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。

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。

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。

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MXene-MB-cDNA材料构建新型传感器方法用于镉离子检测

本研究中,开发了一种新颖的基于过渡金属碳化物-亚甲基蓝-互补DNA(MXene-MB-cDNA)探针构建的竞争型电化学传感器,可用于重金属镉离子(Cd^(2+))的检测。该传感器一部分是基于MXene片层结构扩大MB负载率,用以放大电化学检测信号;另一部分以电极上修饰的Cd^(2+)Apt做为纽带连接MXene-MB-cDNA。当Cd^(2+)存在时,与cDNA竞争性结合Apt,引起双链结构变化,产生电化学信号,其最低检测限达到0.0034 mg·L^(-1),并在0.01至1.6 mg·L^(-1)范围内呈现良好的线性关系(R2=0.991)。相较传统方法,该方法更简单灵敏,为环境保护、食品安全、生物医药等研究方向中镉离子的检测提供了新的思路。

Preparation of Sulfhydryl Functionalized Mesoporous Silica Particles and Application in Adsorption of Cd²⁺

An improved soft template method to prepare sulfhydryl functionalized mesoporous silica nanoparticles is proposed. It is shown that the prepared nanoparticles maintain a relatively uniform spherical structure with a particle size range of 20 - 30 nm and a large specific surface area of about 926 m2/g. The sample is used to absorb heavy metal Cadmium ions (Cd2+) in water. The experimental results show that the sulfhydryl functionalized mesoporous silica is sensitive to Cadmium ions and has good selectivity. The detection limit can be estimated to be as low as 1.35 μg/L.

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.

Fluorescence properties of divalent and trivalent europium ions in CdWO_4 single crystals grown by the Bridgman method

Optical absorption,excitation,and fluorescence were investigated in Eu ion-doped CdWO4 single crystal grown by a modified Bridgman method.The results indicate that Eu^2＋ and Eu^3＋ ions coexist in CdWO4 crystal and an energy transfer occurs between these Eu^2＋ and Eu^3＋ ions.When the crystal is excited by 266-nm light,the energy corresponding to the 4f65d to 8S7/2 transition of Eu^2＋ ions results in the excitation of the Eu^3＋ ions to the 5DJ level.The effect on fluorescence of annealing in oxygen at various temperatures was investigated.The excitation intensity of Eu^2＋ ions at 266 nm decreases as annealing temperature increases from 300 K to 1073 K,but it remains at a certain equilibrium level when the annealing temperature is further increased.

The curve of ion exchange ratio(%)-pH of the interaction between suspended particles with Cd(Ⅱ) in the Yellow River

The curve of ion exchange ratio(%) pH of the interaction between suspended particles with Cd(II) in the Yellow River was studied. The effects of lysine on this curve have been also investigated. The results showed that (1) Cadmium in Cd(OH) + form in the suspended particles exchanges with the cations. The exchange ratio of Cd 2+ is nearly at its greatest value in the range of pH (8.0—8.5) in natural aquatic system; (2) Ion exchange ratio decreases as the concentration of Cd 2+ raises from 8.9×10 -6 mol/L to 2×8.9×10 -6 mol/L; (3) At the lysine concentration of 6 8×10 -6 mol/L, it can promote the ion exchange ratio; (4) Adsorption of the suspended particles to cadmium is weaker in seawater and Jin Sha River than in the Yellow River.