selectivity to the interplay between the transport resistance for the ions in the aqueous solution outside the EDL, and the voltage-dependent ion adsorption capacity of the EDLs. Exact analytical expressions are presented for the excess ion adsorption in planar EDLs (Gouy-Chapman theory) for mixtures containing both monovalent and divalent cations.     

The adsorption of alkylpyridinium chlorides and their effect on the interfacial behavior of quartz

This research was directed at understanding cationic surfactant adsorption phenomena on wet-ground natural quartz, mainly with dodecylpyridinium chloride as the model surfactant. How these surfactant ions adsorb at the interface was delineated through measurements of adsorption isotherms, zeta potentials, suspension stability, contact angles, induction times, and flotation response. Hydrocarbon chain association of adsorbed surfactant ions (or self-association) leads to four distinct adsorption regions as the concentration of surfactant is increased in solution. The same four regions manifest themselves in the behavior of all of the interfacial processes studied. At low concentrations, adsorption is controlled primarily by electrostatic interactions, but when the adsorbed surfactant ions begin to associate into hemimicelles at the surface, hydrophobic chain interactions control the adsorption process. The results of experiments with alkylpyridinium chlorides of 12, 14 and 16 carbon atoms can be normalized in terms of their CMCs, which clearly show that surface aggregation phenomena are driven by the same hydrophobic interactions that lead to micelle formation in bulk solution.     

Waste cigarette filters: activated carbon as a novel sorbent for uranium removal

Uranium is important in the nuclear fuel cycle as both as an energy source and as radioactive waste. Herein, activated carbon (AC) prepared from waste cigarette filters by convenient carbonization and functionalization was chosen as the raw materials for radionuclides adsorption. Batch adsorption experiments showed that AC presented comparable UO₂²⁺ adsorption capacity (106 mg g^?1) and very outstanding selectivity. The adsorption process accorded with Langmuir model and the pseudo-second-order kinetics model well. This work combines the waste cigarette filters with the radioactive nuclear treatment materials, which may provide a new strategy for the future treatment of waste cigarette butts.

     

Adsorption of Cr(VI) from aqueous solutions by HNO3-purified and chemically activated pyrolytic tire char

Pyrolytic tire char adsorbents either demineralized by nitric acid (purified char, PC) or activated with KOH-calcination (activated char, AC) were used for Cr(VI) removal from aquatic solutions and studied by adsorption kinetics, isotherms, and thermodynamics. Adsorbent’s physicochemical characteristics were studied by several techniques such as X-ray diffraction, porosimetry, scanning electron microscopy, elemental analysis, and Boehm titration. For PC, acid treatment leads partially to a mesoporous structure while for AC, KOH activation creates also a microporosity enhancing the specific surface area at 443 m²g^?1. Cr(VI) adsorption onto both adsorbents followed better second-order kinetics and Langmuir isotherm models and it was exothermic (ΔH < 0) and spontaneous (ΔG < 0). The maximum Cr(VI) adsorption capacity for AC and PC was 114 and 79.47 mg g^?1, respectively, at pH = 4. The present work reveals that AC and PC can be efficient sorbents for the removal of heavy metal ions, contributing both positively to wastewater treatment and waste tire pyrolysis plants.