Effect of nanoparticle aggregation at low concentrations of TiO2 on the hydrophilicity, morphology, and fouling resistance of PES-TiO2 membranes.

This paper reports the fabrication and characterization of polyethersulfone-TiO(2) (PES-TiO(2)) nanoparticle composite membranes made from synthesis casting solution consisting of various compositions of polymer solvents (DMF and EtOH) and TiO(2) additive. The results also revealed that the membrane permeation and rejection rates, pore size, and porosity were dependent on the TiO(2) and EtOH concentrations. Nanoparticles were characterized by zeta potential measurements, TEM observations, and measurement of particle size distributions. Zeta potential measurements in aqueous solution demonstrated that the TiO(2) particles size is dominated by electric double layer interactions. Addition of EtOH promotes the increase of the clusters size as consequence of a double effect: reduction of the dielectric constant of solution and the depletion of the suspension field determined by the action of the polymer chains. The observed effects as result of EtOH addition and increase of TiO(2) concentration were similar: both procedures provoked an increase of macrovoid dimensions. The modified membranes by TiO(2) incorporation showed a structural change from a sponge-like to a finger-like structure. Strong correlations were observed between the hydrophilicity and the permeability of manufactured membranes. The formation mechanism of TiO(2)-blended membranes was altered, in a similar way, as result of EtOH at different contents of nanoparticles. Fouling resistance of modified membranes was significantly improved showing that EtOH addition is a suitable procedure for the membrane performance improvement. The rejection potential of membranes is hardly affected by the nanoparticles and EtOH incorporation into the polymeric solution.

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.