Browsing by Subject "Silver nanoparticles"

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    Graphene oxide and graphene oxide functionalized with silver nanoparticles as adsorbents of phosphates in waters. A comparative study
    (Elsevier B.V, 2019-12-12) Vicente Martínez, Yésica; Química Analítica
    Phosphate removal is an important factor thatmust be taken into account in eutrophizedwaters. For this reason, many studies on differentways of removing phosphates fromwater have been published nowadays. In thiswork, a comparative study between the use of graphene oxide (GO) and graphene oxide functionalized with silver nanoparticles (GO@AgNPs) as adsorbents to remove phosphates from water samples has been carried out. Experimental conditions, including the pH, adsorbent dose, contact time and temperature, have been analyzed to achieve the highest adsorption efficiency. Although both adsorbents can be considered suitable for removing phosphates from aqueous solutions, GO@AgNPs provided a maximum removal efficiency of 100%, reaching the equilibrium conditions instantaneously under straightforward experimental conditions. Moreover, a much lower adsorbent dose was necessary than with graphene oxide. When GO was used, the maximum removal efficiency was 75%, 9 minwere necessary to reach the equilibriumconditions and 20mgof adsorbentwere needed. Both adsorbents can be regenerated in an acid medium, giving recovery percentages of 98% and 80% for GO and GO@AgNPs respectively, which allows them to be recycled and used again.
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    Magnetic core‑modified silver nanoparticles for ibuprofen removal: an emerging pollutant in waters
    (Nature Research, 2020-10-26) Vicente Martínez, Yésica; Solana González, Ruben; Soto Meca, Antonio; Caravaca, Manuel; Química Analítica
    In this work we present a novel procedure for ibuprofen adsorption from waters employing magnetic core-modified silver nanoparticles. We demonstrate that 93% adsorption of ibuprofen is achieved in 45 min by means of a simple method, for neutral pH and room temperature, also using a low dose of adsorbent, equal to 7 mg in 500 �L of suspension. The characterization of the adsorbent, before and after adsorption, was carried out by means of field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, BET analysis, Fourier-transform infrared spectroscopy and differential scanning calorimetry. It is worth pointing out that ibuprofen can be desorbed and the adsorbent can be reused, remaining unaltered for the first three cycles, and showing 89.3% adsorption efficiency after the third regeneration. A three-parameter model and the Langmuir isotherm characterize the kinetics and isotherm of adsorption.
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    Simultaneous adsorption of mercury species from aquatic environments using magnetic nanoparticles coated with nanomeric silver functionalized with L-Cysteine
    (Elsevier Ltd., 2021-06-04) Vicente Martínez, Yésica; Química Analítica
    We introduce a novel, efficient and fast method for the total and simultaneous removal of monomethylmercury, dimethylmercury, ethylmercury and Hg (II) from aquatic environments using magnetic core nanoparticles, coated with metallic nanomeric silver and functionalized with L-Cysteine. As far as the authors know, simultaneous removal has not been achieved previously. The experimental design was based on exploring a wide range of experimental conditions, including pH of the medium (2􀀀 12), contact time (up to 20 min), adsorbent dose (50–800 μL) and temperature (293–323 K), in order to achieve the highest adsorption efficiency. The results show that, for a pH equal to 6.2 at room temperature, 400 μL of nanoparticles is sufficient to achieve 100% adsorption efficiency for all the studied Hg species after a contact time of 30 s. The adsorbent was characterized by means of Scanning Electron Microscopy, Energy Dispersive X-ray Analysis, Fourier-Transform Infrared Spectroscopy and a BET test. Moreover, the procedure allows the total recovery and recycling of the nanoparticles using 50 μL of 0.01 M KI. As regards reuse, the adsorbent exhibits no loss of adsorption capacity during the first three adsorption cycles. Thermodynamics reveals that adsorption is of a physicochemical nature, the equilibrium isotherms being described by a Langmuir model for all the Hg species. The ability of the method to simultaneously adsorb all species of mercury present in water, achieving full adsorption in just a few seconds, along with the simple experimental conditions and its cost-effectiveness, strongly support the approach as an alternative to current procedures.