Amino-grafted mesoporous MCM-41 and SBA-15 recyclable adsorbents: Desert-rose-petals-like SBA-15 type as the most efficient to remove azo textile dyes and their mixture from water

Amino-grafted Mobil Composition of Matter N. 41 (MCM-41/NH2) and Santa Barbara Amorphous (SBA-15/NH2) type mesoporous adsorbents were successfully used and compared in this work to remove azo dyes (and their mixture) from highly colored solutions. This paper reports a very fast removal and recycle (in 5 min) of great amounts of textile dyes (about the 100%) by materials characterized by high adsorption/desorption capacities. A qmax ≈ 250 mg/g for each adsorption cycle, that should be potentially increase to ≈ 1250 mg/g, under appropriate experimental conditions, was found for the proposed adsorbents. The UV–Vis absorption spectra of dyes were used to support this finding, determining the rate of adsorption. Several parameters affecting the adsorption process were investigated: the contact time, dyes solution pH values and amount of the adsorbent materials, ranging from 0.4 mg to 12 mg, and dyes (5 × 10−5 M and 1 × 10−5 M). Further, the Nitrogen adsorption/desorption isotherms, SAXS patterns, TG analyses, Zeta-potential measurements and microscopic imaging techniques, such as SEM and TEM, were used to detail the nature of interaction between dyes and adsorbents, and to investigate the morphology and the mesoporous array of the amino grafted MCM-41 and SBA-15.