Enhancement of elemental mercury adsorption by silver supported material

Mercury, generally found in natural gas, is extremely hazardous. Although average mercury levels are relatively low, they are further reduced to comply with future mercury regulations,which are stringent in order to avoid releasing to the environment. Herein, vapor mercury adsorption was therefore investigated using two kinds of supports, granular activated carbon（GAC） and titanium dioxide（Ti O2）. Both supports were impregnated by silver（5 and 15 wt.%）,before testing against a commercial adsorbent（sulfur-impregnated activated carbon, SAC）. The adsorption isotherm, kinetics, and its thermodynamics of mercury adsorption were reported.The results revealed that Langmuir isotherm provided a better fit to the experimental data.Pseudo second-order was applicable to describe adsorption kinetics. The higher uniform Ag dispersion was a key factor for the higher mercury uptake. Ti O2 supported silver adsorbent showed higher mercury adsorption than the commercial one by approximately 2 times.Chemisorption of mercury onto silver active sites was confirmed by an amalgam formation found in the spent adsorbents.

ADSORPTIVE STRIPPING VOLTAMMETRIC PROPERTIES OF DBPPH AT MERCURY ELECTRODE

Cyclic voltammetry shows that DBPPH has a pair of cathodic and anodic peaks at Hg electrode.Epc=-1.49 V and Fpa=-1.43 V(vs.Ag/AgCl).The cathodic peak shows adsorptive characteristics.The adsorbed species is DBPPH neutral molecule. The method for measuring trace amount of DBPPH by adsorptive stripping voltammetry is established.

Alkynyl carbon materials as novel and efficient sorbents for the adsorption of mercury(Ⅱ) from wastewater

For the first time, a series of alkynyl carbon materials（ACMs） were prepared via the mechanochemical reaction of CaC2 with six polyhalogenated precursors, namely CCl4,C2Cl6, C2Cl4, C6Cl6, C6Br6, and C14H4Br10（ACM-1, ACM-2, ACM-3, ACM-4, ACM-5, and ACM-6,respectively） and used for the adsorptive removal of mercury from aqueous solutions.Based on preliminary investigations, the adsorption of mercury on ACM-5 was studied in depth. Specifically, the effect of p H on mercury adsorptivity, adsorption kinetics,thermodynamics, isotherms, and recyclability was studied. The adsorptivity of mercury on ACMs was found to be closely related to the hydrocarbon precursor, specific surface area of sorbent, and the alkynyl content. ACM-5 showed the best performance and is among the best raw carbonaceous sorbents reported so far, with a Langmuir saturated adsorption capacity of 191.9 mg g-1. The promising mercury adsorption performance mainly arises from the strong Lewis soft acid–soft base interactions between the alkynyl groups and mercury ions. The adsorption isotherms could be satisfactorily correlated with the Langmuir equation. The results show that the ACMs can be used as efficient sorbents for the removal of mercury and may also be useful for the adsorption of other heavy metals.

Mercury removal from coal combustion flue gas by modified fly ash

Fly ash is a potential alternative to activated carbon for mercury adsorption. The effects of physicochemical properties on the mercury adsorption performance of three fly ash samples were investigated. X-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy, and other methods were used to characterize the samples. Results indicate that mercury adsorption on fly ash is primarily physisorption and chemisorption. High specific surface areas and small pore diameters are beneficial to efficient mercury removal. Incompletely burned carbon is also an important factor for the improvement of mercury removal efficiency, in particular. The C-M bond, which is formed by the reaction of C and Ti, Si and other elements, may improve mercury oxidation. The samples modified with CuBr2 , CuCl 2 and FeCl3 showed excellent performance for Hg removal, because the chlorine in metal chlorides acts as an oxidant that promotes the conversion of elemental mercury （Hg0） into its oxidized form （Hg2＋）. Cu2＋ and Fe3＋ can also promote Hg 0 oxidation as catalysts. HCl and O2 promote the adsorption of Hg by modified fly ash, whereas SO2 inhibits the Hg adsorption because of competitive adsorption for active sites. Fly ash samples modified with CuBr2 , CuCl2 and FeCl3 are therefore promising materials for controlling mercury emissions.

A facile approach towards high-performance poly(thioether-thioester)s with full recyclability

Developing new chemically recyclable polymers is important for a circular plastics economy.Herein,we prepared a class of 1,4-dithian-2-one(DTO)with thioether and thioester functionalities.These sulfur-substituted monomers(DTO)showed excellent reactivity for ring-opening polymerization(turnover frequency(TOF)up to 2.3×10^(4)h^(-1)),which afforded poly(thioetherthioester)s(P(DTO)s)with high air stability,high crystallinity,and commercial high-density polyethylene-like mechanical property(σB=29.59±1.08 MPa andεB=749%±36%).Intriguingly,chemical recycling of P(DTO)to monomer could be accomplished with excellent efficiency in dilute solution(1 min)at room temperature or even from a commodity plastic waste mixture under catalyst-free thermal bulk condition(180°C),thus establishing its circular life cycle.P(Me-DTO)could be applied for selective removal of Hg^(2+)with>99%removal efficiency.More importantly,Me-DTO could be recovered in high yield after utilization for Hg^(2+)adsorption.

Novel sulfhydryl functionalized covalent organic frameworks for ultra-trace Hg^(2+) removal from aqueous solution

Two kinds of novel sulfhydryl functionalized covalent organic frameworks were fabricated as adsorbents for the removal of ultra-trace concentrations of Hg^(2+)from water.The two kinds of sulfhydryl functionalized covalent organic frameworks were obtained via a thiol-ene click reaction between the thiol groups of trithiocyanuric acid(TTC)or bismuththiol(BMT)and vinyl groups on the surface of covalent organic frameworks.The material structure was characterized by XRD,SEM,EDS,FT-IR,BET,and TG analysis.Due to their rich sulfur content,both adsorbents(COF-SH-1 and COF-SH-2)exhibited a high level of selective Hg^(2+)removal from aqueous solution with maximum adsorption capacities of 763.4 mg g^(-1) and526.3 mg g^(-1),respectively.Furthermore,in the presence of ultra-low concentrations of Hg^(2+)both materials exhibited excellent performance,achieving rapid Hg^(2+)removal at concentrations from 10μg L^(-1) to less than 0.02 ng L^(-1).Analysis of the adsorption mechanism indicates that the sulfur containing chelating groups exhibit a strong binding capacity for Hg^(2+).Results show that the structure determines the performance,with the amount of adsorption sites being related to the adsorption capacity.Therefore,as sulfhydryl functionalized covalent organic frameworks contain an abundance of adsorption sites,these materials can effectively achieve the removal of ultra-low trace Hg^(2+)concentrations and have promising future application potential for the environmental detection of heavy metals.

Preparation of polyacrylamide/silica composite capsules by inverse Pickering emulsion polymerization

Polyacrylamide/silica （PAM/SiO2） composite capsules were synthesized by inverse Pickering emulsion polymerization. Silica nanoparticles modified with methacryloxypropyltrimethoxysilane （MPS） were used as a stabilizer. Transmission electron microscopy （TEM）, scanning electron microscopy （SEM）. Fourier transform infrared （FTIR） spectroscopy, and thermal gravimetric analysis （TGA） were used to characterize the morphology and composition of the composite capsules. SEM and TEM images showed that capsules consisted of a particle shell and a polymer inner layer. The capsule size depends on the nanoparticle concentration in the continuous phase. The composite rigidity largely depends on the acrylamide concentration. FTIR and TGA results indicated the existence of polyacrylamide and SiO2 in the composite particles. Aqueous Hg（ll） removal testing by the PAM/SiO2 composite capsules indicated promising potential for removing heavy metal ions from wastewater.