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.

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.

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.

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.

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.

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.

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.

Nanozyme Based Detection of Heavy Metal Ions and its Challenges: A Minireview

Naznozymes have become an important alternative to natural enzymes for many sensing applications,due to their relatively high stability,easy synthesis,and cost-effectiveness.Nanozyme-based assays,especially paper-based assays are portable,and therefore,are convenient for use in field operations,especially in remote parts of the world.Decreasing water levels,depletion of water resources,and large scale mining create the need for rapid detection of heavy metal ions in various water samples.In comparison with traditional methods of heavy metal ion detection,nanozyme-based systems enable rapid and cheap screening on the spot with a very simple instrument such as a UV-Vis absorption spectrophotometer.The sensing mechanism of a nanozyme-based sensor is highly dependent on its surface properties.They often encounter selectivity issues,unlike natural enzyme-based assays.Therefore,different types of target recognition and inhibition/enhancement mechanisms have been reported to achieve high selectivity.In this short review,we mainly focus our discussion on various interaction of the heavy metal ions with the nanozyme,and their responses towards the catalytic activity in the sensing of target metal ions.

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.

Adsorption Properties and Cost of Dicarboxylic Nanocellulose on Copper Ions for Wastewater Treatment

The accumulation of Cu^(2+)in water is a potential threat to human health and environment.Dicarboxylic nano-cellulose(DNC)with rich carboxyl groups was prepared through the NaIO_(4)–NaClO_(2) sequential oxidation meth-od to efficiently remove copper ions,and the Cu 2+adsorption properties and cost were studied.The maximum adsorption capacity reached 184.2 mg/g at pH 6 and an adsorbent dose of 5 g/L.Theoretically,the maximum adsorption capacities of monocarboxylic nanocellulose(MNC),DNC,and tricarboxylic nanocellulose(TNC)with carboxyl groups as the main adsorption sites were calculated to be 228.7,261.3,and 148.1 mg/g,respectively.The Cu^(2+)adsorption costs of MNC,DNC,and TNC were calculated and compared with those of powdered activated carbon(PAC).The Cu^(2+)adsorption capacity of DNC is higher than that of PAC,and the adsorption cost is close to or lower than that of PAC,demonstrating that the DNC prepared by sequential oxidation of NaIO_(4)–NaClO_(2) has competitive adsorption capacity and cost in the treatment of wastewater containing Cu^(2+).

Using NH_(2)-MIL-125(Ti)for efficient removal of Cr(Ⅵ)and Rh B from aqueous solutions:Competitive and cooperative behavior in the binary system

The coexistence of inorganic and organic contaminants is a challenge for real-life water treatment applications.Therefore,in this research,we used NH_2-MIL-125(Ti)to evaluate the single adsorption of hexavalent chromium(Cr(Ⅵ))or Rhodamine B(RhB)in an aqueous solution and further investigate simultaneous adsorption experiments to compare the adsorption behavior changes.The main influencing factors,for example,reaction time,initial concentration,reaction temperature,and pH were studied in detail.In all reaction systems,the pseudo-second-order kinetic and Langmuir isotherm models were well illuminated the adsorption progress of Cr(Ⅵ)and RhB.Thermodynamic studies showed that the adsorption process was spontaneous and endothermic.As compared to the single system,the adsorption capacity of Cr(Ⅵ)in the binary system gradually decreased as the additive amount of RhB increased,whereas the adsorption capacity of RhB in the binary system was expanded brilliantly.When the binary reaction system contained 100 mg/L Cr(Ⅵ),the removal rate of RhB increased to 97.58%.The formation of Cr(Ⅵ)-RhB and Cr(Ⅲ)-RhB complexes was the cause that provided facilitation for the adsorption of RhB.These findings prove that the interactions during the water treatment process between contaminants may obtain additional benefits,contributing to a better adsorption capacity of co-existing contaminant.

Hardening Properties of Foamed Concrete with Circulating Fluidized Bed Boiler Ash, Blast Furnace Slag, and Desulfurization Gypsum as the Binder

Recently, a large amount of circulating fluidized bed boiler ash (CFBA) and desulfurization gypsum (DSG) has been produced, and it is essential to develop technology to utilize them. These materials have CaO and SO3, which are considered to be a stimulant for blast furnace slag (BFS). This study presents an experimental investigation of the compressive strength and heavy metal ions immobilization properties of cement-free materials comprising CFBA, BFS, and DSG. The feasibility of manufacturing foamed concrete using these materials was examined, and field test of foamed concrete was conducted. Experimentally, the flow, compressive strength, and heavy metal ions concentration were evaluated via inductively coupled plasma atomic emission spectroscopy (ICP-AES) of the paste and foamed concrete. The experimental investigation revealed the self-healing hardening ability of fluidized bed boiler ash. In addition, the compressive strength was increased with the increasing replacement rates of BFS and DSG in the CFBA paste, and the compressive strength of 14.6 - 17.2 MPa was recorded over 28 days of curing. From the result obtained, the feasibility of manufacturing foamed concrete with a foam volume of 120 L, incorporating the aforementioned materials, is confirmed. It was also found that after 28 days of age, a 7.9-MPa compressive strength of the foamed concrete was attained, and heavy metal ions elution in this foamed concrete was also significantly reduced. Therefore, CFBA, BFS, and DSG could be used as a binder for the foamed concrete.

Preparation of Al2O3–SiO2 composite aerogels and their Cu2+absorption properties

In order to remediate heavy metal ions from waste water,Al2O3–SiO2 composite aerogels are prepared via a sol–gel and an organic solvent sublimation drying method.Various characterisation techniques have been employed including X-ray diffraction(XRD),Fourier transform infrared spectrometry(FTIR),scanning electron microscope(SEM),Energy-dispersion X-ray spectroscopy(EDX),Brunauer–Emmett–Teller(BET)N2 adsoprtion isotherm,and atomic absorption spectrometer(AAS).XRD and FTIR suggest that the aerogels are composed of mainly Al2O3 and minor SiO2.They have a high specific surface area(827.544 m^2/g)and high porosity(86.0%)with a pore diameter of~20 nm.Their microstructures show that the distribution of Al,Si,and O is homogeneous.The aerogels can remove~99%Cu^2+within~40 min and then reach the equilibrium uptake(~69 mg/g).Preliminary calculations show that the Cu2+uptake by the aerogels follows pseudo second-order kinetics where chemical sorption may take effect owing largely to the high surface area,high porosity,and abundant functional groups,such as Al–OH and Si–OH,in the aerogel network.The prepared aerogels may serve as efficient absorbents for Cu^2+removal.

Selective sensing of Cr^(VI) and Fe^(Ⅲ) ions in aqueous solution by an exceptionally stable Tb^(Ⅲ)-organic framework with an AIE-active ligand

We herein report a new lanthanide metal-organic framework(MOF) that exhibits excellent chemical stability,especially in the aqueous solution over a wide pH range from 1 to 14.In contrast to many reported lanthanide MOFs,this Tb-based MOF emits cyan fluorescence inherited from the integrated AIEactive ligand,rather than Ln3+ ions.More remarkably,its fluorescence signal features a highly selective and sensitive "turn-off" response toward CrO_(4)^(2-),Cr_(2)O_(7)^(2- )and Fe^(3+) ions,highlighted with the low detection limits down to 68.18,69.85 and 138.8 ppm,respectively.Thus,the exceptional structural stability and sensing performance render this material able to be a superior luminescent sensor for heavy metal ions in wastewater.

Orderly Porous Covalent Organic Frameworks-based Materials:Superior Adsorbents for Pollutants Removal from Aqueous Solutions

Covalent organic frameworks(COFs)are a new type of crystalline porous polymers known for chemical stability,excellent structural regularity,robust framework,and inherent porosity,making them promising materials for capturing various types of pollutants from aqueous solutions.This review thoroughly presents the recent progress and advances of COFs and COF-based materials as superior adsorbents for the efficient removal of toxic heavy metal ions,radionuclides,and organic pollutants.Information about the interaction mechanisms between various pollutants and COF-based materials are summarized from the macroscopic and microscopic standpoints,including batch experiments,theoretical calculations,and advanced spectroscopy analysis.The adsorption properties of various COF-based materials are assessed and compared with other widely used adsorbents.Several commonly used strategies to enhance COF-based materials’adsorption performance and the relationship between structural property and sorption ability are also discussed.Finally,a summary and perspective on the opportunities and challenges of COFs and COF-based materials are proposed to provide some inspiring information on designing and fabricating COFs and COF-based materials for environmental pollution management.

Two Bisligand-Coordinated Luminescent Zn(Ⅱ)-Coordination Polymers for Sensing of Ions and Pesticides in Aqueous Solutions

Two coordination polymers(CPs) [Zn(PTA)(DTP)(HO)]·(DMF)(CP-1) and [Zn(BTC)(DTP)]·(CHCN)·(HO)(CP-2) with one-and two-dimensional architectures were synthesized from Zn(Ⅱ) ion and different organic linkers like terephthalic acid(HPTA), benzene-1,3,5-tricarboxylic acid(HBTC), and 3,5-di(1,2,4-triazol-1-yl) pyridine(DTP). The fluorescent sensing experiments showed that the two CPs displayed effective, sensitive, and selective abilities towards Feand CrO. For sensing the pesticides, CP-1 outperforms in sensing of metamitron(MMT) and CP-2 is ultrasensitive towards imidacloprid(IMI). The possible mechanisms involved in the quenching of the fluorescence intensity include the inner filter effect(IFE) and the fluorescence resonance energy transfer(FRET) effect.

Preparation and application of novel chitosan-cellulose composite materials to adsorb Pb(Ⅱ)and Cr(Ⅵ)ions from water

This paper reported the preparation and application of novel chitosan-cellulose composite absorbents for the adsorption of Pb(II)and Cr(VI)ions in water.First,oxycellulose or dialdehyde cellulose(DAC)was prepared by sodium periodate oxidation of microcrystalline cellulose(MCC).Second,based on the mechanism of the Mannich reaction,a chitosan/cellulose-based adsorbent(TSFCD)was produced through a cross-linking reaction of thiosemicarbazide(TS)with DAC and chitosan(CS),which was designed specifically for the adsorption of Cr^(6+)ions from water.Similarly,another chitosan/cellulose-based adsorbent(DBFCM)was also prepared with 2,5-dithiobiurea(DB)as the cross-linking agent for the adsorption of Pb^(2+)ions in water.The adsorption performance of TSFCD and DBFCM for Cr^(6+)and Pb^(2+)ions,respectively,was investigated under various process conditions.Variables included adsorption temperature,time,initial metal ion concentration,pH,and adsorbent dosage.The adsorption kinetics of TSFCD and DBFCM were studied,and isothermal models were developed.Results showed that the adsorption amount increased with the increase of the reaction time,and reached a maximum at about 300 min for the TSFCD/Cr^(6+)system,and at about 240 min for DBFCM/Pb^(2+)system.The adsorption performance of TSFCD for Cr^(6+)and DBFCM for Pb^(2+)improved at higher temperature,and leveled off at 40℃ and 50℃,respectively.In addition,the removal rate of Cr^(6+)increased from 49.96%to 70.22%when the TSFCD dosage increased from 0.5 g/L to 3.5 g/L.Similarly,the removal rate of Pb^(2+)increased from 22.23%to 99.45%with the increase of DBFCM dosage from 0.5g/L to 5.0g/L.The adsorption processes of Pb^(2+)and Cr^(6+)were in line with the pseudo-second-order kinetic and the Langmuir isothermal model.

Enzymatic Hydrolysis Lignin(EHL)and its applications for value-added products,a quick review

Enzymatic hydrolysis lignin(EHL)has a variety of active groups,which endow it with excellent properties and broad application prospects.Research work on EHL will promote better utilization of lignin resources and sustainable development of ecological environment.This paper briefly reviewed the research progress on EHL structures,properties,modifications and applications.Future research and development on EHL were also discussed.

Novel eco-friendly spherical porous adsorbent fabricated from Pickering middle internal phase emulsions for removal of Pb(Ⅱ) and Cd(Ⅱ)

Spherical porous materials prepared from the emulsion template used in the water treatment have displayed a vast prospect, as the high surface area, abundant porous structure, convenient operation and excellent adsorption performance. But the tedious fabrication process, high consumption of organic solvent and surfactant limited the application widely. Herein, a facile and eco-friendly spherical porous adsorbent(SPA) is fabricated from the green surfactant-free(corn oil)-in-water Pickering medium internal phase emulsions(Pickering MIPEs) via the convenient ion crosslinking procedure. The Pickering MIPEs synergistically stabilized with the semi-coke(SC), which is the natural particle produced from the shale oil distillation, and sodium alginate(SA) has excellent storage and anti-coalescence stability. The as-prepared porous adsorbent possessed the abundant pore structure, which provided favorable conditions for effective mass transfer in adsorption, and could be tuned by varying the SA dosage. The saturation adsorption capacities of Pb(II) and Cd(II) can be achieved with 460.54 and 278.77 mg/g within 45 min at 25 ℃, respectively. Overall, this study supplied a viable and eco-friendly route for fabricating the spherical porous adsorbent with a tunable porous structure for heavy metal ion wastewater.