Avilés Miranda, Amarillys

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    Sorption mechanism of organosilanol and dimethyl sulfone compounds in water by zeolite beta
    (2023-05-11) Avilés Miranda, Amarillys; Tarafa Vélez, Pedro J.; College of Engineering; Suárez, Oscar Marcelo; Suleiman Rosado, David; Muñoz Barreto, Jonathan; Department of Civil Engineering; Ortiz Albino, Reyes M.
    Organosilanol compounds and dimethyl sulfone create concerns about water contamination of their difficult removal by adsorption with activated carbon due to their low affinity or ion exchange resin. As an alternative, this research evaluated the viability of zeolite beta (both ammonium and hydrogen beta) in the adsorption of trimethylsilanol and dimethylsilanediol as organosilanol compound models and dimethyl sulfone. Batch experiments assessed each adsorbent's adsorption capacity, and the non-linear regression analyzed the best isotherm model. Measuring the adsorption at different pH, time, and temperature brought an understanding of adsorbate-adsorbent interactions, estimating the thermodynamic parameters, and identifying the rate-limiting step in the mass transfer analysis. Results showed that hydrogen zeolite beta exhibited higher adsorption capacities than ammonium zeolite beta for organosilanol compounds; however, for dimethyl sulfone, higher adsorption was obtained using ammonium zeolite beta. Besides, trimethylsilanol showed stronger attraction forces for the adsorbents than dimethylsilanediol and dimethyl sulfone, yielding higher removals efficiency. Both external and internal diffusivities affect the rate-limiting phase during the transfer of the adsorbate from the bulk solution to the internal adsorbent, with the internal diffusion (surface and pore diffusion) having more impact. Thermodynamic parameters demonstrate the feasible sorption of organosilanol compounds using both adsorbents, whereas dimethyl sulfone adsorption requires external energy. The adsorbents have heterogeneous surfaces, an exponential distribution of active sites on them, and the ability to adsorb several layers of the adsorbates as their adsorption mechanism.
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    Immobilization of titanium dioxide in crushed recycled glass for atrazine photo-degradation
    (2016) Avilés Miranda, Amarillys; Tarafa Vélez, Pedro J.; College of Engineering; Suárez, O. Marcelo; Hwang, Sangchul; Department of Civil Engineering; Acevedo Rullán, Aldo
    The release of toxic chemicals, as herbicides from agricultural activities is causing contamination of surface water by runoffs action after precipitation. This research studied the degradation of atrazine (herbicide) by a porous glass substrate, embedded with photo-catalytic titanium dioxide (TiO2) nanoparticles. Porous substrate was attained by sintering clear recycled glass cullets (MG-30) in a furnace at temperatures between 950ºC to 975ºC for 45 to 75 minutes. The TiO2 nanoparticles were deposited within or onto the glass substrate and immobilized by heat treatment. The polymorph phase of the immobilized TiO2 was analyzed after the heat treatment by x-ray diffraction (XRD). Also, a percolation and compressive strength were studied to evaluate the thermo-mechanical properties of the material. The experimental results demonstrated that the TiO2 immobilization was favored by sintering nanoparticles within the glass particles, under UV light exposure atrazine degradation capacity was low. On the other hand, the immobilization of the nanoparticles onto the surface increased after the heat treatment. In addition, the XRD analyses confirmed the anatase polymorph phase of the nanoparticles. For the deposition onto the glass substrate, atrazine degradation fell below detection limits after 12 h of UV light exposure with possible exhaustion of the TiO2 nanoparticles after 36 h of treatment. Finally, that percolation rate declined for longer sintering time and higher sintering temperature. Conversely, the compressive strength increases for similar sintering parameter changes.