New ways to use the red mud waste as raw material for inorganic- organic hybrid hydrogels

The present paper was aimed at developing innovative hybrid composites by using cheap filler, like red mud (RM). The study importance refers to RM recycling, a recent trend in environmental science. Besides its causticity, large amounts of RM are produced yearly, calling for recovery measurements. Herein, poly (acrylic acid)- based inorganic-organic hybrid hydrogels (PAA hydrogels) incorporating RM were synthesized.

Furthermore, the possibility of involving inorganic additives (kaolin and/or sodium silicate) together with RM was investigated. Incorporation of all three inorganic compounds (RM + Kaol + Sil) in hydrogels was also evaluated, novel hybrids being prepared. The obtained hybrids were characterized by different techniques (DR UV-VIS; DRIFT; TGA/DTG; SEM) and in terms of swelling behavior. DRIFT and DR UV-VIS confirmed the occurrence of characteristic bands of raw materials. Final properties (water uptake, thermal stability, porosity) can be controlled by modifying preparation conditions. Hydrogels yielded, by calcinations, iron- rich ceramic foams, able to promote water removal of sulfide ions from wastewaters.