Abstract
The safe treatment of heavy metals in wastewater is directly related to human health and social development. In this paper, a new type of recyclable adsorbent is synthesized through the ...oxidation of enhancer and modification with magnetic nanoparticles. The new adsorbent not only inherits the advantages of multiwall carbon nanotubes (6O-MWCNTs), but also exhibits a new magnetic property and further improved adsorption capacity, which is conducive to the magnetic separation and recovery of heavy metals. The adsorption results indicate that multiwall magnetic carbon nanotubes (6O-MWCNTs@Fe
3
O
4
) have a good performance for Pb(II) selective adsorption, with a maximum adsorption capacity of 215.05 mg/g, much higher than the existing adsorption capacity of the same type of adsorbents. Under the action of an external magnetic field, 6O-MWCNTs@Fe
3
O
4
that adsorbed metal ions can quickly achieve good separation from the solution. The joint characterization results of FTIR and XPS show that under the action of both coordination and electrostatic attraction, the C=O bond in the –COOH group is induced to open by the metal ions and transforms into an ionic bond, and the metal ions are stably adsorbed on the surface of 6O-MWCNTs@Fe
3
O
4
. Pb(II) has a stronger attraction than Cu(II) and Cd(II) to the lone pair of electrons in oxygen atoms to form complexes, due to the covalent index of Pb (6.41) is more larger than that of Cu (2.98) and Cd (2.71).These data provide a new type of recyclable adsorbent for the efficient treatment of heavy metal ions in wastewater and enrich relevant theoretical knowledge.
Industrial waste salt is classified as hazardous waste to the environment. The organic impurity and its occurrence in industrial waste salt affect the salt resource utilization. In this paper, ...composition quantitative analysis, XRD, TG-DSC, SEM/FIB-SEM coupled with EDS, FTIR, XPS and GC-Ms were chosen to investigate the organic impurity and its occurrence in industrial waste salt. The organic impurities owe small proportion (1.77%) in the specimen and exhibit weak thermal stability within the temperature of 600°C. A clear definition of organic impurity, including 11 kinds of organic compounds, including aldehyde, benzene and its derivatives etc., were detected in the industrial waste salt. These organic impurities, owing (C-O/C-O-C, C-OH/C = O, C-C/CHx/C = C etc.)-containing function group substance, are mainly distributed both on the surface and inside of the salt particles. Meanwhile, the organic substance may combine with metal cations (Ni2+, Mg2+, Cu2+ etc.) through functional groups, such as hydroxide, carbonyl etc., which increases its stability in the industrial waste salt. These findings provide comprehensive information for the resource utilization of industrial waste salt from chemical industry etc.
High-sulfur waste residues (HSWR) is a typical byproduct produced in the printing and dyeing industry that has hazardous properties, such as flammability and reactivity, etc. It is of great ...significance for the directional and harmless treatment of waste residues in the later stage on the research in-depth of the occurrence characteristics of each component in HSWR. In this paper, the combinatorial analysis method is employed to perform in-depth research on the phase composition, surface chemical situation of element, and the occurrence state of functional groups of the waste residue from multiple perspectives. The results show that the organic and inorganic components in HSWR are intricately interwoven, and exhibit significant thermal instability at high temperatures, with a maximum weight less of 86.66%. Carbon mainly exists in the states of C-H/C-OH/C-C, C-O/C-NH
2
, and C=O/C-N/C-S/CH
x
and constitutes the main chain of the carboxylic ring. Sulfur mainly occurs in three forms, namely, amorphous aggregated sulfur, sulfur-containing inorganic salts such as sulfate, and nitrogen-heterocyclic organic compounds containing sulfhydryl groups and methyl sulfur groups. These organic compounds constitute branch chains of the organic phase, and combine with metal cations through hydroxyl or carboxyl groups, and deposit on the surface of inorganic agglomerated sulfur. This wrapping structure increases the stability of volatile compounds in the slag and increases the difficulty of sulfur and chlorine removal. These findings provide a material basis for the later development of safe and effective HSWR disposal techniques.
Arsenic contamination has been a major problem in copper slag utilization. Arsenic is easily incorporated into the silicate-based matrix, making the arsenic difficult to volatilize. In this study, ...pyrite was selected to depolymerize the matrix structure and volatilize the glassy arsenic by sulfide-reduction-volatilization reaction. The optimum technological parameters and mechanism of glassy arsenic volatilization by pyrite were further studied. The optimum operating parameters for glassy arsenic volatilization by pyrite were determined to be a temperature of 1200 °C, a holding time of 60 min, a heating rate of 5 °C/min, a basicity of 0.3, and a pyrite addition content of 15%. The arsenic volatilization ratio reached 80.9% under these experimental conditions. Besides, the mechanism of glassy arsenic volatilization was elucidated by XRD, XPS, FTIR, and SEM analyses. These results indicate that, with the increase in temperature, the pyrite decomposes to generate a variety of sulfur-based reducing substances (FeS, FeS1-x, S2(g)). Through “oxygen capture reaction”, these sulfur-based reducing substances depolymerize the bridging oxygen structure from the glass former (AsO4, FeO4, and SiO4) by the conversion of (Q2 +Q3)→(Q0 +Q1) and result in the precipitation of glass former (AsO4, FeO4 and SiO4) combining with the nearby cation. In this process, the glassy arsenic is released by the glass network and participates in reductive volatilization reaction with sulfur-based reducing substances, converting the glassy arsenic with high thermal stability to volatile arsenic oxide and arsenic sulfide. These findings provide a theoretical support for the in situ volatilization of arsenic in copper smelting and centralized control of arsenic contamination.
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•Pyrite is proposed to volatilize glassy arsenic by sulfide-reduction-volatilization reaction.•The optimum process parameters for pyrite volatilizing glassy arsenic have been studied.•The mechanism of arsenic volatilization by pyrite has been determined.
Copper smelters are the main anthropogenic source of arsenic. In this study, the formation pathway of arsenic-lead particulate matter in a heat recovery steam generator (HRSG) of a copper smelting ...facility were investigated. Lead monoxide and arsenic trioxide reacted easily with each other to form particulate matter with a high arsenic content, while the relative content of lead arsenate and lead arsenite in the particulate matter varied with the fluctuation of the smelting flue gas. The dissociation mechanism by pyrite of particulate matter containing arsenic and lead were also studied for the first time. The structures and components of the resultant composites were characterized by ion chromatography plasma optical emission spectrometry, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. Pyrite promoted the dissociation of lead arsenate and lead arsenite due to the formation of more lead sulfate, and then further inhibited the formation of lead arsenate and lead arsenite. This study is of great significance for the control of arsenic in flues.
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•Formation and dissociation of arsenic-lead particulate matter were investigated.•Lead monoxide and arsenic trioxide easily reacted with each other.•Pyrite promoted the dissociation of lead arsenate and lead arsenite.•Pyrite reacted with lead arsenate and lead arsenite to form lead sulfate and gaseous arsenic.
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•The occurrence state of zinc in the copper slag is obtained theoretically.•Zn(II) substitutes for the iron sites in the internal SiOFe(II) (M2) bond to form Fe2-xZnxSiO4.•Formation ...mechanism is actually an ion exchange process between Zn(II) and Fe(II).•The priority of the substituting for the iron site in the fayalite structure is proved by MS software calculation.
The interactions between Fe2SiO4 and ZnO play an essential role in the recovery of zinc from copper slag. The dissolution and substitution mechanism of ZnO in fayalite were investigated by using TG-DSC, XRD, PPMS DynaCool, XPS, Mossbauer and SEM-EDS analyses and compared with MS calculation results. The results indicate that the dissolution and substitution are actually processes of the penetrating dissolution of Zn(II) ions that can be divided into three steps: 1) ZnO dissociates into Zn1-yO and Zn(II) ions; 2) Zn(II) penetrates the gap of the octahedron outer layer to substitute Fe(II) sites in the internal structure of SiOFe(II) (M2) to form (Fe2-x, Znx)SiO4; 3) Fe(II) is forced to migrate to the surface of (Fe2-x, Znx)SiO4 to form (Zn1-y, Fe(II)y)O. These findings can be derived the occurrence state and distribution of zinc in copper slag theoretically.
The presence of organic impurities hinders the resource utilization of industrial waste salt (IWS). In this study, pyrolysis treatment was chosen to remove these organic impurities. The optimal ...process parameters for the pyrolysis of organic impurities were as follows: a temperature of 500 °C and a holding time of 20 min. Under these optimal conditions, the total organic carbon (TOC) removal rate was 96.32%, inducing a decrease in the TOC mass fraction from 1.88 to 0.08%. Fourier transform infrared spectroscopy (FTIR) results obtained during this process showed that prolonging the pyrolysis time (10–70 min) for IWS resulted in a gradual decrease in the relative content of characteristic functional group, such as C-O in ether groups, and the disappearance of functional group, such as benzophenone carbonyl group and ester carbonyl. Organic impurities can release gas-containing compounds that destroy the initially smooth IWS surface, and the resulting particles with rough and irregular shapes fuse into large or lumpy particles during the pyrolysis process. GC‒MS results clearly showed that the number of different semivolatile organic compounds in the IWS was reduced from 35 to 19 as a result of the pyrolysis process. Correspondingly, organic impurities with molecular formulas containing 5–10 carbon atoms converted into compounds containing 6–20 carbon atoms. These findings provide theoretical support for IWS resource utilization.
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•The sulfidation roasting behavior of ZnFe2O4 was investigated in detail.•The sulfur inducing and sulfur-oxygen interface exchange mechanism was proposed.•The three-successive-layer ...structure of sulfidation products was found.
The sulfidation roasting behavior was analyzed in detail to reveal the reaction mechanism. Information about the sulfidation reaction, including phase transformation, ionic migration behavior and morphological change, were obtained by XRD, 57Fe Mossbauer spectroscopy, XPS and SEM analysis. The results showed that the sulfidation of zinc ferrite is a process of sulfur inducing and sulfur-oxygen interface exchange. This process can be divided into six stages: decomposition of FeS2, formation of the oxygen-deficient environment, migration of O2− induced by S2(g), formation of ZnFe2O4-δ, migration of Fe2+ accompanied by the precipitation of ZnO, and the sulfur-oxygen interface exchange reaction. The sulfidation products were zinc blende, wurtzite, magnetite and a fraction of zinc-bearing magnetite. These findings can provide theoretical support for controlling the process during which the recovery of Zn and Fe is achieved through the combined flotation-magnetic separation process.
Arsenic residue is of great concern due to its environmental hazard. In this study, we first propose to use cullet as the host to immobilize sodium arsenate. All samples have successfully formed ...glasses in 1200°C detected by X-ray diffraction spectra (XRD). High arsenic immobilization ratio has been achieved in the experiment. Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS) have been used to explore the process of arsenic immobilized into the cullet. It can be concluded that the arsenic exists in the form of AsO4 tetrahedron and forms chemical bonds with SiO4 tetrahedron via bridging oxygen, resulting in strengthening the Qn structure and new formation of Si-O(BO)-As, which makes arsenic stable in the glass.
Fig. 1 The mechanism of arsenic immobilized in the glass. Display omitted
•Sodium arsenate has been vitrified by cullet.•High arsenic immobilization ratio has been achieved after being vitrified.•The Qn structure has been strengthened by the vitrification of sodium arsenate.•Si-O(BO)-As has formed in the glass.
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•A novel and simple method for treating high-As-CuSO4 flue dusts was investigated.•>92% As was volatilized as As2O3 and >95% Cu was retained in the calcine.•FeS2 promoting As release ...mechanism of high-As-CuSO4 flue dusts has been proposed.
Arsenic is the most important hazardous trace element in copper concentrates. In order to separate arsenic from the smelting processes, a pyrometallurgical treatment with additives was developed to deal with high-arsenic copper smelter flue dust high in copper sulfate. Under the optimized conditions of mixing 30 wt% pyrite and roasting at 550 °C under an inert atmosphere for 30 min, more than 92% arsenic was volatilized as a high purity arsenic trioxide by-product while most copper was retained in the calcine to be returned to smelting as a high-copper feed. The high separation of arsenic is due to the transformation from the limited vaporization of arsenate to volatile arsenic trioxide by pyrite at above 460 °C. Two reaction paths of pyrite were identified as follows: one followed the pattern FeS2 → Fe2O3 → FeAsO4 → Fe3O4/Fe2O3 and the other was FeS2 → FeS + S2 (g) → Fe3O4/Fe2O3.
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