Synergistic adsorption‑photocatalytic degradation of tetracycline by microcrystalline cellulose composite aerogel dopped with montmorillonite hosted methylene blue

Abstract

A flexible and recyclable metal-freephotodynamic aerogel composite was synthesized by simple entrapping montmorillonite particles hosting methylene blue (MT-MB) into microcrystalline cellulose aerogel (MCC/MT-MB) without the use of chemical modifiers. The MT-MB particles act as adsorbent and photocatalyst for tetracycline for the first time. The mechanism of tetracycline adsorption and photodegradation by MCC/MT-MB aerogel was investigated by confocal imaging and radical scavenger experiment. Singlet oxygen was found to play a main role in the degradation confirming Type II photoexitation mechanism. The MCC/MT-MB aerogel exhibited 97% tetracycline removal efficiency within 120 min. This enhanced performance of the aerogels could be an integrated result of interconnected open porous aerogel structure, multi-adsorption mechanisms of the pollutant on the aerogel, and degradation and direct contact of methylene blue with tetracycline. Furthermore, MCC/MT-MB aerogel showed high stability and photocatalytic degradation recyclability upto 10 cycles of uses, and the recycling process was environmentally friendly. The degradation intermediate products were analyzed by HPLC-MS, and two photodegradation pathways were proposed. In addition, MCC/MT-MB aerogel showed tetracycline removal rate of 90% under red-light irradiation and > 90% under UVA or daylight irradiation from dairy manure samples collected from Central Valley California, USA, respectively.These results confirmed the advantageous functions and practicality of the photoactive porous aerogel in wastewater treatments.