Studies of Adsorption of Cadmium Ions by Biowaste Adsorbent from Aqueous Solutions with Ion-Selective Electrodes and ICP-OES

Using environment-friendly and low-cost biowaste adsorbents as toxic metal ion removal substrates from aqueous solutions has a great economic advantage. This work evaluated pumpkin and potato peel biowastes for the adsorption of cadmium ions. The biowastes were treated with acid or base. Batch experiments were carried out by introducing a known concentration of metal ion solution into the biowaste sorbent at various pH levels. The pH and metal ion concentration was monitored with pH and cadmium ion-selective electrode continuously for two hours, and the final concentration for the metal ion after 24 hours was measured with the cadmium electrode and then confirmed with ICP-OES. L-type isotherms were obtained that fit to Freundlich model. Adsorption isotherms showed chemical adsorption and the kinetics following the second order model. Equilibrium adsorption capacity is higher than 29 mg/g at pH 5.6 when the initial concentration is 220 ppm. Dynamic cadmium adsorption capacity is 17 mg/g from aqueous solution when the feed solution is 220 ppm with pumpkin peel biowaste sorbent. The biowaste materials can be regenerated with acid washing.

Removal of Cadmium Ions from Aqueous Solution by Silicate-incorporated Hydroxyapatite

This article reports a preliminary research on silicate-incorporated hydroxyapatite as a new environmental mineral used to remove cadmium ions from aqueous solutions. The silicate-incorporated hydroxyapatite was prepared by coprecipitation and calcining, and silicate was incorporated into the crystal lattice of hydroxyapatite by partial substitution of phosphate. The amount of cadmium ions removed by silicate-incorporated hydroxyapatite was significantly elevated, which was 76% higher than that of pure hydroxyapatite. But the sorption behavior of cadmium ions on silicate-incorporated hydroxyapatite was similar to that of pure hydroxyapatite. Morphological study revealed that silicate incorporation confined the crystal growth and increased the specific surface area of hydroxyapatite, which were in favor of enhancing the cadmium ion sorption capacity of the samples. Incorporation of silicate into hydroxyapatite seems to be an effective approach to improve the environmental property of hydroxyapatite on removal of aqueous cadmium ions.

STUDIES ON THE COMPETITION FOR CADMIUM ION BETWEEN CHELATING AGENTS AND BOVINE SERUM ALBUMIN

Eleven chelating agents were studied for their capabilities to mobilize the cadmium bound tp bovine serum albumin(BSA).The parameter F,which is defined as the ratio between the percentages of cadmium bound to BSA in the presence and absence of chelating agents,can be used as the criterion to evaluate the mobilizing capability of chelating agent.The F values determined experimentally lead to a mobilizing capability order:DTPA>EDTA>EGTA>NTA>TR1EN>PEN>CYS>HIS>SAThe polyaminopolycarboxylate type chelators mobilize cadmium effectively.A linear relationship was found between 1gF and lg k'CdL (conditional stability constant of the cadmium chelate).

Removal of cadmium ions from aqueous solution via micellar-enhanced ultrafiltration

To separate cadmium ions from aqueous solution efficiently, micellar-enhanced ultrafiltration(MEUF) of hollow ultrafiltration membrane was used, with sodium dodecyl benzene sulfonate (SDBS) and sodium dodecyl (sulfate) (SDS) as surfactants. The important parameters affecting the rejection of cadmium, the permeate flux and the secondary resistance were investigated, including surfactant species, surfactant concentration, operating time, trans-membrane pressure, the addition of electrolyte and solution pH. The results show that the rejection rate of cadmium reaches 97.8%. Trans-membrane pressure and the addition of electrolyte (NaCl) are less influential while surfactant species, surfactant concentration and pH value are important for micellar-enhanced ultrafiltration. The optimum concentration of surfactant is the critical micelle concentration, and SDBS is better than SDS. (Micellar-)(enhanced) ultrafiltration with SDBS can separate cadmium ions from aqueous solution efficiently.

Removal of lead and cadmium ions by single and binary systems using phytogenic magnetic nanoparticles functionalized by 3-marcaptopropanic acid

The present research study is focused on green fabrication of superparamagnetic Phytogenic Magnetic Nanoparticles(PMNPs), and then its surface functionalization with 3-Mercaptopropionic acid(3-MPA). The resulting material(i.e. 3-MPA@PMNPs) characterized by FTIR, powder XRD, SEM, TEM, EDX, VSM, BET and TGA techniques and then further employed for the investigation of the adsorptive removal of lead(Pb^2+) and cadmium(Cd^2+) ions from aqueous solutions in single and binary systems. The material showed fastest adsorptive rate(98.23%) for Pb^2+ and(96.5%) Cd2+within the contact time of 60 min at pH 6.5 in the single system. The experimental data were fitted well to Langmuir isotherm, indicated monolayer adsorption of both metal ions onto 3-MPA@PMNPs and an estimated comparable adsorptive capacity of 68.41 mg·g^-1(Pb2+) and 79.8 mg·g^-1(Cd2+) at p H 6.5. However, kinetic data agreed well with pseudo-second-order model, and indicated that the removal mainly supported chemisorption and/or ion-exchange mechanism. Thermodynamic parameters such asΔGo,ΔHo, and ΔSo, were-3259.20, 119.35 and 20.73 for Pb^2+, and-1491.10, 45.441 and 7.87 for Cd^2+ at temperature 298.15 K, confirmed that adsorption was endothermic, spontaneous and favorable. The material demonstrated higher selectivity of Pb2+ and its removal efficiency was(98.20 ± 0.3)% in binary system experiments. The material persisted performance up-to seven(07) consecutive treatment cycles without losing their stability and offered comparable fastest magnetic separation(35 s) from aqueous solutions. Therefore, it is recommended that the prepared material can be employed to remove toxic heavy metal ions from water/wastewaters and this "green" method can easily be implemented at large scale in low economy countries.

Alumina/Iron Oxide Nano Composite for Cadmium Ions Removal from Aqueous Solutions

Magnetic alumina nano composite (MANC) was prepared for combination of the adsorption features of nano activated alumina with the magnetic properties of iron oxides to produce a nano magnetic adsorbent, which can be separated from the medium by a simple magnetic process after adsorption. MANC was characterized using XRD, SEM, TEM, EDX and surface area (BET). Quantum design SQUID magnetometer was used to study the magnetic measurement. The present study was conducted to evaluate the feasibility of MANC for the removal of cadmium ions from aqueous solutions through batch adsorption technique. The effects of pH, adsorbent dose, temperature, contact time and initial Cd2+ concentration on cadmium ions adsorption were studied. Equilibrium data were fitted to Langmuir, Freundlich and Temkin isotherms. The equilibrium data were best represented by the Langmuir isotherm. The kinetic data were fitted to pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models, and it was found to follow closely the pseudo-second-order model. Thermodynamic parameters were calculated for the Cd2+ ion-MANC system and the positive value of ΔH° showed that the adsorption was endothermic in nature. Furthermore, a single-stage batch adsorber was designed for the removal of Cd2+ ions by MANC based on the equilibrium data obtained.

Modeling Date Palm Trunk Fibers (DPTF) Packed Bed Adsorption Performances for Cadmium Removal from Aqueous Wastewater

In this study,the potential of a low-cost bio-adsorbent,taken directly from Date Palm Trunk Fibers(DPTF)agricultural wastes,for cadmium ions removal from wastewaters is examined.The performances of this adsorbent are evaluated by building breakthrough curves at different bed heights and flow rates while keeping other parameters,such as the initial feed concentration,pH,and particle size,constant.The results indicate that the maximum cadmium adsorption capacity of DTPF can be obtained from the Thomas model as 51.5 mg/g with the most extended mass transfer zone of 83 min at the lowest flow rate at 5 ml/min.The saturation concentrations(NO)and the rate constant(kab)obtained from the BDST(bed depth service time)model are 7022.16 mg/l and 0.0536 l/mg.min,respectively.Using the Yon-Nelsen Model,it is found that operating at a lower flow rate leads to a larger value of the elapsed needed time to reach a 50%breakthrough.The Wolborska model indicates that the bed capacity increases with decreasing the flow rate,and the adsorbent can achieve a greater external mass transfer kinetic coefficient(2.271/min)at a higher flow rate.

Quantum Chemistry Study on Benzimidazoledithi Derivatives' Selective Pre-enrichment of Cadmium Cation

This work reports the mechanism of benzimidazoledithi(BDT) derivatives’ selective pre-enrichment of Cd2+under the stimulation of glutathione(GSH). The geometric and electronic properties of five BDT-M2+complexes(M = Cd, Cu, Hg, Pb, Co) have been investigated using density functional theory(DFT) at the B3 LYP/6-311 G(d,p) level with the GAUSSIAN 09 package program. The results show that BDT ligand exhibits alternative behaviors to different metal ions with the binding affinity in the order of Cu2+> Cd2+> Pb2+> Hg2+> Co2+. After adding the BDT-M2+complex into the GSH solution, the new S–S bonds can be formed, resulting with benzimidazole-metal ions(MBI-M2+) falling off into the GSH solution. Furthermore, the weak interaction between the new glutathione derivative(GSHD) and MBI-M2+were found. However, the strong chelation was detected between GSHD and MBI-M2+(M = Cu, Pb, Hg, Co) to hinder the adsorbed Cu2+, Pb2+and Hg2+, Co2+completely falling into the GSH solution, which suggests porous silicon composite modified by BDT has a certain selective pre-enrichment of Cd2+ion.

等温滴定量热法研究镉离子与GMP的亲合机理

利用等温滴定量热法研究镉离子与鸟嘌呤核糖核苷酸(GMP)的亲合过程,重点分析不同比例的镉离子和GMP结合时的异同,实验结果显示:(1)镉离子和GMP的浓度比不同会对二者的结合过程产生显著影响,在低浓度比下,反应为焓驱动的放热反应;在高浓度比下,反应为吸热反应。从镉离子和GMP浓度比为20∶1时的ITC滴定曲线和OneSite模型拟合结果可知,镉离子和GMP是接近并按照1∶1的比例结合的,二者的亲合力K值为1.21E 4±2.26E 3。(2)推测GMP与镉离子有两个结合位点,一个为放热结合位点,一个为吸热结合位点,在低浓度比下,只有放热结合位点发生结合。当浓度比到达一定值后,会激活吸热结合位点,同时发生吸热结合和放热结合。因为吸热结合位点的结合能力更强,最终可能呈现为吸热反应。(3)通过反滴法和正滴法的比较,同一浓度下,不同的滴加方式也会对结合结果造成较大的影响。该研究所采用的方法可以很好地从宏观的热力学角度分析金属镉离子与GMP的亲合机理,以期为后续镉离子印迹物制备过程中功能单体的筛选提供重要的试验基础和理论指导。

抗生素和重金属镉单一和复合污染对集胞藻PCC6803的影响

为评估抗生素和重金属对藻类生态系统的影响,本研究探讨了四环素(tetracycline,TC)/磺胺甲噁唑(sulfamethoxazole,SMX)与Cd^(2+)的4个单一处理(100 ng/L TC;100 ng/L SMX;0.001 mg/L Cd^(2+);0.5 mg/L Cd^(2+))以及4个复合处理(100 ng/L TC+0.001 mg/L Cd^(2+);100 ng/L TC+0.5 mg/L Cd^(2+);100 ng/L SMX+0.001 mg/L Cd^(2+);100 ng/L SMX+0.5 mg/L Cd^(2+))对集胞藻的生长、光合活性以及抗氧化系统的影响。结果显示,100 ng/L SMX刺激集胞藻的生长和光合活性,而用100 ng/L TC处理则无明显影响;0.001 mg/L Cd^(2+)对集胞藻的各项指标均无明显影响,但0.5 mg/L Cd^(2+)明显抑制集胞藻的生长和光合作用,破坏抗氧化系统,损伤细胞膜,刺激集胞藻分泌胞外多糖。抗生素与镉复合污染处理方面,100 ng/L TC与0.001 mg/L Cd^(2+)共存时,增强集胞藻酯酶活性、刺激分泌胞外多糖;100 ng/L SMX与0.001 mg/L Cd^(2+)共存时,促进集胞藻生长、增强光合作用和酯酶活性;100 ng/L SMX与0.5 mg/L Cd^(2+)共存时,SMX能缓解高浓度Cd^(2+)造成的氧化损伤,较单一高浓度Cd^(2+)处理组的ROS产量减少、SOD酶活降低、MDA含量降低、协同刺激集胞藻酯酶活性;而100 ng/L TC不能显著缓解高浓度Cd^(2+)对细胞的损伤。研究结果表明,低浓度四环素对细胞生长影响较小,也基本不改变Cd^(2+)对集胞藻细胞的毒性,而低浓度磺胺甲噁唑会促进细胞生长,且能够减轻Cd^(2+)对集胞藻细胞的毒性,在污染评估时需综合考虑抗生素和重金属的复合污染。

阳极溶出伏安法测定微量镉实验的课程思政设计

阳极溶出伏安法测定微量镉是一项经典的仪器分析基础实验。然而,该实验项目的传统教学内容较难使学生体会所学知识对实际生产生活的价值,不能有效落实课程思政建设的要求。本文旨在通过对教学内容的创新设计,更好地实现思政育人目标。引导学生对新闻事件、学科发展历史、科学家的故事和行业发展最新动态进行调研与讨论,增加设计性和探索性内容,提高本实验的高阶性。采用实际购得的大米等粮食替代以往预先配制的镉溶液,并采用自己独立制备的汞膜电极替代商业化的极谱仪电极,使学生在巩固实验操作技能的基础上,了解分析仪器的发展及改造方式,并掌握分析化学的基本研究范式。对本实验内容的优化,有助于培养学生的科学精神与科研素养,使学生体会专业知识对解决实际生产生活问题的意义,帮助其树立职业追求目标并养成良好的社会责任意识。

Sorption of Heavy Metal and Organic Pollutants on Modified Soils

Sorption characteristics of both an organic pollutant (phenol) and a heavy metal (cadmium ion) on the clay layer of a Lou soil (Eum-orthic Anthrosol in Chinese Soil Taxonomy) along with the sorption mechanism were investigated using three soil treatments: modification with a cationic surfactant cetyltrimethylammonium bromide added at an amount equivalent to 50% and 100% of the soil CEC (50%CB and 100%CB), modification with an amphoteric surface-modifying agent dodecyldimethylbetaine (commercially known as BS-12) added at an amount equivalent to 50% and 100% of the soil CEC (50% BS and 100%BS), and an unmodified control (CK). Results showed that the BS soil treatments increased sorption of both the heavy metal Cd2+ and the organic pollutant phenol. The equilibrium sorption amount of Cd2+ decreased in the order: 50%BS > 100%BS > CK > 50%CB > 100%CB, with the BS soil treatments being about 1.3 to 1.8 times higher and the CB soil treatments about 23% to 41% lower than CK. Both the single-site and two-site Langmuir models could be applied to describe the sorption of Cd2+ in each soil treatment. The equilibrium sorption amount of phenol on the soil samples decreased in the order: 100%CB > 50%CB > 100%BS > 50%BS > CK, with the CB soil treatments being 41.0 to 79.6 times higher and the BS soil treatments 4.0 to 8.3 times higher than CK. The Freundlich equation could also be used to describe the sorption characteristics of phenol. In the BS soil treatments, both an organophobic long carbon chain and hydrophilic charged groups resulted in a relatively strong sorption ability for both heavy metals and organic pollutants. In addition, the sorption ratio K, the ratio of phenol sorption amount of the modified soil to that of CK, increased initially and decreased later with the amount of phenol added, and the critical sorption ratio KC, the peak value of the sorption ratio curve plotted against the added phenol concentration, was a good index for evaluating the sorption ability of phenol in the soil.

镉离子微波钟研究进展

基于囚禁离子的微波原子钟在小型化及可移动方面具有优势,因而受到广泛关注。其中,113 Cd+离子因其所需激光数量少,基态超精细能级分裂大等优势,成为新一代实用离子微波钟的主要候选离子。近几十年来,国内外多个实验团队开展了镉离子微波钟的研究工作。本文按照时间顺序,详细介绍了国内外不同实验团队在镉离子微波钟研究方面采用的技术路线及最新进展。

Fe_(3)O_(4)基核壳纳米结构材料的制备及顺磁性研究

以Fe_(3)O_(4)为磁核,SiO_(2)为外壳,制备了Fe_(3)O_(4)@SiO_(2)核壳纳米结构材料,使用三乙氧基硅烷对Fe_(3)O_(4)@SiO_(2)进行表面亲水改性,研究了亲水改性对Fe_(3)O_(4)@SiO_(2)顺磁性能和催化性能的影响。结果表明:立方相结构的Fe_(3)O_(4)是核壳材料中主要的晶体相,表面的SiO_(2)为非晶态,表面亲水处理后未改变Fe_(3)O_(4)@SiO_(2)的晶格结构,Fe_(3)O_(4)@SiO_(2)为80~110 nm的不规则颗粒状,SiO_(2)包覆在Fe_(3)O_(4)外部,亲水处理后改善了颗粒的分布均匀性。亲水处理的Fe_(3)O_(4)@SiO_(2)的饱和磁化强度降低至20.31 emu/g,具有超顺磁性。以含Cd^(2+)的金属废水为吸附降解对象,表面亲水处理后的Fe_(3)O_(4)@SiO_(2)去除率提高至94.2%,二级动力学模型更适合于Fe_(3)O_(4)@SiO_(2)对Cd^(2+)的吸附,模型的相关系数为0.9943,拟合效果更好,表明了Fe_(3)O_(4)@SiO_(2)对Cd^(2+)的吸附速率受化学吸附的影响较大。

循环伏安法测定氯化铵镀镉溶液中镉离子浓度

以玻碳电极作为工作电极,采用三电极体系建立了循环伏安法测定氯化铵镀镉溶液中Cd^(2+)浓度的电化学分析方法。系统分析了电位扫描范围、测定体系pH和扫描速率对于氯化铵镀镉液中Cd^(2+)浓度测试的影响,并予以优化。在优化后的测试条件下建立Cd^(2+)浓度与氧化峰电流之间的关系曲线为I_(p)=0.164x-2.238(R^(2)=0.995)。结果表明,循环伏安方法的相对标准偏差RSD小于1%,加标回收率在98%~110%之间,对共存组分的干扰研究表明,Fe^(3+)、Co^(2+)和Cu^(2+)对于Cd^(2+)测试结果的影响较小。

纳米氧化锌溶解性及共存镉离子的影响

纳米ZnO是应用最为广泛但具有一定生物毒性的金属型纳米颗粒之一,其致毒机制之一可能来自其溶解释放的锌离子。共存重金属离子可能会影响纳米ZnO的溶解,反之,纳米ZnO可能吸附去除重金属离子,但是其相关作用尚不清楚。文章通过批试验探讨了不同纳米ZnO投加量(200、400、1000和2000 mg/L)在不同震荡时间(12、24和36 h)时纳米ZnO的溶解性及共存镉离子的影响。结果表明,去离子水中纳米ZnO投加量1000 mg/L时锌的溶出量最大(3.71 mg/L),但不受震荡时间的影响。添加1 mg/mL的镉离子显著增加了纳米ZnO的溶解,在纳米ZnO投加量为200 mg/L时,锌离子的溶出量和溶出率高达95 mg/L和55%;增加纳米ZnO投加量降低锌离子含量和溶出率,但增加震荡时间没有增加其溶解性。同时,纳米ZnO能够降低镉离子浓度,说明纳米ZnO可以吸附水中的镉离子。总之,共存镉离子能够改变纳米ZnO的环境行为,并可能因而影响其生物毒性。

Cd^(2+)浓度对好氧颗粒污泥EPS各组分形成的影响

为探究重金属Cd^(2+)对好氧颗粒污泥系统运行的影响,采用紫外分析法和三维荧光光谱分析法研究了SBR反应器中不同浓度的重金属Cd^(2+)对好氧颗粒污泥EPS总量以及各组分(LB-EPS、SB-EPS、TB-EPS)的产生与组成成分的影响。试验结果表明:低浓度Cd^(2+)(小于0.1mg/L)促进EPS的产生,高浓度Cd^(2+)(大于3mg/L)抑制EPS的产生;SB-EPS随着Cd^(2+)浓度的增加逐渐减少,其中蛋白质含量增加,多糖、腐殖酸明显减少;当Cd^(2+)浓度小于0.1mg/L时TB-EPS显著增加,其中主要增加的成分是蛋白质;当Cd^(2+)浓度大于3mg/L时,TB-EPS的分泌受到抑制,但蛋白质含量仍高于空白对照组,多糖、腐殖酸含量显著降低;LB-EPS受到的影响因素较多,其含量变化不规律。采用扩展DLVO理论剖析了EPS各组分含量的变化对好氧颗粒污泥沉降性能的影响,以期为好氧颗粒化技术在工业废水处理中的应用提供有力的支持。

微晶纤维素基碳酸钙复合材料对Cd^(2+)和Pb^(2+)的捕集与回收研究

以微晶纤维素(MCC)和碳酸钙(CaCO_(3))为基底,通过冷却活化和离子交换反应制备了MCC@CaCO_(3)复合材料。研究捕集时间、浓度及pH等因素对溶液中Cd^(2+)和Pb^(2+)去除的影响。结果表明,当Ca^(2+)的投加量为0.1 mol、pH值为5时,MCC@CaCO_(3)对Cd^(2+)的吸附容量达503.47 mg/g,对Pb^(2+)的吸附容量达1 076.05 mg/g,去除率99.7%。

基于玉米秸秆和荔枝树枝生物炭的电化学传感器对水中镉离子的检测

以玉米秸秆和荔枝树枝为原料,500℃下制备生物炭。采用扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和傅里叶变换红外(FTIR)光谱仪对两种生物炭进行表征。通过滴涂法将两种生物炭材料分别修饰在玻碳电极(GCE)表面,成功构建了Y-BC/GCE和L-BC/GCE电化学传感器,并在醋酸盐缓冲液中用微分脉冲伏安法(DPV)研究了镉金属离子(Cd^(2+))在不同电极上的电化学行为。结果表明,两种生物炭修饰电极对Cd^(2+)的检测都取得较好的效果。在最优条件下(Y-BC/GCE:沉积电位-1.6 V、沉积时间100 s、pH=4;L-BC/GCE:沉积电位-1.3 V、沉积时间100 s、pH=5),两种生物炭传感器在浓度范围为0.2~20μmol/L内都有良好的线性关系,Cd^(2+)检出限分别低至0.06和0.05μmol/L。同时这两种生物炭传感器具有良好的稳定性、重复性以及抗干扰性,对实际样品中的Cd^(2+)具有良好的回收率(Y-BC/GCE:96.97%~102.57%;L-BC/GCE:97.01%~99.10%)。