Effects of heavy metal ions Cu^(2+)/Pb^(2+)/Zn^(2+)on kinetic rate constants of struvite crystallization

Struvite(MAP)crystallization technology is widely used to treat ammonia nitrogen in waste effluents of its simple operation and good removal efficiency.However,the presence of heavy metal ions in the waste effluents causes problems such as slow crystallization rate and small crystal size,limiting the recovery rate and economic value of the MAP.The present study was conducted to investigate the effects of concentrations of three heavy metal ions(Cu^(2+),Zn^(2+),and Pb^(2+))on the crystal morphology,crystal size,average growth rate,and crystallization kinetics of MAP.A relationship was established between the kinetic rate constant Ktcalculated by the chemical gradient model and the concentrations of heavy metal ions.The results showed that low concentrations of heavy metal ions in the solution created pits on the MAP surface,and high level of heavy metal ions generated flocs on the MAP surface,which were composed of metal hydroxides,thus inhibiting crystal growth.The crystal size,average growth rate,MAP crystallization rate,and kinetic rate constant Ktdecreased with the increase in heavy metal ion concentration.Moreover,the Ktdemonstrated a linear relationship with the heavy metal concentration ln(C/C~*),which provided a reference for the optimization of the MAP crystallization process in the presence of heavy metal ions.

Synthesis and Characteristics of A Novel Heavy Metal Ions Chelator

Polyacrylamide-urea-sulfanilamide（PUS） was prepared as a novel heavy metal ions chelator and successfully used to simultaneously remove heavy metals from wastewater effluents.The effects of reaction parameters（sodium hydroxide,material ratio,temprature and contact time） were monitored to specify the best synthesis conditions.PUS was chemically characterized by means of infrared spectroscopy（FTIR） and ultraviolet-visible（UV-Vis）.The simultaneous chelation performance of PUS towards selected heavy metals ions,Ni2＋,Cu2＋,Pb2＋,Zn2＋,Cd2＋ was discussed,showing that Ni2＋,Cu2＋,Pb2＋,Zn2＋ could be better chelated.It is indicated that the synthesized PUS is a potential remediation material when used for the treatment of wastewater containing metal ions.

Enhancement of removal efficiency of heavy metal ions by polyaniline deposition on electrospun polyacrylonitrile membranes

This paper describes the preparation of a membrane of polyacrylonitrile(PAN)and its corresponding membrane coated with polyaniline(PANI)for the adsorption of heavy metal ions.Scanning electron microscopy micrographs revealed that all the membranes exhibited nanofibrous morphology.The prepared membranes were characterized by Fourier transform infrared spectroscopy(FTIR).The prepared membranes were used as an adsorbent for hazardous heavy metal ions Pb^(2+) and Cr_(2)O^(2-)_(7).The adsorption capacity and the removal efficiency of the membranes were examined as function of the initial adsorbate concentration and pH of the medium.Coated membranes with PANI showed better adsorption performance and their direct current(DC)conductivities were correlated to heavy metal ion concentrations.Adsorption isotherms were also performed,and the adsorption process was tested according to the Langmuir and Freundlich models.The regeneration and reuse of the prepared membranes to re-adsorb heavy metal ions were also investigated.The enhancement in adsorption performance and reusability of PANI-coated membranes in comparison with non-coated ones is fully discussed.The results show that the maximum adsorption capacities of lead and chromate ions on the PANI-coated membranes are 290.12 and 1202.53 mg/g,respectively.

Comparative adsorption of heavy metal ions in wastewater on monolayer molybdenum disulfide

To maximize the potential of monolayer molybdenum disulfide(MoS2)sheet in the disposal of heavy metal ions in wastewater,we compared the adsorption of several common heavy metal ions(including Cr^(3+),Ni^(2+),Cu^(2+),Zn^(2+),Cd^(2+),Hg^(2+),and Pb^(2+))in wastewater on the monolayer MoS2 sheet through first-principles calculation.Our simulation results show that the monolayer MoS2 sheet is a potential heavy metal adsorption material because of the attractive interaction between them.The most negative adsorption energy determines that the TMo site is the most stable adsorption site for the heavy metal ions.The attractive interaction is considered as chemical adsorption,and it is closely related to charge transfer.The orbital hybridization between S p and heavy metal ions p and d states electrons contributes to the adsorption,except the orbital hybridization between S p and Pb p states electrons contributes to the Pb^(2+) adsorption.All the results show that the monolayer MoS2 sheet is most suitable for removing Ni^(2+) and Cr^(3+) ions from wastewater,followed by Cu^(2+) and Pb^(2+).For the ions Cd^(2+),Zn^(2+),and Hg^(2+),its adsorption strength remains to be improved.

Sorption Characteristics for Multiple Adsorption of Heavy Metal Ions Using Activated Carbon from Nigerian Bamboo

Sorption characteristics of multiple adsorption of six heavy metal ions often found in refinery waste waters using activated carbon from Nigerian bamboo was investigated. The bamboo was cut, washed and dried. It was carbonized between 350℃ - 500℃, and activated at 800℃ using nitric acid. Simultaneous batch adsorption of different heavy metal ions (Cd2+, Ni2+, Pb2+, Cr3+, Cu2+ and Zn2+) in same aqueous solution using activated carbon from Nigerian bamboo was carried out. The adsorption process had a better fit for the Freundlich, Temkin isotherm and Dubinin-Radushke-vich (DRK) isotherm models but could not fit well into Langmuir isotherm. Adsorption isotherms showed that there is competition among various metals for adsorption sites on Nigerian bamboo. The DRK model was used to determine the nature of the sorption process and was found to be physical and chemical, with sorption energy of metal ions ranging from (7 - 10 kJ/mol). The adsorption of Cd2+, Zn2+, Pb2+ and Ni2+ ions was chemisorptions and that of Cu2+ and Cr3+ ions was cooperative adsorption. Therefore, this study revealed that Nigerian bamboo can serve as a good source of activated carbon with multiple and simultaneous metalions—removing potentials and may serve as a better replacement for commercial activated carbons in applications that warrant their use.

Electrochemical Sensing of Heavy Metal Ions based on Monodisperse Single-crystal Fe_3O_4 Microspheres

Single-crystal FeOwith monodisperse microspheres structure has been used for individual electrochemical detection of heavy metal ions. Morphology and structure of the as-prepared FeOmicrospheres were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and X-ray diffraction(XRD). Meanwhile the electrochemical properties of the FeOmicrospheres modified glass carbon electrodes(GCE) were characterized by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS), and the enhanced electrochemical response in stripping voltammetry for individual detection of Pb(Ⅱ), Hg(Ⅱ), Cu(Ⅱ), and Cd(Ⅱ) was evaluated using square wave anodic stripping voltammetry(SWASV). With high specific surface area and excellent catalytic activity toward heavy metal ions, the as-prepared monodisperse and single-crystal FeOmicrospheres show a preferable sensing sensitivity(22.2 μA/μM) and limit of detection(0.0699 μM) toward Pb(Ⅱ). Furthermore, the electrochemical sensor of FeOmicrospheres exhibits excellent stability and it also offers potential practical applicability for the determination of heavy metal ions in real water samples. This study provides a potential simple and low cost iron oxide for the construction of sensitive electrochemical sensors applied to monitor and control the pollution of toxic metal ions.

Robust Waterborne Polyurethane/Wool Keratin/Silk Sericin Freeze-Drying Composite Membrane for Heavy Metal Ions Adsorption

Wool keratin(WK)and silk sericin(SS)have the ability to interact with metal ions.In order to take advantage of this potential,a novel environmentally friendly waterborne polyurethane(WPU)/WK/SS membrane named as WPU&WK&SS membrane with crosslinked structure was constructed by freeze-drying via self-assembly style.Surface morphology and chemical structure characterization were investigated by scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FT-IR).In addition,the adsorption experiments of Cu2+and Cr6+were performed to evaluate the adsorption of WPU&WK&SS membrane,including adsorption kinetics,adsorption isotherm models and various factors affecting adsorption.Further investigation indicates that the maximum adsorption capacity of Cu2+and Cr6+can reach 54.21 mg·g-1and 85.21 mg·g-1,respectively,which are higher than most of the reported adsorbents.Through adsorption kinetics and thermodynamic analysis,it is find that the pseudo-second-order kinetic equation and the Langmuir adsorption isotherm model are more suitable for the static adsorption of Cu2+and Cr6+by WPU&WK&SS membrane.

Adsorption of Ammonium and Heavy Metal Ions on Industrial Vermiculite from the Yuli Mine in Xinjiang, China

The present work discusses the mineralogy, saturated adsorption of ammonium and adsorption of heavy metal ions （Cu^2＋, Pb^2＋ and Zn^2＋） on industrial vermiculite samples from the Yuli Mine in Xinjiang Autonomous Region. The saturated adsorption capacity of ammonium and the affection factors of adsorption of Cu^2＋, Pb^2＋ and Zn^2＋ are discussed on the basis of the mineralogical characteristics of the industrial vermiculite samples. The saturated adsorption capacities of ammonium are between 56.02 and 98.42 mmol/100g. The time of adsorption equilibrium is about 30-60 min, and the pH values and concentration of the ion solution significantly affect the adsorption capacities of the heavy metal ions. The adsorption capabilities of the heavy metal ions on industrial vermiculite are almost the same in the low ion concentration solutions, characterized by a sequence of Zn^2＋〉Pb^2＋〉Cu^2＋ for adsorption capacity in solutions with relatively high ion concentration. The results have practical significance for the application of the industrial vermiculite to treating wastewater containing ammonium or heavy metal ions.

Comments on“Adsorption behavior of heavy metal ions by carbon nanotubes grown on microsized Al_2O_3 particles”

Recently, Hsieh and Horng [1] published the paper entitled as above. In section 3 results and discussion, the authors mentioned the first and the second order kinetic models without any quotations. In fact these two kinetic models have been published [2-5]. In order to distinguish a kinetics model based on the ad- sorption capacity of a solid from the one based on the concentration of a solution, Lagergren＇s first-order rate equation has been called pseudo-first-order [6-7]. The Lagergren＇s equation has been widely cited, but there are far more mistakes made in the quotation and in the reference section of papers, including the title, the author＇s name, journal title, year of publishing, volume, and page number [3]. In addition, the second order kinetic expression for the adsorption systems of divalent metal ions using sphagnum moss peat has been reported by Ho [8].

An AuNPs/Mesoporous NiO/Nickel Foam Nanocomposite as a Miniaturized Electrode for Heavy Metal Detection in Groundwater

Heavy metals,notably Pb2+and Cu^(2+),are some of the most persistent contaminants found in groundwater.Frequent monitoring of these metals,which relies on efficient,sensitive,cost-effective,and reliable methods,is a necessity.We present a nanocomposite-based miniaturized electrode for the concurrent measurement of Pb2+and Cu^(2+)by exploiting the electroanalytical technique of square wave voltammetry.We also propose a facile in situ hydrothermal calcination method to directly grow binder-free mesoporous Ni O on a three-dimensional nickel foam,which is then electrochemically seeded with gold nanoparticles(Au NPs).The meticulous design of a low-barrier Ohmic contact between mesoporous Ni O and Au NPs facilitates target-mediated nanochannel-confined electron transfer within mesoporous Ni O.As a result,the heavy metals Pb2+(0.020 mg.L^(-1)detection limit;2.0–16.0 mg.L^(-1)detection range)and Cu^(2+)(0.013 mg.L^(-1)detection limit;0.4–12.8 mg.L^(-1)detection range)can be detected simultaneously with high precision.Furthermore,other heavy metal ions and common interfering ions found in groundwater showed negligible impacts on the electrode’s performance,and the recovery rate of groundwater samples varied between 96.3%±2.1%and 109.4%±0.6%.The compactness,flexible shape,low power consumption,and ability to remotely operate our electrode pave the way for onsite detection of heavy metals in groundwater,thereby demonstrating the potential to revolutionize the field of environmental monitoring.

Adsorptive removal of heavy metal ions from industrial effluents using activated carbon derived from waste coconut buttons

Activated carbon （AC） derived from waste coconut buttons （CB） was investigated as a suitable adsorbent for the removal of heavy metal ions such as Pb（II）, Hg（II） and Cu（II） from industrial effluents through batch adsorption process. The AC was characterized by elemental analysis, fourier transform infrared spectroscopy, X-ray diflraction, scanning electron microscopy, thermal gravimetric and diflerential thermal analysis, surface area analyzer and potentiometric titrations. The eflects of initial metal concentration, contact time, pH and adsorbent dose on the adsorption of metal ions were studied. The adsorbent revealed a good adsorption potential for Pb（II） and Cu（II） at pH 6.0 and for Hg（II） at pH 7.0. The experimental kinetic data were a better fit with pseudo second-order equation rather than pseudo first-order equation. The Freundlich isotherm model was found to be more suitable to represent the experimental equilibrium isotherm results for the three metals than the Langmuir model. The adsorption capacities of the AC decreased in the order： Pb（II） Hg（II） Cu（II）.

Progress on sensors based on nanomaterials for rapid detection of heavy metal ions

The heavy metal ions,especially Cd^(2+),Pb^(2+) and Hg^(2+),show extremely hazard to the environment and human being.The measurement of heavy metal ions using sensors is catching more and more attention for its advantages of high sensitivity and selectivity,low-cost,convenience to handle and rapid detection.In recent years,nanomaterials such as gold nanoparticles(NPs),magnetic nanoparticles,graphene and nanocomposite materials are applied in sensors for improving sensitivity and selectivity,making the research on electrochemical(EC) sensors,spectrometric biosensors and colorimetric biosensors become a hot spot in the application to investigate heavy metal ions,in particular,Cd^(2+),Pb^(2+) and Hg^(2+).In this short review,the research of advanced detection of Cd^(2+),Pb^(2+) and Hg^(2+) and its progress based on nanomaterial sensors in recent years is reviewed.

Adsorption of Heavy Metal Ions from Aqueous Solutions by Zeolite Based on Oil Shale Ash： Kinetic and Equilibrium Studies

Na-A zeolite was successfully synthesized via the alkaline fusion method with oil shale ash as the raw material. The adsorption capacity of it was tested by removing Cu2＋, Ni2＋, Pb2＋ and Cd2＋ from aqueous solutions. The results reveal the maximum adsorption capacity of adsorbent for Pb2＋, Cu2＋, Cd2＋ and Ni2＋ were 224.72, 156.74, 118.34 and 53.02 mg/g, respectively. The effects of contact time and pH value of solutions on the adsorption effi- ciency of the zeolite were evaluated. Besides, The equilibrium adsorption data and the batch kinetic data were correlated with Langmuir and Freundlich models and the pseudo-first-order and pseudo-second-order models separately. The results show that the Langmuir isotherm and the pseudo-second-order equation were more suitable for the adsorption of Na-A zeolite for the metal ions. In addition, Thermodynamic parameters of the adsorption（the Gibbs free energy, entropy, and enthalpy） were also evaluated and discussed. The results demonstrate that the adsorption process was spontaneous and endothermic under natural conditions and the synthesized zeolite was an effective adsorbent for the removal of metal ions from aqueous solution.

SYNTHESIS AND CHARACTERISTICS OF A CHELATING RESIN AS AN EXTRACTANT AND CHROMOGENIC REAGENT OF HEAVY METAL IONS IN SOLID PHASE EXTRACTION

A new chelating resin （CPS-DMA-SABA） was synthesized with the chloromethylated crossqinked polystyrene porous beads （CPS） as raw materials, which were bonded with salicylidene-o-aminobenzoic acid （SABA） on the surface via a quaternary ammonium unit as a linker. The results showed that CPS-DMA-SABA would easily change into a zwitterionic chelating resin （CPS-DMA-SABZ） when washed with distilled water. CPS-DMA-SABA was characterized by elemental analysis, infrared spectra and thermo-gravimetric analysis. The ion sorption capacities of CPS-DMA-SABA were found to be 1916 μg/g for Zn2＋ withpH at 4.5, 1620μg/g for Cu2＋ with pH at 6.2, 1291 μg/g for Ni2＋ withpH at 6.6 and 780 μg/g for Cr3＋ withpH at 5.5, respectively. The experiments showed CPS-DMA-SABA also changed its color when meeting with the metal ion in the aqueous solution. As a consequence, CPS-DMA-SABA can not only be used as a solid phase extractant but also an indicator for confirming the heavy metal ion in solutions.

A compact fluorescence/circular dichroism dual-modality probe for detection, differentiation, and detoxification of multiple heavy metal ions via bond-cleavage cascade reactions

Selective detection of multiple analytes in a compact design with dual-modality and theranostic features presents great challenges. Herein, we wish to report a coumarin-thiazolidine masked D-penicillamine based dual-modality fluorescent probe COU-DPA-1 for selective detection, differentiation, and detoxification of multiple heavy metal ions(Ag^(+), Hg^(2+), Cu^(2+)). The probe shows divergent fluorescence(FL)/circular dichroism(CD) responses via divergent bond-cleavage cascade reactions(metal ion promoted C-S cleavage and hydrolysis at two distinctive cleavage sites): FL “turn-off” and CD “turn-on” for Ag+(no hydrolysis), FL “turn-on” and CD “turn-off” for Hg^(+)(imine hydrolysis), and FL “self-threshold ratiometric” and CD “turn-off” for excess Cu^(2+)(lactone and imine hydrolysis), providing the first example of a fluorescence/CD dual-modality probe for multiple species with complimentary responses. Moreover, the bond-cleavage cascade reactions also lead to the formation of D-penicillamine heavy metal ion complexes for potential detoxification treatments.

Chelating Properties of Salicylhydroxamic Acid-functionalized Polystyrene Resins and Its Application to Efficient Removal of Heavy Metal Ions from Aqueous Solutions

Salicylhydroxamic acid（SHA） was covalently bound onto crosslinked polystyrene spheres（CPSs） via the Friedel-Crafts alkylation reaction between chloromethylated CPSs and SHA in the presence of SnCI4 as the Lewis acid catalyst. The resulted SHA-CPSs possessed very strong chelating ability for heavy metal ions. In particular, the saturated adsorption amount of SHA-CPSs for Cu2＋ ions could reach as high as 34.2 mg/g at 318 K. The chelating capability of SHA-CPSs towards heavy metal ions was pH and temperature dependent. SHA-CPSs also showed se- lective metal coordination with the chelating capacity decreasing in the order of Cu2＋ 〉Zn2＋〉〉Pb2＋. The adsorption isotherms conformed well to the Langmuir model, and the adsorption process was found to be entropy-driven and endothermic. Besides, SHA-CPSs possessed the excellent reusability.

Heavy Metal Ions Removal by Nano-sized Spherical Polymer Brushes

Nano-sized spherical polymer brushes （SPBs） consisting of both a polystyrene （PS） core and a brush shell of poly（acrylic acid） （PAA）, poly（N-acrylcysteamine） （PSH）, or poly（N-acrylcysteamine-co-acrylic acid） （P（SH-co-AA））, were prepared by photo-emulsion polymerization. The core-shell structure was observed by dynamic light scattering and transmission electron microscopy. Due to the strengthened Donnan effect, the PAA brush can adsorb heavy metal ions. Effects of the contact time, thickness of PAA brush and pH value on the adsorption results were investigated. Due to the coordination between the mercapto groups and heavy metal ions as well as the electrostatic interactions, SPBs with mercapto groups are capable to remove heavy metal ions selectively from aqueous solutions. The order of adsorption capacity of the heavy metal ions by SPBs with mercapto groups is： Hg2＋ ≈ Au3＋ 〉 Pb2＋ 〉 CH2＋ 〉 Ni2＋. The adsorbed heavy metal ions can be eluted from SPB by aqueous HCI solution, and the SPBs can be recovered. After three regenerations the recovered SPBs still maintain their adsorption capacity.

Fast removal of heavy metal ions and phytic acids from water using new modified chelating fiber

The graft copolymerization of acrylic acid（AA） onto polyethylene glycol terephthalate（PET） fiber initialed by benzoy peroxide （BPO） was carried out in heterogeneous media.Moreover,modification of the grafted PET fiber（PET-AA） was done by changing the carboxyl group into acylamino group through the reaction with dimethylamine.The modified chelating fiber（NDWJN1） was characterized using elementary analysis,SEM and FT-IR spectroscopy.Adsorption kinetic curves indicated that NDWJNl could fast remove heavy metal ions and phytic acids from water effectively.Furthermore,batch kinetic studies indicated that heavy metal ions adsorbed to NDWJNl could be filted well by both pseudo-first-order and pseudo-second-order adsorption equations,but the intra-particle diffusion played a dominant role in the adsorption of phytic acids.

Amorphous molybdenum sulfide mediated EDTA with multiple active sites to boost heavy metal ions removal

The rational design of strong affinity adsorbents for heavy metal ions removal remains a critical challenge for water treatment.In this study,amorphous molybdenum sulfide composites(EDTA-MoSx(x=2,3))were fabricated via a facile hydrothermal method mediated by EDTA,which was applied to heavy metal ions(Cu^(2+),Cd^(2+),Pb^(2+),Zn^(2+)and Ni^(2+))removal from aqueous solutions.A case study for Cu^(2+)ions showed that the adsorption capacity of EDTA-MoSx(x=2,3)was superior to crystalline phase MoS2 at pH 6.0 with an initial concentration of 200 mg/L.Adsorption mechanisms of different sulfide groups and—COOH of EDTA-MoSx(x=2,3)were verified systematically via a series of experiments,characterizations,and density functional theory(DFT)calculations.Both bridging S_(2)^(2-)and—COOH covalently bonded with Cu^(2+)ions were ascribed to the critical factors for this enhanced removal efficiency on the surface of EDTA-MoSx(x=2,3).This work offers a new method to enhance the adsorption performance of molybdenum sulfide-based materials by controlling crystallinity mediated with an organic complex small molecule.

Bioremediation Process and Bioremoval Mechanism of Heavy Metal Ions in Acidic Mine Drainage

Acidic mine drainage（AMD） containing acidity and a broad range of heavy metal ions is classified as hazardous, and must be properly treated. The removal mechanism of heavy metal ions in acidic mine drainage containing Cu^2＋, Fe^2＋, and Zn^2＋ with biological method was studied here. Using 20 mmol/L ethanol as carbon source, Desulfovibrio marrakechensis, one of sulfate reducing bacteria（SRB） species, grew best at 35℃ and pH=6.72 with concentrations of 10, 55 and 32 mg/L for Cu^2＋, Fe^2＋ and Zn^2＋, respectively. The removal efficiency for each ion mentioned above was 99.99%, 87.64% and 99.88%, respectively. The mineralogy and surface chemistry of precipitates were studied by means of energy dispersive spectrometer（EDS）, X-ray photoelectron spectroscopy（XPS）, X-ray diffraction（XRD） combined with control tests. The experimental results demonstrate that the removal mechanism of heavy metal ions by Desulfovibrio marrakechensis is comprehensive function of chemical precipitation, adsorption and bioprecipitation. The biogenic iron sulfide solid was characterized as greigite（Fe3S4）, while the zinc sulfide solid was characterized as sphalerite（ZnS）.