Adsorption of congo red by three Australian kaolins

This study investigated the potential use of kaolin as alternative adsorbents for removal of congo red from wastewater. The effect of adsorbent dosage, dye concentration, pH and temperature were experimentally studied to evaluate the adsorption capacity, kinetics and equilibrium. Experimental results revealed that optimal adsorption took place at acidic pH and high dye concentration. Ceram kaolin had the highest removal efficiency among studied kaolins, followed by K15GR and Q38. The dye uptake process obeyed the pseudo-second order kinetic expression and was best described by the Langmuir isotherm. Intra-particle diffusion studies showed that the adsorption mechanism was not exclusively controlled by the diffusion step and was more likely to be governed by external mass transfer. Thermodynamic studies showed congo red adsorption on all kaolins was exothermic and spontaneous in nature. Recovered Q38 and K15GR kaolin demonstrated an enhanced adsorption capability. The results indicate that these local kaolins could be employed as low-cost alternatives for removal of anionic dyes from industrial wastewater.     

Facile synthesis of SBA-15/polyaniline nanocomposites with high electrochemical activity under neutral and acidic conditions

A facile synthesis of SBA-15/polyaniline (PANI) nanocomposites was developed via chemical polymerization in a pH 3 solution based on the electrostatic adsorption of positively charged anilinium ions on negatively charged SBA-15. X-ray diffraction, N₂ sorption isotherms, transmission electron microscopy and scanning electron microscopy characteristics indicated that PANI chains were distributed both on the inside and outside surfaces of the SBA-15 pores. A possible synthetic scheme for the creation of nanocomposites has been proposed. The SBA-15/PANI nanocomposites showed high, stable electrochemical activity in neutral and acidic conditions. The preliminary use of the SBA-15/PANI nanocomposites as an electroactive support for the selective detection of uric acid (UA) in the presence of a large excess of ascorbic acid (AA) demonstrates this material’s potential for use in electrochemical biosensors.     

Molecularly imprinted smart cryogels for selective nickel recognition in aqueous solutions

Smart polymers with fast response to slight changes show high practicability in separation and removal applications, such as water and wastewater treatment. Molecular imprinted polymers (MIPs) are designed to possess specific binding sites enabling the recognition of the target analytes. In this article, the newly synthesized smart adsorbents were used for the selective removal of nickel [Ni(II)] ions from aqueous solutions, which have dual (pH and temperature) memory for the recognition of Ni(II) ions due to the self-assembled recognition sites in MIP structure. The Ni(II)-MIP smart cryogels were prepared by cryopolymerization of N-isopropylacrylamide (NIPAm) and N-methacryloyl-l -histidine (MAH) monomers to incorporate their smart features for removal of Ni(II) ions in a selective and temperature-modulated way. The maximum binding capacity of Ni(II) ions onto MIP smart cryogel was determined at pH 6 as 414 μg g⁻¹ at 20°C and only 104.5 μg g⁻¹ at 40°C, respectively. The adsorption reached an equilibrium within 30 min, while 85% of the bound amount of Ni(II) ions was achieved in only 15 min. This unique MIP cryogel as a smart and selective adsorbent was able to remove Ni(II) ions immediately by a significant temperature and pH change as an alternative application for water and wastewater treatment.     

An adsorption study of gelatin onto the Fuller's earth surfaces

An adsorption study of gelatin was performed from its aqueous solution onto the Fuller's earth surfaces at room temperature. The dynamics of the adsorption process were followed spectrophotometrically; and various adsorption and kinetic parameters, such as adsorption coefficient, rate constants for adsorption and desorption, and penetration rate constant, were evaluated. The adsorption was found to vary sensitively with pH variation and show minima in both the media, that is, in acidic and basic. It was also observed that the presence of anions reversed their impact on adsorbed amount at their high concentration. The effect of cations and temperature were also investigated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 42–52, 2005     

Bacterial cellulose/PANi mat for Cr(VI) removal at acidic pH

Remediation of hexavalent chromium - Cr(VI) at acidic pH using polyaniline coated bacterial cellulose porous mat (BC/PANi) is presented and the possible mechanism is discussed. The efficacy of BC/PANi mats in remediation of Cr(VI) was studied by varying pH (pH 1, 2, 3, and 5) and initial Cr(VI) concentrations (250–1000 ppm) of the solution. The BC/PANi (50 mg) mat was able to completely reduce 2000 ppm Cr(VI) into Cr(III) in a 20 ml solution at pH ~ 1 in 24 h. An increasing chromium removal efficiency was observed with decreasing solution pH; reaching a maximum removal capacity of ~920 mg/g at pH 1. The proposed mechanism of negatively charged Cr(VI) ions removal by BC/PANi mat is adsorption and simultaneous reduction into Cr(III), followed by desorption of Cr(III) from the mat. The role of temperature and co-existing anions like sulphate, nitrate and chloride found in industrial sludge were also investigated for removal efficiency of Cr(VI) at acidic pH ~ 1. The adsorption kinetics of Cr(VI) on polyaniline surface followed a pseudo-second-order model with reduction of Cr(VI) into Cr(III) as rate-limiting step. The reduced Cr(III) from the media was further recovered by neutralizing the pH of the solution.     

Oxidized and Ethylenediamine-Functionalized Multi-Walled Carbon Nanotubes for the Separation of Low Concentration Arsenate from Water

In this work multiwalled carbon nanotubes (MWCNTs) modified by oxidation (o-MWCNTs) and by aminofunctionalization (e-MWCNTs) were examined as potential adsorbents for arsenate removal from water. Adsorption characteristics of raw and modified MWCNTs were investigated in batch adsorption experiments. The influence of solution pH (pH range 3–10), contact time, and temperature (25, 35, and 45°C) were studied. Ethylenediamine-functionalized MWCNTs have the greatest affinity for arsenate ions, followed by o-MWCNTs and raw-MWCNTs. The obtained experimental data for raw- and o-MWCNTs fitted Sips isotherm model, while for the e-MWCNTs, the Freundlich model provided the best fit to the experimental points. The maximum adsorption capacity for arsenate ions was achieved using e-MWCNTs, 12.18 mg g^?1. The presence of the arsenate on the adsorbent is confirmed by FTIR spectroscopy. Thermodynamic studies indicated the spontaneity and endothermic nature of the adsorption. Sodium hydroxide solution (0.1 M) was found to desorb about 70% of arsenate from e-MWCNTs. The results with spiked drinking water samples demonstrated that e-MWCNTs, due to the present basic and acidic groups, were very efficient for the removal of arsenate ions, as well as of some cations, at pH 4.     

改性铝锆柱撑膨润土去除水中氟离子

采用微波辅助制备锆铝柱撑膨润土(MAZPB)作为吸附剂,研究其对水中F-的去除性能,探讨了MAZPB投加量、溶液pH值、水中共存离子、再生能力等对氟吸附的影响. 结果表明,在较宽的pH范围(3.5~10)内,MAZPB有较好的除氟效果,去除率均达89%以上. 高浓度的Fe3+及CO32-共存能明显抑制MAZPB对氟的吸附. 该吸附过程遵循Lagergren拟二级反应动力学. MAZPB吸附F-符合Freundlich吸附等温模型. 在实验条件下的吸附体系中,吸附机制主要为物理吸附. 采用明矾对吸附F-饱和的MAZPB进行再生后,其对F-的去除率仍达81.93%.     

Lithium selective adsorption on low-dimensional titania nanoribbons

Mesoporous titania nanoribbons were synthesized via an optimized soft hydrothermal process and the derived titania ion-sieves with lithium selective adsorption property were accordingly prepared via a simple solid-phase reaction between Li₂CO₃ and TiO₂ nanomaterials followed by the acid treatment process to extract lithium from the Li₂TiO₃ ternary oxide precursors. First, mesoporous titania nanoribbons were prepared and the formation mechanism was discussed; second, the physical chemistry structure and texture were characterized by powder X-ray diffraction (XRD), (high-resolution) transmission electron microscopy (TEM/HRTEM), selected-area electron diffraction (SAED) and N₂ adsorption–desorption analysis (BET); third, the lithium selective adsorption properties were tested by the adsorption isotherm, adsorption kinetics measurement and demonstrated with the distribution coefficient of a series of alkaline and alkaline–earth metal ions.     

Removal of copper(II) from an aqueous solution with copper(II)‐imprinted chitosan microspheres

Ion‐imprinted chitosan (CS) microspheres (MIPs) were prepared with Cu(II) as a template and epichlorohydrin as a crosslinker for the selective separation of Cu(II) from aqueous solution. The microspheres showed a higher adsorption capacity and selectivity for the Cu(II) ions than nonimprinted chitosan microspheres (NMIPs) without a template. The results show that the adsorption of Cu(II) on the CS microspheres was affected by the initial pH value, initial Cu(II) concentration, and temperature. The kinetic parameters of the adsorption process indicated that the adsorption followed a second‐order adsorption process. Equilibrium experiments showed very good fits with the Langmuir isotherm equation for the monolayer adsorption process. The maximum sorption capacity calculated from the Langmuir isotherm was 201.66 mg/g for the Cu–MIPs and 189.51 mg/g for the NMIPs; these values were close to the experimental ones. The selectivity coefficients of Cu(II) and other metal ions on the NMIPs indicated a preference for Cu(II). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis,Characterization, and Applications of a New Chelating Resin Containing 4-2-(Thiazolylazo) Resorcinol (TAR)

A new phenol–formaldehyde based chelating resin containing 4-(2-thiazolylazo) resorcinol (TAR) functional groups has been synthesized and characterized by Fourier transform infrared spectroscopy and elemental analysis. Its adsorption behavior for Cu(II), Pb(II), Ni(II), Co(II), Cd(II), and Mn(II) has been investigated by batch and column experiments. The chelating resin is highly selective for Cu(II) in the pH range 2 ～ 3, whereas alkali metal and alkaline earth metal ions such as Na(I), Mg(II), and Ca(II) are not adsorbed even at pH 6. Quantitative recovery of most metal ions studied in this work except Co(II) is achieved by elution with 2M HNO₃ at a flow rate of 0.2 mL min^?1. A similar trend is observed for distribution coefficient values. The quantitative separations achieved on a mini-column of chelating resin include Cd(II) – Cu(II), Mn(II) – Pb(II), Co(II) – Cu(II), Mn(II) – Ni(II), and Mn(II) – Co(II) – Cu(II). The recovery of copper(II) is quantitative (98.0–99.0%) from test solutions (10–50 mg/L) by 1 mol/L HNO₃-0.01 mol/L EDTA. The chelating resin is stable in acidic solutions below 2.5 M HNO₃ or HCl as well as in alkaline solution below pH 11. The adsorption behavior of the resin towards Cu(II) was found to follow Langmuir isotherm and second order rate.     

Selective Biosorption of Zirconium and Hafnium from Acidic Aqueous Solutions by Rice Bran,Wheat Bran and Platanus Orientalis Tree Leaves

Abstract

The Zr(IV) and Hf(IV) biosorption characteristics of rice bran, wheat bran and Platanus orientalis tree leaves were examined as a function of initial pH, contact time, temperature, and initial metal ions concentration. Adsorption equilibriums were achieved in about 1, 5 and 40 min for rice bran, wheat bran, and leaves respectively. The biosorption behavior of leaves was significantly affected by solution pH whereas rice bran and wheat bran adsorption efficiencies were slightly affected by solution pH. The Freundlich and Langmuir adsorption equations, which are commonly used to describe sorption equilibrium for metals removal by biomasses, were use to represent the experimental and equilibrium data fitted well to the Langmuir isotherm model. The negative Gibbs free energy values obtained in this study with rice bran wheat bran and Platanus orientalis tree leaves confirmed the feasibility of the process and the spontaneous nature of sorption. In the optimum conditions, the adsorption efficiencies of other metal ions such as Fe³⁺, Cu²⁺, Pb²⁺, Hg²⁺, La³⁺, Ce³⁺ were significantly lower than Zr(IV) and Hf(IV) ions and these biomasses are excellent sorbents for the selective uptake of proposed ions from acidic aqueous solutions.     

Investigation of Pb(II) adsorption onto natural and synthetic polymers

Adsorption of toxic metal ion Pb(II) onto two different insoluble humic acids (IHAs) obtained from Beysehir (BIHA) and Ermenek (EIHA) low grade lignites and two synthesized terpolymers: styrene-divinylbenzene-methacrylic acid (SDBM) and styrene-divinylbenzene allylmethacrylate (SDBAM) were investigated and compared with commercial activated carbon (AC). The synthesized polymers were characterized by FTIR. Effects of pH (in neutral and acidic range), time, and initial metal concentration on the effectiveness of IHAs and terpolymers were determined. All synthesized adsorbents could adsorb Pb(II) with much higher capacity at half of the retention of AC in acidic medium. The adsorption capacities varied in the range of 51–76 mg g⁻¹. The affinity order of polymers in acidic medium for Pb(II) ions was observed as: SDBAM>SDBM>BIHA≈EIHA>AC. IHAs fit Freundlich model while SDB polymers were fitting Langmuir isotherm. The maximum adsorption capacities in neutral medium were 48 mg g⁻¹ for SDBM and 15 mg g⁻¹ for BIHA. Desorption studies for the polymer of highest performance indicated that about 90% desorption was achieved at 5 h by using EDTA regenerant solution. The polymer can be used repeatedly in Pb(II) adsorption with close capacities to initial use. The higher selectivity of SDBAM to Pb(II) ions in multimetal solution was also indicated in the study. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation of aminoalkyl celluloses and their adsorption and desorption of heavy metal ions

Aminoalkyl celluloses (AmACs) were prepared from 6-chlorodeoxycellulose and aliphatic diamines H₂N(CH₂)_mNH₂ (m = 2, 4, 6, 8). Their adsorption and desorption of divalent heavy metal ions such as Cu²⁺, Mn²⁺, Co²⁺, Ni²⁺ and their mixtures were also investigated in detail. Adsorption of metal ions on AmACs was remarkably affected by the pH of the solution, the metal ion and its initial concentration, and also the number of methylene units in the diamines. No adsorption of metal ions occurred on AmACs in strongly acidic solutions. However, metal ions were adsorbed rapidly on AmACs from weakly acidic solutions and the amount of adsorption increased with increasing pH. The effectiveness of AmACs as adsorbents decreased with increasing length of the methylene moiety, and AmACs from ethylenediamine (m = 2) was most effective. The adsorption of metal ions on AmACs was in the order Cu²⁺ > Ni²⁺ > Co²⁺ > Mn²⁺. Accordingly, their behavior followed the Irving-Williams series and Cu²⁺ ions were preferentially adsorbed from solutions containing metal ion mixtures. The adsorbed ions were easily desorbed from the AmACs by stirring in 0.1 M HCl.     

Recovery of Lithium from Seawater Using a New Type of Ion-Sieve Adsorbent Based on MgMn2O4

Abstract

A new type of ion-sieve manganese oxide, HMnO(Mg), was prepared by an acid treatment of MgMn₂O₄. The HMnO(Mg) showed a remarkably high selectivity for lithium ions among alkali metal and alkaline earth metal ions. The selectivity sequences were Na ? K ? Li for alkali metal ions and Mg ≤ Ca ≤ Sr ≤ Ba for alkaline earth metal ions at pH 8. The HMnO(Mg) showed a high selectivity for lithium ions in seawater. The lithium uptake increased with increasing solution pH and adsorption temperature. The maximum lithium uptake from native seawater reached 8.5 mg/g, corresponding to a lithium content of 1.8% in the form of Li₂O. The adsorbed lithium could easily be eluted with a dilute acid solution. The adsorptive capacity for lithium ions gradually decreased through repeated adsorption/elution cycles. The HMnO(Mg) after 4 cycles showed a lithium adsorptivity which was about 60% of the initial value.     

Effects of Acylation and Crosslinking on the Material Properties and Cadmium Ion Adsorption Capacity of Porous Chitosan Beads

Abstract

Chitosan is a novel glucosamine biopolymer derived from the shells of marine organisms. This biopolymer is very attractive for heavy metal ion separations from wastewater because it is selective for toxic transition metal ions over less toxic alkali or alkane earth metal ions. Highly porous, 3-mm chitosan beads were prepared by an aqueous phase-inversion technique for casting gel beads followed by freeze drying. In the attempt to simultaneously improve material properties and adsorption capacity, chitosan was chemically modified by 1) homogeneous acylation of amine groups with nonanoyl chloride before bead casting, and 2) heterogeneous crosslinking of linear chitosan chains with the bifunctional reagent glutaric dialdehyde (GA) after bead casting but before freeze drying. The random addition of C₈ hydrocarbon side chains to about 7% of the amine groups on uncrosslinked chitosan beads via N-acylation improved the saturation adsorption capacity from 169 to 216 mg Cd²⁺/g-bead at saturation (pH 6.5, 25°C) but only slightly reduced solubility in acid solution. Crosslinking of the N-acylated chitosan beads with 0.125 to 2.5 wt% GA in the crosslinking bath increased the internal surface area from 40 to 224 m²/g and rendered the beads insoluble in 1 M acetic acid (pH 2.36). However, crosslinking of the N-acylated chitosan beads reduced the saturation adsorption capacity to 136 mg Cd²⁺/g-bead at 0.75 wt% GA and 86 mg Cd²⁺/g-bead at 2.5 wt% GA. Crosslinking also significantly reduced the compression strength. There was no clear relationship between internal surface area and adsorption capacity, suggesting that the adsorbed cadmium was not uniformly loaded into the bead.     

电纺zein-SLS纤维膜的制备及其离子吸附性能研究

选用玉米醇溶蛋白（zein）作为鞘层包裹材料、木质素磺酸钠（SLS）作为芯层强化材料，采用同轴电纺技术制备了可有效吸附重金属离子的zein-SLS纤维膜。优化了膜制备工艺条件，确定纺丝电压适宜为14 kV，芯鞘层进料速率比适宜为1∶1。TEM证实，SLS被成功包埋于zein纤维膜中，但其负载量、包埋率和流失率受溶液pH的影响。离子吸附测试结果表明，SLS的加入可强化zein纤维膜对三种金属离子Ni²⁺、Zn²⁺、Cd²⁺的吸附效果，其中对Zn²⁺吸附能力的强化效果最为显著，上述吸附过程符合准二级吸附动力学模型。同时，在酸性条件下，随着pH的上升，zein纤维膜对Ni²⁺、Zn²⁺、Cd²⁺的吸附能力逐渐提高。     

PAMAM接枝稻草对Nd3+、Sm3+、La3+的吸附特性

以环氧氯丙烷为交联剂,将聚酰胺胺树状大分子(PAMAM)接枝到稻草基体上,利用FTIR、SEM、XRD、TG等对其结构进行了表征和分析。考察了其对Nd~(3+)、Sm~(3+)、La~(3+)稀土金属离子的吸附性能,探讨了吸附时间、稀土金属离子浓度、吸附温度、溶液pH等因素对吸附性能的影响。同时对吸附过程的动力学、吸附等温线和吸附热力学进行了研究。结果表明,所制备的吸附剂对Nd~(3+)、Sm~(3+)、La~(3+)稀土金属离子的吸附平衡时间约为4 h,平衡吸附量分别为47.14、40.11和50.12 mg/g。吸附过程符合拟二级动力学模型和Freundlich等温线,表明此吸附过程是属于化学吸附过程。吸附热力学研究表明,此吸附过程是自发进行的,同时吸附过程是一个混乱度增加的熵增过程。     

Selective separation and concentration of Pd(II) from Fe(III), Co(II), Ni(II), and Cu(II) ions using thiourea‐formaldehyde resin

Thiourea‐formaldehyde (TUF), a well‐known chelating resin, has been synthesized and it was used in the adsorption, selective separation, and concentration of Pd(II) ions from Fe(III), Co(II) Ni(II), and Cu(II) base metal ions. The composition of the synthesized resin was determined by elemental analysis. The effect of initial acidity/pH and the adsorption capacity for Pd(II) ions were studied by batch technique. The adsorption and separation of Pd(II) were then examined by column technique. FTIR spectra and SEM/EDS analysis were also recorded before and after the adsorption of Pd(II). The optimum pH was found to be 4 for the adsorption. The adsorption data fitted well to the Langmuir isotherm. The maximum adsorption capacity of the TUF resin for Pd(II) ions was found to be 31.85 mg g⁻¹ (0.300 mmol g⁻¹). Chelating mechanism was effective in the adsorption. Pd(II) ions could be separated efficiently from Fe(III), Cu(II), Ni(II), and Co(II) ions using TUF resin. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The Adsorption of Gold,Palladium, and Platinum from Acidic Chloride Solutions on Mesoporous Carbons

Studies on the adsorption characteristics of gold, palladium, and platinum on mesoporous carbon (CMK-3) and sulfur-impregnated mesoporous carbon (CMK-3/S) evaluated the benefits/drawbacks of the presence of a layer of elemental sulfur inside mesoporous carbon structures. Adsorption isotherms collected for Au(III), Pd(II), and Pt(IV) on those materials suggest that sulfur does enhance the adsorption of those metal ions in mildly acidic environment (pH 3). The isotherms collected in 1 M HCl show that the benefit of sulfur disappears due to the competing influence of large concentration of chloride ions on the ion-exchanging mechanism of metal ions sorption on mesoporous carbon surfaces. The collected acid dependencies illustrate similar adsorption characteristics for CMK-3 and CMK-3/S in 1-5 M HCl concentration range. Sorption of metal ions from diluted aqueous acidic mixtures of actual leached electronic waste demonstrated the feasibility of recovery of gold from such liquors.     

A supported liquid membrane system for the selective recovery of rare earth elements from neodymium-based permanent magnets

The rare earth elements (REEs) play a vital role in the development of green energy and high-tech industries. In order to meet the fast-growing demand and to ensure sufficient supply of the REEs, it is essential to develop an efficient REE recovery process from post-consumer REE-containing products. In this research effort, we have developed a supported liquid membrane system utilizing polymeric hollow fiber modules to extract REEs from neodymium-based magnets with neutral extractants such as tetraoctyl digylcol amide (TODGA). The effect of process variables such as REE concentration, molar concentration of acid, and membrane area on REE recovery was investigated. We have demonstrated the selective extraction and recovery of REEs such as Nd, Pr, and Dy without co-extraction of non-REEs from permanent NdFeB magnets through the supported liquid membrane system. The extracted REEs were then recovered by precipitation followed by the annealing step to obtain crystalline REE powders in nearly pure form. The recovered REE oxides were characterized by X-ray diffraction, scanning electron microscope coupled with energy-dispersive X-ray spectroscopy, and inductively coupled plasma–optical emission spectroscopy.