Copper removal from aqueous solution is necessary from the stances of both environmental protection and copper resource recycling. It is important to develop a new chemical precipitation method ...suitable for removing copper particularly at low concentration as the case of waste mine water, with regards to the various problems related to the current precipitation methods by using strong alkalis or soluble sulfides. In this research, we studied a possible chemical precipitation of copper ions at concentration around 60 mg/L or lower by cogrinding copper sulfate in water with calcium carbonate (CaCO3) using wet stirred ball milling. With the aid of ball milling, copper precipitation as a basic sulfate (posnjakite: Cu4 (SO4) (OH)6·H2O) occurred at a very high copper removal rate of 99.76%, to reduce the residual copper concentration in the solution less than 0.5 mg/L, reaching the discharge limit, even with the addition amount of CaCO3 as a stoichiometric ratio of CaCO3/Cu2+at 1:1. It is more interesting to notice that, at the same conditions, other heavy metals such as Ni, Mn, Zn and Cd do not precipitate obviously just with CaCO3 addition at CaCO3/M2+at 1:1 so that the precipitate without the impurities can be processed as good source to recover copper. This newly proposed concept can be further developed to treat wastewaters with other metals to serve both purposes of environmental purification and resource recovery in a similar way.
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•Ball milling to activate CaCO3 for chemical precipitation of wastewater.•High efficiency of copper removal even at low concentration.•Selective copper precipitation from other heavy metals.•Easy operation without pH etc. adjustment.
Layered double hydroxides (LDH) have been extensively studied because of their unique characteristics. The available reviews have dealt with the applications of LDH normally prepared with aqueous ...solution approaches. Recently mechanochemical ways to synthesize LDH and intercalated LDH have received more and more attention from researchers and several mechanochemical processes have been reported. This article reviews the recent advances in the preparation and intercalation of layered double hydroxides by mechanochemical approaches. Although conventional solution methods for the syntheses of LDH were widely studied, several problems remain to be resolved; such as treatment of aqueous waste, high energy consumption, complex operation etc. It is believed that mechanochemical methods may have potentials to effectively overcome the difficulties and also to synthesize various new types of LDH with further development of this new technique.
•The syntheses of LDH by mechanochemistry, the processes and the characterization methods of the products have been reviewed.•The mechanochemical intercalations of LDH with and without solvent have been compared.•The characterization techniques used in mechanochemical approaches to synthesize LDH has been summarized.•The mechanochemical approaches may contribute new applications for LDH.
Efficient lead removal from metal-containing wastewater, such as acid mine drainage (AMD), is an important step in environmental purification and secondary resources recovery. In this paper, a novel ...approach by mechanochemically activating CaCO3 through simply wet ball milling in metal-containing solution was developed, where selective Pb2+ precipitation in the form of PbCO3 was achieved based on its reaction with the CO32− from the activated CaCO3. By such milling operation, the removal efficiency of Pb2+ from aqueous solution could reach over 99%, while more than 99% Zn2+ (as well as Mn, Ni and Cd) was remaining in the solutions, demonstrating the feasibility and high effectiveness of precipitating Pb2+ and serving the purpose of recovering other metals without Pb impurity. The solubility differences between Pb carbonate and other carbonates of Zn, Mn, Ni or Cd were understood to be the main pathway and using CaCO3 would offer an easy operation and environmental friendly process to purify the metals-containing wastewater by precipitating Pb, compared with the difficulties when using alkaline neutralization to treat them. In addition, basic zinc carbonate (a zinc-containing ore waste) as an alternative precipitant to CaCO3 in the separation process was also confirmed to increase the zinc recovery in the solution while maintaining high Pb2+ removal efficiency.
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•Simple ball milling enabled CaCO3 to react with Pb2+, but not Zn2+ in the solution.•The reaction resulted in the transformation of CaCO3 into PbCO3.•Over 99% Pb2+ precipitated and over 99% Zn2+ remained in the solution.•Efficient Pb removal was also possible from other solutions of Mn, Ni, Cd, etc.
•Ball milling α-Bi2O3 to generate abundant oxygen vacancy.•Formation of insoluble BiOI by simply agitating the milled oxide in iodine-containing solution.•Possible treatment of radioactive iodine ...source.•Enrichment of iodine from dilute source.
Efficient iodine enrichment into a particular substance is of great importance from both stances of iodine recovery from dilute source and iodine removal from a radioactive source. Ball milling α-Bi2O3 was first proposed to generate abundant oxygen vacancy for enhancing the incorporation of iodide anion (I−). A set of characterization techniques, such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and X-ray photo-electron spectroscopy (XPS) were performed to understand the mechanism of I− incorporation into bismuth oxide. Gradual distortion of the crystalline structure of bismuth oxide was induced by mechanical activation to result in the occurrence of oxygen vacancy and amorphous state after prolonged milling operation. Formation of insoluble BiOI was obtained by simply agitating the activated bismuth oxide in an iodine-containing solution to achieve efficient iodine enrichment. This newly proposed strategy opens up a green technique with great potential for environmental remediation and iodine recovery when dealing with iodine sources.
Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) have received high concerns due to their extreme persistence, and very few technologies have been reported for their complete ...destruction. For sound PFCs wastes disposal, mechanochemical method was employed using a planetary ball mill. Potassium hydroxide (KOH) was identified as the best comilling reagent and nearly complete destruction of both PFOS and PFOA was realized. The measured water-soluble fluoride accounted for most of the organic fluorine. The final products of PFOS after treatment were shown to be KF and K2SO4 by XRD analysis. The mass ratio between PFOS and KOH significantly affected the fluoride recovery but not for PFOS destruction and the sulfate recovery. The gradual formation of sulfate and fluoride reveals that the degradation of PFOS is initiated with the dissociation of the sulfonate group. FTIR spectra further showed the disappearance of the −CF3 and −CF2– groups with the generation of sulfate. The cleavage of C–F bonds in PFOS and the formation of fluoride ion were also identified by XPS spectra. On the basis of these results, possible reaction pathways were proposed. The approach was also successfully applied for the destruction of PFOS and PFOA homologues with different chain lengths.
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► Mechanochemical solid-state reaction. ► Synthesis of perovskite complex oxides, ABO3, (A, B: trivalent metals like La, Al). ► Synthesis of complex oxides, ABO4 from A2O3 and B2O5 ...(A: trivalent metals, B: pentavalent metals like P). ► Halides synthesis. ► Sulfides conversion. ► Doping oxide.
This paper reviews mechanochemical (MC) syntheses of functional materials by means of dry grinding operation without heating. First of all, the authors have shown that the MC reaction is dependent on not only material function such as Gibbs free energy change of formation (ΔG<0) and structure type of the starting samples but also machine function enabling us to storage and accumulate the stress energy to the target materials. Then, they have concentrated the former one that the solid-phase reaction can be achieved by the necessary condition like ΔG<0 as well as the structure of the starting samples. The first example is MC synthesis of perovskite complex oxides, ABO3, where A and B trivalent oxides, respectively. Then, another type of complex ones such as ABO4 from A2B3 and B2O5, where B is pentavalent oxides, were shown. In these reactions, the structure of the starting samples are very important to determine the reaction completion or not. A reaction/non-reaction map has been introduced in this paper, and it is seen from the data that the radius (rA, rB and rO) of the each metal elements in the reaction systems are crucial parameters in the reaction systems. The paper has extended to the synthesis of halides and sulfides conversion, and final example is a doping with non-ferrous metal element into oxide like TiO2, attempting the improvement of its visible light photoreactivity. These information would be helpful to understand and estimate the MC solid-state reaction of the starting materials.
Precursor of MgAl LDH was simply obtained by dry milling of Al(OH)3 and Mg(OH)2 in two-step process and used as adsorbent to remove phenol and p-nitrophenol from water. The precursor samples before ...and after adsorption were characterized through Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR). The equilibrium adsorption data were well fitted to Langmuir model and were characterized with excellent adsorption capacities of 82.6 mg/g phenol and 356.4 mg/g p-nitrophenol, respectively. Pseudo-second-order kinetic model indicated that phenols were well adsorbed on the precursor. The enhanced adsorption mechanism was investigated and observed that the disorderly precursor have more active sites than the other adsorbents with stable crystalline structures. Comparison between the precursor and LDH product clearly demonstrated the advantage of precursor over the LDH, providing a new concept of using the easily obtained precursor as efficient adsorbent for wastewater treatment.
•Dry ball milling can effectively dehalogenate haloorganics in polymers.•Cheap Fe-SiO2 reagent debrominates decaBDE in polypropylene within 8 h.•Dehalogenation rate is roughly proportional to ...polymer-to-haloorganics mass ratio.•Mechanochemically dehalogenated polymer is viable feedstock for chemical recycling.
Chemical recycling technologies are the most promising for a waste-to-energy/material recovery of plastic waste. However, 30% of such waste cannot be treated in this way due to the presence of halogenated organic compounds, which are often utilized as flame retardants. In fact, high quantities of hydrogen halides and dioxin would form. In order to enabling such huge amount of plastic waste as viable feedstock for recycling, an investigation on mechanochemical pre-treatment by high energy ball milling is carried out on polypropylene containing decabromodiphenyl ether. Results demonstrate that co-milling with zero valent iron and quartz sand ensures complete debromination and mineralization of the flame retardant. Furthermore, a comparative experiment demonstrates that the mechanochemical debromination kinetics is roughly proportional to the polymer-to-haloorganics mass ratio.
CdS/Mg–Al LDH-precursor composites were synthesized by a mechanochemical method. X-ray diffraction analysis confirmed the formation of the CdS/Mg–Al LDH-precursor composites. SEM-EDS analysis ...demonstrated the uniform distribution of CdS nanoparticles among LDH-precursor matrix. The obtained nanocomposites exhibited much higher photocatalytic activities on methylene blue (MB) degradation under visible light irradiation. The high photocatalytic activity could be ascribed to the special structure of the wide-distribution of CdS nanoparticles within LDH-precursor matrix. A detailed investigation on the mechanism and the reaction kinetics for the photocatalytic process were also performed. This work provides a very simple and environment-friendly way to prepare a series of photocatalysts based on LDH-precursor with transition metal sulfide well dispersed inside.
•A mechanochemical pathway to synthesize CdS/Mg-Al LDH precursor composite photocatalysts was proposed.•This composite showed enhanced removal performance for MB over CdS and MgAl LDH precursor.•A novel method to prepare nanosized transition metal sulfide catalysts among LDH precursor matrix
The disposal of scrap cathode ray tube (CRT) funnel glass has become a global environmental problem due to the rapid shrinkage of new CRT monitor demand, which greatly reduces the reuse for ...remanufacturing. To detoxificate CRT funnel glass by lead recovery with traditional metallurgical methods, mechanical activation by ball milling was introduced to pretreat the funnel glass. As a result, substantial physicochemical changes have been observed after mechanical activation including chemical breakage and defects formation in glass inner structure. These changes contribute to the easy dissolution of the activated sample in solution. High yield of 92.5% of lead from activated CRT funnel glass by diluted nitric acid leaching and successful formation of lead sulfide by sulfur sulfidization in water have also been achieved. All the results indicate that the application of mechanical activation on recovering lead from CRT funnel glass is efficient and promising, which is also probably appropriate to detoxificate any other kind of leaded glass.
