Characterization and Spectroscopic Study of a Heat-Treated and Acid-Leached Halloysite Used in Congo Red Adsorption

Abstract

Algerian halloysite was heated at 600 °C and treated with HCl 5N. The materials were characterized by chemical analysis, TEM, and FT-IR spectroscopy, and used in the elimination of Congo red (CR) from aqueous solution. The effects of contact time and temperature were investigated. The thermal treatment at 600 °C results in the formation of dehydroxylated structure. Acid attack involves an increase in SiO2 content, due to the leaching of Al ions from octahedral sheet. Thermo-chemical treatment also diminishes the percentage of impurities and maintains the tubular morphology. Kinetic data follow the pseudo-second order model, whilst thermodynamic parameters lead to a not spontaneous and endothermic process. Significant changes occur in the vibrational spectrum of H600-5N (halloysite treated at 600 °C and with HCl 5N), after adsorption of Congo red, with the involvement of amino and sulfoxide groups. The mechanism highlights an outer-sphere surface complexation of SiOH....H2O species, i.e., SiOH linked to H2O via H-bonds.

Uses of Nanoclays and Adsorbents for Dye Recovery: A Textile Industry Review

“…It is important to consider that HNT properties derive mostly from their specific geological deposit, which is explained in the consulted literature [155][156][157][158][159][160]. Their biocompatibility makes them very useful for adsorbing dyes [161,162], such as methylene blue (MB) [163][164][165][166][167][168][169][170][171], azo dyes [172][173][174][175][176][177][178], triaryl and diaryl methane dyes [179][180][181][182][183][184][185][186][187], and xanthine dyes [161,[188][189][190], and also for the biosorption of heavy metals [191]. One study has eliminated Orange G from simulated and real waters by combining halloysite with ZnO nanoparticles and by photocatalytic degradation.…”