Versatile use of droplet coagulation: Shaping fine-grained SiO 2 and Al 2 O 3 waste streams into monodisperse microspheres

Abstract

The versatile use of droplet coagulation to recycle complex waste resources (fly ash FA, rice husk ash RHA and alum sludge AS) was investigated. Monodisperse microspheres were shaped, creating higher impact on the applicability of the waste resources. In order to obtain a suspension with appropriate rheological properties, pre-processing was required for the AS powder in contrast to the RHA and FA powders. Furthermore, the impact of the shaping process and waste stream properties on the calcination and sintering was determined and correlated to the microstructure of the sintered spheres. The porosity of the sintered AS microspheres was significantly lower (4%) as compared to the FA (50%) and RHA (67%) microspheres. Consequently, the crushing strength of the sintered microspheres varied for the different waste resources. Due to the enhanced densification, the highest crushing strength (185 MPa) was obtained for the AS microspheres.

Iron(III) removal from acidic solutions using mesoporous titania microspheres prepared by vibrational droplet coagulation

“…The procedure to prepare the titania microspheres was slightly modified as compared with the previously reported studies on alumina and silica microspheres. [24][25][26][27] In the first step a 4 wt% sodium-alginate aqueous solution was prepared by using a Eurostar 60 (IKA) type mixer. Then a mixture of the titania dispersion and distilled water was added, resulting in a suspension containing 20 wt% TiO2 and 0.75 wt% alginate.…”

“…In this study we investigate an alternative method to obtain titania microspheres starting from a non-porous titania nanopowder, similar to previous studies on alumina. [24][25][26] The titania particles are dispersed into an alginate solution which is dripped into a calcium solution to obtain titania loaded Ca-alginate hydrogel microspheres. In the last step, these spheres are dried and thermally treated.…”