Jesús M. Arsuaga

Aqueous heavy metals removal by adsorption on amine-functionalized mesoporous silica

Amino functional mesoporous silica SBA-15 materials have been prepared to develop efficient adsorbents of heavy metals in wastewater. Functionalization with amino groups has been carried out by using two independent methods, grafting and co-condensation. Three organic moieties have been selected to incorporate the active amino sites: aminopropyl (H(2)N-(CH(2))(3)-), [2-aminoethylamino]-propyl (H(2)N-(CH(2))(2)-NH-(CH(2))(3)-) and [(2-aminoethylamino)-ethylamino]-propyl (H(2)N-(CH(2))(2)-NH-(CH(2))(2)-NH-(CH(2))(3)-). Materials have been characterized by XRD, nitrogen sorption measurements and chemical analysis. We have found that all materials preserve the mesoscopic order and exhibit suitable textural properties and nitrogen contents to act as potential adsorbents. Metal removal from aqueous solution has been examined for Cu(II), Ni(II), Pb(II), Cd(II), and Zn(II); adsorption performances of materials prepared by the two functionalization methods have been compared. In addition, copper adsorption process has been thoroughly studied from both kinetic and equilibrium points of view for some selected materials. Aqueous Cu(II) adsorption rates show that the overall process is fast and the time evolution can be successfully reproduced with a pseudo-second-order kinetic model. Whole copper adsorption isotherms have been obtained at 25 degrees C. Significant maximum adsorption capacities have been found with excellent behavior at low concentration.

Binary metal oxides for composite ultrafiltration membranes

A new ultrafiltration membrane was developed by the incorporation of binary metal oxides of the type Ti(x)Zr(1−x)O2 inside polyethersulfone. Physico-chemical characterization of the binary metal oxides demonstrated that the presence of Ti in the TiO2–ZrO2 system results in an increase of the size of the oxides, and also their dispersity. The crystalline phases of the synthesized binary metal oxides were identified as srilankite and zirconium titanium oxide. The effect of the addition of ZrO2 can be expressed in terms of the inhibition of crystal growth of nanocrystalline TiO2 during the synthesis process. For photocatalytic applications the band gap of the synthesized semiconductors was determined, confirming a gradual increase (blue shift) in the band gap as the amount of Zr loading increases. Distinct distributions of binary metal oxides were found along the permeation axis for the synthesized membranes. Particles with Ti are more uniformly dispersed throughout the membrane cross-section. The physico-chemical characterization of membranes showed a strong correlation between some key membrane properties and the spatial particle distribution in the membrane structure. The proximity of metal oxide fillers to the membrane surface determines the hydrophilicity and porosity of modified membranes. Membranes incorporating binary metal oxides were found to be promising candidates for wastewater treatment by ultrafiltration, considering the observed improvement in flux and anti-fouling properties of doped membranes. Multi-run fouling tests of doped membranes confirmed the stability of permeation through membranes embedded with binary TiO2–ZrO2 particles.

Nanofiltration removal of pharmaceutically active compounds

Abstract Capability of nanofiltration membranes (NF) to remove pharmaceutical active compounds from wastewater streams was investigated. Sulfamethoxazole, diclofenac sodium, hydrochlorothiazide, 4-acetamidoantipyrine, nicotine and ranitinide hydrochloride were selected as model compounds since they are widely produced as pharmaceutical agents. Two commercially available polyamide nanofiltration membranes (NF-90 and NF-270 from Dow FilmTec) were tested. Solute retention by NF-90 membrane was very high in all cases (over 95%), whereas NF-270 retention systematically appeared lower ranging from 75% (nicotine) to 95% (ranitidine hydrochloride). Temporal evolution of flux decline was also investigated. The influence of physicochemical properties of both membrane and solutes on membrane performance was analyzed to explore the main solute-membrane interactions that determine the solute transfer across the membrane. The influence of operation pressure on NF-90 and NF-270 rejection was also studied.

Magnetic, structural and surface properties of functionalized maghemite nanoparticles for copper and lead adsorption

In this study, magnetic nanocomposites were developed and used as adsorbents for lead and copper from aqueous media. Structural, surface, magnetic and textural properties of functionalized maghemite nanoparticles synthesized by alkaline co-precipitation were studied. The surfaces of the iron oxide nanoparticles (Nps) were modified with different chemical agents such as fatty and amino acids, silica (SiO2), mesoporous silica (SBA-15), hydroxyapatite, multiwall carbon nanotubes (MWCNTs) and ethylenediaminetetraacetic acid (EDTA), obtaining NPs with mean particle sizes ranging from 7 to 16 nm according to Rietveld refinement and TEM images analysis. The physicochemical surface properties of the functionalized materials were studied via zeta potential (ζ) and Fourier transform infrared (FTIR) spectroscopy. Mossbauer spectroscopy (MS) as a function of temperature and DC magnetometry were used to study the magnetic properties. The superparamagnetic relaxation was studied by MS. The resolved spectra at 20 K confirm the presence of nanomaghemite phase. Besides, the saturation magnetization varies from 12 to 62 emu g−1. A nitrogen adsorption–desorption technique was used to determine the specific surface area and to study the porous structure. The functionalized γ-Fe2O3 Nps exhibited a Brunauer–Emmett–Teller (BET) specific surface area ranging from 74 to 214 m2 g−1 and revealed remarkable uptake capacities to remove Cu(II) and Pb(II) species from aqueous solutions.

Heavy metals removal from water by adsorption on propylthiol-functionalised mesoporous silica obtained by co-condensation

Propylthiol-functionalised mesoporous silica SBA-15 prepared by co-condensation has been tested for heavy metal removal. Adsorption from aqueous solution was examined for Cu(II), Pb(II), Cd(II), and Hg(II). Adsorption isotherms were determined at 20°C and Langmuir and Freundlich models were fitted to experimental data. The results from adsorption experiments indicate that mercury is efficiently removed from water. Copper, lead and cadmium uptakes from aqueous solution are noticeable but significantly smaller than mercury removal; moreover, lead and cadmium adsorption isotherms exhibit no adsorption maximum within the investigated range of concentration. The influence of solution pH on lead adsorption was also investigated.

Enthalpies of Dilution of Cobalt–Amine-Type Salts in Aqueous Solutions at 25°C

The enthalpies of dilution for aqueous solutions of [Co(en)3]Br3, [Co(pn)3]Cl3, and [Co(tn)3]Cl3 (where en = 1,2-diaminoethane, pn = 1,2-diaminopropane, and tn = 1,3-diaminopropane) have been measured at 25°C, and up to m = 1 mol-kg−1, using an isoperibol calorimeter by the “long-jump” method. Relative apparent molar enthalpies Lφ have been extracted as an empirical equation relating Lφ and m. Previously reported experimental data and theoretical predictions in the restricted primitive model (RPM) for 3:1 and 1:3 aqueous electrolytes are shown together with the new experimental material.