Silver nanoparticles synthesised within the silica matrix in hyperstoichiometrical of mercury from aqueous solutions

Mercury adsorption of silver containing silica-based nanocomposites was evaluated. Maximum adsorption capacity of 0.4 mmol g-1 was achieved at silver loading of 0.5 mmol g-1. Nevertheless, if to calculate in respect to silver content the mercury adsorption capacity was generally elevated along with decreasing silver nanoparticle diameter. It has been demonstrated that silver particle diameters and loading should collectively be taken into consideration in designing the optimal mercury removal process. Further recommendations have been proposed with the aim of increasing the mercury removal efficiency using silver nanoparticles deposited on the surface of silica with lover silver loading, while achieving similar or even higher efficiencies due to observed hyperstoichiometry effect

Assessment of total mercury content in water of the Balkyldak Lake-reservoir, Pavlodar, Kazakhstan

This study aimed at determining the levels of total mercury in water samples collected in the vicinity of the Lake-reservoir Balkyldak in Pavlodar, Kazakhstan. Legacy of the chloralkali process in Pavlodar which involved the mercury cell method while producing a chlorine-free sodium hydroxide leads to serious environmental problems. At the time of the unit continuous operation in between 1971-1993 approximately 1000 metric tons of metallic mercury has been released into the wastewater holding pond at the chemical plant. For many years, mercury collected in the wastewater pond was a subject of the Kazakhstan sharply continental climate fluctuation and overflow to the Balkyldak Lake-reservoir, creating a significant mercury contamination issue for the whole region. Mercury emitted from industrial eluents in environment carries predominantly anthropogenic pollutants. Due to its natural cycle through atmosphere, water and soil in different forms prompts the widespread global mercury pollution. In present investigation, samples collected in a close proximity of the Balkyldak Lake were analyzed in respect to the geological location of collection

Sustainable production of pure silica from rice husk waste in Kazakhstan

This study aimed at developing a new synthesis method for the production of high purity silica from rice husks originated from different regions of Kazakhstan. The proposed eco-friendly method is compared with the conventional one reported in the literature which is accompanied by the use of significant amount of inorganic alkali and acids and direct combustion. In order to reduce the environmental impact, the mineral acid pre-treatment stage was either removed or replaced with organic acid pre-treatment, which reduced the amount of chemicals used during the synthesis and treatment process. The calcination temperature of 600 °C was selected based on thermogravimetric analysis. The average purity of silica samples obtained via different methods ranged from 84.81 to 99.66 wt%. The purity of the produced silica by use of the greener method was high reaching 98.67% with surface area up to 625 m 2 /g

Optimized production of coal fly ash derived synthetic zeolites for mercury removal from wastewater

Coal fly ash (CFA) derived synthetic zeolites have become popular with recent advances and its ever-expanding range of applications, particularly as an adsorbent for water and gas purification and as a binder or additive in the construction industry and agriculture. Among these applications, perpetual interest has been in utilization of CFA derived synthetic zeolites for removal of heavy metals from wastewater. We herein focus on utilization of locally available CFA for efficient adsorption of mercury from wastewater. To this end, experimental conditions were investigated so that to produce synthetic zeolites from Kazakhstani CFAs with conversion into zeolite up to 78%, which has remarkably high magnetite content. In particular, the effect of synthesis reaction temperature, reaction time, and loading of adsorbent were systematically investigated and optimized. All produced synthetic zeolites and the respective CFAs were characterized using XRD, XRF, PSA and porosimetric instruments to obtain microstructural and mineralogical data. Furthermore, the synthesized zeolites were studied for the removal of mercury from aqueous solutions. A comparison of removal eficiency and its relationship to the physical and chemical properties of the synthetic zeolites were analyzed and interpreted

Two-phase homogeneous diffusion model for the fixed bed sorption of heavy metals on natural zeolites

In this work, the fixed bed removal kinetics of Pb2+, Zn2+, Mn2+, Cr3+, Fe3+ and Cu2+ from aqueous solutions on natural zeolites was studied. For this aim, a non-dimensional two-phase homogeneous solid diffusion model including axial dispersion and equipped with a universal double-selectivity equilibrium model is developed and applied. In total 9 isotherms, representing 128 experimental points and 25 breakthrough curves, representing 764 experimental points are used in modeling. The application of the model is satisfactory resulted in an average deviation from the experimental data of 11.19 ± 5.53%. The solid phase diffusion coefficients are between 10−7 and 10−9 cm2/s depending on the metal, flow rate and particle size in the decreasing order of Cu > Fe, Cr > Zn, Pb > Mn. The study is supplemented by an extended literature review on fixed bed models and experimentally derived solid phase diffusion coefficients in zeolites

Synthetic coal fly ash-derived zeolites doped with silver nanoparticles for mercury (II) removal from water

Coal fly ash-derived zeolites have attracted considerable interest in the last decade due to their use in several environmental applications such as the removal of dyes and heavy metals from aqueous solutions. In this work, coal fly ash-derived zeolites and silver nanoparticles-impregnated zeolites (nanocomposites) were synthesized and characterized by TEM/EDX, SEM/EDX, XRD, XRF, porosimetry (BET), particle size analysis (PSA) and zeta potential measurements. The synthesized materials were used for the removal of Hg2+ from aqueous solutions. The results demonstrated that nanocomposites can remove 99% of Hg2+, up to 10% and 90% higher than the removal achieved by the zeolite and the parent fly ash, respectively. Leaching studies further demonstrated the superiority of the nanocomposite over the parent materials. The Hg2+ removal mechanism is complex, involving adsorption, surface precipitation and amalgamation

Iodide removal by use of Ag-modified natural zeolites

In the present work Ukrainian clinoptilolite was modified with Ag and applied for the removal of iodide from aqueous solutions. The effect of three different modifications was studied, one resulting in an Ag+ ion exchanged form, and two resulting in zeolites decorated with silver oxide and zero valent metallic nanoparticles. The results indicated the strong potential affinity of the Ag-modified zeolite materials towards iodide

Mineralogical, microstructural and thermal characterization of coal fly ash produced from Kazakhstani power plants

Coal fly ash (CFA) is a waste by-product of coal combustion. Kazakhstan has vast coal deposits and is major consumer of coal and hence produces huge amounts of CFA annually. The government aims to recycle and effectively utilize this waste by-product. Thus, a detailed study of the physical and chemical properties of material is required as the data available in literature is either outdated or not applicable for recently produced CFA samples. The full mineralogical, microstructural and thermal characterization of three types of coal fly ash (CFA) produced in two large Kazakhstani power plants is reported in this work. The properties of CFAs were compared between samples as well as with published values

In situ production of high purity noble metal nanoparticles on fumed silica and catalytic activity towards 2-nitrophenol reduction

In-situ synthesis of chemically pure noble metal (Au, Pt, Pd, Ru) nanoparticles was performed via redox reaction under ambient conditions from aqueous noble metal salt solutions on non-porous fumed silica. Nanoparticles of average sizes Au > Ru > Pt

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

In this work, a novel silver nanoparticles-doped synthetic sodalitic composite was synthesized and characterized using advanced characterization methods, namely TEM-EDS, XRD, SEM, XRF, BET, zeta potential, and particle size analysis. The synthesized nanocomposite was used for the removal of Hg2+ from 10 ppm aqueous solutions of initial pH equal to 2. The results showed that the sodalitic nanocomposites removed up to 98.65% of Hg2+, which is ∼16% and 70% higher than the removal achieved by sodalite and parent coal fly ash, respectively. The findings revealed that the Hg2+ removal mechanism is a multifaceted mechanism that predominantly involves adsorption, precipitation and Hg-Ag amalgamation. The study of the anions effect (Cl−, NO3−, C2H3O2−, and SO42−) indicated that the Hg2+ uptake is comparatively higher when Cl− anions co-exist with Hg2+ in the solution