Impacts of calcium-alginate density on equilibrium and kinetics of lead(II) sorption onto hydrogel beads

Chronic exposure to Pb²⁺ above the 15-μg/L US Environmental Protection Agency action level for drinking water has been shown to cause a host of health problems in humans. Thus, it is important to study new methods available for the treatment and removal of Pb²⁺ from drinking water and wastewater, where elevated levels of heavy metals are found. Alginate-based beads represent one such possible method for heavy metal removal. The impact of alginate density on the equilibrium and kinetics of Pb²⁺ sorption onto hydrogel beads was investigated using Ca-alginate beads ranging from 1% to 8% (w/v) and exposed to Pb²⁺ concentrations ranging from 100 to 1,000 mg/L. When Ca-alginate beads were characterized using Fourier transform infrared analysis, the carboxylic acid groups of the mannuronate and guluronate residues in alginate were the primary functional groups that interacted with Pb²⁺. Hydration of Ca-alginate beads was also examined and found to decrease as Ca-alginate density increased. A positive correlation was observed between Ca-alginate hydration and Pb²⁺ sorption. Sorption of Pb²⁺ was fast, reaching equilibrium after approximately 4 h, and is well described by the Langmuir adsorption isotherm. Maximum sorption capacities for 1%, 4%, and 8% beads were 500 ± 100, 360 ± 30, and 240 ± 20 mg/g (dry weight), respectively. The kinetics of sorption were best described by the pseudo-second-order Lagergren model, with rate constants determined as 3.2 ± 0.1 × 10⁻⁴, 1.0 ± 0.1 × 10⁻⁴, and 1.6 ± 0.1 × 10⁻⁴ g mg⁻¹ min⁻¹ for 1%, 4%, and 8% beads, respectively.     

Arsenic sorption by modified clinoptilolite–heulandite rich tuffs

Recent works show that modified natural zeolites improve the remotion of anionic or non-polar organic pollutants from water. In this work the arsenic sorption from aqueous solutions onto clinoptilolite–heulandite rich tuffs modified with lanthanum, hexadecyltrimethylammonium or iron was investigated considering the arsenic chemical species and the pH of the arsenic solutions. Clinoptilolite–heulandite rich tuffs were characterized by scanning electron microscopy and X-ray diffraction analysis. The elemental composition of the zeolitic samples was also determined. According to the Langmuir isotherm model the arsenic (V) sorption capacity of the zeolites was 75.4 μg As/g at pH 3, 3.9 μg As/g at pH 5 and 53.6 μg As/g at pH 6, for the lanthanum, HDTMA and iron modified clinoptilolite–heulandite rich tuff from Chihuahua (México), respectively. In general, the results suggested that the arsenic retention depends on the precedence of zeolitic material, the nature of arsenic chemical species, pH as well as the characteristics of modified natural zeolites. In this work the arsenic adsorption mechanisms are also discussed.     

Determination of Lead and Cadmium in Sea‐ and Freshwater by Anodic Stripping Voltammetry with a Vibrating Bismuth Electrode

A solid, bismuth (Bi), disk, electrode is used to determine lead (Pb) in natural waters including seawater. The diffusion layer thickness was lowered from 93 to 29 µm by stirring, and to 18 µm by using the vibrated version of the Bi electrode. The Bi electrode does not require removal of dissolved oxygen, which facilitates in situ detection. The electrode was tested for the determination of Pb in coastal seawater samples. The detection limit for Pb was 0.15 nM in acetate buffer and 0.5 nM in seawater using a 2 min deposition time. Cadmium can be determined together with Pb but the sensitivity is about 10×lower. The Bi electrode compares unfavourably to a mercury electrode in terms of sensitivity.     

Alumina modified by dimethyl sulfoxide as a new selective solid phase extractor for separation and preconcentration of inorganic mercury(II)

Dimethyl sulfoxide (DMSO) was simply immobilized to neutral alumina via quite strong hydrogen bonding between sulfoxide oxygen and surface alumina hydroxo groups. The produced alumina-modified dimethyl sulfoxide (AMDMSO) solid phase (SP)-extractor experienced high thermal and medium stability. Moreover, the small and compact size of DMSO moiety permit high surface coverage evaluated to be 2.1 ± 0.1 mmol g⁻¹ of alumina. Hg(II) uptake was 1.90 mmol g⁻¹(distribution coefficient log K_d = 5.658) at pH 1.0 or 2.0, 1.68 mmol g⁻¹ (log K_d = 4.067) at pH 3.0 or 4.0 while the metal ions Ca(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) showed low values 0.513-0.118 mmol g⁻¹ (log K_d < 3.0) in the pH range 4.0-7.0. A mechanism was suggested to explain the unique uptake of Hg(II) ions by binding as neutral and chloroanionic species predominate at pH values ≤ 3.0 of a medium rich in chloride ions. A direct and fast batch separation mode was achieved successfully to retain selectively Hg(II) in presence of other eight coexisting metal ions. Thus, Hg(II) was completely retained; Ca(II), Co(II), Ni(II) and Cd(II) were not retained, while Pb(II), Cu(II), Zn(II) and Fe(III) exhibited very low percentage retention evaluated to be 0.42, 0.49, 1.4 and 5.43%, respectively. The utility of the new modified alumina sorbent for concentrating of ultratrace amounts of Hg(II) was performed by percolating 2 l of doubly distilled water, drinking tap water, and Nile river water spiked with 10 ng/l over 100 mg of the sorbent packed in a minicolumn used as a thin layer enrichment bed prior to the determination by CV-AAS. The high recovery values obtained (98.5 ± 0.5, 98.5 ± 0.5 and 103.0 ± 1.0) based on excellent enrichment factor 1000, along with a good precision (R.S.D.% 0.51-0.97%, N = 3) demonstrate the accuracy and validity of the new modified alumina sorbent for preconcentrating ultratrace amounts of Hg(II) with no matrix interference.     

Analytical investigation of calcium oxalate films on marble monuments

This paper describes an analytical approach to investigate the origin of oxalate films on marble. Calcium oxalate films were collected on buildings of historical importance in Lucca and Pisa (Italy) and characterised by optical microscopy (OM), scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX), Fourier transform infrared (FTIR) spectroscopy (equipped with diamond cell), and gas chromatography-mass spectrometry (GC-MS). The morphology of the films was investigated by optical and electronic microscopy. FTIR analyses highlighted the presence of calcium oxalate (both as whewellite and weddellite), gypsum, calcite, nitrates, silicates and apatite, while EDX maps showed the distribution of elements. Several samples showed traces of organic compounds, identified by GC-MS as paraffin wax, lipids of animal origin and egg. The correlation between organic material and oxalate contents suggests the origin of the films from degradation processes of past surface treatment.     

Separation of trace amounts of titanium by the sorption of the titanium peroxocomplex on silica gel

Summary The possibility of the analytical use of the sorption of titanium peroxocomplex on silica gel for the determination of trace amounts of titanium was studied. The exchange capacity of silica gel in dependence on the time and the composition of the titanium peroxocomplex sorbed were described. A simple and very efficient separation procedure has been developed for the determination of traces of titanium in various waters and water-soluble salts.     

硫酸铅分离-EDTA滴定法测定铜闪速冶炼烟尘中的铅

建立了用硫酸形成硫酸铅沉淀加以分离,再用EDTA络合滴定法测定铜闪速冶炼烟尘中铅量的方法。试样用盐酸、硝酸、硫酸、氟化氢铵和高氯酸溶解,用硫酸沉淀铅与其它干扰元素分离,沉淀溶解于乙酸-乙酸钠缓冲溶液中,以巯基乙酸掩蔽铋,抗坏血酸掩蔽铁,二甲酚橙作指示剂,用Na2EDTA标准滴定溶液滴定溶液中铅含量,采用火焰原子吸收光谱法测定滤液中铅含量加以补正。实验结果表明,沉淀时硫酸(1+24)加入量为50 mL,无水乙醇加入量为10 mL,乙酸-乙酸钠缓冲溶液加入量为30 mL。方法相对标准偏差(RSD)在0.35%~1.5%,加标回收率为在99.0%~101%。完全满足生产控制分析的要求,同时也可以作为类似物料中铅分析的参考方法。     

Separation of strontium ions from a simulated highly active liquid waste using a composite of silica-crown ether in a polymer

To partition Sr(II) from highly active liquid waste (HLW), a macroporous silica-based 4,4',(5')-di(t-butylcyclohexano)-18-crown-6 (DtBuCH18C6)-tri-n-butyl phosphate (TBP) polymeric composite, (DtBuCH18C6+TBP)/SiO(2)-P, was synthesized. It was done by impregnation and immobilization of DtBuCH18C6 and TBP into the pores of the SiO(2)-P particles, where DtBuCH18C6 was modified with TBP. The sorption of Sr(II) and some co-existent elements contained in a simulated HLW onto (DtBuCH18C6+TBP)/SiO(2)-P was investigated at 323 K. It was found that in 2.0 M HNO(3), Sr(II) exhibited strong sorption ability and high selectivity over all the tested metals except Ba(II). Chromatographic partitioning of Sr(II) from 2.0 M HNO(3) containing 5 mM of the tested elements was performed by (DtBuCH18C6+TBP)/SiO(2)-P packed column. La(III), Y(III), Na(I), K(I), Cs(I), Ru(III), Mo(VI), and Pd(II) had almost no sorption and flowed into effluent along with 2.0 M HNO(3). Sr(II) adsorbed strongly by (DtBuCH18C6+TBP)/SiO(2)-P was then eluted effectively by water, while Ba(II) flowed into effluent along with Sr(II) due to the similar chemical properties. In addition, the bleeding of total organic carbon in aqueous phase was evaluated. The results demonstrated that in 2.0 M HNO(3), application of the macroporous silica-based DtBuCH18C6 polymeric composite in chromatographic partitioning of Sr(II) from the simulated HLW is feasible.     

Development of an ELISA procedure to study sorption of atrazine onto a sewage sludge-amended luvisol soil

Pesticides may contaminate ground and surface waters and one of the major factors governing this property is soil sorption. Sorption can be assessed by batch equilibrium technique which produces lots of extracts with high dissolved organic carbon concentration in which the pesticide concentration has to be determined. We developed an ELISA procedure to analyse atrazine based on polyclonal antibodies (C193) for which tracer structure and dilutions of immunochemical reagents were adapted to fit the purpose. After a 1000-fold dilution (or after an SPE clean-up procedure) extracts of a sewage-sludge amended luvisol (used as an example application of the methodology developed) could be reliably analysed. The Freundlich model is able to describe adsorption for this system (r² = 0.977) delivering a distribution coefficient K_F of 1.6 ± 0.2 (mg kg⁻¹) (mg L⁻¹)^−N and an isotherm nonlinearity factor N of 0.70 ± 0.09.     

Evaluation of sorption of uranium onto metakaolin using X-ray photoelectron and Raman spectroscopies

Metakaolin prepared from a natural clay mineral ore of aluminium kaolinite is a promising low cost and high activity aluminosilicate material that has been investigated for studying the sorption behavior of uranium. Here, metakaolin was characterized using X-ray photoelectron spectroscopy (XPS) and the effects of pH, contact time and initial metal ion concentration on its sorption behavior were studied. The sorption process was found to initially be rapid (∼60% at time 0 min) but became slower with time; equilibrium was established within 24 h (∼80% sorption). The data were applied to study the kinetics of the sorption process. The Langmuir and Dubinin-Radushkevich (D-R) sorption isotherms were used to describe partitioning behavior for the system at room temperature. The binding of metal ions was found to be pH dependent, with optimal sorption occurring at pH 5. The retained metal ions were eluted with 5 mL of 0.1 M HNO₃. Raman spectroscopy and XPS were used to evaluate the sorption mechanism of U(VI).     

A novel separation/preconcentration system based on solidification of floating organic drop microextraction for determination of lead by graphite furnace atomic absorption spectrometry

Solidified floating organic drop microextraction (SFODME) was successfully used as a sample preparation method for graphite furnace atomic absorption spectrometry (GFAAS). 20 μL of 1-undecanol containing dithizone as the chelating agent (2 × 10⁻⁴ mol L⁻¹) was transferred to the water samples containing lead ions, and the solution was stirred for the prescribed time. The sample vial was cooled in an ice bath for 5 min. The solidified extract was transferred into a conical vial where it melted immediately, and then 10 μL of it was analyzed by GFAAS.Factors that influence the extraction and complex formation, such as pH, concentration of dithizone, extraction time, sample volume, and ionic strength were optimized. Under the optimized conditions, a good relative standard deviation of ±5.4% at 10 ng L⁻¹ and detection limit of 0.9 ng L⁻¹ were obtained. The procedure was applied to tap water, well water, river water and sea water, and accuracy was assessed through the analysis of certified reference water or recovery experiments.     

新型螯合棉分离抑制动力学光度法测定痕量铅

研究了在硼砂 氢氧化钠介质中 ,以 2 ,2′ 联吡啶为活化剂 ,Pb2 +对过氧化氢氧化偶氮氯磷 (Ⅲ )褪色反应具有的作用及其动力学条件 ,从而建立了一种测定痕量铅的新的动力学光度法 ,该方法的检出限为 3 9× 1 0 - 1 1 g/mL ,线性范围为 0～ 1 0 μg/1 0mL ,采用自制的MBM新型螯合棉纤维分离富集 ,可用于环境样品中痕量Pb2 +的测定。     

Lead leaching behaviors during panel-funnel glass waste separation from cathode-ray tube glass using thermosol,acid etching or mechanical cutting methods

Discarded cathode-ray tube (CRT) glass is considered harmful waste because it contains poisonous lead. Hence, a study on the disposal of CRT glass and the potential risk of lead leaching is needed. This work performs the research on the panel-funnel glass separation method, an important step for CRT glass recycling. In the thermosol method, moderate temperatures of 565 ～ 572 °C and 5 ～ 7 min holding time are suitable for a complete panel-funnel glass separation. The acid etching method can achieve panel-funnel glass separation with low energy consumption by using a 10 wt% nitric acid solution as an agent. Panel-funnel glass can be quickly separated by a mechanical cutting method within four minutes and achieve a high glass recovery. A glass size of 2–10 mesh, a rotary shaking speed of 240 rpm, and a retention time of 120 h can accelerate the lead leaching of 133.34 mg/L from CRT glass in the leaching solution at pH 4.93. This work gives a systematic exploration into panel-funnel glass separation and lead leaching from CRT glass, which is potentially beneficial for CRT glass waste recycling, management, and disposal.     

有机-无机介孔材料分离富集痕量铅及其火焰原子吸收光谱法测定

以正辛胺及γ-巯丙基三乙氧基硅烷在氯化钾溶液中反应,制得一种有机-无机介孔材料,并应用于分离富集痕量铅,试验了溶液pH值、温度、洗脱条件及干扰离子对铅(Ⅱ)分离富集的影响,结果发现该材料对铅(Ⅱ)的吸附具有较高的选择性和较大的吸附容量。在pH 6.0、试验温度为(20±1)℃条件下,铅(Ⅱ)可被该材料定量吸附。其静态饱和吸附容量为26.37 mg·g~(-1)。吸附的铅(Ⅱ)可用0.2 mol·L~(-1)硝酸-0.5 mol·L~(-1)乙酸混合酸溶液洗脱,再用火焰原子吸收光谱法测定。该方法测定铅(Ⅱ)的检出限(3s/k)达到1.5μg·L~(-1),线性范围在0.80 mg·L~(-1)以内。此法应用于环境水样中痕量铅的测定,加标回收率在96.7%～105.0%之间。测定值的相对标准偏差(n=7)在1.66%～2.05%之间。     

黄原脂棉分离-石墨炉原子吸收光谱法测定咸味食品中Pb~(2+)

利用单因素试验对黄原脂棉吸附溶液中Pb~(2+)的条件进行了实验优化,结果显示:在pH=5.0的溶液体系中,于温度20℃,振荡吸附15min,黄原脂棉对Pb~(2+)的吸附效果最佳;吸附的Pb~(2+)用6.0mL 3.0mol/L HCl,于40℃下解吸15min,可将Pb~(2+)从黄原酯棉上完全洗脱。采用石墨炉原子吸收光谱法,将该条件用于测定咸味食品中痕量Pb~(2+),结果表明:黄原脂棉能有效消除盐类基体给测定Pb~(2+)带来的干扰,方法的相对标准偏差为1.56%~2.31%(n=6);回收率为97.0%~102.7%;检出限为0.047mg/kg。本法灵敏、准确、可靠,可用于咸味食品中痕量Pb~(2+)的测定。     

The membranes (Nafion and LDPE) in binary liquid mixtures benzene + methanol - sorption and swelling

Sorption studies provide valuable information about the interactions of the components of the liquid mixture with the polymer. In the present paper, the behaviour of Nafion and low-density polyethylene membranes in binary mixtures benzene + methanol was examined with respect to their application in separation processes. The individual sorption isotherms, the separation factors, and the composition of the swollen membranes were derived from the experimental data. The results confirm that Nafion as a polar material sorbs the more polar component of the mixture (methanol) preferentially to the less polar component (benzene) whereas non-polar polyethylene prefers non-polar benzene in the whole concentration range. Volume measurements of the swollen membranes indicate that the ideal sorption behaviour cannot be considered for the selected systems.     

Preconcentration and separation of Cr(III) and Cr(VI) using sawdust as a sorbent

A simple, inexpensive method based on solid-phase extraction (SPE) on sawdust from Cedrus deodera has been developed for speciation of Cr(III) and Cr(VI) in environmental water samples. Because different exchange capacities were observed for the two forms of chromium at different pH—Cr(III) was selectively retained at pH 3 to 4 whereas Cr(VI) was retained at pH 1—complete separation of the two forms of chromium is possible. Retained species were eluted with 2.5 mL 0.1 mol L⁻¹ HCl and 0.1 mol L⁻¹ NaOH. Detection limits of 0.05 and 0.04 μg mL⁻¹ were achieved for Cr(III) and Cr(VI), respectively, with enrichment factors of 100 and 80. Recovery was quantitative using 250 mL sample volume for Cr(III) and 200 mL for Cr(VI). Different kinetic and thermodynamic properties that affect sorption of the chromium species on the sawdust were also determined. Metal ion concentration was measured as the Cr(VI)–diphenylcarbazide complex by UV–visible spectroscopy. The method was successfully applied for speciation of chromium in environmental and industrial water samples.     

Removal of Thoron and Arsenazo III from radioactive liquid waste by sorption onto cetyltrimethylammonium-functionalized polyacrylonitrile

A surfactant-functionalized polyacrylonitrile (SFPAN) was synthesized in the present investigation via gamma radiation-induced polymerization and was applied for sorbing two hazardous organics, Thoron (TH) and Arsenazo III (ARIII), from radioactive liquid waste. Efficient removals were achieved for both organics over a wide range of pH. The sorption kinetic studies of TH and ARIII revealed that the equilibrium time is significantly dependent on the solution pH. Among the tested sorption kinetic models, the kinetic data of TH and ARIII fit well to the pseudo-second-order one. The sorption equilibrium data obtained for TH and ARIII were analyzed using Freundlich, Langmuir, Temkin and Dubinin–Radushkevich (D–R) isotherm models. The obtained results demonstrated that the equilibrium data are well described by Freundlich and D–R models. The calculated values of the sorption energy (E) and the Gibbs free energy change (ΔG ^o) suggested that the sorption process of TH and ARIII onto SFPAN is governed by physisorption. SFPAN was further tested for the uptake of the concerned organics from radioactive process wastewater. The obtained results suggest its applicability for the treatment of liquid organic radioactive wastes.     

Equilibrium,kinetics and thermodynamics studies of Cd sorption onto a dithizone-impregnated Amberchrom CG-300m polymer resin

Amberchrom CG-300m, a styrene acrylic ester polymer resin, was studied for the first time as sorbent for metal ion sorption in a solid-phase extraction system. The polymer sorbent was modified via impregnation with dithizone to improve its efficiency. Efficiency of the modified sorbent improved by more than 47%. The loading capacity of the resin is 3.2 mg dithizone per gram of sorbent. The mechanisms of Cd(II) sorption from aqueous solutions are presented. Capacity of the modified resin for Cd(II) was investigated in batch experiments as a function of pH, initial metal ion concentration, temperature and time. Maximum capacity of 0.551 mg Cd(II) per gram of sorbent was achieved. The dimensionless separation factor, 0 < R_L < 1, associated with the Langmuir isotherm (at T = 294 K) signifies sorption of Cd(II) was favorable, as do negative values of free energy of sorption (ΔG) at temperatures exceeding 293 K. Sorption was endothermic (ΔH > 0) while ΔS > 0 reflects the affinity of the sorbent towards Cd(II). The pseudo-second order model proved to be the best fit model for Cd(II) sorption kinetics data. Particle-diffusion models suggest sorption follows film as well as pore diffusion mechanisms.     

氧化铟改性聚丙烯酰胺复合材料吸附水中铅的研究

环境中铅污染将威胁到生命体安全,因此去除过量的铅显得尤为重要。采用一锅法制备了复合材料吸附剂氧化铟改性的聚丙烯酰胺,通过扫描电子显微镜、N_(2)吸附-脱附仪和热重分析仪对吸附剂进行了表征。结合火焰原子吸收光谱法,研究其对水中的铅吸附性能。优化了溶液pH值及振荡时间对铅吸附的影响,并运用动力学和热力学研究了复合材料对铅的吸附行为。实验结果表明:在初始浓度为10 mg/L,溶液pH值为6.0,振荡时间为100 min时,铅的最大吸附量为9.689 mg/g;吸附行为符合拟二级动力学方程和Freundlich方程;当T=293.15 K时,ΔG=-8.38 kJ/mol,ΔH=23.90 J/mol,证明了复合材料对铅的吸附是自发进行,并且是吸热过程;经过3次吸附—解吸实验,复合材料对铅的解吸率仍大于87%,说明吸附剂的再生性能良好。