56 research outputs found
Experimental and Modeling Studies of Sr2+and Cs+Sorption on Cryogels and Comparison to Commercial Adsorbents
No full textIn this work, two cryogels with the key monomers methacrylic acid and 2-acrylamido-2-methyl-1-propansulfonic acid (named AAC and SAC, respectively) with various functional groups were used as adsorbents for the removal of cesium and strontium ions from aqueous solutions. Kinetics, equilibrium, and column studies were carried out including experiments in different water matrices (ultrapure, tap, and river water) and comparison to commercial adsorbents. AAC reached sorption capacity of 362 mg g-1 for Cs+ and 209 mg g-1 for Sr2+, whereas SAC polymer showed maximum removal capacities of 259 and 211 mg g-1 for Cs+ and Sr2+, respectively. The five cycles of adsorption/desorption experiments showed a maximum of 8% loss of effectiveness for both cryogels. Batch kinetics adsorption data were modeled by using a rigorous diffusional model coupled to a novel fractal-like expression for variable surface diffusivity. The model revealed that the surface diffusivity dependence on time is nonmonotonic, with the occurrence of a maximum. Also, both fluid film and intraparticle transport resistances were shown to be important, with the internal one being more influential. The cryogels and two commercial materials (ion-exchange resin and zeolite) were tested for the removal of Cs+ and Sr2+ in ultrapure, tap, and river water; the results showed that the cryogels exhibit competitive effectiveness
Distributed 2D temperature sensing during nanoparticles assisted laser ablation by means of high-scattering fiber sensors
No full textThe high demand in effective and minimally invasive cancer treatments, namely thermal ablation, leads to the demand for real-time multi-dimensional thermometry to evaluate the treatment effectiveness, which can be also assisted by the use of nanoparticles. We report the results of 20-nm gold and magnetic iron oxide nanoparticles-assisted laser ablation on a porcine liver phantom. The experimental set-up consisting of high-scattering nanoparticle-doped fibers was operated by means of a scattering–level multiplexing arrangement and interrogated via optical backscattered reflectometry, together with a solid-state laser diode operating at 980 nm. The multiplexed 2-dimensional fiber arrangement based on nanoparticle-doped fibers allowed an accurate superficial thermal map detected in real-time
Municipal Solid Waste Management in US: Similarities, differences and suggestions for a more efficient system
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Automotive shredder residue (ASR) : a rapidly increasing waste stream waiting for a sustainable response
No full textRecycling scrapped cars plays an important role in reducing pollution by decreasing the amount of waste that ends up in landfills. Directive 2000/53/EC regulates the management of ELVs. ELVs are collected and dismantled to remove the battery, tyres, fluids and any parts that can be re-used and the wreck is shredded. The metallic parts are separated by physical processes and recovered as ferrous scrap and nonferrous metals, all of which is recycled. The 25% remainder is the automotive shredder residue (ASR), which is composed mainly of plastics, contaminated with any metallic and other parts that could not be separated. This is often disposed of in landfills as solid urban waste and is not recycled. ASR generation in EU is approximately 2-2.5 million tonnes /year, constituting 10% of total hazardous waste in the EU. The study suggests that recovery rates for ELVs set in the EU Directive on end-of life vehicles will not be met until the volume of the ASR is further reduced. Treatment of the ASR focuses on recovering any useable materials, reducing the volume of the ASR to cut down on the quantity that will end up in landfill, and recovering the energy from the petrochemical content of the plastics. Up-to-date there are 8 post-shredder technologies (PST) used or potentially used for the treatment of auto shredder residues (ASR). The aim of this study is to give an overview of what problem the ASR presents to modern society and what the options are for processing this waste into recovered products or materials, or energy, with a minimum of useless by-products for which landfilling is the only route
Mercury reduction and chemisorption on the surface of synthetic zeolite silver nanocomposites : equilibrium studies and mechanisms
No full textThis work presents the utilization of a coal power plants waste, namely coal fly ash for the synthesis of zeolites and zeolite silver nanocomposites for the removal of Hg2+ from water. Equilibrium data are derived for all materials for mercury concentration range of 10–500 mg/L and models are applied. The removal mechanisms are discussed in detail and complemented by XRD, XRF, SEM-EDS, and TEM characterizations and water phase mercury speciation modeling. According to findings, the adsorption capacity of zeolites is about 4 mg/g and increased by almost 5 times after the modification with silver nanoparticles to 20.5–22.3 mg/g. Langmuir equilibrium model fits well the experimental data of the nanocomposites indicating monolayer adsorption process. The mechanism is complex, involving Hg2+ reduction to Hg+ and possibly Hg0 followed by formation of calomel and amalgams on the surface of the nanocomposites. The mercury reduction is accompanied by Ag0 oxidation to Ag+ and subsequent formation of silver chloride
Silver nanoparticles synthesised within the silica matrix in hyperstoichiometrical of mercury from aqueous solutions
No full textMercury 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
Sustainable production of pure silica from rice husk waste in Kazakhstan
No full textThis 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
Two-phase homogeneous diffusion model for the fixed bed sorption of heavy metals on natural zeolites
No full textIn 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
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