Synthetic sodalite doped with silver nanoparticles: Characterization and mercury (II) removal from aqueous solutions

In silico modeling of the antagonistic effect of mercuric chloride and silver nanoparticles on the mortality rate of zebrafish (Danio rerio) based on response surface methodology

In this study, in silico modeling was designed to examine the antagonistic effect of mercuric chloride (HgCl₂) and silver nanoparticles (AgNPs) on the mortality rate of zebrafish (Danio rerio) based on response surface methodology (RSM). Adult zebrafish (Danio rerio) with an average weight of 0.75 ± 0.16 g were used in this study. An interaction between HgCl₂ and AgNPs was evaluated using DLS, TEM, and EDX mapping. In addition, RSM was applied to determine and predict the mortality rate of zebrafish induced by HgCl₂ in the presence of non-lethal concentrations of AgNPs and to optimize dependent and independent variables. Following exposure to HgCl₂, in vitro observations showed an increase in the hydrodynamic size of AgNPs and the formation of irregular nanoparticles. EDX mapping analysis also demonstrated the deposition of Hg ions on the surface of AgNPs, indicating the interaction between HgCl₂ and AgNPs (i.e., the amalgamation of Hg and AgNPs). Moreover, in silico and in vivo findings illustrated that the mortality rate of zebrafish increased significantly in a concentration-dependent manner; however, the mortality rate reduced greatly in the presence of AgNPs during 96-h exposure. Statistically significant correlation and regression were also observed for the mortality rate between the actual and predicted values based on the ANOVA results, showing that the proposed model fits well. The most critical conditions of mortality rate were occurred by HgCl₂ concentration of 0.23 mg L^-1 and AgNP concentration of 0.04 mg L^-1 that yielding maximum fish mortality rate of 96.541%. Additionally, the obtained value for model desirability was equal to 1.000 (i.e., the highest possible value). In conclusion, this statistical model could accurately describe the relationship between independent and dependent variables, and consequently boost substantially the experimental design of ecotoxicological studies by reducing the number of model organisms, toxic and chemical substances, time, and budget.

Synthesis of zeolites from residual diatomite using a microwave-assisted hydrothermal method

Population growth directly affects the industrial production sector, as well as the quantities of waste generated in this sector. Diatomite is a typical example of such industrial waste and is used for the filtration of various products. With the aim of increasing its value, the present study employs this residue, following its usage in beer filtration, as a silicon source for the synthesis of zeolites. Two synthetic routes are used, namely, hydrothermal treatment with and without a pre-treatment step in a conventional microwave for 3-24 h. The results of the compositional and morphological characterization show that the use of a few minutes of microwave radiation reduces the process of zeolite synthesis to 15 h compared to the synthesis without pre-treatment, as well as reducing the production costs. The efficiency of microwave radiation is assessed with regards to solubilizing the residue, the possibility of employing a device of conventional use and the possibility of putting to use the diatomite residue, turning it into a versatile material that can be applied in several areas and process, such as industrial catalysts, the adsorption of environmental pollutants (ions and molecules) and water treatment via ion-exchange resins.

Magnetic Fe3O4-Ag0 Nanocomposites for Effective Mercury Removal from Water

In this study, magnetic Fe3O4 particles and Fe3O4-Ag0 nanocomposites were prepared by a facile and green method, fully characterized and used for the removal of Hg2+ from water. Characterizations showed that the Fe3O4 particles are quasi-spherical with an average diameter of 217 nm and metallic silver nanoparticles formed on the surface with a size of 23–41 nm. The initial Hg2+ removal rate was very fast followed by a slow increase and the maximum solid phase loading was 71.3 mg/g for the Fe3O4-Ag0 and 28 mg/g for the bare Fe3O4. The removal mechanism is complex, involving Hg2+ adsorption and reduction, Fe2+ and Ag0 oxidation accompanied with reactions of Cl− with Hg+ and Ag+. The facile and green synthesis process, the fast kinetics and high removal capacity and the possibility of magnetic separation make Fe3O4-Ag0 nanocomposites attractive materials for the removal of Hg2+ from water.

Surface Interactions and Mechanisms Study on the Removal of Iodide from Water by Use of Natural Zeolite-Based Silver Nanocomposites

In this work a natural zeolite was modified with silver following two different methods to derive Ag2O and Ag0 nanocomposites. The materials were fully characterized and the results showed that both materials were decorated with nanoparticles of size of 5-25 nm. The natural and modified zeolites were used for the removal of iodide from aqueous solutions of initial concentration of 30-1400 ppm. Natural zeolite showed no affinity for iodide while silver forms were very efficient reaching a capacity of up to 132 mg/g. Post-adsorption characterizations showed that AgI was formed on the surface of the modified zeolites and the amount of iodide removed was higher than expected based on the silver content. A combination of experimental data and characterizations indicate that the excess iodide is most probably related to negatively charged AgI colloids and Ag-I complexes forming in the solution as well as on the surface of the modified zeolites.

Adsorption Processing for the Removal of Toxic Hg(II) from Liquid Effluents: Advances in the 2019 Year

Mercury is a toxic metal, thus, it is an element which has more and more restrictions in its uses, but despite the above, the removal of this metal, from whatever the form in which it is encountered (zero valent metal, inorganic, or organic compounds), and from different sources, is of a widespread interest. In the case of Hg(II), or Hg2+, the investigations about the treatment of Hg(II)-bearing liquid effluents (real or in most cases synthetic solutions) appear not to end, and from the various separation technologies, adsorption is the most popular among researchers. In this topic, and in the 2019 year, more than 100 publications had been devoted to this field: Hg(II)-removal-adsorption. This work examined all of them.