RESUMEN
This work introduces a new sustainable alternative of powdered activated carbon (PAC) - magnetically harvestable and reusable after regeneration via inductive heating - for the adsorptive removal of organic micropollutants (OMP) from secondary wastewater effluents. For this purpose, two commercial PACs - lignite "L" (1187 m2/g) and coconut "C"-based (1524 m2/g) - were modified with magnetic iron oxide following two different synthesis approaches: infiltration ("infiltr") and surface deposition ("depos") route. The resulting magnetic powdered activated carbons (mPAC) and their precursor PACs were fully characterized before application. The iron oxide content of the modified "L" and "C" samples was â¼30 % and â¼20 %, respectively. Iron oxide gives the PAC beneficial magnetic properties for easy magnetic separation and simultaneously acts as an inductively heatable agent for the carbon regeneration. The infiltrated samples displayed better inductive heating performance and regeneration than their deposited counterparts. Tests with real wastewater showed fast adsorption kinetics of the organic load following the pseudo-second-order kinetic model. Adsorption isotherms were compliant with the Freundlich isotherm model. Sample "L-infiltr" had the best overall adsorption performance throughout 5 reuse cycles when intermediately inductively regenerated (<3 % drop in organics removal per cycle with intermediate regeneration vs. â¼10 % drop per cycle without regeneration). The treated supernatant was additionally tested for 31 representative organic micropollutants and their transformation products (pharmaceuticals, personal care products, industrial chemicals, etc.), where 26 OMPs had consistently high removal (>85 %) throughout 5 cycles with intermediate regeneration and for 28 OMPs the total adsorption efficiency dropped by <5 % after 5 cycles.
RESUMEN
Phase change materials (PCMs) are an effective thermal mass and their integration into the structure of a building can reduce the ongoing costs of building operation, such as daily heating/cooling. PCMs as a thermal mass can absorb and retard heat loss to the building interior, maintaining comfort in the building. Although a large number of PCMs have been reported in the literature, only a handful of them, with their respective advantages and disadvantages, are suitable for building wall construction. Based on the information available in the literature, a critical evaluation of PCMs was performed in this paper, focusing on two aspects: (i) PCMs for building wall applications and (ii) the inclusion of PCMs in building wall applications. Four different PCMs, namely paraffin wax, fatty acids, hydrated salts, and butyl stearate, were identified as being the most suitable for building wall applications and these are explained in detail in terms of their physical and thermal properties. Although there are several PCM encapsulation techniques, the direct application of PCM in concrete admixtures is the most economical method to keep costs within manageable limits. However, care should be taken to ensure that PCM does not leak or drip from the building wall.
RESUMEN
Herein, a simple model setup is presented to spray fine liquid droplets containing nanoparticles in an air stream transporting this toward a filter material. The nanoparticles are made of silica and tagged with a fluorescent dye in order to render the trace of the particles easily visible. The silica nanoparticles, in a first approximation, mimic virus (severe acute respiratory syndrome coronavirus 2) particles. The setup is used to evaluate different tissues, nowadays, in times of the coronavirus pandemic, commonly used as facemasks, with regard to their particle retention capability. The setup enables adjusting different "breathing scenarios" by adjusting the gas flow speed and, thereby, to compare the filter performance for these scenarios. The effective penetration of particles can be monitored via fluorescence intensity measurements and is visualized via scanning electron micrographs and photographs under UV light. Ultimately, a strong increase of particle penetration in various mask materials as function of flow speed of the droplets is observed and an ultimate retention is only observed for FFP3 and FFP2 masks.
RESUMEN
Surface modified superparamagnetic iron oxide nanoparticles are assembled into nanostructured micro-raspberry particles via spray drying. The micro-raspberry powder is readily redispersed to individual nanoparticles or nanostructured sub-units, depending on the initially adjusted nanoparticle modification. In this work, it is demonstrated how the technique of magnetic zero-field-cooled/field-cooled (ZFC/FC) measurements can be used to judge the degree of agglomeration, i.e. the extent of hard-agglomerates and soft-agglomerates in a system and predict the redispersibility of the powder particles. Furthermore, the uniformity of surface modification of the individual nanoparticles can be judged via this method. In addition, the technique can be applied to characterise complex nanostructured particle systems composed of iron oxide nanoparticles mixed with another type of nanoparticulate building-block. Thus, this work shows that magnetic measurement techniques are a promising approach to characterise agglomeration states of nanoparticles, their degree of surface modification and their distribution in complex particle and composite systems.
RESUMEN
Despite immense progress in nanoscience and technology, one of the yet unsolved challenges is the redispersion of nanoparticles from dry powders back to the individual, primary particles. Herein, an easy to handle powder consisting of nanostructured micron sized raspberry-like particles is presented. These nanostructured micro-raspberries are composed of individual nanoparticles which are equipped with molecules that introduce a separating effect or "spring" functionality. Thereby, a powder system is obtained that allows for an easy and complete redispersibility of the agglomerates down to the level of individual nanoparticles in solvents and polymers. The mechanism of redispersibility involves mechanic stimuli/force as well as solvent like disintegration aspects ("like dissolves like" effect). Furthermore, by tailoring the degree of spacer-equipped particles, the bursting behavior can also be tuned, yielding different redispersion degrees. The redispersibility of the nanostructured micro-raspberries is demonstrated in solvents and silicone-based nanocomposites.
RESUMEN
Active silica nanoparticle-based raspberry-like container depots for agents such as antimicrobial substances are presented. The nano raspberry-containers are integrated into coatings in a way that they form a mole-hill structure; i.e., they are partly standing out of the coating. As an application example, it is demonstrated that the containers can be filled with antimicrobially active agents such as nano ZnO or Ag or organic molecules such as thymol. It is demonstrated that the containers can be partly chopped-off via abrasion by rubbing over the surface. This mechanism proves to be an attractive approach to render surfaces refreshable. A first proof of principle for antimicrobial activity of the intact containers in the coatings and the abrasion treated, chopped-off (and thereby reactivated) containers is demonstrated.