Papers by Keyword: Heavy Metal Ions

Abstract: Purification of heavy metal ions from wastewater is of prime importance for a clean environment and human health. Different reported methods were devoted to heavy metal ions removal from various wastewater sources. These methods could be classified into adsorption-, membrane-, chemical-, electric-, and photocatalytic-based treatments. This article reviews and discusses these methods in terms of used agents/adsorbents, removal efficiency, operating conditions, and the pros and cons of each method. Generally, it was noticed that most of the recent studies have focused on adsorption techniques. Even though the chemical and membrane methods are practical, the large-volume sludge formation and post-treatment requirements are vital issues that need to be solved for chemical techniques. Fouling and scaling inhibition could lead to further improvement in membrane separation.

Abstract: The need to protect technogenic soils from contamination with heavy metal ions determines the relevance of the topic under study. The aim of the work is to thermodynamically substantiate the ability of gypsum and magnesia stone to neutralize heavy metal ions. Such properties of gypsum and magnesia stone can be called geoecological protection, and the substances themselves can be called mineral geoantidotes. The main method for substantiating geoecological protection properties is a thermodynamic assessment of the reactions of interaction between ions of heavy metals and mineral geoantidotes, as well as an assessment of the solubility product of substances formed during their interaction. As a result of the research, the values of changes in the Gibbs energy during the interaction of mineral geoantidotes and heavy metal ions have been determined; it has been shown that possible products of interaction reactions can be minerals similar to natural ones. Calculations have shown the possibility of reactions occurring under non-standard conditions (1 to 40°C). The experiments carried out made it possible to determine the geoecological protective capacity of gypsum and magnesia stone in non-standard conditions and showed the absence of dependence of the geoecological protective capacity on the ambient temperature in the range from 1 to 40°C. The materials of the article can be useful for the development of technological solutions to reduce harmful pollution by ions of heavy metals of technogenic soils using gypsum and magnesia stone.

Abstract: In this study, municipal solid waste incineration fly ash (hereinafter called MSWI fly ash) was used as a main raw material, and it was prepared into a solidified body for MSWI fly ash with geopolymer by a single-component chemical alkali excitation method. The results were shown that when the content of MSWI fly ash was 50%, SiO₂/Al₂O₃ was between 3.51-4.04, and Na₂O/Al₂O₃ was between 0.24-0.30, with the increasing of SiO₂/Al₂O₃ and Na₂O/Al₂O₃, the 28d compressive strength of the solidified body showed a trend of increasing first and then decreasing, the maximum 28d compressive strength was 17.7MPa. When SiO₂/Al₂O₃ was 4.04 and Na₂O/Al₂O₃ was 0.30, the minimum leaching concentrations of Pb²⁺ and Cd²⁺ were 0.018mg/L and 0.027 mg/L. When the content of MSWI fly ash was increasing, the 28d compressive strength of the solidified body gradually decreased, and the heavy metal ions leaching concentration gradually increased. The result of XRD and FTIR indicated that the MSWI fly ash was involved in the polymerization reaction, and the heavy metal ions in MSWI fly ash were also chemically solidified into the geopolymer structure.

Abstract: Silica fibers were prepared from the agricultural waste-rice straw via a slow calcination process. A possible formation mechanism of the obtained silica fiber was explained. The phytoliths/vascular composite fibers of rice straw work as the structural directing templates for the formation of silica fibers under the slow calcination process. Owing to the potassium silicate active site, the separable silica fiber showed great capability in removal of Cu²⁺, Ni²⁺, Cd²⁺ and Pb²⁺ from aqueous solution with efficiency higher than 99%. Additionally, over 90% of equilibrium adsorption capacity can be reached within 10 minutes, showing the easily accessible paths and active sites for ion transportation and adsorption in the as-prepared fiber. These results of this work are beneficial for scientists pursuing new synthetic route for valuable and widely applicable silica fiber materials from the agricultural waste, also helping to solve disposal of the agricultural waste and pollution problems.

Abstract: The article highlights the results of a study of the sorption capacity of some types of carbon fiber materials (CFM) with respect to the ions of heavy metals and oil products. A sorption method for the wastewater treatment, which allows cleaning the wastewater from oil products, ions of heavy metals, and other pollutants to the MPC, was suggested, and some recommendations for the implementation of the method were given. It was found that the use of CFMs for the sorption of heavy metal ions and oil products was more effective than that of some other known sorbents. The regeneration possibility of CFM, simplicity, and variability provide for a number of advantages compared to other known methods. The suggested method can be implemented both as a standalone and in conjunction with other methods to improve the biological treatment of wastewater.

Abstract: The adsorption of lead ions (Pb (II)) ions from aqueous solutions was studied. Different types of carbon materials, such as high-porous carbon, BAU-A activated carbon, multi-walled carbon nanotubes (pristine and oxidized), were used as adsorbents. To describe kinetic dependences for the Pb (II) extraction from aqueous solutions with those materials, the following models were implemented: pseudo-first-and pseudo-second-order, intraparticle diffusion, and Elovich. The adequacy of applying the pseudo-second-order equation was presented for characterizing the Pb (II) adsorption on the carbon materials under study. Thus, it was found that the interaction between the adsorbed ions and the functional groups of the adsorbents makes an important contribution to the overall rate of the process. Finally, the time of achieving equilibrium, the adsorption rate constants and the maximum adsorption capacity were empirically determined for all the adsorbents.

Abstract: Ionic exchange of multi-components titanium tungstophosphate nanoparticles (TiWP-NPs) were prepared using sol-gel reaction of titanium isoperoxide and tungestophosphoric acid (TPA) in presence of CTAB surfactant. The X-ray, BET and TEM characterizations showed that the nanoparticles exhibit the characteristic structure of titanium tungstophosphate and a BET surface area of 74 ± 3 m²/g was achieved. The TPA has shown an effect on the self-assembly process and maintains the TPA content to minimum would be beneficial for obtaining higher surface area of TiWP nanoparticles. Metal ions adsorption of Cu(II), Pb(II) or Cd(II) using the resulting titanium tungstophosphate nanparticles materials is investigated and up to 95% removal percentage was achieved. Using this method, nanoparticles of ionic exchange titanium tungstophosphate can be synthesized in the form of powder and amenable to mass production.

Abstract: The development of the city traffic and its increasing traffic flux are the signs of the development of the society, but causing a serious pollution on the city's ecological environment. Cement hydration reactions are needed to generate Ca (OH)₂, C-S-H gel, and AFt, as well as other hydrated products. Meanwhile, heavy metal ions are contained and fixed in a cement paste under physical encapsulation, absorption, isomorphous replacement, and double decomposition. This paper mainly discusses the impact of hydration environment on the adsorption law of materials adsorbing heavy metal ions and the adsorption mechanism under different pH values and temperatures, analyzing specific reasons from the perspective of micro-structure. Through the analysis it can be seen that, in addition to zinc ions, the cement-based materials’ capacity of adsorbing heavy metal ions increases as the pH value and the temperature increase. Micro-structure analysis shows that cement-based materials’ main adsorption methods are different when pH values are different.

Abstract: A novel hydrogel was successfully synthesized through doping 4A molecular sieve (4A-MS) into poly (acrylic acid-co-acrylamide) and used for the removal of Cu²⁺, Ni²⁺, Cd²⁺ and Pb²⁺ in the solution. The composite hydrogel all exhibited high sorption capacity (SC) and high elution percentage (EP) for the four above heavy metal ions. Simultaneously, the water uptake (WU) of the hydrogel was dramatically decreased and the mechanical strength of the absorbent hydrogel was improved with increasing 4A-MS content.

Abstract: One Bis-Boc-L-alanine-1,8-naphthyridine ligand containing amino acid by amido bond named 2,7-Bis-Boc-L-alanine-1,8-naphthyridine (L1) was synthesized and characterized. And there absorption and fluorescence spectra in methanol is presented. It exhibits electronic absorption spectra with λmax at about 340 nm, which can be tentatively assigned to π→π* transition. The emission spectra of L1 in CH₃OH shows a mirror symmetry peak with λ_max at about 375 nm. Then, the comprehensive study of spectroscopic properties upon titration of L1 with heavy metal ions as ion source in CH₃OH was investigated.